Formation mechanism analysis of the type-II boundary of dissimilar steel joint with the filler metal of ER309
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摘要: 对填充ER309焊丝的1Cr18Ni9Ti/Q235异种钢接头二型边界形成机理进行了研究. 结果表明，二型边界是由碳钢侧不均匀混合区内Ni质量分数为5% ~ 6%的位置所形成的凝固界面向焊缝中心一侧迁移而形成的. 当部分熔合区和不均匀混合区内Ni质量分数小于5% ~ 6%的区域(N区)为熔池凝固提供δ相基底，或者部分熔合区提供γ相基底且N区提供δ相基底的情况下，碳钢侧熔合边界附近均会形成二型边界；当部分熔合区提供δ相基底且N区提供γ相基底，或者部分熔合区和N区均提供γ相基底的情况下均不会形成二型边界.Abstract: Formation mechanism of the type-II boundary of 1Cr18Ni9Ti/Q235 dissimilar steel joint with the filler metal of ER309 was studied. The results showed that the type-II boundary was formed by the migration of the solidified boundaries γ/γ from the position of the 5% ~ 6% Ni mass fraction in the unmixed zone to weld center. Under the condition that the partial fusion zone and the zone of Ni mass fraction less than 5% ~ 6%(N zone) in the unmixed zone provided the substrate of δ phase, or the partial fusion zone provided the substrate of γ phase and N zone provided the substrate of δ phase, the type-II boundary all could form near the fusion boundary of the carbon steel side. The type-II boundary could not form under the condition that the partial fusion zone provided the substrate of δ phase and N zone provided the substrate of γ phase, or the partial fusion zone and N zone provided the substrate of γ phase.
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图 1 细颗粒焊剂约束电弧UNGW示意图
Figure 1. Schematic diagram of UNGW with constricted arc by fine granular flux
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图 2 异种钢接头碳钢侧熔合区的结构示意图
Figure 2. Structure schematic diagram of the fusion zone by the carbon steel side of dissimilar steel joint
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图 3 熔合过渡区附近的二型边界形貌
Figure 3. Morphology of type-Ⅱ boundary by the transition zone of fusion. (a) the first morphology; (b) the second morphology; (c) the third morphology
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图 4 异种钢接头碳钢侧熔合边界的凝固组织示意图(部分熔合区及Q区均提供δ相基底)
Figure 4. Schematic diagram of solidified microstructure of the fusion boundary by the carbon steel side of dissimilar steel joint (Partial fusion zone and Q zone provide the substrate of δ phase)
表 1 焊接参数
Table 1 Welding parameters
电弧电压U/V 焊接电流I /A 焊接速度vh/(mm·s−1) 焊丝伸出长度Ls/mm 脉冲频率 f /Hz 29.6 296 7.3 24 139 
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表 2 母材和焊丝成分(质量分数，%)
Table 2 Compositions of the base metal and wire
材料 C Mn Si Cr Ni Ti S P Fe Q235 ≤ 0.20 ≤ 1.40 ≤ 1.35 — — — ≤ 0.045 ≤ 0.045 余量 ER309 0.050 1.33 0.60 22.60 13.22 — 0.009 0.022 余量 1Cr18Ni9Ti ≤ 0.12 ≤ 2.00 ≤ 1.00 18.00 10.50 ≤ 0.80 ≤ 0.030 ≤ 0.035 余量
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