[SMM Analysis] how is Rolls-Royce made in a ship? Analysis of stainless Steel for China's first Polar Exploration Cruise

SMM, Sept. 18 / PRNewswire-FirstCall-Asianet /-the first polar adventure cruise ship in the history of Chinese shipbuilding built by China Merchants Industrial Group was officially named and delivered at Haimen Base in Jiangsu Province. The 2205 duplex stainless steel produced by Hongxing stainless Steel Branch of Jiuquan Iron and Steel Co., Ltd., has been used in this 104.4-meter-long ship.

Stainless steel branch technicians said that as a 2205 duplex stainless steel used in polar adventure cruise ships, in addition to strict corrosion resistance, mechanical and welding properties, the surface quality requirements are also very high. "Polar adventure cruise ships are different from ordinary passenger ships and cargo ships, equivalent to Rolls-Royce in ships, and the requirements for all the indicators of the steel used are very stringent."

In addition, the stainless steel branch will also supply the second domestic polar exploration cruise ship, and follow-up orders are also being negotiated. The technician said: "in recent years, stainless steel branch continues to strengthen product structure adjustment, I believe that in the future Jiuquan stainless steel will be more widely used in more high-end equipment."

This time, the 2205 duplex stainless steel pipe produced by Jiuquan Iron and Steel Co., Ltd. is defined as stainless steel, which accounts for half of the ferrite phase and austenite phase in the solid quenching structure of Jiuquan Iron and Steel Co., Ltd., referred to as 2205 stainless steel pipe. The actual phase ratio is 45% ferrite and 55% austenite. The excellent properties of 2205 duplex stainless steel are guaranteed by the appropriate proportion of two-phase structure.

2205 duplex stainless steel pipe has excellent mechanical properties, corrosion resistance and good weldability, and has a wide range of applications in oil and gas industry, marine engineering, chemical industry and other industries. At present, the length of oil and gas pipelines laid with duplex stainless steel materials in the oil and gas industry has exceeded 850km, most of which are 2205 duplex stainless steel seamless steel tubes (some are S31803 duplex stainless steel pipes and 2507 duplex stainless steel pipes). Due to the strong corrosiveness of natural gas medium, 2205 duplex stainless steel is used in high pressure pipelines.

Duplex stainless steel has been used to build the liquefaction tank of chemical carriers-the inner liners on the inside of the hull of chemical carriers. The construction of chemical cargo carriers is mainly concentrated in China, Japan and South Korea. Chemical carriers can be equipped with 50 liquefied tanks, each of which is equipped with an independent pump group and piping system to avoid cross contamination. When toxic chemicals are carried, the liquefied tanks are made of stainless steel. Austenitic steels such as 316LN and 317L have been commonly used in the past, but dual-phase steels (mainly 2205) have been gradually adopted and are now popular materials because of their thinner tank walls and reduced weight, so they save more fuel.

Because of its good strength / weight ratio, corrosion resistance and easy maintenance, the application of stainless steel, especially duplex stainless steel, has increasingly become the trend of shipbuilding materials. The expansion of its scope of application also depends on the consideration of fuel cost. The more fuel costs increase, the more shipyards will use dual-phase steel in order to reduce the dead weight and fuel of ships.

According to SMM, the advantages of duplex stainless steel are as follows:

The yield strength of austenitic stainless steel is 2 times higher than that of ordinary austenitic stainless steel and has the plasticity and toughness needed for forming.

2. It has good resistance to stress corrosion cracking, even the duplex stainless steel with the lowest alloy content has higher stress corrosion cracking resistance than austenitic stainless steel, especially in the environment containing chloride ion.

3. It has good local corrosion resistance. Compared with austenitic stainless steel with similar alloy content, its wear corrosion resistance and fatigue corrosion resistance are better than austenitic stainless steel.

4. The linear expansion coefficient of austenitic stainless steel is lower than that of austenitic stainless steel, close to carbon steel, suitable for connecting with carbon steel, and has important engineering significance, such as the production of composite plate.

5. Under dynamic or static load conditions, duplex stainless steel has higher energy absorption capacity than austenitic stainless steel. For example, to deal with unexpected accidents such as collision, bao explosion, duplex stainless steel has obvious advantages and has practical application value.

As the shipbuilding industry is a high-risk major equipment manufacturing industry, the common norms of the International Association of Classification Societies have very high entry threshold and quality requirements for shipbuilding and upstream supporting industry chain, and the requirements for product inspection and certification are very strict.

SMM believes that 2205 duplex stainless steel can be effectively used in the casting of polar adventure cruise ships in China, indicating that 2205 duplex stainless steel has outstanding advantages over austenitic stainless steel. First of all, duplex stainless steel accounts for half of ferrite phase and austenite phase in its solid quenching structure, in which ferrite accounts for 45% and austenite accounts for 55%. On the basis of austenitic stainless steel, increase the content of Cr or add other ferrite elements to form, so that the steel has austenitic ferrite two-way structure, but also saves the Ni alloy. Therefore, for the choice of materials for the manufacture of major equipment for polar exploration equipment, the use of 2205 duplex stainless steel can indeed meet the challenges in the outdoor polar environment, and strong corrosion resistance and quality will provide safety for the final product.

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