Stainless steel heat resistance and corrosion resistance

Heat resistance performance
Heat resistance refers to the ability of stainless steel to maintain its excellent physical and mechanical properties at high temperatures.
The influence of carbon: Carbon is an element that strongly forms and stabilizes austenite and expands the austenite zone in austenitic stainless steel. The ability of carbon to form austenite is about 30 times that of nickel. As a interstitial element, carbon can significantly improve the strength of austenitic stainless steel through Solid solution strengthening. Carbon can also improve the stress and corrosion resistance of austenitic stainless steel in highly concentrated chloride solutions (such as 42% MgCl2 boiling solution).
However, in austenitic stainless steel, carbon is often regarded as a harmful element, which is mainly because under some conditions of stainless steel corrosion resistance (such as welding or heating at 450~850 ℃), carbon can form a high chromium Cr23C6 type Carbon compounds with chromium in steel, thus leading to local chromium depletion, which reduces the corrosion resistance of steel, especially the intergranular corrosion resistance. Therefore. Since the 1960s, most of the newly developed chromium nickel austenitic stainless steels have a carbon content of less than 0.03% or 0.02% ultra-low carbon type. It can be known that as the carbon content decreases, the sensitivity of the steel to intergranular corrosion decreases. When the carbon content is less than 0.02%, the most obvious effect is achieved. Some experiments have also pointed out that carbon can also increase the tendency of chromium austenitic stainless steel to point corrosion. Due to the harmful effects of carbon, not only should the carbon content be controlled as low as possible during the smelting process of austenitic stainless steel, but also during subsequent hot, cold working, and heat treatment processes, it is necessary to prevent surface carburization of stainless steel and prevent the precipitation of chromium carbides.
Corrosion resistance
When the number of chromium atoms in steel is not less than 12.5%, it can cause a sudden change in the electrode potential of the steel, rising from negative potential to positive electrode potential. Prevent electrochemical corrosion.