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利用Cr-Mo-Ni-W系焊丝对Q345钢进行堆焊,焊后对各堆焊试样分别空冷及300、400、500℃回火处理。通过金相显微分析、硬度以及冲击试验,研究了焊后不同处理条件下熔覆层的组织、硬度及韧性。结果表明:焊后空冷条件下,熔覆层主要表现为粗大的片状马氏体,硬度分布不均,韧性较低脆性较高,断口表现为典型的脆性断裂;焊后随着回火温度的升高,熔覆层中粗大片状马氏体逐渐减少,硬度分布逐渐均匀化,同时,韧性逐渐改善。当回火温度达到400℃时,熔覆层中组织为细小的板条状回火马氏体,硬度及韧性较高,断口中出现大量的断裂韧窝;当回火温度达到500℃时,熔覆层出现大量的粒状回火索氏体,硬度较低。
The Cr-Mo-Ni-W wire was used to build Q345 steel. After welding, the samples were air-cooled and tempered at 300, 400 and 500 ℃, respectively. The microstructure, hardness and toughness of cladding layer under different treatment conditions were studied by metallographic analysis, hardness and impact test. The results show that under the condition of air-cooling after welding, the cladding layer mainly shows coarse sheet martensite with uneven distribution of hardness, high toughness and high brittleness, and the fracture shows typical brittle fracture. With the increase of tempering temperature , The lamellar martensite in the cladding layer gradually decreases and the hardness distribution gradually becomes uniform, meanwhile, the toughness gradually improves. When the tempering temperature reaches 400 ℃, the microstructure of the cladding layer is small lath tempered martensite with high hardness and toughness, a large number of fracture dimples appear in the fracture surface. When the tempering temperature reaches 500 ℃, The cladding layer appears a large number of granular tempered sorbite, hardness is low.