0Cr18Ni9 

 0Cr18Ni9 stainless steel heat-resistant steel as the most widely used for food equipment, general chemical equipment, industrial equipment, atomic energy use. Popular talk 0Cr18Ni9 stainless steel is 304 stainless steel, 0Cr18Ni9 stainless steel is 321, one national standard, one is American Standard. 321 is not good because the original smelting technology, developed not only reduce the carbon content, and now because of improved smelting technology, low carbon steel smelting is very common, so the 321 has been out of the trend. The current 321 production has been very small. Only some of the military are still using. 0Cr18Ni9 steel (AISI304) is an austenitic stainless steel, is 18-8 in the first invention of the austenitic stainless steel on the basis of the evolution of the steel, the steel is stainless steel body, with its output accounting for stainless steel production music more than 30%. Because of this austenitic steel with a structure, it can not be strengthened by means of heat treatment, cold deformation can only be used to improve the strength of purpose. Austenitic steel structure gives it a good cold and hot processing performance, non-magnetic and good low temperature performance. 

 Feature 
 Has good corrosion resistance, heat resistance, low temperature strength and mechanical properties, hot stamping and bending process is good, no-hardening heat treatment, non-magnetic. 

 Use 
 Household goods, cabinets, indoor pipes, water heaters, boilers, bathtubs, automotive parts, medical equipment, building materials, chemical, food industry, agriculture, ship parts. Edit this paragraph the chemical composition 
 Carbon C: ≤ 0.07 Si Si: ≤ 1.00 Manganese Mn: ≤ 2.00 S S: ≤ 0.030 P P: ≤ 0.035 Cr-Cr: 17.00 ~ 19.00 Ni-Ni: 8.00 ~ 11.00 [2] Edit this section mechanical properties 
 Tensile strength σb (MPa): ≥ 520 conditions yield strength σ0.2 (MPa): ≥ 205 Elongation δ5 (%): ≥ 40 Reduction of ψ (%): ≥ 60 Hardness: ≤ 187HBS; ≤ 90HRC; ≤ 200HV [3 

 Microstructure 
 Organizing for the austenitic type. 

 Heat treatment 
 1) solution treatment; its purpose is to make carbon at room temperature to fully dissolve and remain in the austenite, which at room temperature by single-phase austenite, the steel has the highest resistance to corrosion. Solution treatment temperature is generally higher the heating, between the 1050-1100C, according to the level of carbon content to make appropriate adjustments. As the poor thermal conductivity of 18-8 stainless steel, not only to warm up and then quenched by heating, but also in the solution heat treatment (quenching) when the holding time is longer. Solution treatment, we should pay special attention to prevent the growth of carbon. 18-8 will increase because of increased carbon steel intergranular corrosion tendencies. Cooling medium, generally water. After solution treatment organizations are generally single-phase austenite, but titanium, niobium, molybdenum stainless steel, especially when the castings, also contains a small amount of ferrite. Hardness after solution treatment is generally 135HBS so. 2) In addition to stress annealing; in order to eliminate the residual stress after cold working, processing at lower temperatures. Usually heated to 250-425C, is frequently used 300-350C. For the non-titanium or niobium steel should not exceed 450C, in order to avoid chromium carbide precipitation caused by intergranular corrosion. In order to eliminate the residual stress after welding, eliminating the stress corrosion susceptibility of steel to the processing at higher temperatures. Heating temperature is not lower than 850C. Cooling, the steel containing titanium or niobium can be directly cooled in the air; that do not contain titanium or niobium steel should be cooled to 500C after cooling in the air again. 3) stabilization process; titanium and niobium in order to prevent the welding of austenitic stainless steel or solid solution treatment, due to a decrease in TiC and NbC cause reduced resistance to intergranular corrosion, this stainless steel will be heated to a certain temperature (the temperature to completely dissolve in austenitic chromium carbide, and only partial dissolution of TiC and NbC) and then slow cooling. In the cooling process, so full of carbon steel with titanium and niobium compounds, precipitation of stable TiC and NbC, without precipitation of chromium carbides, thereby eliminating the 18-8 austenitic stainless steel intergranular corrosion tendencies, such process is called stabilization treatment.