[dry goods] how to apply calcium-aluminum alloy in storage battery this is the most complete interpretation

The lead-acid battery industry in China has a history of more than one hundred years. Due to the characteristics of cheap materials, simple technology, mature technology, low self-discharge and maintenance-free requirements, it will still occupy a dominant position in the market in the next few decades. In many application fields, the technological progress of lead-acid batteries has made a real contribution to the improvement of national competitiveness. Calcium alloy has high hydrogen potential and strong corrosion resistance. It can be used to make lead-acid battery grid, which can improve the compound efficiency of negative electrode to oxygen in battery and increase the cycle efficiency of positive electrode in deep discharge. At the 2019 (14th) Shanghai lead and Zinc Summit hosted by SMM, Gao Yunpeng, director of the R & D center of Baotou Zhongsheng Metal Materials Co., Ltd., told the guests about the application of calcium and aluminum alloy in batteries.

Origin

In China, calcium appears in the form of metal, which can be traced back to one of the key projects of Soviet assistance to China before 1958, a military enterprise in Baotou City. Among them, the liquid cathode method (electrolysis) gold belongs to the calcium production line. Calcium was produced on a small scale in 1961.

Development

From the late 1980s to the early 1990s, with the state's strategic adjustment of military enterprises and the proposal of the slogan "military to civilian", gold calcium began to enter the civilian market. In 2003, with the increasing demand for gold calcium in the market, Baotou has become the largest gold calcium production base in China, with four electrolytic calcium production lines, with an annual production capacity of 5000 tons of gold calcium and products.

Appearance of calcium Aluminum Alloy

Because of the high melting point (851 ℃) of gold calcium, the burning loss of calcium in the process of adding gold calcium to molten lead solution is as high as 10%, resulting in higher cost, difficulty of composition control, long time consumption of energy and so on. Therefore, it is necessary to form alloys with metal aluminum and gold calcium in order to melt slowly layer by layer. The emergence of calcium aluminum alloy is aimed at the defects existing in the preparation of lead calcium aluminum alloy.

The fabrication of calcium-aluminum alloy is a process of melting and fusion at high temperature according to the ratio of calcium and aluminum in vacuum.

Classification of calcium and aluminum alloys

Calcium-aluminum alloy generally contains 70-75% calcium, 25-30% aluminum, 80-85% calcium and 15-20% aluminum, and 70-75% aluminum contains 25-30% calcium, which can also be processed according to the needs of users.

Calcium aluminum alloy has metallic luster, active properties, and fine powder is easy to burn in air. It is mainly used as intermediate alloy, refining and reducing agent in metal smelting.

The products are supplied in the form of natural blocks, and can also be processed into different granularity products according to the needs of users.

Quality requirements of calcium Aluminum Alloy

As a master alloy, the quality requirements of calcium aluminum alloy are extremely strict.

The main results are as follows: (1) the content of calcium fluctuates in a very small range;

(2) there should be no segregation in the alloy;

(3) the harmful impurities must be controlled in a reasonable range;

(4) there can be no oxidation on the surface of the alloy;

At the same time, the process of making, packaging, transportation and storage of calcium-aluminum alloy must be strictly regulated. And our supply of calcium and aluminum alloy manufacturers must have formal qualifications.

Matters needing attention in production, Transportation and Storage of calcium and Aluminum Alloy

The chemical properties of calcium aluminum alloy are very active. Easy to oxidize, fire, water and serious impact, very easy to burn.

1. Packaging

After the calcium aluminum alloy is broken according to certain specifications, put it into a plastic bag, weigh it, fill it with argon, seal it with heat, and then load it into an iron bucket (international standard bucket). The iron bucket has good waterproof, air isolation and anti-impact function. Packing specification: 10Kg/ bag, 10Kg × 15 bag / iron bucket.

2. Loading and unloading

Loading and unloading process should use forklift or crane (electric hoist) loading and unloading, do not allow the iron bucket upside down rolling and throwing, in order to prevent the bag damage and loss of protection, more serious state may lead to the combustion of calcium and aluminum alloy in the bucket.

3. Transport

In the process of transportation, emphasis should be placed on fire prevention, waterproofing and impact prevention.

4. Storage

The shelf life of calcium aluminum alloy is 3 months without opening the bucket. Calcium and aluminum alloys should not be stored in open space, but should be stored in a dry, rain-free warehouse. After opening the bag should be used as much as possible, once endless alloy, to drain the air in the bag with a rope tight mouth, put back in the iron bucket, put on the cover of the sealing rubber ring, the iron bucket will be re-sealed to prevent alloy oxidation.

5. It is strictly forbidden to break calcium aluminum alloy in an iron bucket containing calcium aluminum alloy or in a packing bag to avoid fire. The crushing of calcium aluminum alloy should be carried out on the aluminum plate.

6. Once calcium aluminum alloy combustion occurs, must not use water to extinguish the fire. The unburned calcium-aluminum alloy should be quickly isolated before using dry sand or dry soil to cover the burned alloy.

Distribution of calcium production and consumption

Application of calcium Aluminum Alloy in Iron and Steel Industry

With the increasing requirements for the quality of cast steel, the deoxidation of some high-grade castings only with aluminum can not meet the requirements, so the compound deoxidation of aluminum and calcium has been paid more and more attention.

During the final deoxidation, the combined use of aluminum and calcium can not only further reduce the oxygen content in steel, but also improve the non-metallic impurities.

Because the calcium density is only 1 to 5 of that of steel, the boiling point is 1492 ℃, which is lower than the temperature of molten steel, and its activity is very strong, it is difficult to control accurately when it is used in steelmaking. This restricting factor limits the popularization and application of calcium in cast steel.

In the past 20 years, the understanding of the role of calcium in steel has been deepened, and the application process has gradually matured. Now, it has been widely used.

Application of calcium-aluminum alloy in storage battery

Lead-acid batteries have a history of nearly 160 years. Its mass specific energy and volume specific energy can not be compared with Ni-Cd, Ni-MH, Li ions and Li polymer batteries. However, due to its low price, good high current discharge performance and no memory effect, it can be made into single large capacity battery (4500Ah) and other excellent performance. Therefore, it is still widely used in automobile, telecom, electric power, UPS, railway, military and other fields, and its sales are still in the forefront of chemical power products.

How to widely use lead-calcium alloy in battery industry

1. In order to reduce battery water decomposition and battery maintenance, in 1935 Hanring and Thomas [50] invented lead-calcium alloy, which is used in the production of casting machine grille for fixed batteries used in communication centers.

2. The grid material commonly used in maintenance-free battery is Pb-Ca alloy. According to the content, it can be divided into high calcium, medium calcium and low calcium alloys.

3. The lead-calcium alloy is precipitated and hardened, that is, the Pb3Ca, intermetallic compound precipitates in the lead matrix and becomes a hardening network in the lead matrix.

Grid is the most important non-active material in lead-acid battery. Since the invention of lead-acid battery, Pb-Sb alloy has been the most important material for grid. With the emergence of maintenance-free lead-acid battery, Pb-Sb alloy can not meet the maintenance-free performance requirements of the battery, and is gradually replaced by other alloys.

It is found that Pb-Ca alloy has excellent maintenance-free performance, but its intergranular corrosion is serious and the calcium content is not easy to control. In particular, the high impedance passivation film formed on the surface of the battery grid seriously hinders the charge and discharge process of the battery, aggravates the early capacity loss of the battery, and thus greatly shortens the service life of the battery. Among them, the influence of positive grid is the most important. The addition of a small amount of aluminum has the effect of protecting calcium. It is found that tin can improve the performance of passivation film and improve the deep cycle performance of battery.

Lead acid battery grid

Grid is one of the basic structures of lead-acid battery, which accounts for 20% of the total mass of lead-acid battery.

Effect of grid alloy on the properties of positive plate

Effect of grid alloy on the properties of negative plate

1. The alloy additive of negative grid may reduce the hydrogen evolution overpotential.

2. Alloy additives can also affect the softening and shedding of negative active materials.

There are three types of added elements in grid alloy:

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