Effect of holding time at stabilization annealing on properties of 08CH18N10T austenitic stainless steel

Abstract

Titanium-stabilized austenitic stainless steel 08Ch18N10T is often used in nuclear power facilities due to its favourable properties. Many parts of the primary circuit of VVER 440 and VVER 1000-type nuclear power plants are manufactured of this steel. This means that the material must possess very good corrosion resistance and thermal stability of structure. Yield strength of at least 177 MPa at 350 °C is required. Heat treatment of this steel comprises several important stages which affect the resulting mechanical properties. In particular, the solution and stabilization annealing after forging or rolling are time and energy consuming. Therefore, various ways to optimize these processes are being sought. A combination of solution annealing at 1020 °C for 15 and 30 minutes and stabilization annealing at 720 °C with dwell of 2.5 hours to 15 hours was tested on 08Ch18N10 steel samples. The aim was to establish the effects of stabilization annealing and solution annealing times on mechanical properties. Longer solution annealing has a pronounced effect on the reduction of scatter in mechanical properties. All annealing routes led to yield strengths at 350 °C higher than 200 MPa and tensile strengths of more than 380 MPa.