1. Solution treatment
After solution treatment (1000 ~ 1050 ℃, 1h, air-cooled) tissue obtained is austenite plus a small amount of ferrite, making adjustments in subsequent processing 500 ~ 800 ℃, since atoms in ferrite diffusion rate than in austenite fast, and ferrite with high chromium content, carbide (Cr23C6) Easy and r the phase interface precipitation along α (δ), but also reduces the content of carbon and alloying elements in austenite, thereby enhancing Ms point of this kind of steel, making it more of martensite. α (δ) ferrite can not be too much, or not conducive to thermal processing, nor participate in martensitic transformation, it will reduce the strength of steel.
2. Adjust handle
Intermediate processing performed after solution treatment, generally known as adjustment processing, in order to obtain a certain amount of martensite, thereby strengthening the steel, the following three methods commonly used:
(1) Intermediate aging method (referred to T approach) solution treatment and then heated to (760 ± 15) ℃, insulation 90min, due Cr23C6 carbide precipitation from the austenite, reduce carbon and austenite content of alloying elements, the Ms point rises to 70 ℃, then cooled to room temperature then get martensite + α ferrite and retained austenite, the retained austenite in the subsequent aging only 510 ℃ decomposition finish.
(2) high temperature adjustment and cryogenic treatment method (R approach) after solution, the line first heated to 950 ℃ insulation 90min. Since the rise of Ms point, cooled to room temperature, to obtain a small amount of martensite; after then by -70 ℃ cold treatment, heat 8h, you can get a certain amount of martensite.
(3) cold deformation method (C approach) solution treatment at room temperature, cold deformation, cold deformation martensite formation and deformation of the quantity and composition of stainless steel related. Generally the amount of deformation in the 15% to 20% will be able to obtain the necessary amount of martensite, excessive deformation martensite hardening will occur, the plastic significantly.
3. The aging process (H process)
After the adjustment process, shall be subjected to an aging process. Aging is another way to strengthen the type of steel. When the aging temperature is higher than 400 ℃, intermetallic compounds (eg Ni3Ti etc.) will precipitate from the martensite, were highly dispersed, from the precipitation hardening effect. Usually at about 500 ℃ aging, a high strength and hardness.