模具及温度对1 500 MPa级热成形钢组织性能的影响

采用光学显微镜、扫描电镜，以及单向拉伸试验等手段，研究了模具形状及加热温度对1 500 MPa级热成形钢组织性能及其回弹性的影响。结果表明，初始冷轧钢板组织主要是铁素体和珠光体。随着加热温度的升高，热成形后钢板的强度显著升高后逐渐降低，加热温度860 ℃时性能较优。由于U型件在热成形时发生变形，侧面的抗拉强度比底部的低，在860 ℃时的回弹最小，平均为16.6°。在加热温度860 ℃后采用U型模具的热成形钢的各项性能较优。 

Influence of die and temperature on microstructure and properties of 1 500 MPa thermoforming steel

This paper studies the effects of mould shape and heating temperature on microstructure and resilience of thermoforming steel of 1 500 MPa gradeutilizing optical microscope, scanning electron microscope, and unidirectional tensile test. Results show that the microstructure of the initial cold-rolled steel sheet is mainly composed of ferrite and pearlite. With the increase of heating temperature, the strength of the thermoforming steel sheet increases significantly at first and then decreases gradually. The optimal heating temperature is 860 ℃. Due to the deformation of the U-shaped part during thermal forming, the tensile strength of the sides is lower than that of the bottom part, which will cause the work piece rebound. According to experiments, U-shaped parts rebound most slightly at 860 ℃ with an average rebound angle of 16.6. In conclusion, thermoforming steel with optimum properties can be produced by adopting U-shaped mould when the material temperature reaches 860 ℃.