预热温度对盾构刀盘堆焊组织和性能的影响

为解决大直径刀盘拼装焊接后残余应力大、产生延迟裂纹的问题，提出通过控制预热温度提高堆焊质量的方案。试验采用自保护药芯焊丝对盾构刀盘使用的Q345R材料进行堆焊，分别研究预热温度为50、100、150、200 ℃时堆焊组织和性能的变化。结果表明： 经过100 ℃预热后，残余应力最小，冲击韧性最好，显微硬度梯度变化幅度最小，综合力学性能最佳。将试验得出的结论用于指导刀盘堆焊时预热温度的选取，证明通过选取合适的预热温度，刀盘焊接后UT探伤结果一次合格率达到100%，在实际应用中取得了良好的效果。

Influence of Preheating Temperature on Surfacing WeldingMicrostructure and Properties of Shield Cutterhead

Large residual stress and delayed crack would be produced after assembly and welding of large diameter cutterhead, hence, the scheme of improving the surfacing welding quality by controlling preheating temperature is put forward. The self protecting flux cored wire is used to weld the shield tool plate by material Q345R, and the variations of surfacing welding structure and performance at the preheating temperature of 50, 100, 150 and 200 ℃ are studied respectively. The results show that after preheating by 100 ℃, the residual stress is the least, the impact toughness is the best, the microhardness gradient variation is the least, and the comprehensive mechanical property is the best. The conclusions obtained by the test are used to guide the selection of preheating temperature for surfacing welding of the cutterhead. It has been proved in practice that by selecting the appropriate preheating temperature, the one time pass rate of UT flaw detection results after welding of the cutterhead reaches 100%, and good results have been achieved in practical application.