Cr18Ni8 < FONT > Austenitic stainless steel heat treatment process: due to its high nickel content and austenitic single-phase structure at room temperature, it has high corrosion resistance compared with Cr13 stainless steel, and it has high corrosion resistance at low temperature, room temperature and high temperature. All have high plasticity and toughness, as well as good cold forming and weldability. However, the strength at room temperature is low, the tendency of intergranular corrosion and stress corrosion is large, and the machinability is poor.
Austenite does not transform when heated, so it cannot be strengthened by heat treatment. Heat treatment can only be performed to improve the corrosion resistance of the steel:
Solution treatment: The purpose is to fully dissolve the carbide and retain it in austenite at room temperature, so as to obtain a single-phase austenite structure at room temperature, so that the steel has the highest corrosion resistance.
The heating temperature of solution treatment is generally high, between 1050-1100 ℃, and it is adjusted appropriately according to the level of carbon content. Due to the poor thermal conductivity of 18-8 stainless steel, it is not only necessary to perform quenching and heating after preheating, but also the holding time during solution treatment (quenching and heating) is long. During solution treatment, special attention should be paid to preventing carbon increase. Because carbon increase will increase the intergranular corrosion tendency of 18-8 steel. The cooling medium is generally clean water. The structure after solution treatment is generally single-phase austenite, but stainless steel containing titanium, niobium, and molybdenum, especially when it is cast, also contains a small amount of ferrite. The hardness after solution treatment is generally around 135HBS.