Q460钢焊接接头组织及动态断裂行为的研究
发布人：上海艾荔艾合金股份有限公司www.shailiai.cn
更新时间：2016-03-25
通过调整焊接热输入研究了 Q460 低合金高强钢 CO2 气体保护药芯焊接接头的组织及其对不同温度下动态断裂韧性(JId)的影响规律, 探究了影响接头动态断裂行为的机理.
Q460钢焊接接头组织及动态断裂行为的研究STUDY ON MICROSTRUCTURE AND DYNAMIC FRACTURE BEHAVIOR OF Q460 STEEL WELDING JOINTS 通过调整焊接热输入研究了 Q460 低合金高强钢 CO2 气体保护药芯焊接接头的组织及其对不同温度下动态断裂韧性(JId)的影响规律, 探究了影响接头动态断裂行为的机理. 结果表明, 低热焊接输入的接头熔合区(FZ)柱状晶界面处存在仿晶界型铁素体; 随热输入增加, FZ 柱状晶形态特征逐渐减弱、仿晶界铁素体消失, FZ 以针状铁素体组织为主, 且随热输入的增加针状铁素体平均尺寸增大. 在室温至-70 ℃范围内, 中等热输入的焊接接头均表现出优异的动态断裂韧性, 而低热输入的接头动态断裂韧性值最低. 随温度由室温降低至-70 ℃, Q460 钢焊接接头动态断裂机制发生了由延性断裂逐渐向解理脆性断裂的转变. 低热输入焊接接头 FZ 柱状晶界面具有平面生长特征的仿晶界铁素体, 易诱发低温下裂纹沿晶快速扩展. 研究发现细小针状铁素体组织, 在低温动态断裂过程中, 由于可有效地阻碍裂纹扩展, 成为其维持高动态断裂韧性的要因。
Effects of welding heat input on the microstructure and dynamic fracture toughness (JId) of the CO2 shielded arc welded joints of Q460 high strength low alloy steel were investigated. The mechanism of effects on the dynamic facture behavior of the welded joint was also discussed. The results showed that there existed the allotriomorphic ferrite at the columnar interface in the fusion zone of welded joint under the condition of low heat input. The morphological characteristics of columnar crystal in the fusion zone gradually decreased and the allotriomorphic ferrite disappeared as the heat input increased. The fusion zone was mainly composed of acicular ferrite, and its average size increased with increasing heat input. The welded joint exhibited the optimal dynamic fracture toughness under the condition of medium heat input while it showed the lowest value under low heat input within the temperature range of -70 ℃ to room temperature. When the temperature decreased from room temperature to -70 ℃, the dynamic fracture mechanism of Q460 welded joint changed from ductile fracture to brittle cleavage fracture. Under the condition of low heat input, the allotriomorphic ferrite characterized by the planar growth at the columnar interface in the fusion zone of welded joint can lead to the rapid intergranular crack propagation at low temperature. The fine acicular ferrite in the fusion zone of the welding joint obtained at medium heat input which can hinder the crack propagation during the dynamic fracture at low temperature to the greatest extent is the reason why the welded joint exhibits high dynamic fracture toughness.
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