Today, let's learn about the heat treatment of austenitic stainless steel flange, one of the stainless steel flanges, which is very helpful to understand the performance of the flange and various impact tensile tests in production.
The following figure shows the curve of austenitic stainless steel flange raw material heat treatment.
The precipitation formation temperatures of austenitic stainless steel flange raw materials during heat treatment are as follows:
δ- Fe formation temperature range (above about 1100 ℃)
Solid solution heat treatment temperature range (about 950-1000 ℃)
Ti stabilization temperature range (about 870-950 ℃)
δ Phase precipitation temperature range (about 620-840 ℃)
Cr23C6 precipitation temperature range (about 450-870 ℃)
Precipitation and dissolution of alloy carbides during heat treatment of austenitic stainless steel flanges
1) Carbon solubility
304 (18Cr-8Ni), solubility of 1200 ℃ carbon is 0.34%, solubility of 1000 ℃ carbon is 0.18%. The solubility of carbon at 600 ℃ is 0.03%. 304 carbon content is not more than 0.08%. Carbon above 1000 ℃ is dissolved in austenite. Due to the small radius of carbon atoms, carbon atoms precipitate along the grain boundary when the temperature decreases. The curve is as follows, which is the rule summarized by our austenitic stainless steel flange heat treatment experiment
What is the intercrystalline chromium deficiency of austenitic stainless steel flanges? See the following figure for details
Carbon solubility: when the temperature decreases, the solubility decreases.
Carbon atom radius: small atom radius, reduced solubility and precipitation along grain boundary.
Stability: the precipitated carbon atoms are unstable and produce stable Cr23C6 or (FeCr) 23c6 with Cr and Fe.
Atomic diffusion rate: the carbon atom has a small radius and a large diffusion rate. Chromium atom has a large radius and a small diffusion rate.
