中部槽构件摆动电弧窄间隙GMAW不同打底衬垫焊接成形及组织性能

Weld bead formation,microstructure and properties of middle trough component by swing arc narrow gap GMAW with different backings

【目的】进行I形坡口窄间隙焊接时通常涉及到使用衬垫,不同材料的衬垫会对窄间隙焊接打底焊缝的显微组织及力学性能产生影响。为了研究不同打底衬垫对焊接过程的影响规律,该文采用窄间隙摆动电弧GMAW并配合使用陶瓷、铜及钢3种不同材料衬垫对中部槽所用的50 mm厚的ZG30SiMn/NM450(简称ZG/NM)组合进行了焊接。【方法】焊接完成后,对打底焊道进行了显微组织观察、硬度及拉伸等力学性能测试。【结果】试验结果表明,在摆动电弧的作用下,成功抑制了焊缝的侧壁未熔合缺陷,体现出窄间隙摆动电弧GMAW对ZG/NM构建具有良好的适应性。由于衬垫材料的不同,接头打底焊道过热区宽度与组织及焊缝组织存在差异。过热区随衬垫导热系数的升高逐渐变窄,晶粒尺寸逐渐减小,焊缝中块状铁素体含量也逐渐变少。焊缝中心硬度最低,由于冷却速率的差异,导致陶瓷衬垫焊缝中心的硬度最低,而水冷铜的硬度最高。水冷铜打底焊道的高强度归因于较低的块状铁素体含量。【结论】该研究通过窄间隙摆动电弧GMAW技术和不同衬垫材料的应用,为ZG/NM组合的焊接提供了有益的试验结果,对焊接接头的性能和微观结构进行了深入分析,为相关领域的进一步研究提供了参考依据。

[Objective]When performing I-groove narrow gap groove welding,the use of backings was usually involved.Different materials of backings would have an influence on microstructure and mechanical properties of root weld by narrow gap welding.In order to study effects of different backings on welding process,in this study,narrow gap oscillating arc GMAW combined with ceramic,copper,and steel backings was to used weld 50 mm thick ZG30SiMn/NM450(short for ZG/NM)combination in middle trough.[Methods]After welding,root weld was observed for microstructure and tested for hardness,tensile strength and other mechanical properties.[Results]The experimental results showed that under the action of oscillating arc,incomplete fusion defects on the sidewalls of the weld were successfully suppressed,demonstrating good adaptability of narrow gap oscillating arc GMAW to ZG/NM combination.Due to different materials of backings,there were differences in width and microstructure of heat-affected zone in root weld,as well as in microstructure of weld.Width of heat-affected zone became narrow with the increase of thermal conductivity of backings,grain size gradually decreased,and content of blocky ferrite in the weld gradually decreased.The lowest hardness was found in the center of weld,ceramic backing pad had the lowest hardness in the center of weld due to differences in cooling rate,while water-cooled copper had the highest hardness.High strength of water-cooled copper root weld was attributed to its lower content of blocky ferrite.[Conclusion]Through the application of narrow gap oscillating arc GMAW technology and different backing materials,this study provided valuable experimental results for the welding of ZG/NM combination,and offered a thorough analysis of performance and microstructure of welded joints,providing a reference for further research in related fields.