Heat resistance

Heat resistance means that stainless steel can maintain its excellent physical and mechanical properties at high temperatures.

Carbon effect: Carbon is strongly formed and stabilized in austenitic stainless steel. Austenite is formed and the elements of the austenite region are enlarged. The ability of carbon to form austenite is about 30 times that of nickel. Carbon is a kind of interstitial element, which can significantly increase the strength of austenitic stainless steel by solid solution strengthening. Carbon also improves the stress and corrosion resistance of austenitic stainless steels in highly concentrated chlorides such as 42% MgCl2 boiling solutions.

However, in austenitic stainless steels, carbon is often considered a harmful element, mainly due to some conditions in the corrosion resistance of stainless steel (such as welding or heating at 450~850 °C), carbon can be used in steel.

Chromium forms a high chromium Cr23C6 type carbon compound which leads to partial chromium depletion, which reduces the corrosion resistance of the steel, especially the intergranular corrosion resistance. therefore. The newly developed chromium-nickel austenitic stainless steels since the 1960s are mostly ultra-low carbon with a carbon content of less than 0.03% or 0.02%. It can be known that as the carbon content decreases, the intergranular corrosion sensitivity of steel decreases, when the carbon content is lower than 0.02% has the most obvious effect, and some experiments also pointed out that carbon also increases the tendency of pitting corrosion of chromium austenitic stainless steel. Due to the harmful effects of carbon, not only the lowest possible carbon content should be controlled during the austenitic stainless steel smelting process, but also the carbonation of the stainless steel surface is prevented during the subsequent heat, cold working and heat treatment, and the chromium carbide is avoided. Precipitate.