焊后热处理对Q235钢熔覆层组织和耐磨性的影响

Effect of Postweld Heat Treatment on Microstructure and Wear Resistance of Q235 Steel Hardfacing Layer

利用药芯焊丝对Q235钢进行堆焊,堆焊后分别采取直接空冷和焊后450℃×3h回火处理,并对回火前后熔合线两侧的热影响区和熔覆层进行了显微组织、显微硬度梯度以及熔覆层的耐磨性能试验。试验结果表明:焊后空冷条件下,靠近熔合线的热影响区存在大量的魏氏组织,熔覆层为粗大的片状马氏体和大量残余奥氏体,且基体与熔覆层显微硬度梯度较大;堆焊后经回火处理,热影响区的魏氏组织基本消失,熔覆层组织转变为回火屈氏体+少量残余奥氏体,硬度较高,耐磨性较好,相比焊后空冷熔覆层的耐磨性提高约24%,同时基体与熔覆层间的最大显微硬度梯度值减小了约70HV。

Surfacing welding experiment was carried out with Q235 steel materials as matrix using flux-cored wire, the specimens were air-cooled directly and tempered treatment at 400 ℃for 3 h respectively after welding. Then, microstructure, microhardness and wear resistance were measured. The results show that there is a large number of Widmanstatten structure in heat affected zone, a large amount of thick plate Martensite and residual Austenite in cladding layer, and the microhardness gradient between substrate and the cladding layer is larger under the condition of air cooling after welding; After tempering treatment, the Widmanstatten structure of the heat affected zone disappears, and the microstructure of the hardfacing layer transforms into temper Troostite and a small amount of residual Austenite. It has high hardness and wear resistance. The wear resistance of the sample heat treated by tempering increases 24% compared with the direct air-cooled. Meanwhile, between the substrate and the cladding layer, the maximum microhardness gradient reduces about 70 HV.