压下率对真空热轧NM360/Q345R复合板微观组织和拉伸断口的影响

Effect of reduction rates on microstructure and tensile fracture for vaccum hot-rolled NM360/Q345R clad plate

采用真空热轧法轧制NM360/Q345R复合板,借助光学显微镜、扫描电镜和元素能谱分析等手段,对压下率分别为30%、50%、70%和80%时的复合板进行了界面微观组织和拉伸断口分析.结果发现:复合界面平直,耐磨钢侧发生明显的脱碳现象,随着压下率增加,脱碳层厚度减小;当压下率为30%和50%时,界面附近有长条状或黑色点状夹杂物,经EDS分析为Mn和Si的氧化物,这些夹杂物的存在对界面结合质量有严重影响,拉伸断裂后复合界面出现明显的分层开裂;当压下率达到70%时,界面结合紧密,未发现孔洞和裂纹,断裂面上有大量明显韧窝,拉伸断口为典型韧性断裂方式.

NM360/Q345R clad plates were in a vacuum hot-rolled.The interficial microstructure and the tensile fracture of NM360/Q345R at30%,50%,70%and80%reduction ratios were studied by OM,SEM and EDS.It was found that the interface was flat.A significant decarbonization of the NM360occurred at the bonding interface.As reduction ratio increases,the width of the decarbonization becomes thin.When the reduction ratios are30%and50%,there are long strips or black dots of particles appearing near the interface.The black particles are Mn and Si oxides from the EDS,which have a negative effect on the bonding interface.Some obvious cracks were observed after the tensile tests.When the reduction ratio reached up to70%,the interface combined tightly and no voids or cracks existed,a large amounts of dimples appeared on the interface,indicating that the fracture type was ductile fracture.