Structure-Processing Relationships for Welding New Steels with Small Alloying Additions

拟议的研究将解决该行业每天在确定焊接某些合金的可行性、是否需要进行热处理或是否有可能开裂时遇到的焊接性实际问题。目前，钢的焊接主要是基于经验知识的积累，而对相变和加工现象的基本知识的定量使用很少。虽然目前的经验知识基础对传统钢很有帮助，但它不能为含有少量影响组织的合金元素的现代钢提供可靠的指导。在不太了解焊接的钢中，有耐火钢、抗震钢、高级微合金化管线钢，以及新修订标准中接受的微合金化元素的传统结构钢。目前行业中的故障排除工作旨在通过试错来扩展经验知识库，当需要在多个应用程序中重复时，这是一种缓慢、昂贵和浪费的方法。这项拟议工作的科学目标是通过使用实际中可获得的焊接参数，如电流、电压功率、行进速度、热输入和熔敷速度来预测焊缝的性能，如硬度、强度、残余应力或冷裂纹敏感性。项目方法既是理论的，也是实验的。理论部分涉及冶金、热和质量传输、相变理论、移动热源以及质量和能量平衡理论。实验部分包括金相学和膨胀学、机械性能测试、焊接热成像和全尺寸原型测试。产生的新知识将作为一套可靠的量化指南转移到加拿大工业，用于设计当前成分的钢的焊接件的最佳实践。加拿大工业将受益于处理新钢的能力的扩大，焊接程序的更快发展，以及以更高质量和更高生产率焊接的能力。

The proposed research will address practical problems of weldability which are encountered by the industry on a daily basis when determining the feasibility of welding certain alloys, the need for heat treatment, or the potential for cracking. The welding of steel is currently based mostly on an accumulation of empirical knowledge, and quantitative use of fundamental knowledge of phase transformations and processing phenomena is rare. While the current empirical base of knowledge has been helpful with traditional steels, it is unable to provide reliable guidelines for modern steels which have small amounts of alloying elements that affect the microstructure. Among the steels not well understood for welding are fire-resistant steels, seismic steels, high grade microalloyed pipeline steels, and traditional structural steels with microalloying elements accepted in the new revised standards. Current troubleshooting efforts in industry aim at expanding the empirical knowledge base by trial and error, which is a slow, expensive, and wasteful approach when it needs to be repeated across multiple applications. The scientific objective of the proposed work is to predict the properties of a weld such as hardness, strength, residual stresses, or cold cracking susceptibility by using weld parameters accessible in practice such as current, voltage power, travel speed, heat input, and deposition rate. The project approach is simultaneously theoretical and experimental. The theoretical part involves metallurgy and heat and mass transport, and theories of phase transformations, moving heat sources, and mass and energy balances. The experimental part involves metallography and dilatometry, testing of mechanical properties, thermal imaging of welding, and testing of full-scale prototypes. The new knowledge generated will be transferred to Canadian industry as a set of reliable, quantitative guidelines for best practices in the design of weldments for steels with current compositions. Canadian industry will benefit from expanded abilities to deal with new steels, faster development of welding procedures, and a capability to weld with higher quality and higher productivity.