Effect of Quenching and Tempering Temperature on High Temperature Properties of 1Cr-11 / 4Mo-1/ 4V Steel

Abstract

1Cr-1¹/₄ Mo-1/4V steel has been widely used as steam turbine rotor shaft material. It is susceptible to notch brittlness during creep unless it is properly heat treated. The present study was carried out to make clear the effect of quenching and tempering temperature on the creep rupture (smooth and notched) properties of 1Cr-1¹/₄Mo-1/4V steel.
No. 1 specimen was quenched with 70°C/mn from various temperatures between 900 and 1050°C and tempered at 660°C for 68 h. No. 2 specimen was quenched with 70°C/mn from 955°C and tempered at various temperatures between 600 and 700°C. The obtained results are, summarized as follows.
Low-temperature quenched material had very fine grains, low smooth rupture strength, high ductility and was not susceptible to notch. However, with an increase of quenching temperature it showed coarser grains and higher tensile and creep rupture strengths, but lower rupture elongation, lower ductility and higher notch sensitivity during creep. Impact properties were very susceptible to quenching temperature. With an increase of tempering temperature the material showed lower tensile strength, higher ductility and lower notch sensitivity. Notch sensitivity was associated with either high quenching temperature or low tempering temperature.