大气环境下1180MPa级超高强钢延迟开裂寿命研究

通过对试验钢进行拉深成形模拟超高强钢实际应用时的应力、应变状态,研究了盐雾和大气环境下DP1180钢、MS1180钢和QP1180钢这3种1180 MPa级超高强汽车薄板钢拉深冲杯试样的延迟开裂寿命。试验结果表明:在盐雾条件下,DP1180钢的抗延迟开裂性能最好,QP1180钢的抗延迟开裂性能最差;但大气环境下,DP1180钢的抗延迟开裂性能最好,MS1180钢的抗延迟开裂性能最差,最易出现延迟开裂。在大气环境下,超高强钢在拉应力和拉应变与环境中氢的共同作用下易出现延迟开裂现象,并且首次发现冲杯试样在最大拉应力、最大拉应变的杯底外表面边缘处开裂。此外,在试验钢中存在岛状马氏体和块状铁素体组织,有利于降低其延迟开裂敏感性。

Research on delayed cracking life for 1180MPa ultra-high strength steel in atmospheric environment

The stress and strain state of ultra-high strength steel in practical application were simulated by deep-drawing with test steel,and the delayed cracking lifes for three kinds of ultra-high strength automotive sheet steels such as DP1180 steel,MS1180 steel and QP1180 steel in salt spray and atmospheric environments were studied respectively.The results show that in the salt spray condition,DP1180 steel has the best anti-delayed cracking performance,and QP1180 steel has the worst.However,in the atmospheric environment,DP1180 steel has the best anti-delayed cracking performance,and MS1180 steel has the worst,which is most prone to delayed cracking.Furthermore,in the atmospheric environment,ultra-high strength steel is easy to delay cracking under the combined action of tensile stress/tensile strain and environmental hydrogen,and for the first time,the cracking of deep-drawing cup sample cracking is found at the edge of outer surface in the cup bottom with the maximum tensile stress and the maximum tensile strain.In addition,the existence of island martensite and massive ferrite in the test steel is beneficial to reduce its delayed cracking sensitivity.