Thu, 13 Sep 2018 02:56:21 +0000
Heat treatment technology of stainless steel
Chromium is a stainless element of this kind of material. It was found in the past that the content of chromium must be more than 12% in order to form a dense oxide film on the surface and achieve corrosion protection. Therefore, any heat treatment of stainless steel must take into account whether there is any change in the composition of chromium.
(1) Martian stainless steel:
This type of stainless steel is a body-centered cubic (BCC) structure that attracts magnets. It is made from Austin’s quenching temperature. It has the best corrosion resistance, but the material is hard and brittle. Carbon atom diffusion precipitation and chromium formation network of chromium carbide caused the consumption of chromium in the adjacent region to reduce the chromium content, can not form a protective film, and loss of corrosion resistance, so special attention should be paid. The following is the heat treatment temperature of all kinds of Matian stainless steel.
(a) 403, 410, and the temperature of 416se is 650-750 degrees.
(b) the temperature of 414 is 650-730 C.
(c) the temperature of 431 is 6.
(d) 440-A, 440-B, 440-C, 420, the temperature is 680-750 C.
(2) fat grain iron stainless steel:
This stainless steel is a body-centered cubic (BCC) structure that can be used as magnets for attraction in the automotive or chemical industries. Its strength will not be changed by heat treatment, but can be increased by cold working.
(3) austenitic stainless steel:
This stainless steel is a face-centered cubic structure (FCC) which does not work on magnets. As mentioned above, this kind of material is easy to process, so it can be processed by different heat treatments to eliminate the residual stress of the material.
(4) precipitation hardening stainless steel:
The strength or hardness of this stainless steel can be increased by quenching at low temperatures and by precipitating aluminum or copper elements along differential sliding surfaces or grain boundaries to form inter metallic compounds. The commonly used precipitation hardening stainless steel is 17-4 PH, while the others are 17-7 PH, PH15-7MO, AM-350, AM-355 and so on.
(5) all kinds of stainless steel after welding heat treatment:
After welding, the chromium element in stainless steel often diffuses and precipitates into chromium carbide in the high temperature region (heat affected zone), resulting in a local decrease in chromium content and failure to form a protective film. Corrosion, such as perforation, often occurs in these heat affected zones. In order to remedy this situation, the industry often finishes welding. The effect of heat treatment is to diffuse chromium from other regions to the chromium deficient region for protection.