热输入对Q550钢焊接接头动态拉伸变形行为的影响

Effect of Heat Input on Dynamic Tensile Deformation Behavior of Q550 Steel

研究了不同热输入焊条电弧焊Q550钢接头的显微组织特征,及其在不同应变速率下的力学行为。结果表明,在热输入小于18 k J/cm时,随着热输入的增加接头熔合区针状铁素体的含量增多,热影响区粗晶区的晶粒尺寸增大。随着应变速率的提高接头断裂延伸率和抗拉强度均有不同程度的提高,断口的大韧窝深度变大,小韧窝区域减少。在高速拉伸过程中位错滑移的阻力增大,位错滑移速度远低于载荷增大速度,随着应变速率的提高屈服强度和抗拉强度都提高。随着热输入的增加接头熔合区针状铁素体的比率增大,这是其拉伸性能对应变速率的敏感性增大的主要原因。

Q550 steel was welded by shielded metal arc welding with varying heat inputs, and then the microstructure of the weld joint was characterized, while the effect of strain rate on its mechanical be- havior were examined. The results show that when the heat input below 18 kJ/cm, with the increasing heat input, acicular ferrite content of the fusion zone and the grain size of the heat affected zone in- creased. With the increasing strain rate, the elongation and tensile strength of the welded joint increased to different extents. With the increasing heat input, the depth of large dimples increased, while the area of small dimples decreased in the fractured surface. During high speed tension, the resistance to disloca- tion slip increased, however the propagating rate of dislocation slip far behind the increasing speed of load, which led to increase in yield strength and tensile strength with the increase of strain rate. With the increasing heat input, acicular ferrite content of fusion zone increased, which is the main reason for the in- crease of sensitivity of tensile property to strain rate.