Can solution treatment restore metal properties?
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After years of use, the impact toughness of the inlet pipe of the catalytic hood has been reduced a lot. There is a suggestion.: I would like to inquire about restoring metal properties through solid solution treatment at 1050-1200 degrees.: Can the properties of sensitized stainless steel be restored through solution treatment after use?
There are many types of stainless steel. Stainless steel is divided into typical normalizing structures.: Ferritic (F) type stainless steel, martensitic (M) type stainless steel, austenitic (A) type stainless steel and austenitic-ferritic (AF) duplex stainless steel and precipitation hardening or transition type) stainless steel. Only the heat treatment of austenitic stainless steel can be called solid solution treatment. In addition, stabilization treatment and stress relief treatment can also be carried out. Solution treatment is mainly to restore and improve corrosion resistance! (1) Solid solution treatment. The main purpose of heating the steel to 1050~1150℃ and then water quenching is to dissolve the carbides in the austenite and keep this state at room temperature, so that the corrosion resistance of the steel will be greatly improved. As mentioned above, in order to prevent intergranular corrosion, solution treatment is usually used to dissolve Cr23C6 in austenite and then rapidly cooled. For thin-walled parts, air cooling can be used, and water cooling is generally used. (2) Stabilization treatment. It is usually carried out after solid solution treatment, and is often used for 18-8 steel containing Ti and Nb. After solid solution treatment, the steel is heated to 850-880°C and kept warm and then air-cooled. At this time, the carbides of Cr are completely dissolved, while the carbides of titanium are not completely dissolved and are fully precipitated during the cooling process, making it impossible for carbon to form lattice carbides, thus effectively eliminating intergranular corrosion. (3) Stress relief treatment. Stress relief treatment is a heat treatment process that eliminates the residual stress of steel after cold working or welding. It is generally heated to 300~350℃ and tempered. For steel that does not contain stabilizing elements Ti and Nb, the heating temperature should not exceed 450t to avoid the precipitation of chromium carbides and cause intergranular corrosion. For cold-worked parts and welded parts of ultra-low carbon and alloyed Ti and Nb stainless steels, they need to be heated at 500 to 950°C and then slowly cooled to eliminate stress (the upper limit temperature is used to eliminate welding stress), which can reduce the tendency of intergranular corrosion and improve the stress corrosion resistance of steel.