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

这项建议的目的是确定、表征和模拟在高纯铁基合金中观察到的一种新的凝固裂纹机制。这些合金被认为不受凝固裂纹的影响，其惊人的抗裂性与当前的理论背道而驰。本课题研究了系统添加Ni、Mn、Mo、Nb、Ti、B、O等元素的超低碳铁合金的凝固开裂敏感性及开裂机理。该研究计划将建模与实验研究相结合，包括用Varestraint测试来测量合金的凝固开裂倾向，并用俄歇能谱对断口进行表征。差热分析(DTA)确定了选定合金中糊状区的长度，Gleeble和DTA确定了固态相变对焊接收缩应力的膨胀/收缩效应。%“清洁”铁基合金具有抗凝固开裂的能力，这一点很重要，因为它们代表了在船舶、桥梁和建筑应用中选择高强度、高韧性结构合金的当前趋势。

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.***