The raw materials of austenitic stainless steel blind flange are divided into intergranular corrosion, sensitization treatment, solid solution treatment and stabilization treatment
What is the intergranular corrosion of austenitic stainless steel blind flange?
Under the action of corrosive medium, austenitic stainless steel flange produces a corrosion phenomenon between grains, which is called intergranular corrosion. The necessary condition for the raw materials of stainless steel blind flange to have corrosion resistance is that the mass fraction of chromium must be greater than 10-12%. Because the solubility of carbon in the raw materials of austenitic stainless steel blind flange has a great influence on the temperature, when the temperature rises, the carbon in austenitic stainless steel blind flange combines with chromium and precipitates at the grain boundary during hot working or welding, and the formed carbide makes the grain boundary appear "chromium poor zone". Under the action of corrosive medium, "chromium poor area" loses its corrosion resistance and produces intergranular corrosion. Intergranular corrosion test is also used in the inspection of stainless steel blind flange.
Sensitization mechanism of austenitic stainless steel blind flange:
When the austenitic stainless steel blind flange of 18-8 steel system is heated for a short time in the temperature range of 450 ℃ ~ 850 ℃ (this range is often referred to as the sensitization temperature), high chromium carbide (Cr23C6) will precipitate. When the chromium content falls below the corrosion resistance limit, there is poor chromium at the grain boundary, which will produce intergranular corrosion and turn into powder in severe cases. This method is generally only used in intergranular corrosion test of stainless steel blind flange.
