中碳钢水下湿法激光焊接焊缝成形行为与性能

Forming Behavior and Properties of Medium Carbon Steel by Direct Underwater Laser Beam Welding

为了探索水下湿法激光焊接的可行性,使用光纤激光器探讨了激光功率、离焦量、水深等因素对45钢湿法焊缝成形性的影响,对比研究了空气中焊接和水下焊接焊缝的组织性能。结果表明,水下湿法激光焊接过程中,在水中入射激光和工件表面之间形成了一个“激光通道”,这个通道能否稳定存在影响着焊接的稳定性。不同的激光功率对应不同的水深阈值,当水深超过此阈值后,水会对激光产生强烈的屏蔽作用,导致焊接无法进行。激光功率、离焦量和水深影响湿法焊接焊缝的成形性,激光功率增加有利于形成外观良好的焊缝,适当的负离焦有利于形成具有较大深宽比的焊缝,水深增加不利于焊缝成形。空气中焊接焊缝中心主要是珠光体+铁素体,而水下焊接的焊缝主要是马氏体和少量残余奥氏体。水下焊接焊缝硬度高于空气中焊接,拉伸强度达606 MPa,达到基体拉伸强度的94.8%,断后伸长率降低至3.1%。

To discuss the feasibility of direct underwater laser beam welding(ULBW),an optical fiber laser was used to investigate the effects of the laser power,the defocus distance and the depth of water on the underwater wet welding of 45 steel.The microstructure and properties of onshore welding and underwater welding was comparatively studied.Results show that a‘beam channel’is formed in the water between the incident laser beam and the surface of workpiece during the process of direct underwater laser welding.The stability of the welding is upon that of the‘beam channel’.The water depth thresholds vary according to different laser powers.Once the water depth exceeds the certain threshold,a strong hindering effect on the laser induced by the water is formed,which leads to the failure of the welding.The laser power,the defocus distance and the depth of water have significant influence on the quality of the weld bead.The increase of laser power improves the welding quality,and the appropriate negative defocus leads to the higher depth-width ratio welds.However,the increase of water depth has the negative effects.The microstructure of onshore welding is mainly composed of pearlite and ferrite.However,it is martensite and a small amount of residual austenite in underwater welding.The microhardness of the underwater welding is higher than that of the onshore welding.The tensile strength of the underwater welding is 606 MPa,which is 94.8%of the substrate,while the percentage elongation after fracture is only 3.1%.