淬火温度对45Mn2V/Q345复合锯片用钢组织性能的影响

Effect of quenching temperature on microstructure and properties of 45Mn2V/Q345 composite steel for saw blade

测定了45Mn2V/Q345复合锯片用钢的力学性能,结合对显微组织及拉伸断口形貌的观察讨论了淬火温度对其组织性能的影响。结果表明:当淬火温度由860℃降至830℃时,试验钢的强度明显增加,伸长率有所降低,且拉伸断口上沿复合界面处产生了严重的分层现象。显微组织的观察显示,与860℃淬火试验钢相比,淬火温度为830℃时45Mn2V覆板的组织有所细化,硬度上升,由于此温度高于45Mn2V覆板的Ac3温度而低于Q345基板的Ac3温度,故Q345组织中出现了较多的铁素体,硬度相应降低,这导致两者的硬度差增加;此外,较低的淬火温度也降低了碳原子的扩散能力,使复合界面处的过渡层厚度变小。上述因素不仅使各层金属在拉伸过程中形成更大的不均匀变形,而且也加剧了复合界面处的应力集中,导致断口上产生更严重的分层。因此,为使45Mn2V/Q345复合钢板获得更优的综合力学性能,进而增加锯片的使用寿命,其淬火温度应略高于Q345基板的Ac3温度。

The mechanical properties of 45Mn2V/Q345 composite steel for saw blade were measured,then the effects of quenching temperature on the microstructure and properties of the tested steel were discussed by the observation of microstructure and morphology of tensile fracture.The results show that when the quenching temperature decreases from 860℃to 830℃,the strength of the tested steel increases obviously,while the elongation decreases and serious delamination occurs along the composite interface at the tensile fracture.The microstructure observation shows that compared with the tested steel quenched at 860℃,the microstructure of 45Mn2V cladding is refined and its hardness increases when the quenching temperature is 830℃.Since 830℃is higher than the Ac3 temperature of 45Mn2V cladding but lower than that of Q345 substrate,more ferrite appears in the microstructure of Q345 and the hardness decreases correspondingly,which leads to the increase of the hardness difference between 45Mn2V steel and Q345 steel.Moreover,the lower quenching temperature also decreases the diffusion ability of carbon atoms,which results in the decrease of thickness of the transition layer at the interface.These factors not only make the deformation of each layer more inhomogeneous in tensile process,but also intensify the stress concentration at the composite interface,which results in the more serious delamination on the fracture.Therefore,to obtain better integrated mechanical properties of 45Mn2V/Q345 composite steel plate and prolong service life of saw blade,the quenching temperature should be slightly higher than the Ac3 temperature of Q345 substrate.