Stainless layman's terms, that is not easy to rust stainless steel, in fact, part of the stainless steel, both of stainless steel, but also acid resistance (corrosion resistance). Stainless steel and corrosion resistance of stainless steel is due to its chromium-rich oxide film on the surface (passivation film) formation. This stainless steel and corrosion resistance is relative. Tests showed that the steel in the atmosphere, water and other weak medium and nitric acid oxidizing medium, the corrosion resistance of steel with the increase of chromium content increases, when the chromium content reaches a certain percentage, the occurrence of corrosion resistance of steel mutations that the rust from easy to rust, never corrosion to corrosion. Many classification of stainless steel. Classification by structure organized at room temperature, there are martensitic, austenitic, ferritic and duplex stainless steel; by major chemical composition, can basically be divided into chromium stainless steel and chrome-nickel stainless steel two systems; BY PURPOSE there are nitric acid-resistant stainless steel, acid-resistant stainless steel, water-resistant stainless steel, etc., can be divided into types by corrosion pitting corrosion of stainless steel, stress corrosion of stainless steel, resistance to intergranular corrosion of stainless steel; classification according to features can be divided into no magnetic stainless steel, free cutting steel, cold steel, high strength stainless steel and so on. Because stainless steel has excellent corrosion resistance, formability, compatibility and a wide temperature range of strength and toughness, and other characteristics, so get was widely used in heavy industry, light industry, household goods industry and building decoration industry .
Austenitic stainless steel production process with good performance, especially in chrome-nickel austenitic stainless steel, the use of conventional means of production of special steels can be successfully used to produce a variety of specifications of the plate, pipe, tape, wire, bar and forgings and castings. Due to the alloying elements (especially Cr) content and carbon content and low, the use of electric arc furnace plus argon oxygen decarbonization (AOD) or vacuum-deoxy decarbonization (VOD) method for mass production of such stainless steel, for senior grades of small Bulk product can be vacuum or non-vacuum induction furnace, ESR increase, if necessary.
Chrome-nickel austenitic stainless steel excellent thermoplastic makes it easy to impose forging, rolling, extrusion and other hot piercing and thermal processing, steel ingot heating temperature is 1150 ~ 1260 ℃, deformation temperature range is generally 900 ~ 1150 ℃, copper, nitrogen and titanium, niobium stabilized grades are biased against low temperatures, high chromium, molybdenum steel biased against high temperatures. Due to poor thermal conductivity, holding time should be longer. After air-cooled heat workpiece can be. Cr-Mn austenitic stainless steel thermal cracking susceptibility strong steel ingot billet to small deformation, multi-pass, should heap cold forging. Can be cold-rolled, cold-drawn and cold-spinning and other crafts and stamping, bending, curling and folding and other forming operations. Chrome-nickel austenitic stainless steel hardening tendency weaker than the chromium-manganese steel, once after annealing cold deformation amount may reach 70% to 90%, but the Cr-Mn austenitic stainless steel due to the large deformation resistance, hardening a strong tendency, should increase a softening annealing times. Generally a softening annealing is 1050 ~ 1100 ℃ water cooling.
Austenitic stainless steel also can produce castings. In order to improve the fluidity of molten steel to improve casting performance, cast steel alloy composition should be adjusted: increase of silicon content, relaxed range of chromium and nickel content, and increases the maximum sulfur content of impurity elements.
Austenitic stainless steel should be carried out before using the solution treatment, in order to maximize the carbide steel and other precipitates austenite matrix solution, but also enables organizations to homogenize and eliminate stress, thus ensuring excellent corrosion resistance and mechanical properties. The correct solution treatment after 1050 ~ 1150 ℃ heating cooling (thin pieces can be air-cooled). Alloying steel solution treatment temperature depends on availability: no or low molybdenum molybdenum steel should be low (≤1100 ℃), and a higher alloyed grades such as 00Cr20Ni18Mo-6CuN, 00Cr25Ni22Mo2N etc. should be higher (1080 ~ 1150 ℃).
Production extensive use of advanced technologies, such as refining rate of 95% continuous casting ratio exceeds 80%, the high speed rolling and finishing, quick forging machine universal. In particular, to realize computer control in the smelting and processing, to ensure product quality and reliable performance and stability.
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