Heat treatment process of precipitation hardening stainless steel pipe

In the process of processing of stainless steel pipe, the more common one is heat treatment. As a process with certain technical content, the heat treatment of each type of stainless steel pipe can be slightly different.

Solid solution treatment

Precipitation hardening stainless steel tube after solid solution treatment (1000 ~ 1050 , 1 h, air cooling), the microstructure is austenite can be obtained with a small amount of ferrite, and then in 500 ~ 800 ℃ to adjust processing, austenite and ferrite alloy element chromium content is higher in the organization, and the carbide (Cr23C6) easily along the alpha (delta) and r phase interface precipitation, also reduce the austenite content of carbon and other alloying elements in the organization, and thus increase the Ms point of this kind of steel, make it get more martensite microstructure. Alpha (delta) ferritic quantity cannot be too much, otherwise it will have negative effect on heat processing, and will not participate in martensite transformation, thus reducing the strength of stainless steel tube. 

Adjust the handle

The intermediate treatment, which is carried out after the stainless steel tube solid solution treatment process, is usually also called adjustment treatment, to obtain a certain amount of martensitic tissue to strengthen the stainless steel tube.

There are three kinds of commonly used method, the first is in the middle as statutes) (hereinafter referred to as T treatment after solid solution treatment and then heated to 760 + 15 , the heat preservation, 90 min, by Cr23C6 carbide precipitation from austenite, reduce the content of carbon and alloy elements in the austenite, the Ms point rise to 70 , then cooled to room temperature will get martensite + + alpha ferrite residual austenite, the residual austenite in 510 ℃ ageing followed up.

Followed by high temperature adjustment and cryogenic treatment method after processing method (R) solid solution, first heated to 950 ℃ warm after 90 minutes. Because it increases Ms point, cools to room temperature, can obtain a small amount of martensite; And then after – 70 ℃ cold treatment, 8 hours heat preservation, can get a certain amount of martensite.

The third method is the cold deformation on the stainless steel tube method (C treatment) after solid solution treatment, cold deformation at room temperature, the amount of cold deformation martensite formed when related to the deformation and the composition of stainless steel tube. Generally, the amount of martensite can be obtained by 15% ~ 20%, and the excessive deformation will harden the martensite and make the plasticity drop significantly.

Aging treatment (H treatment)

The stainless steel tube needs to be treated after adjustment. This aging treatment process is another way for such stainless steel tubes to be strengthened. When processing the aging temperature higher than 400 , precipitation from martensite structure intermetallic compounds (such as Ni3Ti, etc.), a highly dispersed distribution of precipitation hardening effect. Usually at about 500 ℃ for aging treatment, can get satisfactory hardness and high strength.

Source: China Stainless Steel Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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