580DP与700DP热轧双相钢的力学性能与成形性能

Mechanical Property and Formability of 580DP and 700DP Hot-Rolled Dual Phase Steel

研究了580DP与700DP热轧双相钢的拉伸性能、扩孔性能和成形极限曲线,并与QStE550TM热轧微合金高强钢的进行对比;采用成形极限经验公式和MK模型对成形极限曲线进行预测,并与试验结果进行对比;对热轧双相钢的成形极限曲线最低点的主应变进行拟合,进而对成形极限经验公式进行修正。结果表明:与QStE550TM钢相比,580DP与700DP钢的断后伸长率和加工硬化指数较高,屈强比较低,加工性能较好;580DP与700DP钢的扩孔率均低于QStE550TM钢的,扩孔性能较差;580DP钢的成形极限曲线高于700DP钢的,且均高于QStE550TM钢的,热轧双相钢的成形性能较好;成形极限经验公式与MK模型均不能很好地预测580DP与700DP钢的成形极限曲线;采用修正的成形极限经验公式计算得到的热轧双相钢的成形极限曲线与试验结果较吻合,其中580DP钢的相对误差小于5.6%,700DP钢在平面应变区域的相对误差小于9.4%,在其他区域的相对误差小于6.5%。

The tensile properties,hole-expansion properties and forming limit curves of 580 DP and 700 DP hot-rolled dual phase steel were studied and compared with those of QStE550 TM hot-rolled microalloyed high strength steel.The forming limit curves were predicted by forming limit empirical formulas and MK model,and compared with test results.The main strains at valley point of forming limit curves for hot-rolled dual phase steels were fitting to modify the forming limit empirical formula.The results show that compared with QStE550 TM steel,580 DP and 700 DP steel had higher percentage elongation after fracture and work-hardening index and lower yield ratios,indicating better processability.The hole-expansion ratios of 580 DP and 700 DP steel were smaller than that of QStE550 TM steel,and the hole-expansion properties were worse.The forming limit curve of 580 DP steel was higher than that of 700 DP steel,and both were higher than that of QStE550 TM steel,indicating hot-rolled dual phase steel had better formability.The empirical formulas and MK model did not predict the forming limit curves of580 DP and 700 DP steel well.The forming limit curves of hot-rolled dual phase steels calculated by modified forming limit empirical formula agreed with the test results;therelativeerrorwaslessthan5.6%for580 DPsteel,and less than9.4%inplane strain regionandlessthan6.5%inotherregions for 700 DP steel.