Hot Deformation Behavior of a New 9% Cr Heat Resistant Steel G115

Abstract

The hot deformation behavior of a new heat resistant steel G115 designed for 650 °C ultra-supercritical (USC) power plants was experimentaly studied. Hot compression test was carried out in the temperature range of 900−1200°C and the strain rate range of 0.1–20 s⁻¹ by using Gleeble-3800 thermal-mechanical simulator, and the corresponding flow curves were obtained. Experimental results show that the flow stress increases with the decrease of deformation temperature and the increase of strain rate. The hot deformation activation energy of G115 steel was determined to be 494 kJ/mol and the constitutive equation was also obtained. For convenience of the practical application, a good approximate equation was obtained for calculating the peak stress values of G115 steel under different deformation conditions. At the strain value of 0.9, natural logarithm of the critical Zener-Holomon parameter Zc of G115 steel was determined to be in the scope of 0.9, natature and 50.65, above which there wil be no dynamic recrystaliza-tion (DRX). And natural logarithm of the critical Zener-Holomon parameter Zs of G115 steel was determined to be in the scopes of 45.58 and 46.27, below which ful DRX may occur. Then, the status diagram of dynamic micro-structures of G115 steel was established. In addition, the strain rate sensitivity of G115 steel is not constant during the test temperature range and it increases linearly from 900 to 1200 °C. Therefore, hot deformation at higher temperatures would obtain beter workability.