Abstract:

The microstructure, properties and fracture morphology of 2.25Cr-1Mo-0.25V steel tempered respectively at 690 ℃ and 705 ℃ for 1-150 h were studied by using optical microscope, scanning electron microscope, tensile test and impact test. The results show that tempering temperature and tempering time have great influence on the microstructure, strength and toughness of the tested steel. In the studied range of temperature, the strip-like carbides in the microstructure are gradually spheroidized and gathering towards the grain boundary with the extension of tempering time. With the increase of tempering time, the strength index shows a tendency of gradual stability after a sharp decline, but the toughness index first increases, then decreases and stabilized. In this study, the reduction of area and the impact toughness with the change of tempering time show the same trend at tempering temperatures of 690 ℃ and 705 ℃.

Key words: 2.25Cr-1Mo-0.25V steel, tempering, microstructure, mechanical properties