通过对不同焊接工艺下热成形钢板USIBOR1500P^+电阻点焊焊核直径及接头力学性能的测试及分析,得出其最佳焊接工艺参数为:焊接电流9.5 k A,焊接时间20 cyc,电极压力3000 N。焊接参数过小或者过大都会导致一系列的缺陷产生。最佳工艺参数...通过对不同焊接工艺下热成形钢板USIBOR1500P^+电阻点焊焊核直径及接头力学性能的测试及分析,得出其最佳焊接工艺参数为:焊接电流9.5 k A,焊接时间20 cyc,电极压力3000 N。焊接参数过小或者过大都会导致一系列的缺陷产生。最佳工艺参数下USIBOR1500P^+钢焊接接头显微组织和显微硬度分析结果表明,从母材至焊核区域,其硬度值快速增加,原因是该区域内的马氏体含量快速增加。展开更多
In the sheet forming process with stretch, diffuse instability and localized instability usually occur in the process one after another. The necking rate has a great impact on the instability process and the forming l...In the sheet forming process with stretch, diffuse instability and localized instability usually occur in the process one after another. The necking rate has a great impact on the instability process and the forming limits of the rate sensitive material, such as USIBOR1500 steel sheets at elevated temperature. The available reports about this steel mainly focus on hot uniaxial tensile, martensitic transformation and forming process, but there are few investigations on instability behavior and forming limits. Based on Inoue Kachiro＇s flow stress constitutive model at elevated temperature, combined with Swift＇s diffuse instability rule and Hill＇s localized instability nile, the relation is theoretically deduced between the diffuse necking rate along with the localized necking rate and the exponent of strain rate sensitivity together with the strain rate in the case of the USIBOR1500 steel sheets at elevated temperature. According to the time-temperature characteristics of the hot stamping process, tensile tests of the steel sheets were carried out on Gleeble3800, and the stress-strain curves were obtained at different temperatures and different strain rates. Then the values of the exponent of strain rate sensitivity and the hardening exponent were obtained through fitting the curves by least squares. The tests also helped to provide the distribution laws of the major strain of the specimens and the uniform strains as well as the necking width. The uniform strains obtained from the tests are matched well with the theoretical calculations.展开更多
文摘通过对不同焊接工艺下热成形钢板USIBOR1500P^+电阻点焊焊核直径及接头力学性能的测试及分析,得出其最佳焊接工艺参数为:焊接电流9.5 k A,焊接时间20 cyc,电极压力3000 N。焊接参数过小或者过大都会导致一系列的缺陷产生。最佳工艺参数下USIBOR1500P^+钢焊接接头显微组织和显微硬度分析结果表明,从母材至焊核区域,其硬度值快速增加,原因是该区域内的马氏体含量快速增加。
基金supported by New Energy Vehicle Special Project of Shanghai Science & Technology Pillar Program of China (Grant No. 08DZ1150305)
文摘In the sheet forming process with stretch, diffuse instability and localized instability usually occur in the process one after another. The necking rate has a great impact on the instability process and the forming limits of the rate sensitive material, such as USIBOR1500 steel sheets at elevated temperature. The available reports about this steel mainly focus on hot uniaxial tensile, martensitic transformation and forming process, but there are few investigations on instability behavior and forming limits. Based on Inoue Kachiro＇s flow stress constitutive model at elevated temperature, combined with Swift＇s diffuse instability rule and Hill＇s localized instability nile, the relation is theoretically deduced between the diffuse necking rate along with the localized necking rate and the exponent of strain rate sensitivity together with the strain rate in the case of the USIBOR1500 steel sheets at elevated temperature. According to the time-temperature characteristics of the hot stamping process, tensile tests of the steel sheets were carried out on Gleeble3800, and the stress-strain curves were obtained at different temperatures and different strain rates. Then the values of the exponent of strain rate sensitivity and the hardening exponent were obtained through fitting the curves by least squares. The tests also helped to provide the distribution laws of the major strain of the specimens and the uniform strains as well as the necking width. The uniform strains obtained from the tests are matched well with the theoretical calculations.
