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

拟议的研究将解决工业界在确定焊接某些合金的可行性、热处理的需要或开裂的可能性时每天遇到的可焊性的实际问题。钢的焊接目前主要基于经验知识的积累，而定量使用相变和加工现象的基础知识是罕见的。虽然目前的经验知识基础对传统钢有帮助，但它无法为具有少量影响微观结构的合金元素的现代钢提供可靠的指导。对于焊接还不太了解的钢有耐火钢、抗震钢、高等级微合金管线钢和具有新修订标准中接受的微合金元素的传统结构钢。当前工业中的故障排除努力旨在通过试错来扩展经验知识库，当需要在多个应用中重复时，这是一种缓慢、昂贵且浪费的方法。拟议工作的科学目标是通过使用实践中可获得的焊接参数（例如电流、电压功率、移动速度、热输入和熔敷率）来预测焊接性能，例如硬度、强度、残余应力或冷裂敏感性。项目方法同时是理论和实验。理论部分涉及冶金学和热量和质量传输，相变理论，移动热源，质量和能量平衡。实验部分包括金相学和金相测量、机械性能测试、焊接热成像和全尺寸原型测试。所产生的新知识将转移到加拿大工业，作为一套可靠的，定量的指导方针，用于当前成分钢的焊接件设计的最佳实践。加拿大工业将受益于扩大能力，以处理新的钢材，更快地发展焊接程序，并有能力焊接更高的质量和更高的生产率。

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.