Such as commonly used 06Cr19Ni10 (304) or 12Cr18Ni9 (commonly known as 18-8 steel) austenitic stainless steel. The phase transition does not occur during heating, and the mechanical properties cannot be enhanced by the heat treatment method. The strength is low, and the plasticity and toughness are high.
For austenitic stainless steels generally required to improve corrosion resistance and resistance to plasticity, eliminating cold work hardening fasteners, should be solution treatment; for the complex shape, not solution treatment fasteners, stress relief annealing; Stainless steel containing titanium or niobium can be subjected to stable annealing and sensitization treatment in order to obtain stable corrosion resistance.
The solution treatment is suitable for austenitic stainless steels of any composition and grade. The recommended heating temperature range is generally 950°C to 1050°C, and the process of rapid cooling after a certain period of time is maintained. It is important to choose the temperature of the stabilization annealing heating. The selection principle should be higher than the dissolution temperature of (FeCr)23C6, generally between 750 and 860°C.
The stress relief treatment mainly removes the stress generated during the machining process or removes the residual stress after processing. It can be heated to 1010 to 1120°C, and slowly cooled after being heated and insulated. The sensitization treatment system is usually heated to 650°C and kept in air for 5 to 6 hours. For some special occasions, to more strictly assess the material's resistance to intergranular corrosion, depending on factors such as the temperature of the future use of fasteners and the carbon content of the material, and whether or not it contains molybdenum and other factors, adopt different sensitization systems.
Austenite stainless steel can not be strengthened by heat treatment, but it can be strengthened by cold working deformation (cold hardening, deformation strengthening), so that the strength is increased and the plastic toughness is decreased.
Austenitic stainless steel bolts, nuts, and products have been subjected to greater machining stress after cold forging and cold extrusion. This stress causes increased stress corrosion sensitivity when used in a stress corrosion environment. , affect the stability of the size. To reduce stress, stress relief can be used. It is usually heated to 260-400°C, and air-cooled or slow-cooled after 2 to 6 hours of incubation.
The stress relief treatment not only reduces the stress of the fastener, but also improves the hardness, strength and fatigue limit without any major change in elongation after breaking.
Austenitic stainless steel can not be used to adjust the mechanical properties of heat treatment, but can be used to improve cold harden, used in the manufacture of stainless steel bolts, cold hardening effect is related to carbon content and deformation of steel, with the cold processing compression ratio increases , Cold hardening effect is enhanced.
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