When the chromium-nickel austenitic stainless steel is heated to a temperature range of 450-800 ° C, carbon often precipitates from the saturated austenitic metallurgical structure in the form of Cr23C6, thereby causing intergranular corrosion.
The affinity of titanium and carbon in stainless steel is greater than that of chromium. To avoid intergranular corrosion, the content of Cr23C6 should be reduced, so that the carbide exists completely in the form of TiC. The formation temperature of Cr23C6 is 650 ° C, and 900 ° C is the TiC formation temperature. When the stainless steel is heated above 700 ° C, the chromium carbide begins to transform into the titanium carbide. Therefore, the titanium-containing stainless steel must be stabilized after solution treatment. Stabilization is to heat the stainless steel to 850-930 ° C for 1 hour. At this time, the chromium carbide will completely decompose to form stable gray or black titanium carbide, and the resistance of the stainless steel to intergranular corrosion is optimized.
In addition, titanium is added to the stainless steel, and under certain conditions, the Fe2Ti intermetallic compound can be dispersed to increase the high temperature strength of the stainless steel.
However, titanium also jeopardizes the performance of stainless steel. For example, inclusions such as TiO2 and TiN are easily present, and their content is high and unevenly distributed, which reduces the purity of stainless steel to some extent; it also deteriorates the surface quality of stainless steel ingots, resulting in an increase in the amount of process grinding, which is easy. It causes waste; the polishing performance of the finished product is not very good, and the processing of high-precision surfaces is very difficult.