For martensitic chromium nickel stainless steel, most applications require quenching and tempering heat treatment processes.
Different alloy elements and their added amounts during this process will have varying effects on the hardenability of the material.
Martensitic stainless steel
When quenching martensitic stainless steel, it is subjected to rapid cooling treatment at a temperature of 925-1075 ℃.
Due to the low rate of phase transformation in the organization, both oil cooling and air cooling can achieve a complete degree of hardening.
During the necessary tempering process, a wide range of mechanical properties can be obtained due to different tempering conditions.
In martensitic chromium stainless steel, the addition of chromium can enhance the hardenability of iron carbon alloys, so the application range of quenched martensitic stainless steel is still relatively wide.
The main function of chromium is to reduce the critical cooling rate of quenching, significantly enhancing the hardenability of martensitic stainless steel.
From the C-curve, it can be seen that the addition of chromium slows down the transformation rate of austenite structure, resulting in a significant rightward shift of the C-curve.
The addition of nickel alloy element can enhance the hardenability and hardenability of martensitic chromium nickel stainless steel.
Stainless steel with chromium content close to 20% does not have quenching ability without adding nickel element. Adding 2% -4% nickel element can restore quenching ability.
But the nickel content cannot be too high, otherwise excessive nickel content will not only expand the r-phase region, but also reduce the Ms temperature, which will make the steel become a single-phase austenite structure and lose quenching ability.
Choosing the appropriate nickel content can enhance the tempering stability of martensitic stainless steel and reduce the degree of tempering softening.
In addition, adding molybdenum element to martensitic chromium nickel stainless steel can also increase the tempering stability of martensitic stainless steel.
Although ferritic stainless steel cannot undergo quenching treatment to achieve hardening due to the absence of austenite structure at high temperatures, some martensitic transformation occurs in low chromium stainless steel.
Austenitic stainless steel belongs to the iron chromium nickel series and iron chromium manganese series stainless steel, and has an austenitic structure.
So it will exhibit high strength and excellent elongation performance in a large range from low temperature to high temperature.
Non magnetic austenite structure can be obtained by performing rapid cooling solid solution treatment starting from above 1000 ℃. In order to achieve excellent corrosion resistance and maximum elongation performance.
