The era of large Die casting has come the Development and Reform of Automotive Integrated large lightweight Die Castings

Automobile exhaust pollution continues to threaten the environment, "carbon neutralization" to drive energy saving and emission reduction is imperative. By the end of 2021, the number of motor vehicles in China reached 395 million, an increase of 6.18% over the same period last year, with an annual increase of about 20 million vehicles, with a rapid growth rate in the medium and long term. The high number of motor vehicles makes the vehicle exhaust pollution serious. Nitrogen oxides and volatile organic compounds emitted by motor vehicles reached 5.95 million tons and 1.96 million tons respectively, accounting for 33.3% and 19.3% of the country's total emissions. Therefore, driven by the "Blue Sky Defense War" and "double carbon" policy, the development situation of automobile emission reduction and low carbon is more urgent.

The lightweight of automobile is imperative, and the advantage of aluminum die casting process is remarkable.

1.1 the goal of "carbon neutralization" drives the automobile industry to transform to green, lightening and helping to achieve the goal of saving energy and reducing consumption.

The overall consumption reduction target of fuel passenger vehicles continues to rise, and the potential of new energy vehicles for energy saving and emission reduction is significant. According to the plan of "Energy Saving and New Energy vehicle Technology Roadmap 2.0" officially released in October 2020, the average annual fuel consumption of passenger vehicles in China from 2020 to 2035 has gradually increased, and the pressure of emission reduction has increased year by year. However, according to the 2016-2019 "China passenger vehicle Enterprise average fuel consumption and New Energy vehicle integral Accounting Table" issued by the State Ministry, it can be calculated that the actual average fuel consumption of new traditional energy vehicles from 2016 to 2019 is 6.88L, 6.77L, 6.62L and 6.46L respectively, which is always higher than the standard fuel consumption of 6.7L, 6.4L, 6L, 5.5L. However, affected by the continuous increase in sales of new energy vehicles, the overall average fuel consumption of new vehicles is lower than the standard value, and the pulling range is increasing. Thus it can be seen that new energy vehicles have great potential for energy saving and emission reduction. With the gradual improvement of the permeability of new energy vehicles, the pressure of energy saving and emission reduction in the automobile industry can be further alleviated.

The technology roadmap defines the goal of new energy development, accounting for 50% of energy-efficient and 50% of new energy vehicle sales in 2035. In order to further promote the automobile low-carbon process, the "Energy Saving and New Energy vehicle Technology Roadmap (version 2.0)" proposes that "the total carbon emissions of the automobile industry will reach a peak around 2028 ahead of the national carbon emission commitment." by 2035, total emissions will be reduced by more than 20% from the peak "and" new energy vehicles will gradually become mainstream products, and the automobile industry will achieve electrified transformation "and other vision goals. The specific milestone targets are as follows: by 2035, the annual sales of energy-efficient vehicles and new energy vehicles will each be 50%, the automobile industry will be electrified, the number of hydrogen fuel cell vehicles will reach about 1 million, and commercial vehicles will achieve hydrogen power transformation.

The vehicle weight restricts the reduction of consumption, the improvement of the endurance ability, and the lightweight demand is born. The electric vehicle power system includes three major systems: battery, motor and electric control, which usually account for 30% to 40% of the total mass of the vehicle. Under the current level of energy density of power batteries, the power system mass and space proportion of electric vehicles and generalized new energy vehicles are significantly higher than those of traditional fuel vehicles, and the vehicle weight is higher than that of traditional fuel vehicles by 5% to 25%. The vehicle weight will rise further when equipped with the relevant configuration of Intelligent Network connection in the future. Take Guangzhou Auto Toyota brand C-HR and its pure electric model C-HREV as an example, the equipment quality of pure electric model is 18.27% higher than that of fuel version. At present, due to the problems such as overweight electric drive system and low maturity, the actual battery life of electric vehicles has been seriously restricted, which has become an important factor affecting consumers' car purchase decisions. Therefore, by reducing the vehicle weight to improve the vehicle life ability has become a hot technical route to solve this problem, the lightweight demand of electric vehicles is born.

Lightweight can comprehensively improve the efficiency of consumption reduction and service life, and is one of the effective means of energy saving and emission reduction (figure 1). Under the demand of energy saving and emission reduction and the continuous improvement of long-range range of new energy vehicles, vehicle lightweight is the most direct and effective means at present. For every 10% reduction in the equipment quality of electric vehicles and fuel vehicles, mileage will be increased by 6% to 8%, and exhaust emissions and energy consumption will be reduced by 6% to 8%. In addition, under the premise of ensuring the safety strength, the lighter the vehicle weight is, the shorter the acceleration time is, the more flexible the dynamic response of the car body is, and the braking distance, body vibration and noise will be reduced. With the continuous improvement of consumers' requirements for car driving experience, the improvement of economy, safety and comfort brought about by lightweight will better meet the needs of consumers, and the competitive advantages of car companies that adopt lightweight technology will become more prominent. Therefore, through the lightweight scheme to improve energy saving and electric vehicle consumption reduction and battery life has become the current priority choice.

Fig. 1 main advantages of automobile lightweight

1.2 there are many breakthroughs in lightweight technology, and aluminum die-casting process is comprehensively dominant.

There are many breakthroughs in materials, technology and design, and the three major measures complement each other (figure 2). At present, the path of lightweight mainly includes three directions: material, technology and design. (1) lightweight materials: lightweight materials such as high strength steel, aluminum alloy, magnesium alloy and carbon fiber materials are used instead of ordinary steel materials to achieve weight loss by reducing the amount or density; (2) lightweight technology: the development of integrated die-casting, laser butt-welding, hydroforming, lightweight connection and other manufacturing processes to achieve weight loss by reducing the amount of parts or connectors. (3) lightweight design: through computer automatic design software and mechanical theory to optimize the size, shape and topology of existing parts to achieve product weight reduction. Among them, material lightweight is the basis of process and structure lightweight, according to the selection of lightweight materials, process and structure are further designed for weight reduction; at the same time, aiming at the technological development of process and structure weight reduction, the application range of different lightweight materials can be further expanded. The three major measures of lightweight complement each other and develop together.

Fig. 2 three paths of automobile lightweight

The comprehensive advantage of aluminum die-casting process is outstanding, and the trend of integrated die-casting is becoming more and more prominent. Among different lightweight materials, aluminum alloy has outstanding comprehensive advantages such as performance, density, cost and processability. compared with many kinds of metal alloys and carbon fiber, aluminum alloy is a lightweight material with high performance-to-price ratio and technological maturity. In the manufacturing process, high-pressure die-casting products are formed under high pressure, which has the advantages of high compactness, high strength and surface hardness and good surface finish, so it is suitable for the production of all kinds of complex and thin-walled structural parts. At present, the demand for automotive technology iteration and capacity improvement is accelerating, and the comprehensive advantage of aluminum die-casting scheme is obvious. With the continuous breakthroughs in the research and development of new aluminum alloy materials and large-scale die-casting equipment, automobile companies and die-casting manufacturers have begun to layout large-tonnage die-casting machines one after another, and the maturity of integrated die-casting technology is climbing rapidly. With the large tonnage die casting machine put into production, the trend of using integrated die casting technology to produce large vehicle structures will be more clear. Integrated die-casting technology can produce more complex structural components, thus providing a more reliable production process for lightweight design.

The market space of automobile aluminum alloy is broad, and the application of automotive aluminum castings accounts for the first place.

2.1 Aluminum alloy has comprehensive advantages, and the amount of aluminum used for bicycles has increased significantly.

Steel and aluminum body is the mainstream scheme at present, and the medium-and long-term incremental advantage of aluminum alloy is obvious. According to the existing process and cost factors, high-strength steel and aluminum alloy occupy a large share of the lightweight market. The material cost of high-strength steel has a large span due to different strength, and the technology is mature. At the same time, it has obvious advantages over aluminum and magnesium alloys in anti-collision performance, so it is mostly used in the structural parts and safety parts of white cars. High-strength steel can be lightweight by improving its own strength performance and reducing the amount of body steel. The advantage of aluminum alloy is that its density is lower than that of steel, and its excellent metal properties make it better to combine material weight loss with process and structure lightweight. With the trend of lightweight, the continuous progress of technology and materials, aluminum alloy will become the most important material in the lightweight market. China's lightweight and stage-by-stage goal is planned in the Roadmap of Energy Saving and New Energy vehicle Technology. The consumption of aluminum alloy for bicycles will reach 250 kg and 350 kg, in 2025 and 2030 respectively, which will greatly exceed that of high strength steel. The weight loss effect of magnesium alloy is better than that of aluminum, and it is generally used in interior decoration and transmission parts; at present, magnesium is mainly limited by its active chemical properties, high processing cost, and the price is 3 times higher than that of aluminum, so it can not be widely used in Volkswagen models. Carbon fiber composites have the best weight loss rate, corrosion resistance, good processability and designability, but at present, carbon fiber is limited by the high cost and difficulty of manufacturing and processing, low recycling and other factors, and the price is as high as 120yuan / kg, which is mostly used in luxury cars such as racing cars, overtaking cars and so on.

The weight loss rate of aluminum alloy and the ratio of performance to price are taken into account, and the amount of aluminum used for bicycles increases significantly. Compared with other lightweight materials-high strength steel, magnesium alloy and carbon fiber. (1) from the point of view of cost: the price of aluminum alloy is slightly higher than that of high-strength steel and much lower than that of magnesium alloy and carbon fiber materials; (2) from the point of view of weight loss rate: the density of aluminum alloy is 2.7 g / cm ~ 3, and the weight loss rate is between 40% and 50%, which is only weaker than carbon fiber and magnesium alloy, and much stronger than high-strength steel; (3) from the point of view of process difficulty: the related process of aluminum alloy has been very mature and the production efficiency is high, and the processes of aluminum die-casting, aluminum Calendering, aluminum extrusion and aluminum forging have been applied on a large scale; (4) in terms of recovery rate, the recovery rate of aluminum alloy is the highest. wide application can promote the development of recycled aluminum industry, meet the current urgent demand for energy saving and emission reduction, and further reduce the cost of upstream raw materials. Considering the above advantages such as high specific strength, high weight loss rate and excellent anti-corrosion performance, the consumption of aluminum alloy in automobile is increasing year by year. From 2016 to 2019, the amount of aluminum used by Chinese passenger cars increased by 15.7%, 33.6% and 28.1% respectively, and the growth rate of aluminum used by pure electric vehicles was significantly higher than that of traditional fuel vehicles (figure 3).

Fig. 3 proportion of aluminum materials by weight of bicycles in the world and major countries

2.2 Aluminum alloy industry chain: the upstream is affected by commodity prices, and the downstream transportation industry uses the most.

The upper reaches of the industrial chain are aluminum alloy smelting production, and the downstream deep processing manufacturing has a broad application space. The upstream of the industrial chain is smelting electrolytic aluminum, recycled aluminum and other raw materials and master alloys into aluminum alloy, while downstream are automobile, construction and other manufacturers. The price of raw materials such as upstream pure aluminum and the demand of downstream automobile construction industry have an impact on the production and operation of aluminum alloy processing companies. The upper reaches are affected by commodity prices, and the middle reaches generally do not have a certain bargaining power. The upper reaches of the aluminum alloy industry chain is aluminum alloy smelting, and the aluminum material is divided into electrolytic aluminum and recycled aluminum from the source. Upstream material suppliers are greatly affected by commodity prices, and mid-stream manufacturers generally adopt cost-plus pricing and adjust regularly according to changes in aluminum prices. Aluminum die-casting manufacturers with technical barriers have a certain bargaining power, and can increase product price transfer costs through negotiations with downstream customers, with a certain anti-risk ability. Disturbed by factors such as macroeconomic regulation and control and the continuous influence of the epidemic situation on supply in 2021, aluminum prices fluctuated violently. Q2 and Q3 continued to rise, once exceeding 20,000 yuan / ton. Aluminum die-casting suppliers were affected by aluminum price fluctuations, and gross profit was relatively under pressure.

Downstream deep processing is widely used, and the transportation department (including automobiles) uses the most. Aluminum alloy deep processing covers a wide range of downstream industries, including building materials, transportation (aviation, automobiles, etc.), wires and cables and food and pharmaceutical packaging. The transportation and construction sectors accounted for the highest proportion, accounting for 29% and 26%, respectively. Among them, the proportion of aluminum demand in the transportation sector will continue to maintain, and the total amount will continue to increase, so the order quantity of automotive aluminum alloy manufacturers will be greatly affected by downstream vehicle factories. In addition, the amount of aluminum used by new energy bicycles is generally nearly 42% higher than that of traditional fuel vehicles. With the increase of the permeability of new energy vehicles, the market scale of aluminum alloy for vehicles will continue to expand (figure 4).

Fig. 4 proportion of aluminum demand in various industries

2.3 Application: automotive aluminum alloy is widely used, accounting for more than 70% of automotive aluminum castings.

As a typical light metal, light alloy is widely used in automobile at home and abroad. Automotive aluminum-magnesium alloy components mainly include piston, cylinder head, clutch housing, oil pan, bumper, heat exchanger, bracket, wheel, body plate and decorative components, and so on. The main system components of the automobile are shown in figure 5.

(a) body structure

(B) Drive system

(c) powertrain

(d) chassis structure

Application case of (e) frame parts

(f) forged aluminum alloy control arm and commercial vehicle steering knuckle

Main system components of automobile

2.3.1 Aluminum alloy for vehicles covers a wide range, and the amount of aluminum used for bicycles continues to increase.

At present, automotive aluminum alloy is mainly used in body-in-white, powertrain, chassis and interior decoration, and continues to infiltrate into the rest of the parts. Aluminum alloy is widely used in the whole vehicle, including body-in-white, power system, chassis and so on. From the perspective of the mass distribution of various parts of the car, the body, power and transmission system, chassis and interior decoration account for a relatively large proportion, accounting for 27.2%, 22.5%, 20.4% and 20.4%, respectively, exceeding 90% of the vehicle mass, which is the main breakthrough direction of lightweight. The total amount of aluminum used for bicycles in North American light vehicles totaled 208.2 kg; in 2020, of which 47.2 kg, 38.6 kg, 32.7kg and 26.8 kg, were used for bicycle engines, transmission and transmission, wheels and panels, respectively. It is expected that by 2026, the aluminum alloy permeability of car body structures and panels will increase rapidly; the share of suspension components will also increase to 7%; the three electrical components (such as battery box, motor housing, converter shell, BMS shell, etc.) will become the parts with the largest aluminum increment; and the amount of aluminum used for vehicles will increase to 233.2 kg.

2.3.2 Aluminum alloy processing is divided into casting and deformation, and the die casting process is the most mature and efficient.

The processing technology of automotive aluminum alloy is divided into casting and deformation, and aluminum castings account for the highest proportion of automotive aluminum. (1) cast aluminum alloy: the aluminum alloy is heated to a molten state, flowed into the mold for cooling and forming, and then processed into auto parts. Cast aluminum alloy has good thermal conductivity and corrosion resistance, which can improve the performance of automobile in longitudinal and transverse vibration. Cast aluminum alloy is widely used in engine cylinder, automobile rocker arm, wheel hub, gearbox shell and other positions with high durability and more complex structure. (2) deformed aluminum alloy: deformed aluminum alloy refers to the aluminum alloy whose microstructure and shape are changed by stamping, bending, rolling, extrusion (non-squeeze casting) and other processes. In application, cast aluminum alloy is generally used for parts with more complex structure, while deformed aluminum alloy is suitable for automobile parts with simpler structure and higher requirements for mechanical properties. The current data show that the actual proportion of all kinds of aluminum alloy for automobile is cast aluminum 77%, rolled wood and extruded material each account for 10%, and forging material is the lowest, accounting for about 3% (figure 6).

Fig. 6 Aluminum alloy process classification and application proportion

Deformed aluminum alloy has good mechanical properties, but its application range is limited, so it is impossible to complete automobile precision structural parts. Automotive deformed aluminum alloy mainly includes forging, extruded material and rolled aluminum alloy. the three kinds of deformed aluminum alloy have different stress methods, forming and properties. The main results are as follows: (1) the forged aluminum alloy has good quality and strong impact resistance, so it is used in rollers of large rolling mills, rotors of turbogenerator sets, crankshafts and connecting rods of automobiles and tractors. (2) the process flexibility of extruded aluminum alloy (non-squeeze casting) is high. Extruded aluminum profiles can not only reduce the weight, but also increase the strength of local parts through the special structure of local parts. however, there are some problems, such as large waste loss, high cost caused by tool loss and so on. (3) Rolling is the main forming process of aluminum profile and aluminum plate, which is mainly used in metal profile, plate and pipe. Deformed aluminum alloy has the advantages of high plasticity and good mechanical properties, but it can not complete automobile precision structural parts, and the application range of products is limited.

Casting aluminum alloy process can be divided into two categories: sand casting and special casting, and special casting is more suitable for automobile aluminum alloy processing. Sand casting is the most traditional casting method to produce castings in sand mold, but the precision of the product is not high and the productivity is low. Although the problem of metal mold gravity casting which is further developed on the basis of sand casting can be further improved, however, there are also some problems, such as limiting the casting volume and strictly controlling the mold temperature, otherwise the casting quality will be affected. The casting technology other than sand casting is called special casting, including pressure casting, squeeze casting, investment casting, lost foam casting, centrifugal casting, continuous casting and so on. Among them, the pressure casting process is the most mature and efficient, and the mechanical properties of squeeze casting products are better than the general die casting process, with the advantages of high utilization of liquid metal, simplified process and stable quality, but it is difficult to produce parts with complex structure. affect the scope of product application.

Die casting is one of the most mature and efficient manufacturing technologies in casting technology, which accounts for more than 70% of automobile castings at present. Die casting is a manufacturing process in which molten metal is pressed into the mold under high pressure and cooled under pressure. According to the analysis of industry association data, automotive aluminum medium die castings account for more than 70% of the castings. The advantages of the process are as follows: (1) the metal liquid is subjected to high pressure and fast flow rate during die casting; (2) the product quality is good, the size is stable, and the interchangeability is good; (3) the production efficiency is high and the die casting die is used for many times; (4) it is suitable for mass production with good economic benefits. Process disadvantages: (1) castings are easy to produce small pores and shrinkage, resulting in low plasticity of die castings, which is not suitable to work under impact load and vibration; (2) the service life of high melting point alloy die casting is low, which affects the expansion of die casting production. In order to solve the shortcomings of the above bubbles, die-casting processes such as differential die-casting and vacuum die-casting are also developing and iterating. Previously, die-casting technology is mainly used in engine cylinder head and cylinder block, cantilever frame, transmission, generator bracket, clutch shell, automobile air-conditioning compressor and so on. At present, with the progress of integrated and large-scale die-casting technology, it is gradually extended to the direction of large-scale three electricity, car body structure and so on.

Integrated die casting leads technological change, and process upgrading promotes industry barriers.

3.1 Integrated Die casting: a subversive technological Revolution in Automobile Manufacturing

Traditional car body manufacturing covers four major processes, and the whole car factory cooperates with the parts manufacturers. The traditional car body manufacturing process is completed by the cooperation between the whole car factory and the parts manufacturer. the stamping link is divided into the stamping outer panel of the whole car factory and the stamping structure assembly of the external parts factory. because the size of the structural component is less than 300mm, it generally uses a small and medium-sized press, while the panel size usually needs continuous stamping by a large press above 800mm. After the stamping process is completed, the parts manufacturer uses a number of robots to form a solder joint workshop for component welding, and then sends it to the whole vehicle factory to weld the outer panels into body-in-white, and carries out painting and final assembly (figure 7).

Fig. 7 traditional automobile manufacturing process

Lightweight demand promotes the application of aluminum alloy, and the traditional die-casting process is improved by multi-path. The demand for lightweight automobile promotes that some parts of the body and chassis are gradually replaced by aluminum alloy parts, of which aluminum castings account for the highest proportion. High pressure die casting is a common process for the production of aluminum castings. High-pressure die-casting products have the advantages of precision molding and high production efficiency, but because the gas in the mold cavity can not be effectively removed during high-speed injection, it will form pore defects, resulting in relatively weak mechanical properties of castings. In order to meet the performance and quality requirements of automotive parts, the industry needs to solve the problems existing in the traditional high-pressure die-casting process, including three main technology upgrade paths: reducing pressure, reducing speed or reducing air content (figure 8).

Fig. 8 Die casting process of aluminum alloy

Path 1: low pressure / differential die casting improves the internal quality of castings by reducing filling pressure, the operation of the equipment is more difficult, and the process efficiency needs to be improved. It is more favorable for the forming of large thin-walled castings and is currently used in traditional products such as wheels and cylinder frames. However, some castings require high internal quality and want to crystallize under high pressure, so the crystallization pressure in low pressure casting can not be too high, so differential die casting is developed on the basis of low pressure casting. Compared with the general casting method, differential pressure casting increases the casting strength by about 25% and the elongation by about 50%, but the equipment is huge and the operation is troublesome, so it is only used when there are special requirements, and it is currently used in products such as steering knuckle.

Path 2: ultra-low speed die casting can reduce the injection speed of the process, but the production efficiency is greatly reduced, and it will bring difficulties to the follow-up cleaning work. In addition to reducing the pressure, the ultra-low speed die casting method can also be used to reduce the injection speed in the low speed stage of the die casting process on the basis of ordinary die casting, and keep the liquid metal under high pressure so as to fill the die casting mold cavity by laminar flow. the castings with very low gas content can be obtained by rapid solidification under pressure.

Path 3: vacuum die casting reduces the air content in the cavity, the equipment cost is high, and the technological requirements are high. Vacuum die-casting: by removing the gas from the die-casting mold cavity during the die-casting process, the porosity and dissolved gas in the die-casting parts are eliminated or significantly reduced. Vacuum die-casting can use alloys with lower specific pressure and poor casting properties, it is possible to use small machines to die-casting larger castings, and by improving filling conditions, die-casting thinner castings. However, the sealing structure of the vacuum die casting process is complex, and it is difficult to manufacture and install, so the cost is high, and if it is not controlled properly, the process effect is not very significant. At present, vacuum die casting is used in frame, shock absorption tower and so on.

The welding process of aluminum alloy is difficult, so the integrated die-casting technology finds a new way. With the continuous development and maturity of die-casting technology, the proportion of automobile aluminum die-casting is increasing. However, in the process of assembly and welding, because of the high melting point of the oxide layer on the surface of aluminum alloy, there are some problems in traditional fusion welding, such as deformation caused by excessive heat input, porosity, low welding joint coefficient and so on. at the same time, because the thickness and cross section of profiles are different, there are many kinds of combinations in welding, especially when the thickness is very different, the heat input is very difficult to control. Therefore, the traditional welding process can not meet the connection requirements of aluminum alloy materials. At present, one of the solutions is to develop advanced welding technology, including mainstream friction stir welding and more advanced laser welding. Or develop new connection technologies, including punching and riveting technology, bolt self-tightening technology and bonding technology. The scheme of adopting new welding and connection technology will not only increase the difficulty of the process, but also increase the cost of equipment and time. Therefore, the integrated die-casting technology of changing the traditional car body production process to produce structural components first and then welding and assembly arises at the historic moment, the number of parts required for integrated die-casting is reduced sharply, and the links of welding and glue coating are greatly reduced at the same time, which greatly simplifies the overall production process of car body. The production beat range of the integrated die casting equipment Giga Press given in Tesla's patent is 60 to 120s, which can significantly improve the production efficiency of the car body (figure 9).

Fig. 9 change of automobile manufacturing process

Tesla broke the game and integrated die-casting of car body, setting off a revolution in automobile manufacturing. On September 22nd, Tesla announced that its Model Y would adopt an integrated die-casting rear plate assembly, which could reduce the weight of the lower body assembly by 30% and the manufacturing cost by 40%. As the number of die-casting parts of, Model Y is 79 less than that of Model 3, and the number of solder joints is reduced from 700 to 50; the new alloy material makes the integrated die-casting backplane assembly of Tesla no longer need heat treatment, and the manufacturing time is reduced from 1 to 2 hours in the traditional process to 3: 5 min, to achieve direct supply in the plant, if the traditional stamping welding process is used, it must be multi-line in order to meet the production rhythm. Next, Tesla plans to replace the entire lower body assembly composed of 370 parts with 2 to 3 large die castings. The weight will be further reduced by 10%, and the mileage can be increased by 14%. The success of Model Y demonstrates the improvement of production efficiency and the effective reduction of production costs brought about by integrated die casting. Under the guidance of Tesla, the new car-building forces represented by Wei Xiaoli are actively laying out the integrated die-casting technology, which is expected to lead a new technological revolution in the automobile manufacturing industry.

The lightweight potential of the new energy three-electricity system is huge, and the lightweight of the battery box is an incremental field. With Tesla's successful breakthrough and application in car body parts, the lightweight of other systems and parts is also accelerating. The new energy vehicle is driven by motor, the power transmission system is greatly optimized, and the power source is provided by the on-board battery package. the three electricity system causes the weight of the new energy vehicle to increase by 20000300 kg, compared with the traditional fuel vehicle, which greatly affects the mileage, so the lightweight potential of the three electricity system of the new energy vehicle is huge. After the improvement of battery energy density gradually enters the bottleneck period, the lightweight of battery box has become an important technical path at present. In addition to carrying the battery, the battery box is required to protect the cell from being damaged when it is collided or squeezed by the outside world, so as to improve the safety of the power battery system. on the other hand, it also has higher requirements for its thermal conductivity, electrical conductivity, waterproofing and insulation. Therefore, with the continuous improvement of the permeability of new energy vehicles, the lightweight battery box that meets various safety performance requirements is a new incremental market.

At present, the production process efficiency of battery box is low, and integrated die casting is expected to release the bottleneck of battery box production. at present, extruded aluminum alloy technology is the mainstream production scheme of battery tray. Extruded aluminum alloy battery tray has high rigidity, anti-vibration, extrusion and impact properties, and can also meet different needs through profile splicing and processing, which has the advantages of flexible design, convenient processing, easy modification and so on. However, the welding bead of the battery box is many and long, and at the same time requires the welding bead to be small, which puts forward very high requirements for the production technology. While increasing the production cost, it will also reduce the production efficiency of the battery box, which can not adapt to the rapidly increasing permeability of new energy vehicles. With the continuous breakthrough of large tonnage die casting machine technology and new aluminum alloy materials, integrated die casting technology is expected to produce battery boxes that meet the safety requirements. With reference to the production efficiency of Tesla Giga Press, the integrated die casting process has the potential to replace some of the traditional extrusion welding process capacity, helping the battery box to break through the capacity bottleneck while reducing production costs (figure 10).

Fig. 10 Technical evolution of different battery packs

The continuous simplification of the internal structure of the battery pack is a trend, and the prospect of integrated die-casting battery box is broad.

3.2 Integrated die casting will increase the capital and technical barriers in the production process in an all-round way.

3.2.1 Industry characteristics: automotive aluminum die-casting industry has both capital-and technology-intensive characteristics.

Automotive aluminum die-casting is a capital-intensive industry, integrated die-casting further raise the threshold. In order to ensure the precision, strength, machinability and other technical indicators of products to reach a higher level, automotive aluminum die-casting enterprises need to invest in melting, die-casting, mold production, machining, precision testing and other processing equipment, the early purchase cost is high. In order to improve product quality and production efficiency, some industry leading enterprises continue to promote automation and intelligent strategy, introducing industrial robots to be widely used in die casting, precision machining, deburring, polishing and other production processes, in order to improve production efficiency, reduce production costs, improve the working environment, simplify production employment, reduce defective products and improve product quality stability, put forward higher requirements for enterprises' funds. Since 2021, large-scale and integrated die-casting has further raised the purchase threshold of large-scale die-casting machines, and the purchase and production of integrated die-casting machines have greatly raised the funding threshold of the aluminum die-casting industry (figure 11).

Fig. 11 BYD eight-in-one powertrain

The improvement of new energy permeability drives the acceleration of demand, and the iteration of three-power technology raises the technical threshold. With the rapid improvement of the permeability of new energy vehicles, the mileage problem is an important driving force for the active layout of lightweight technology of new energy vehicles. Tesla tried to use the rear plate of integrated die-casting structural parts for die-casting for the first time in the Model Y model, largely because this part is less likely to be damaged by collision, while the parts of the front body and rear body have higher requirements for the anti-collision performance of die-castings, and the consistency of far-pouring end and near-pouring end performance is also more stringent, which pose a higher challenge to the integrated die-casting technology of large body parts and even the whole body. The three-electricity system of new energy vehicles usually accounts for 30%-40% of the weight of new energy vehicles. The lightweight of the three-power system is the key path for new energy vehicles to achieve lightweight and improve battery life. Therefore, the use of integrated die-casting technology to produce aluminum body structures with complex structure, cylinder block and shell of the three-electric system requires more advanced technology and longer-term parameter accumulation to ensure the quality rate of castings. The increasing diversification and high standardization of new energy customer demand has promoted the technological differentiation and track competition of aluminum die-casting enterprises. The technical barrier of automobile precision die casting industry shows a rising trend.

3.2.2 Raw material barriers: new aluminum alloy materials are the basis of integrated die casting

The large size superimposed complex structure increases the fluidity requirement and reduces the flow length magnification margin to offset the decline of remote performance. The body parts of integrated die casting usually have the characteristics of large size and complex structure, so the flow length of molten aluminum in the mold cavity is longer in the die casting process, which requires good fluidity of raw materials. At the same time, integrated die castings need to meet the different requirements of force, strength and toughness in different parts of the car body. For strength-related structural members, the tensile strength is usually ≥ 210 MPa, elongation ≥ 7%. The tensile strength of toughness-related structural components is usually ≥ 180 MPa, elongation ≥ 10%; however, with the increase of flow length, the mechanical properties of the far end of the raw material filling will decrease, and even have a great difference with the proximal end of the filling, so it is difficult to ensure the consistency of the mechanical properties of the product. At present, on the one hand, on the basis of not changing the shape of the product structure, the mechanical properties of the filling end can be greatly improved by reducing the flow length. From the point of view of material improvement, the decline in mechanical properties at the distal end of filling can be offset by constantly improving the basic mechanical properties of raw materials, and the increasing size of integrated die casting products can be met by magnifying the performance margin of raw materials (figure 12).

Fig. 12 Great Wall seven-in-one gearbox

Traditional aluminum die-casting car body parts usually need heat treatment in order to meet the high elongation performance, but with the increasing size of integrated castings, deformation is easy to occur during heat treatment, resulting in a decrease in the rate of good products. therefore, it is necessary to develop heat-free aluminum alloy materials. Adding new trace elements to existing alloys or adjusting the proportion of trace elements to improve material properties is the mainstream path for the development of heat-free materials. Tesla, Alcoa, Reinfield, Lizhong Group, Shuai Yichi Group, Chinese Express and Shanghai Jiaotong University and other enterprises have layout. Take the heat-free alloy developed by Lizhong Group as an example, the heat-free alloy contains higher silicon content and can have higher strength without hot working. The strength of the new aluminum alloy developed by Tesla can be adjusted to 90,150 MPa. All companies keep the proportion of new materials strictly confidential, and once the new heat-free material formulations are successfully trial-produced and patented, they can form a first-mover advantage over competitors and further build competitive barriers (figure 13).

Fig. 13 working principle of die casting machine

3.2.3 equipment barriers: integrated die casting requires large-scale equipment and customized moulds

Die casting machine is the core equipment of casting production, and the increase of tonnage increases the difficulty of production. Die casting machine is a standardized machine, according to the installation of different moulds to produce a variety of parts and components.

Integrated die casting requires a higher level of technology, and the tonnage of die casting machine continues to break through and improve. At present, the mass-produced aluminum alloy monomer die-casting structural parts, such as rear longitudinal beam, damping tower, tail door inner plate and door frame reinforcement plate, have regular shape, compact structure, small profile change and relatively uniform material thickness, so it is easy to die-casting. However, the integrated die-casting parts include the inner plate of the rear wheel cover on the left and right side of the vehicle, the rear longitudinal beam, the floor connecting plate, the beam reinforcement plate and other parts, and the changes in profile, section and material thickness are more drastic. Therefore, the integrated body has more strict control on the process parameters such as flow pattern, injection specific pressure and speed, and has more stringent requirements on the accuracy and threshold of the equipment and the resistance to impact deformation of the die.

When producing castings such as gearbox housings and engine blocks of passenger cars and commercial vehicles, the clamping force of the die casting machine is approximately less than 5 000 T. With the continuous breakthrough of integrated die casting technology and the demand for lightweight in the industry, the size of the body structure of integrated die casting is gradually increasing, and the tonnage of the required die casting machine is increased accordingly. Therefore, the large tonnage die casting machine required by the integrated die casting process is still an important factor restricting the mass production of the enterprise, but with the continuous tonnage breakthrough of the die casting machine, the problem is about to be solved (figure 14).

Fig. 14 tonnage application of die casting machine for large body structure

Integrated die casting increases mold barriers, pressure resistance and shape design requirements surge. The design and manufacture of die is an important front-end process for the production of integrated die castings. with the improvement of die casting machine locking force, the increase of die casting precision and the trend of "multi-in-one" of die casting, the design complexity increases, the angle of die, hot runner and the difficulty of manufacturing and forming are improved, which leads to the surge of die pressure resistance and shape design requirements. (1) resistance to pressure. The clamping force of integrated die casting is enhanced, and the clamping force of previous die casting machines is mostly less than 5 000 T. with the continuous popularization of 6 000 T, 8 000 T or even 12 000 T die casting machines, the die will bear more pressure when working, resulting in damage. At the same time, in the process of metal melting and casting demoulding, the mold needs to bear the influence of various dimensions of pulling force and thrust, which is easy to cause cracks and affect the service life of the die. (2) shape design. Integrated die castings are often formed by integrated die casting of multiple parts, such as the "all-in-one" shell of the Great Wall and BYD, so the mold volume is larger and the metal flow channel is more complex. In the process of die casting, the liquid metal will flow in the die. With the complication of the die structure, the liquid metal can not be fully filled at the corner of the flow channel to cause defects. At the same time, it is more likely to produce bubbles that have an impact on the yield. Domestic integrated die-casting moulds are gradually developing to customization, and aluminum die-casting enterprises basically have the ability of die self-research. There are differences in the size, space and structure of different models, resulting in that integrated die castings can not become the standard parts commonly used by most automobile companies, so they need to be designed separately and customized according to different models. Due to the improvement of mold barriers, aluminum die-casting enterprises have expanded their technical teams to set up separate subsidiaries or departments to strengthen the ability of self-research and customized development of moulds. With the advancement of integrated die-casting technology, aluminum die-casting enterprises continue to strengthen independent research and development. Some leading enterprises already have the ability to develop large and complex moulds and have the advantage of first-mover.

3.2.4 process barriers: integrated die casting manufacturers need to have both R & D capability and production experience

To provide product solutions to customer needs, R & D capability has become an important competitive link. With the ground application of integrated die casting technology, because the structure of large integrated die casting products is more complex than that of small castings, the mechanical properties and process parameters that different parts need to meet may also be greatly different. therefore, before the production of new products, die-casting enterprises need to be deeply involved in the development and design process of integrated products, that is, to participate in the early scheme design of the products. To optimize the die casting process parameters, mold design and technical transformation according to customer needs and product requirements, we need to go through a large number of experimental demonstration and optimization transformation links before we can pass the production approval process and finally enter the product manufacturing process. Whether it has the ability to develop independently or even Synchronize is an important evaluation standard for automobile first-level parts suppliers and vehicle manufacturers to select suppliers. Product development is a process of joint research and development between customers and the company. the company's technology research and development capability has become one of the core competitiveness, but also one of the important means to obtain orders.

The integrated die casting process is complex, and the operation elements of the whole process ensure the product quality. The trend of large-scale and complex structure of integrated die-casting products puts forward higher requirements for die-casting process parameter control and production process management. (1) melting and treatment of alloy: in the melting process, the pollution of metal impurities should be avoided, the rapid melting should not be overheated, and the oxidation and segregation of liquid metal should be prevented. Oxides and hard inclusions have adverse effects on the casting properties and mechanical properties of castings. It is also necessary to control the melting loss to ensure the high plasticity of the alloy. (2) the way of feeding liquid (pouring): the molten metal enters the mold from the injection entrance, because the structure is complex and the path through which the liquid metal needs to flow is different, how to ensure the performance consistency of different parts of die casting is the key to the integrated die casting process. (3) spray process of release agent: the release agent or lubricant can produce gas into the casting. When selecting the release agent or lubricant, it should be verified to choose the product with low gassing property and good volatility. (4) Die casting process: die casting process is very important for the production of qualified automobile structural parts, and the correct selection of injection mode and parameters is helpful to reduce the defects in die castings. The performance of the die casting machine is stable, and it is necessary to have a flexible programming mode and real-time control system to ensure that the whole die casting process is reasonable and the deviation of process parameters is minimum. The mold temperature should be accurately controlled, and the flow rate and temperature of each cooling circuit can be monitored through the cooling water distributor to form the required temperature distribution. At present, only a few of the manufacturers with traditional high-pressure die-casting production lines master the die-casting process of integrated structures. It can be seen that the integrated die casting process has a higher technical threshold, and the industry pattern will be further concentrated to the head enterprises (figure 15).

Fig. 15 Product design, development and manufacturing flow chart

With the continuous improvement of product precision requirements, the importance of precision machining ability is highlighted. In addition to the high requirements for the melting of raw materials, transport heat preservation and die casting molding, integrated die casting also puts forward new requirements for casting cleaning and post-treatment. The casting needs to be cleaned after die casting, and the product is separated from the slag collection bag of the auxiliary forming sprue exhaust plate, which is realized by means of impact, punching, sawing, etc.; the post-treatment of castings refers to the process of burr grinding to ensure that the products meet the requirements of customers, the internal structure and properties of castings are improved by solid solution, aging treatment or single aging treatment, and the surface quality requirements of castings are achieved through grinding, sandblasting, shot blasting and other processes.

Due to the requirements of the demoulding angle, the die-casting process is limited by the mold manufacturing accuracy and the specific high-pressure die-casting processes such as thermal deformation and demoulding deformation. as a result, the dimensional accuracy and position accuracy of the castings may not meet the design requirements of the drawings. For components such as the three-electric shell, which have extremely high requirements for sealing performance, in addition to meeting the mechanical strength and other properties, it is also necessary to strictly ensure the consistency of the products and the standardization of assembly. ensure the sealing performance of the shell of the three-electric system so as to avoid the failure of the three-electric system in some extreme temperature and high voltage environment. Therefore, the casting blank needs to be accurately machined by precision machining equipment. With the upgrading of the structure of integrated die-casting products, the precision of auto parts requires enterprises to have higher machining capacity.

3.3 Integrated die casting will comprehensively reduce production line, welding, labor and battery costs, and improve material utilization.

The die-casting island is composed of die-casting machine and peripheral equipment, and it is estimated that the cost of Tesla body-in-white integration equipment is about 300 million yuan. The die-casting machine is combined with melting furnace, edge-cutting equipment, machine tools and other equipment to form a die-casting island. From the point of view of Tesla's realization of the car body integrated die casting process, the industry generally follows the technical development idea of the first part and then the assembly, that is, to achieve the lower part of the relatively low difficulty of the next body integrated die casting, and then to achieve the next body integrated die casting, and finally to achieve full body integrated die casting, it is estimated that it will take at least 2 to 3 years for the integrated die casting technology to mature from part of the body to the next body (figure 16).

Fig. 16 feasible scheme of Tesla car body integrated die casting

The all-aluminum die-casting body has a cost advantage over the traditional all-aluminum body, and it is expected to be further explored with the maturity of the technology in the future. Traditional fuel vehicles generally use steel welded body, with the increasing demand for lightweight, steel-aluminum hybrid body or even all-aluminum body has become the choice of new energy vehicles. At first, Volkswagen, BMW and other car companies chose to try all-aluminum welded body on luxury models, although the weight of the car was significantly reduced, but the production and maintenance costs were high. Later, car companies gradually changed from all-aluminum welded body to the widespread use of steel-aluminum hybrid body. From the point of view of improving production efficiency, Tesla developed integrated die-casting technology, which saved a lot of production and welding links, and greatly reduced the manufacturing cost of some car body parts. From the current stage of technological development, because the large-scale die-casting technology is not yet mature, at present, all-aluminum non-die-casting body cost > all-aluminum partial integrated die-casting body cost > steel-aluminum mixed part integrated die-casting body cost > steel-aluminum mixed part integrated die-casting body cost > steel body cost, integrated die-casting will take time to fully mature, and in the future, with the gradual upgrading of technology maturity, the number of parts and welding links required will be gradually reduced. The cost of all-aluminum integrated die-casting body will be further explored with the decrease of solder joints caused by the increase in the number of die-casting parts.

Integrated die casting will comprehensively reduce production line investment, welding costs, labor costs and battery costs, and improve material utilization. (1) reduce the investment in the production line. Integrated die casting significantly reduces the number of parts required for production due to the improvement of integration. In the past, different production lines were needed to produce a single part, and integrated die casting can significantly reduce the number of production lines, equipment and moulds. (2) reduce welding cost. Due to the integral one-time forming of integrated die castings, a large number of welding / glue coating processes are no longer needed, and the technological process is saved. At the same time, there are many welding and riveting processes after stamping, resulting in a large area of equipment, a long overall molding rhythm of a finished product, and integrated die-casting can save site area. (3) save labor cost. Integrated die casting improves production efficiency, greatly improves the automation of production lines and reduces the number of workers, resulting in a reduction in overall labor costs. (4) reduce the cost of battery. (5) improve the utilization rate of materials. Traditional stamping parts are welded by a variety of alloys, so it is difficult to recover raw materials and can only be sold as scrap. The content of aluminum alloy used in die castings is very high, and the degree of material reuse is generally more than 95%, which is significantly higher than that of stamping parts (figure 17).

Figure 17 the first Audi V8 using all-aluminum body technology

Leading car companies bowed into the game, and integrated die-casting was in the ascendant.

Volkswagen: the world takes the lead in trying all-aluminum car body, and the next generation SSP platform introduces integrated die casting.

Based on the research of space architecture technology, Volkswagen took the lead in realizing mass production of all-aluminum body. Volkswagen is the first car company in the world to try to lightweight, optimize the frame structure through Audi space architecture technology (ASF), and apply ultra-high strength materials in key parts and lightweight materials in non-load-bearing parts to achieve the purpose of lightweight vehicles. Volkswagen launched the next generation electric platform SSP, to introduce integrated die-casting technology to compete with Tesla. In July 2021, Volkswagen announced its 2030NEWAUTO strategy to accelerate the transformation to electrified and software-driven mobile operators. According to the latest strategy, the company plans to integrate the fuel platform and electric platform to launch the next generation electric platform SSP (Scalable System Platform) to produce models with better body architecture, compatibility with different batteries for battery life and support for L4 self-driving. The SSP platform plans to introduce integrated die-casting technology, which is expected to produce more than 40 million units in the whole life cycle, and the first model, the Trinity, will be put into production in 2026 (figure 18).

Fig. 18 schematic diagram of new Audi A8 body structural materials

Tesla: take the lead in introducing integrated die casting, setting off a new revolution in automobile manufacturing

Tesla took the lead in mastering the integrated die-casting technology and successfully realized the weight loss of the back plate of Model Y. In September 2020, Tesla announced on Battery Day that Model Y would adopt an integrated die-casting backplane assembly, which replaces the traditional "stamping + welding" process of the car body, which can reduce the weight of the lower body assembly by 30% and the manufacturing cost by 40%. Due to the insufficient tonnage of the die casting machine, Tesla is unable to mold the whole lower car body assembly at one time, and can only divide it into two front / rear soleplates or three front / middle / rear soleplates. At present, Tesla has been able to reduce 79 parts of the die casting machine by locking 6000T to achieve integrated die casting of the rear plate, and the follow-up plan will achieve the replacement of all 370 parts of the lower car body through 2 to 3 die castings. at that time, the quality of the lower floor assembly will be further reduced by 10%. According to Tesla's data, the body weight of 66 kg, after, Model Y integrated die casting is lighter than that of the smaller Model 3. The weight loss effect brought about by the technological revolution is remarkable.

Chemical die casting can reduce solder joint and heat treatment time, reduce manufacturing cost and improve production efficiency. The integrated die-casting technology can reduce the solder joints of Tesla ModelY body-in-white from 70000800 to 50. Compared with the traditional "stamping + welding" process, it is estimated that the backplane after ModelY integrated die-casting reduces the complicated welding process and a large number of personnel, shortens the manufacturing time, reduces the complexity of the factory production line and the cost of later maintenance. At the same time, the integrated die-casting process no longer requires heat treatment compared with the traditional die-casting process. Tesla revealed that the manufacturing time after using integrated die-casting has been further optimized from 1 / 2 h to 3 / 5 min, (figure 19).

Fig. 19 Tesla Model3 body in white

4.3.The new forces of car building quickly follow up, and the traditional OEM is on the eve of change.

ES8 makes an all-aluminum car body, taking the lead in introducing body integration. Integrated die casting has significant advantages in production efficiency and manufacturing cost. due to the driving effect of Tesla, the new forces of domestic car building actively follow the integrated die casting technology. Based on the consideration of lightweight, Ulai independently developed a lightweight all-aluminum body platform from the beginning of the car construction, and high-performance aluminum is also used in the most critical force transmission path and load-bearing parts of the car body. According to official data from Weilai, taking the Weilai ES8 as an example, the weight of the body-in-white 335 kg, is nearly 40% less than that of the traditional steel body, and the rate of aluminum used for the body is as high as 96.4%, the highest in the world. However, because the traditional aluminum die-casting process is still used in ES8, seven connection technologies are still needed, including aluminum spot welding, riveting, bonding, laser welding and so on. In addition to the body structure, the chassis, powertrain and interior and exterior parts of Ultai are more lightweight and faster, and the control arm, subframe and three-electric "shell" are basically made of aluminum (figure 20).

Fig. 20 all-aluminum body of ES8

Traditional automobile enterprises generally adopt traditional aluminum die-casting process, and some leading enterprises are in the early stage of reform. At present, the integrated die-casting process of independent OEM lags behind the new forces of car building, but it remains actively on the sidelines and on the eve of change. On the one hand, the current sales structure of most traditional car companies is still dominated by fuel models and medium-and low-end electric models, and the overall demand for lightweight is not as strong as that of new forces. At the same time, integrated die casting needs to use a new platform, which will involve production line upgrading and supplier renewal. Even large-scale mass production of new energy models will consider the reuse of traditional fuel vehicle production lines and supply chains, so the process of promoting integrated die casting is relatively slow. Mainly to gradually replace small and medium-sized die castings. At present, aluminum die-casting technology has been widely used in powertrain and chassis components of head independent OEM, but traditional aluminum die-casting technology is still used. some leading automobile companies with new energy technology have begun to take the lead in trying integrated die-casting technology on the three-electricity system, and the car body parts are still in the wait-and-see stage. Great Wall, BYD and other independent OEM are still mainly steel body, aluminum alloy proportion is not high, but aluminum die-casting parts such as powertrain and shell are being gradually replaced. For example, the body of the Great Wall lemon platform is still dominated by high-strength steel, accounting for 77%, but the aluminum die-casting process has been gradually adopted in the "three electricity" part, and the situation of BYD DMI is similar.

The tide of integrated die casting has arrived, and the leading enterprises set sail.

5.1 Quanfeng Automobile: based on die-casting ingenuity, deep ploughing new energy to climb the peak

The expansion plan of "2n" is in full swing, and new orders for new capacity need to be released urgently. The company is a high-quality supplier of aluminum die-casting, with traditional businesses such as heat exchange and engines rising steadily, transmission business benefiting from the rapid growth of independent DCT gearbox permeability, and new energy business around the layout of new products and projects around the "three power systems". The company attaches importance to research and development for a long time and is firmly technology-oriented. The forward-looking layout of new energy automobile parts in 2013 has accumulated deeply in the field of Sandian. In 2020, the company keenly captured the trend of large-scale and integrated transformation of aluminum die-casting industry, and actively laid out integrated die-casting. At present, 5000T integrated die casting orders have been steadily supplied, and 6000T and 8000T die casting machines will be gradually put in place in the second half of the year. The lightweight aluminum die-casting track ushered in a golden era of rising volume and price, and the company is expected to consolidate the moat by virtue of its core technological advantages and fully seize the opportunities for the development of the industry (figure 21).

Fig. 21 Quanfeng Automobile operating income and return net profit (100 million yuan,%)

5.2 Wen can shares: leading layout of car body structural components, integrated die casting to seize the first opportunity

It is the first in China to realize the integrated die-casting of car body, and the layout of die-casting technology is comprehensive. Wen can, which has been established for more than 20 years, is the leader of domestic high-pressure casting aluminum structures. after the acquisition of French Bailian Group in 2020, it has completed the full layout of aluminum alloy high-pressure, low-pressure and gravity die-casting process. In November 2021, the company took the lead in mass production of car body rear plate body integrated die casting parts, and the terminal was equipped with Lulai automobile, becoming the first domestic company with body integrated die casting technology after Tesla, with first-mover advantage. Customers, equipment and materials are in the lead in China, and the integrated die-casting technology has the advantage of first-mover. In 2020, the company carried out the equipment and R & D layout of the integrated die-casting track in advance, and purchased 6 000 T large-scale die-casting equipment, which has a strong first-mover advantage. In May 2021, 7 sets of 2 800 to 6 000 T large die casting machines were ordered from Edela, a subsidiary of Lijin Group, for the integrated die casting production of car body structures and battery boxes. In the same month, we bought another 9000T die-casting machine to achieve a more difficult integrated die-casting technology. In the research and development of materials and moulds, the company cooperates with Lizhong Group to develop heat-free alloys. At present, the company is taking the lead in the integrated die-casting track (figure 22).

Fig. 22 operating income and net profit of Wencan shares (100 million yuan,%)

5.3 Xusheng share: Tesla's core supplier, customer structure optimization and growth is expected.

As a leading aluminum die-casting supplier in China, the company specializes in aluminum alloy parts for new energy vehicles. The company signed a contract with Tesla to become a supplier of Tesla's three-power system, and the sales revenue of 2021H1 Tesla accounted for 40% of the company's total revenue. The technology continues to accumulate and gradually upgrade to integration, and the effect of customer structure optimization is remarkable. It has become a rare domestic enterprise with three kinds of aluminum alloy forming technologies: die casting, forging and extrusion. With the trend of integrated die casting led by Tesla, the company, as a supplier of Tesla Sandian, is expected to upgrade the battery box and other products to an integrated structure. In June 2021, Xusheng and Haitian Metal signed a strategic cooperation agreement to order 200 million yuan of die-casting island equipment with a total price of about 200 million yuan from Haitian Metal in the next three years, covering 1 300 million 4 500 T, 6 600 T and 8 800 T. and jointly develop super-large die casting machines used in the field of integrated die casting. In addition, the company invests in the R & D, manufacturing, production and processing projects of automobile moulds and core parts in Huzhou, Zhejiang Province, to further strengthen the improvement of the company's die-casting and mold technology. With the consolidation of the company's leading position and the construction of a comprehensive experience system in the core areas of lightweight aluminum alloy parts, the company's customer structure is also being optimized, which will bring obvious performance flexibility to the company in the future (figure 23).

Fig. 23 operating income and net profit of Xusheng shares (100 million yuan,%)

5.4 Guangdong Hongtu: the first die-casting leader in domestic market share, realizing integrated die-casting bend overtaking

Aluminum die-casting leader with the first market share in China opens up new opportunities for cooperation among new forces in China. Guangdong Hongtu, as a leading enterprise of aluminum die casting, has a good technical foundation and customer reserve, and has been in the first position of domestic market share for a long time. In 2021, H1 company aluminum die-casting business revenue accounted for 63.6%, the main products include powertrain system, transmission system and new energy vehicle structure. Layout of large-scale die-casting equipment + self-developed heat-free alloy, take the lead in the completion of super-large integrated aluminum die-casting structures. In the integrated layout, the company independently developed high strength and toughness heat-free aluminum alloy materials to provide a material basis for large-scale integrated die casting. In the first half of 2021, the company carried out the overall planning of the large-scale die-casting island of the "structural integrated molding" project, and purchased a 6800T die-casting equipment. In January 2022, the 6800T super-large integrated aluminum alloy die-casting structure was successfully trial-produced, and the casting weight was about 100kg, which realized the self-control of super-large integrated die-casting technology. The company took this opportunity to open the research and development of 12 000 T super intelligent die-casting units and key lightweight components such as integrated front cabin assembly, integrated floor assembly and integrated battery tray for new energy vehicles (figure 24).

Fig. 24 Guangdong Hongtu's operating income and net profit (100 million yuan,%)

5.5 Top Group: platform parts faucet to establish an one-stop solution

All-round product layout, rich experience in lightweight field. Based on the original advantages in the field of NVH, Top Group continues to invest in research and development, and is committed to building product matrices in five areas: automotive shock absorber system, trim system, intelligent driving system, chassis lightweight system and thermal management system. With its high sensitivity and rapid response to market changes, the company has obtained a large number of mainframe factory orders such as traditional and new forces at home and abroad. Among them, in the field of lightweight, Topp has gradually established an one-stop lightweight solution, which has six processes of high pressure, vacuum die-casting, low pressure, differential pressure, squeeze casting and forging in the field of light alloy. the mass-produced product types include chassis system, powertrain structure, battery package structure, car body structure and thermal management valve plate, etc., and can provide customers with customized lightweight services. Integrated die-casting R & D multi-pronged approach, the development process of industry-leading. In terms of materials, Top Group, in cooperation with Chinese Express and Shanghai Jiaotong University, is the first in the world to successfully apply its jointly released Tech Cast alloy with high strength and toughness without heat treatment. The fluidity of the material is more than 15% higher than that of the same grade material, and the strength and plasticity are more than 30% higher than that of the same grade material, which ensures that the performance such as vehicle collision reaches a higher dimension. In terms of equipment, the company signed a strategic agreement to purchase 21 sets of die-casting units, including 6 sets of 7 200 T, 10 sets of 4 500 T and 5 sets of 2 000 T die-casting equipment for super-large structural parts of new energy vehicles, such as the production and manufacture of front engine room, rear body and battery shell. The 7200T integrated super-large die-casting rear cabin produced in February 2022 is officially mass-produced (figure 25).

Fig. 25 operating income and net profit of Top Group (100 million yuan,%)

5.6 Aikodi: small and medium-sized precision parts create a moat, seize the opportunity to speed up product transformation

Small and medium-sized aluminum die-casting bibcock, "product supermarket" is becoming more and more perfect. Aikedi is the global layout of small and medium-sized aluminum die-casting leader, the main products are wiper system, transmission system, steering system and other small and medium-sized die castings, with a global market share of 30% of the small and medium-sized products under 400g. Become the "invisible champion" in the subdivision of aluminum die-casting industry. The company's business scope covers the three major continents with developed automobile industries in the United States, Europe and Asia, and the proportion of export revenue continues to be more than 65%. Customers include Valeo, Bosch, Magna, Depco, Nestor and other international well-known automobile Tier 1 enterprises. In addition, the company continues to carry out a comprehensive layout of technology, while improving the value of bicycles, and constantly improving the category of "product supermarket" and expanding the range of customer supporting products, in order to continue to maintain the high penetration of the company in the small and medium-sized product market. We will promote the construction of intelligent chemical plants and introduce large-scale equipment to transform into integrated business. In September 2019, the company built the "5G + digital factory" with the largest scale of the automotive industry chain in the country, introducing 5G, Internet of things and big data analysis technology on the basis of highly automated logistics, warehousing and flexible manufacturing capabilities. greatly improve the company's per capita output value and product quality. In March 2021, Aikedi Intelligent Manufacturing Science and Technology Industrial Park project started construction in Jiangbei, Ningbo. The project covers an area of about 118mu and is expected to produce 65 million pieces of aluminum alloy auto parts per year. The park plans to purchase 35 die casting machines of more than 1 000 T, including 4 sets of 4 400 T, 2 sets of 6 100 T and 2 sets of 8 400 T, reflecting the company's specific measures to adapt to the new development trend in the field of new energy vehicles and expand in the direction of large-scale integration. In its announced product plan, the specification of body parts will reach 40 kg, and the battery system unit will reach 10 kg, compared with the company's existing small and medium-sized products. In addition, with the prosperity of downstream new energy vehicles, the company promotes the expansion of new energy products. In February 2022, the company invested in the construction of an Anhui factory and proposed to purchase new equipment or production lines such as fully automatic die-casting units, processing and assembly units, etc., which will be used to manufacture aluminum alloy parts and automobile structures for the research and development of new energy vehicle three-electricity system units. reflects the company's accelerated layout of new energy business (figure 26).

Fig. 26 operating income and net profit of Aicodi (100 million yuan,%)

5.7 Yitai shares: newly listed cars turn to the leader, the layout of new energy business accelerates

The newly listed car turns to the leader, and the competitive advantage of market segmentation is obvious. Luotai Co., Ltd. was listed in January 2021, and its main business includes aluminum alloy precision die castings for key system assemblies such as automobile steering system, transmission system, braking system and so on. With its long-accumulated comprehensive advantages in technology, quality, management and service, the company has a strong competitive advantage in the subdivision of the (EPS) shell of the electric power steering gear, with a 20% market share in the domestic passenger car market in 2020. We will accelerate the distribution of new energy and realize the growth of new production capacity. In order to break through the bottleneck of existing production capacity and meet the demand of new orders, the company raised funds through IPO to set up a new factory in Zhuhai, which will increase the annual production of 2.88 million key parts of automobile steering system. In addition, in order to seize the opportunity of the rapid development of new energy vehicles in recent years, the company has increased its investment and market development efforts in the three electricity system of new energy vehicle parts, and it is expected that the Yangzhou plant will add 380000 new energy motor shells after it is completed and reach production, so as to enrich the company's product range and achieve a simultaneous increase in volume and price. Moreover, in order to further meet the needs of European and American customers and better expand overseas markets, the company established a Mexican subsidiary in 2016 and plans to invest 220 million yuan to expand production in 2021. It is expected that the production capacity of 1.81 million aluminum alloy shells will be added after reaching production. Start a new round of growth of the company.

Conclusion

Driven by the "carbon neutralization" policy, the permeability of new energy vehicles in China has increased rapidly, reaching 14.2% in 2021. With the higher-than-expected sales of new energy vehicles and mileage anxiety highlighted, the car lightweight track showed an ultra-high boom. As a comprehensive and optimal lightweight scheme, aluminum die-casting is gradually upgraded to large-scale and integration under the background of major breakthroughs in materials, equipment and technology. Integrated die casting is on the eve of the outbreak, the current permeability is low, and the future market space is broad. With the continuous iterative landing of technology in Tesla, the new power of car building and traditional automobile enterprises, the industry is expected to expand its volume quickly.