Direct quenching and tempering （DQ-T） of hot rolled steel section has been widely used in steel mill for the sake of improvement of mechanical properties and energy saving. Temperature history and microstructural ev...Direct quenching and tempering （DQ-T） of hot rolled steel section has been widely used in steel mill for the sake of improvement of mechanical properties and energy saving. Temperature history and microstructural evolution during hot rolling plays a major role in the properties of direct quenched and tempered products. The mathematical and physical modeling of hot forming processes is becoming a very important tool for design and development of required products as well as predicting the microstructure and the properties of the components. These models were mostly used to predict austenite grain size （AGS）, dynamic, recta-dynamic and static recrystallization in the rods immediately after hot rolling and prior to DQ process. The hot compression tests were carried out on 42CrMo4 steel in the temperature range of 900-1 100 ℃ and the strain rate range of 0. 05-1 s^-1 in order to study the high tempera- ture softening behavior of the steel. For the exact prediction of flow stress, the effective stress-effective strain curves were obtained from experiments under various conditions. On the basis of experimental results, the dynamic recrystallization fraction （DRX）, AGS, hot deformation and activation energy behavior were investigated. It was found that the calculated results were in good agreement with the experimental flow stress and microstructure of the steel for different conditions of hot deformation.展开更多
Based on the feasibility of isothermal superplastic solid state welding of steel and copper alloy, the welded surface of steel surface was ultra-fined through laser quenching, and then the welding process tests betwee...Based on the feasibility of isothermal superplastic solid state welding of steel and copper alloy, the welded surface of steel surface was ultra-fined through laser quenching, and then the welding process tests between different base metals of 40Cr and QCr0.5 were made under the condition of non vacuum and non shield gas. The experimental results show that, with the sample surface of steel after laser quenching and that of copper alloy carefully cleaned, and under the pre-pressed stress of 56.684.9 MPa, at the welding temperature of 750800 ℃ and at initial strain rate of （2.57.5）×10-4 s-1, the solid state welding can be finished in 120180 s so that the strength of the joint is up to that of QCr0.5 base metal and the expansion rate of the joint does not exceed 6%. The plastic deformation of the joint was further analysed. The superplastic deformation of the copper alloy occurs in welding process and the deformation of steel are little.展开更多
文摘Direct quenching and tempering （DQ-T） of hot rolled steel section has been widely used in steel mill for the sake of improvement of mechanical properties and energy saving. Temperature history and microstructural evolution during hot rolling plays a major role in the properties of direct quenched and tempered products. The mathematical and physical modeling of hot forming processes is becoming a very important tool for design and development of required products as well as predicting the microstructure and the properties of the components. These models were mostly used to predict austenite grain size （AGS）, dynamic, recta-dynamic and static recrystallization in the rods immediately after hot rolling and prior to DQ process. The hot compression tests were carried out on 42CrMo4 steel in the temperature range of 900-1 100 ℃ and the strain rate range of 0. 05-1 s^-1 in order to study the high tempera- ture softening behavior of the steel. For the exact prediction of flow stress, the effective stress-effective strain curves were obtained from experiments under various conditions. On the basis of experimental results, the dynamic recrystallization fraction （DRX）, AGS, hot deformation and activation energy behavior were investigated. It was found that the calculated results were in good agreement with the experimental flow stress and microstructure of the steel for different conditions of hot deformation.
基金Project(2004 294) supported by the Innovative Talents Foundation in University of Henan Province China+2 种基金 Project(0511050800) supported by the Natural Science Foundation of Henan Province China Project(2003430211)supported by the Natural Sci
文摘Based on the feasibility of isothermal superplastic solid state welding of steel and copper alloy, the welded surface of steel surface was ultra-fined through laser quenching, and then the welding process tests between different base metals of 40Cr and QCr0.5 were made under the condition of non vacuum and non shield gas. The experimental results show that, with the sample surface of steel after laser quenching and that of copper alloy carefully cleaned, and under the pre-pressed stress of 56.684.9 MPa, at the welding temperature of 750800 ℃ and at initial strain rate of （2.57.5）×10-4 s-1, the solid state welding can be finished in 120180 s so that the strength of the joint is up to that of QCr0.5 base metal and the expansion rate of the joint does not exceed 6%. The plastic deformation of the joint was further analysed. The superplastic deformation of the copper alloy occurs in welding process and the deformation of steel are little.
