Stainless Steel Pipe Fittings

Application of duplex stainless steel

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Duplex stainless steel with its excellent corrosion resistance, high strength and easy processing and other excellent performance, in many areas to replace austenitic stainless steel, the market prospect is very broad. The annual output of duplex stainless steel in the world is only about 1% of the total output of stainless steel. Since 1990, the annual growth rate of duplex stainless steel is close to 17%, the annual output increased from 24,000 tons in 1990 to 11 million tons in 1999. Its products are distributed as hot-rolled plates (71% of the total output) for the manufacture of duplex stainless steel tubes (6% of the duplex stainless steel) containers; cold rolled plates accounted for 14%, duplex stainless steel seamless pipe accounted for 8%. Modern duplex stainless steel in the low-grade duplex stainless steel (2304 type), is a low alloyed duplex stainless steel. It has excellent mechanical and physical properties, excellent resistance to stress corrosion cracking and other forms of corrosion performance and good weldability, can replace the standard Austrian stainless steel 304/306; standard duplex stainless steel (2205 type), is a medium alloy The duplex duplex stainless steel. Due to the excellent corrosion resistance, suitable for the production of chloride and hydrogen sulfide media under the conditions of the equipment, especially suitable for use with chloride water or brackish water to do the cooling medium heat exchanger, also applies to dilute sulfuric acid solution and storage Equipment for organic acids. At the same time, 2205 duplex stainless steel due to its high strength in the heavy load of structural applications become austenitic stainless steel ideal alternative material. Due to the good mechanical properties and corrosion resistance of 2005 duplex stainless steel, the service life of the equipment can be reduced. Therefore, in many applications, 2205 stainless steel is an economical choice. At present, it is the main force of duplex stainless steel series, accounting for 80% of the world’s total output of duplex stainless steel; super duplex stainless steel (2507 type), widely used in harsh corrosive environment, the market share of about 13%. Duplex stainless steel is widely used in various fields for its unique advantages: pulp and paper industry: pulp and paper industry is the first use of duplex stainless steel processing industry. Sulfuric acid and sulfuric acid cookers made of 304 and 316 austenitic stainless steels are often scrapped by stress corrosion cracking and sometimes live for just two months. At the same time, with low-carbon steel cooking pot, the wall thickness of up to 43mm, making the total weight of the steamer is high. And the use of duplex stainless steel, that is, corrosion resistance, high strength, wall thickness also reduced a lot. Since 1998, abroad in the pulp and paper factory with duplex stainless steel containers more and more, greatly enhance the service life, the effect is very good. Chemical processing industry: chemical processing industry is involved in a very wide range of conditions are more complex. Preservation of industrial wet-process phosphoric acid storage tanks, usually 316L or 317L Austenitic stainless steel to manufacture, but the wall is very thick. Using duplex stainless steel 2205, the strength is almost higher than the 316L and 317L times, and can reduce the wall thickness, thereby reducing the important and cost of the tank. At the same time, in the industrial sulfuric acid environment, especially in the presence of chloride ions in the case, 2205 resistance to local corrosion better than the austenitic stainless steel. Food and beverage industry: Food and beverage industry production is generally processed in hot solutions containing chloride ions. Duplex stainless steel has a unique advantage in resistance to stress corrosion cracking. Therefore, depending on the use of different environments, can choose different duplex stainless steel, but the total cost of austenitic stainless steel than the dominant. Which SAF2304 the most cheap. At present, some foreign sugar mills, breweries and other equipment used in duplex stainless steel. Transportation: Due to the high strength and excellent corrosion resistance of duplex stainless steel, it has a great advantage when used in the production of chemical tankers. Reducing the importance of the ship, reducing the consumption of fuel, in this regard, the use of the most is 22% chromium duplex stainless steel. At the same time to meet the needs of the goods contained in the corrosion resistance of materials. Construction: In the coastal areas, the air is filled with gas (sea atmosphere) evaporated from sea water. The concentration of chloride in this oceanic atmosphere is much higher than that of inland air, and therefore requires a “seawater” material. The corrosion resistance of duplex stainless steel is with this advantage, while its high strength can also reduce the weight. At present, there are many offshore oil platforms are used duplex stainless steel to create explosion-proof walls. Some of the foreign bridge, the floor of the building also uses a duplex stainless steel. Petrochemical industry: petrochemical and chemical industry Corrosive environment is characterized by high reaction temperature, the medium often contains high concentration or medium concentration of chloride, easy to induce stress corrosion cracking of stainless steel. Therefore, this area requires not only duplex stainless steel, but also more use of super duplex stainless steel. Refining industry is the use of duplex stainless steel one of the more areas, mainly used in atmospheric and vacuum distillation, catalytic cracking hydrodesulfurization and other devices, both at home and abroad have used. In addition, duplex stainless steel in acid gas and oil production in the amount of gradually increased, mainly for the production of pipe lining, shore and offshore piping systems and heat exchangers.

In addition, duplex stainless steel has also been successfully used in wastewater treatment heat exchangers, hot water pipes, water heaters. At present, China has developed five kinds of duplex stainless steel, are the second generation of steel, only 0Cr18Ni5Mo3Si2 steel into the international and mass production, the other by the standard production, production is not. According to the development level of China’s duplex stainless steel and the production conditions and technical level of special steel mills, some domestic duplex stainless steel can replace imports, such as involving large and medium-sized chemical fertilizer plant technological transformation, new, expansion of the required ammonia pump Materials can be made of domestic duplex stainless steel instead of imports of 316L, 329 steel, to achieve the ammonium pump pump material replacement and localization. TISCO, Pu Gang is the main domestic production of duplex stainless steel business. Three Gorges project used in the 2205 duplex stainless steel is TISCO and other enterprises. However, the duplex stainless steel market still needs a large number of imported foreign products. Such as duplex stainless steel applications of the most areas – the chemical industry, most of the equipment is imported, the equipment used in the duplex stainless steel also introduced. At present, some special equipment in the thinner duplex stainless steel can be produced in China, and thicker duplex stainless steel still need to import.

The main use of duplex stainless steel has the following aspects:

Neutral chloride environment

Refining industry

Often decompression device

Catalytic cracking unit

Hydrocracking, hydrotreating unit

Petrochemical and chemical industries

PVC (PVC) stripping tower and heat exchanger

Vinyl chloride production plant

Methanol synthesis reactor

Carbonyl alcohol synthesis reactor

Acetic acid and other organic acid production equipment

Chemical industry pipelines

Oil and gas industry

Pulp and paper industry

Continuous sulfuric acid cooking device

Intermittent digester

Chlorine dioxide bleach cartridge

Paper pressure roller machine

Fertilizer industry

Urea industry

Phosphate fertilizer industry

Seawater environment

Energy and environmental protection industry

Light industry and food industry

Salt chemical plant

Food and pharmaceutical industry equipment

High strength structural parts

Source: China Steel Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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