The steel specimens of nominal composition 0.3C-1.0Cr-1.0Mn-2.0Si-1.0Ni- 0.04 Nb were quenched and tempered or isothermally quenched from various temperatures. It is found that the steel quenched and tempered with a...The steel specimens of nominal composition 0.3C-1.0Cr-1.0Mn-2.0Si-1.0Ni- 0.04 Nb were quenched and tempered or isothermally quenched from various temperatures. It is found that the steel quenched and tempered with a tensile strength of 1 500-1 600 MPa has a K ISCC (critical stress intensity factor) value below 15.0 MPa·m 1/2 . The steel isothermally quenched with a tensile strength of 1 350-1 750 MPa has a K ISCC value about 20.0 MPa·m 1/2 . In addition, with increase of isothermal quenching temperature, the tensile strength decreases greatly and K ISCC value does not pronouncedly change. The microstructure of isothermally quenched specimens is composed of bainite and retained austenite. The delayed fracture resistance is dependent on the stability of austenite, which is in turn related to the retained austenite volume fraction and carbon content in austenite.展开更多
基金Item Sponsored by Provincial Natural Science Foundation of Inner Mongolia of China(9610E22)
文摘The steel specimens of nominal composition 0.3C-1.0Cr-1.0Mn-2.0Si-1.0Ni- 0.04 Nb were quenched and tempered or isothermally quenched from various temperatures. It is found that the steel quenched and tempered with a tensile strength of 1 500-1 600 MPa has a K ISCC (critical stress intensity factor) value below 15.0 MPa·m 1/2 . The steel isothermally quenched with a tensile strength of 1 350-1 750 MPa has a K ISCC value about 20.0 MPa·m 1/2 . In addition, with increase of isothermal quenching temperature, the tensile strength decreases greatly and K ISCC value does not pronouncedly change. The microstructure of isothermally quenched specimens is composed of bainite and retained austenite. The delayed fracture resistance is dependent on the stability of austenite, which is in turn related to the retained austenite volume fraction and carbon content in austenite.