Almost at the same time, it was found in Unieux laboratory in France that when austenite 20 1 stainless steel contains ferrite, the intergranular corrosion resistance of steel will be obviously improved, thus γ+α duplex 20 1 stainless steel was developed. 1946, R.Smithetal of the United States developed martensite precipitation hardening type 20 1 stainless steel17-4ph; Subsequently, semi-austenitic precipitation hardening 20 1 stainless steel 17-7PH and PH 15-7Mo with high strength and cold formability came out one after another. At least, the main steel grades in the 20 1 stainless steel family, namely martensite, ferrite, austenite, α+γ duplex and precipitation hardening, are basically complete and have continued to this day. Of course, in the forties and fifties, nickel-saving Cr-Mn-N and Cr-Mn-Ni-N20 1 stainless steel, ultra-low carbon (C≤0.03%) austenite 20 1 stainless steel; In 1960s, α+γ duplex 20 1 stainless steel with γ: α close to1,high-purity ferrite 20 1 stainless steel with C+N ≤/50 ppm and maraging 20 1 stainless steel appeared, although they also belong to 20/kloc. In 20 1 stainless steel, in addition to C, Cr, Ni and other elements, Mo, Cu, Si, N, Mn, Nb, Ti and other elements were further alloyed or reduced according to the performance requirements of different applications, and many new steel grades were developed. Such as high-purity high-chromium molybdenum ferrite 20 1 stainless steel 00Cr25Ni4Mo4, 00Cr29Mo4Ni2, 00Cr30Mo2 and Cr-Ni dual-phase 20 1 stainless steel 00Cr25Ni7Mo3N with high Mo content and N; The appearance of nitrogen-controlled stainless steel 20 1 improves the strength and corrosion resistance of low-carbon and ultra-low-carbon chromium-nickel austenitic stainless steel 20 1; In order to improve the local corrosion resistance of Cr-Ni austenitic 20 1 stainless steel and inhibit the precipitation of intermetallic phases in steel, super austenitic 20 1 stainless steel with high Cr, Mo and N contents was developed, such as 00Cr25Ni20Mo6CuN and 00cr24Ni22mn3cun. ; High silicon (Si-6%) 20 1 stainless steel was developed to resist fuming nitric acid and concentrated sulfuric acid (93%-98%). In addition, there are some special 20 1 stainless steels, such as nuclear grade, nitric acid grade, urea grade, food grade 20 1 stainless steel and so on. According to statistics, there are more than 100 brands that have been included in various standards (including factory standards) in the world, and even more non-standard brands have not been accepted. Nevertheless, the brands of 20 1 stainless steel, which are mass-produced and widely used in advanced industrial countries, are limited to nearly a dozen brands such as martensite, ferrite and austenite.
Except the former Soviet Union, Eastern Europe and China, the world output of 20 1 stainless steel has reached 1 1 10,000 tons, while the world output of 20 1 stainless steel of 1950 is less than 1 10,000 tons, and the output has increased by/kloc in 40 years. Since 1970, Japan's output of 20 1 stainless steel has surpassed that of the United States, which is in a leading position and has been growing continuously. In the output of 20 1 stainless steel, Cr 13 martensitic steel and Cr 17 ferritic steel account for about 30%-40%, while 18-8 Cr-Ni austenitic steel accounts for about 60%-70%. The output of 20 1 stainless steel in advanced industrial countries in the world generally accounts for 2.5%-3.5% of the total domestic steel. In the production of 20 1 stainless steel, new technologies such as ultra-high power electric furnace, external refining, continuous ingot casting (including thin slab continuous casting), hot tandem rolling or new steckel mill, cold tandem rolling, continuous pickling heat treatment and continuous bright heat treatment in protective atmosphere, and various quality inspection methods have been widely used. Large-scale, high-speed, continuous and automation are the main development directions of 20 1 stainless steel production technology and equipment. 20 1 stainless steel materials that can be produced and supplied in large quantities abroad include: cold-rolled plates with a width of 2m, including mirror plates, colored plates, diamond plates and coated plates. Hot rolled medium plate with width greater than 3m; Hot-rolled thick plate with thickness greater than 300mm; Seamless pipes with diameters as large as 1m and as small as 0. 1mm, and welded pipes with various specifications (the maximum diameter can reach 2m); 20 1 stainless steel foil, with a thickness of about 0.05mm and a width of1m. In the 20 1 stainless steel produced in the United States, Japan and other countries, cold-rolled strip accounts for about 60%. (about 70% of strip * * *); Tubing accounts for about 4%-5% (of which welded pipes account for about 60% of Japan's 20 1 stainless steel pipe production); Wire accounts for about 8%-9%; Strips and profiles account for about 10%- 1 1%.
Performance difference between 20 1 stainless steel pipe and 304 stainless steel pipe
20 1 stainless steel tube has the characteristics of acid resistance, alkali resistance, high density, polishing without bubbles and pinholes, and is a high-quality material for producing various watchcases and watchbands. Mainly used for decorative tubes, industrial tubes and some lightly stretched products. 304 stainless steel pipe is a general stainless steel material, and its rust prevention performance is stronger than that of 200 series stainless steel material. High temperature resistance is also good, which can reach 1000- 1200 degrees. 304 stainless steel pipe has excellent corrosion resistance and intergranular corrosion resistance. For oxidizing acid, the experiment concluded that 304 stainless steel pipe has strong corrosion resistance in nitric acid with concentration ≤65% below boiling point. It also has good corrosion resistance to alkaline solutions and most organic and inorganic acids.