Abstract Dilution represents the contribution from base material to weld metal and its important effects are complicated for multi-pass steel welds. In this study, the dilution was determined for each bead in a 3-pass gas tungsten arc (GTA) weld and a corresponding submerged arc (SA) weld. Different filler materials were used with each process, but both cases involved the deposition of filler wires into grooves in low-alloy (SA508) ferritic steel plates. Martensite and bainite were observed in the heat-affected zone (HAZ) of the base material in both cases. Acicular ferrite dominated the SA weld metal, while this phase was mixed with martensite and bainite in the GTA weld metal. Thermal-metallurgical modelling was performed and it correctly predicted the microstructures in the base-material HAZ for both the GTA and SA weldments. It also captured the GTA weld metal microstructure, when transformations from austenite to acicular ferrite and bainite were treated as being equivalent. However, this approximation led to overestimation of the martensite volume fraction in the SA weld metal. The modelling revealed that increases in dilution favour martensite formation but suppress bainite/ferrite transformations, owing to the melting of greater quantities of the base material, which has a relatively high hardenability.

中文翻译：

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稀释对多道钢焊缝合金含量和显微组织的影响

摘要 稀释是母材对焊缝金属的贡献，对于多道钢焊缝其重要影响是复杂的。在本研究中，对 3 道钨极气体保护焊 (GTA) 焊缝和相应的埋弧焊 (SA) 焊缝中的每个焊道确定了稀释度。每种工艺都使用不同的填充材料，但两种情况都涉及将填充焊丝沉积到低合金 (SA508) 铁素体钢板的凹槽中。在两种情况下，在母材的热影响区 (HAZ) 中都观察到马氏体和贝氏体。针状铁素体在 SA 焊缝金属中占主导地位，而在 GTA 焊缝金属中该相与马氏体和贝氏体混合。进行了热冶金建模，它正确预测了 GTA 和 SA 焊件的母材热影响区中的微观结构。它还捕获了 GTA 焊缝金属微观结构，当从奥氏体到针状铁素体和贝氏体的转变被视为等效时。然而，这种近似导致对 SA 焊缝金属中马氏体体积分数的高估。模型显示，稀释度的增加有利于马氏体的形成，但会抑制贝氏体/铁素体的转变，这是由于大量具有相对高淬透性的基材熔化。