XIONGDA METAL
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25
2024
-
01
Method of heat treatment of stainless steel
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The current industry is getting more and more developed and the requirements for the steel industry are becoming more and more strict. In order to better meet the requirements of the market, large-diameter stainless steel pipes are heat-treated. The performance of large-diameter stainless steel pipes also increases the service life of large-diameter stainless steel pipes. The toughness of large-diameter stainless steel pipes is improved through heat treatment to increase the plasticity of large-diameter stainless steel pipes. After the use of large diameter stainless steel pipe heat treatment, the overall performance of the work has become more in line with the requirements of the current market.
Austenitic stainless steel is an interstitial solid solution formed by chromium, nickel and other elements in γ-Fe, which is a major type of stainless steel. Its main features are: at room temperature with non-magnetic austenite structure, its yield ratio is low, good plasticity, good welding performance, easy smelting and forging hot forming; its composition is characterized by high chromium (≥ 17%), nickel (8%-15%) and other elements to improve corrosion resistance (such as molybdenum, niobium, titanium, etc.). Therefore, austenitic stainless steel not only has good corrosion resistance, but also has good mechanical properties and process properties, so it has been widely used in mechanical equipment.
The heat treatment processes commonly used in general austenitic stainless steel are: solid solution treatment, stabilization treatment and stress relief treatment.
1. Stress relief treatment
Stress relief treatment is a heat treatment process to eliminate the residual stress of steel after cold working or welding, and is generally heated to 300-350 ℃ for tempering. For the steel not containing the stabilizing elements Ti and Nb, the heating temperature is not more than 450 ° C., so as not to precipitate chromium carbide and cause intergranular corrosion. For ultra-low carbon and containing Ti, Nb stainless steel cold working parts and welding parts, need to be heated at 500-950 ℃, and then slow cooling, eliminate stress (eliminate welding stress to take the upper limit temperature), can reduce the tendency of intergranular corrosion, and improve the stress corrosion resistance of steel.
2. Stabilization treatment
Generally, it is carried out after solid solution treatment, which is commonly used in steel containing Ti and Nb. After solid solution treatment, the steel is heated to 850-880 ℃ and then air cooled. At this time, Cr carbides are completely dissolved and fully precipitated in the cooling process, so that carbon cannot form chromium carbides any more, thus effectively eliminating intergranular corrosion.
3. Solution treatment
The steel is heated to 1050-1150 ℃ after water quenching, the main purpose is to dissolve the carbide in the austenite, and this state is retained to room temperature, so that the corrosion resistance of the steel will be greatly improved. This is a heat treatment method to prevent intergranular corrosion. Air cooling can be used for thin-walled parts, and water cooling is generally used.
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