Unique Solidification Cracking Mechanism in Ultra-Low Interstitial Iron and Iron Alloy Weld Metal

本提案的目的是确定，表征和模拟在高纯度铁基合金中观察到的凝固裂纹的新机制。这些合金被认为不受凝固开裂的影响，但它们惊人的抗裂性却违背了目前的理论。在这个项目中，研究了系统添加Ni， Mn, Mo, Nb, Ti， B和O的超低碳铁合金，以确定它们对凝固开裂的敏感性以及开裂发生时的机制。该研究计划将模型与实验研究相结合，包括通过变应变测试来测量合金的凝固开裂倾向，以及通过俄歇光谱来表征断口。差热分析（DTA）确定了所选合金中糊状区的长度，Gleeble和DTA确定了固态相变对焊缝收缩应力的膨胀/收缩影响。重要的是，“干净”的铁基合金能够抵抗凝固开裂，因为它们代表了当前选择用于船舶、桥梁和建筑物的高强度、高韧性结构合金的趋势

Devletian9772052The objective of this proposal is to determine, characterize and model a new mechanism for solidification cracking observed in high purity iron-base alloys. These alloys were thought to be immune to solidification cracking and their surprisingly poor cracking resistance defies current theory. In this project ultra-low carbon iron alloys that contain systematic additions of Ni, Mn, Mo, Nb, Ti, B, and O are examined to determine their susceptibility to solidification cracking and the mechanism of cracking when it occurs. The research plan combines modeling with experimental studies, including varestraint testing to measure the solidification cracking tendencies of the alloys and characterization of fracture surfaces by Auger spectroscopy. Differential thermal analysis (DTA) establishes the length of the mushy zone in the selected alloys and the Gleeble and DTA determine the expansion/contraction effects of solid state phase transformations on weld shrinkage stresses.%%%It is important that "clean" iron-based alloys be resistant to solidification cracking since they represent the current trend in selection of high strength, high toughness structural alloys for applications in ships, bridges and buildings.***