In the past decade, relevant countries such as the United States and South Africa have studied the development of duplex stainless steel with manganese, but in addition to castings, most of the new steels developed have metastable austenite, and the transformation of martensite after cold deformation To improve the strength, it is difficult to use it as a welded part, and it is difficult to adapt to certain environments, such as an environment where stress corrosion will occur. This use is very limited. In recent years, the low manganese low nickel duplex stainless steel developed in Sweden is relatively mature and has a clear goal. Nickel is used to replace the widely used 304, and may even replace the price of 304. The 2304 duplex stainless steel that is not widely used at present has the value of practical promotion and is worth noting.
LDX 2101 duplex stainless steel tube (21.5%Cr, 5%Mn, 1.5%Ni.0.22%N) developed by Avesta Polar it AB, Sweden, due to the increased ammonia in the steel, a stable austenite, phase balance It has good stability with the structure, and is not sensitive to the precipitation of the intermetallic phase. At the most sensitive temperature of precipitation is 650 ℃, the impact value is reduced to 50J after 10 hours of heat preservation, and its structural stability is better than that of 2205 steel. The steel has high strength, corrosion resistance equivalent to 304, can be welded, and its life cycle cost is lower than that of austenitic stainless steel.
LDX 2101 steel has been industrially trial-produced and continuously cast in the AOD/CLU furnace after refining to produce long product casting blanks and plate blanks, but it has not yet been widely promoted and applied. In view of its good comprehensive performance, the potential use range is wide It is especially promising as a structural component. For example, it can replace 2205 duplex stainless steel as a bridge structure. It can also be used as a steel bar in concrete to solve the problem of corrosion of materials in a chloride ion-contaminated environment. In addition, it can also replace 304 and 304. 316 steel manufacturing containers, towers, hot water storage tanks and heaters.
Judging from the consumption of stainless steel in the world, duplex stainless steel only occupies a small share, and its price is still relatively high. From the perspective of price ratio: if 304.304L is 1, then 316L is 1.3, and 2205 is 1.6. Explain that if you want to increase the market share of duplex stainless steel, there should be cheaper new steel grades that can compete with the most popular 304 (304L) steel. Of course, there is still much work to be done in this regard.
It is worth mentioning that the development of manganese-containing super duplex stainless steel pipes has been developed in Germany with 25%Cr, 6%Mn, 6%Ni, a%Mo, 2%W and ~0.5%N, as well as Cu High alloy cast steel, the steel is solid solution strengthened, 002 can reach 550MPa. It is nearly 70MPa higher than similar steel with 0.15%S. The critical pitting temperature (CPT) reaches 70°C, and has good wear and corrosion resistance. BOA 920 (26%Cr, 7%Ni, 3%Mn, 4SMo, 0.35%8) super duplex stainless steel has also been developed, with PREN value of 45, 00.2 -600MPa, AK 100-200J, suitable for small size High-speed components, these two steels are still in the laboratory stage.
1. Chemical and petrochemical processing industry:
This field involves a wide range, complicated working conditions, and a variety of media. It is also an area where duplex stainless steel is used earlier and more. At present, 200,000, large and multiple sets of small and medium-sized methanol below 100,000 tons The catalyst tubes of the synthesis reactor are made of duplex stainless steel, the large and medium-sized devices use 2205 steel pipes, and more imported tubes are used, and the small-scale devices mostly use 18-5Mo-made domestic steel pipes. The media conditions of the cold tube in the oxychlorination reactor of the Qilu Petrochemical Company's mouse acetyl chloride reactor (HC1, steam O engraved, imported 2205 duplex stainless steel tube has been used a few days ago. The chemical agent regenerative cooler uses domestically made DP3 steel 00C25Ni7Mo3WCuN duplex stainless steel as the seawater cooler tube, the seawater outlet temperature is 40t, it has been used for 15 years so far, and the effect is very good. Several coal gasification devices in Henan coal chemical plant The coolers are all made of imported 2205 steel pipes. In the next 5 years, China's petrochemical industry will develop rapidly. Large-scale petrochemical projects under construction and planned to be spread all over the country. According to the current projects under construction and planned construction, the petrochemical industry has adopted stainless steel in 2005. The annual demand for pipes is about 16,000 tons. With the improvement of the quality of domestic stainless steel products and the development of special brand products, the application of stainless steel in China's petrochemical industry will continue to increase in the next five years.
2. Oil and gas industry:
This is one of the main fields of application of duplex stainless steel in foreign countries. The oil and gas pipelines currently laid are 1,000km long. Only a few of the South China Sea oilfields are used domestically and all are imported. In addition, the gas-gathering pipeline from the Tarim Basin in the west of the West-to-East Gas Transmission Project considers the use of duplex stainless steel welded pipes, which are produced and manufactured under domestic conditions. The oil refining industry is the earliest department to use domestic duplex stainless steel. It is mainly used in the top lining (or composite plates), internal components of the tower, air coolers and other atmospheric and vacuum distillation towers in refining and chemical companies such as Nanjing, Zhenhai, Tianjin and Jinan. Water cooler, etc., the longest has been used for 20 years. The production of small duplex stainless steel seamless pipes is relatively mature in China. What is urgently needed to be solved is the production of larger seamless pipes and welded pipes. The production process is yet to be developed. In addition, how to lower the price of duplex stainless steel products is also related to the development of domestic duplex stainless steel. Although expanding production, production is very important for marketable products. It should not be overlooked that new technologies and processes are used, molybdenum oxide balls replace metal molybdenum, nickel oxide replaces metal nickel, reduce smelting costs, and promote the use of duplex stainless steel continuous casting technology. Improve the yield rate.
3. Application in the fertilizer industry:
The fertilizer industry adopts domestically produced 0Cr25Ni6Mo3CuN aging strengthened duplex stainless steel. Using its wear resistance and corrosion resistance, it is used in the internal parts of high-pressure shut-off valves of various specifications in the main process pipeline of the urea plant. The effect is good. At present, the CO2 gas stripping method and NH3 gas stripping method for producing urea mostly use high-alloy austenitic stainless steel or even titanium. Domestically, high-chromium duplex stainless steel has been used in the ammonium pump pump body of large urea plants to replace 316L (urea grade) steel. Since the 1980s, DP-12 (25Cr-7Ni-3Mo containing trace amounts of tungsten and copper) has been used in three high-pressure equipments in the stripping tower, methyl ammonium condenser and high-pressure decomposition tower of the new ACES urea process developed by Toyo Engineering Corporation of Japan -N steel) and R-5 (00Cr25Ni6.5Mo1.5N) duplex stainless steel, the former is used to manufacture gas stripping tubes, condenser tubes, decomposition tubes and delivery pipes, etc., the latter is used for the shell of high-pressure equipment. The annual demand for stainless steel pipes in the petrochemical industry in 2005 was about 7800t, and it is expected to increase to 9600t in 2010. The national standard for stainless steel has not been revised for more than ten years. When the national standard is revised, the acceptance and revision of duplex stainless steel must be considered. Overseas, for the 2205 grade, which accounts for 80% of the output, has specially formulated user acceptance standards for product factory inspection. We should also consider introducing and absorbing, and implement some inspection methods and standards to promote the production and ordering of duplex stainless steel. In addition, vigorously develop the potential market for industrial and civilian use of duplex stainless steel (such as construction industry-structures, bridges, concrete steel reinforcement; such as manufacturing-a container, storage tank, chemical tanker, speed boat, tank truck; and such as household Facility 1 high water tank, electric water heater, housing water and steam piping, etc.), and develop, test and promote some new varieties developed abroad (such as low nickel saving duplex stainless steel) that are suitable for China's national conditions (nickel deficiency and chromium deficiency), I believe China The promotion of duplex stainless steel has a very broad application prospect.
![Application and Development of Duplex Stainless Steel Pipe in China]()