The role of the alloying element nickel in stainless steel is to be fully exerted after it is combined with chromium. Because nickel is an excellent corrosion-resistant material and an important alloying element for alloy steel. Nickel is an important element to form austenite structure in stainless steel, but to obtain pure austenite structure in low-carbon nickel steel, the nickel content needs to be as high as 24%; The corrosion resistance performance in the medium is significantly changed. Therefore, nickel element cannot constitute stainless steel alone.
However, when nickel and chromium exist in stainless steel at the same time, nickel-containing stainless steel has many excellent properties. For example, the structure of high-chromium stainless steel can be changed, so that the corrosion resistance and process performance of stainless steel can be improved.
In addition, manganese and nitrogen can replace nickel in chromium-nickel stainless steel. Although there are many advantages of chromium-nickel austenitic stainless steel, the contradiction between the supply and demand of nickel has appeared in the world because of the small amount of nickel deposits and concentrated distribution in a few areas. Therefore, in the field of stainless steel and many other alloys (such as steel for large castings and forgings, tool steel, heat-strength steel, etc.), especially in countries that lack nickel resources, vigorously develop scientific research and production practices that save nickel and replace nickel with other elements , Manganese and nitrogen are used more in this respect to replace nickel in stainless steel and heat-resistant steel.
The role of manganese in austenitic stainless steel is similar to that of nickel. More precisely, the role of manganese is not to form austenite, but it can reduce the critical quenching rate of steel, thereby increasing the stability of austenite during cooling, and inhibiting the decomposition of austenite structure, and finally making Austenite formed at high temperature can be maintained at room temperature. In addition, the effect of manganese on stabilizing austenite in steel is about half that of nickel, that is, the effect of 2% nitrogen in steel is also on stabilizing austenite, and its effect is stronger than that of nickel.
