Manganese and nitrogen can replace nickel in chromium-nickel stainless steel. Although there are many advantages of chromium-nickel austenitic steel, in recent decades, due to the large-scale development and application of nickel-based heat-resistant alloys and hot-strength steels containing less than 20% nickel, as well as the increasing development of the chemical industry, the demand for stainless steel has increased.
The bigger the nickel, the smaller the nickel deposits and the concentrated distribution in a few areas, so there is a contradiction between the supply and demand of nickel in the world. Therefore, in the fields of stainless steel and many other alloys (such as steel for large castings and forgings, tool steel, heat-strength steel, etc.), especially in countries where nickel resources are relatively scarce, the science of saving nickel and replacing nickel with other elements has been widely carried out. In research and production practice, manganese and nitrogen are used to replace nickel in stainless steel and heat-resistant steel.
The effect of manganese on austenite is similar to that of nickel. But to be more precise, the role of manganese is not to form austenite, but to reduce the critical quenching rate of steel, increase the stability of austenite during cooling, inhibit the decomposition of austenite, and make the Austenite can be maintained to normal temperature.In improving the corrosion resistance of steel, manganese has little effect. For example, the content of manganese in steel varies from 0 to 10.4%, and the corrosion resistance of steel in air and acid does not change significantly. This is because manganese has little effect on improving the electrode potential of iron-based solid solution, and the protective effect of the formed oxide film is also very low. etc.), but they are not available as stainless steel.
The role of manganese in stabilizing austenite in steel is about half that of nickel, that is, the role of 2% nitrogen in steel is also stabilizing austenite, and the effect is greater than that of nickel. For example, in order to obtain an austenitic structure in a steel containing 18% chromium at room temperature, low-nickel stainless steel with manganese and nitrogen instead of nickel and chromium-manganese-nitrogen stainless steel with nickel element have been applied in industry, and some have been successful. ground instead of the classic 18-8 chrome-nickel stainless steel.
