Among many stainless steel material heat treatment processes, if you want to choose a suitable heat treatment process, you need to make a targeted selection based on the characteristics of the stainless steel material. For example, you can choose annealing during the heat treatment of ferritic stainless steel. Let’s talk about various types of stainless steel materials. Appropriate heat treatment technology.

In ferritic stainless steel, because it does not undergo martensite transformation, the mechanical properties of this type of stainless steel basically do not change with heat treatment. The heat treatment that can be used is annealing, whose purpose is to restore the cold-worked ferritic stainless steel to its pre-processing state. However, it is very easy to coarsen the grains above 900°C. In addition, ferritic stainless steel will become embrittled when heated or cooled to around 475°C. It is not only cold brittle but also hot brittle, so the time at this temperature should be minimized as much as possible.

Martensitic stainless steel is the same as quenched and tempered steel and can be quenched, tempered and annealed. The difference is that the austenite structure generated at high temperature is not prone to high temperature decomposition during cooling, so there is no normalizing treatment. The hardness of this type of stainless steel does not change significantly when tempered below 500°C. The mechanical properties of martensitic stainless steel are similar to those of quenched and tempered steel. When the hardness increases, its strength will be higher, while its plasticity and toughness will decrease.

There are three types of heat treatment for austenitic stainless steel. One is solid solution treatment, which means that all carbides will be completely dissolved at 1000-1100°C. This is because the martensite structure formed by cold working will also completely transform into an austenite structure. . After solid solution and then rapid cooling to room temperature, the high-temperature single-phase structure can be maintained, so that the softest and most ductile state can be obtained.

The second is stabilization treatment, which adds a small amount of titanium and niobium to stainless steel in order to avoid intergranular corrosion. In order to achieve the best stabilization effect, stabilization treatment is required, which is to heat to 900°C to form stable carbides from carbon, titanium and niobium.

The third is stress relaxation treatment. The internal stress generated by cold working can be eliminated by annealing at a lower temperature. After this heat treatment, although the elongation has not changed, the various strengths, especially the proportional limit, have increased a lot.