1000MPa级汽车用双相超高强钢低温脆性研究

Study on low temperature brittleness of 1000 MPa grade dual phase ultra high strength steel for automobile use

为了确定1000 MPa级汽车用双相超高强钢在不同应变条件下的低温脆性及其相互关系,采用二次加工脆化试验、夏比摆锤冲击试验、低温拉伸试验相结合的试验方法对HCT980X+Z钢板的低温脆性进行了研究。结果表明,HCT980X+Z钢板的二次加工脆化温度为-40℃,随着温度的降低,材料逐渐由韧性转变为脆性。预应变会使HCT980X+Z钢板的冲击韧性下降,并且预应变水平越大,材料脆性越高;随着试验温度降低,冲击韧性有所下降,但直到-60℃也未出现韧脆转变温度。HCT980X+Z钢板的屈服强度和抗拉强度随试验温度的降低均有所升高,在温度降低到-45^-50℃以下时屈服强度呈现快速上升趋势;断后伸长率从室温下降至-60℃时变化不明显;断口分析显示温度下降到-40℃以下时HCT980X+Z钢板逐渐由韧性向脆性过渡。

In order to determine the brittleness under different strain conditions and their relationships of 1000 MPa grade dual phase ultra high strength steel for automobile use,the low temperature brittleness of HCT980 X ＋ Z was studied by using secondary work embrittlement test,Charpy pendulum impact test and tensile test at low temperature. The results show that the secondary work embrittlement temperature of HCT980 X ＋ Z is-40 ℃,as the temperature decreases,the material changes from ductile to brittle. Pre-strain can reduce the impact toughness of HCT980 X ＋ Z,and the higher the pre-strain level,the higher the brittleness of the material. The impact toughness decreases with the decrease of the test temperature,but the ductile brittle transition temperature does not appear till the test temperature decreases to-60 ℃. The yield strength and tensile strength of HCT980 X ＋ Z increase with the decrease of test temperature,and the yield strength shows a rapid increasing trend when the temperature drops below-45 ℃ to-50 ℃. The decline of the elongation is not obvious when the test temperature drops from room temperature to-60 ℃. The fracture analysis shows that HCT980 X ＋ Z is gradually transformed from ductile to brittle when the temperature drops below-40 ℃.