Method development for the avoidance of liquid metal embrittlement during resistance spot welding of advanced high strength steels

先进高强度钢电阻点焊过程中避免液态金属脆化的方法开发

• 批准号: 426686311
• 负责人: Professor Dr.-Ing. Gerson Meschut
• 金额: --
• 依托单位: Laboratorium für Werkstoff- und Fügetechnik (LWF)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/426686311?language=en
• 关键词: Method; development; avoidance; liquid; metal

Until today, investigations on liquid metal embrittlement (LME) mainly focus on single aspects of the phenomenon only – or analyze specific influencing factors, material thickness combinations (MTC) or crack intensities. As a result, some of the existing studies state controversial results. Consequently, it is impossible to identify principal correlations between the various investigations. So far, a holistic approach is missing, which systematically investigates influencing factors of LME with a consistent method. Investigations on advanced high strength steel (AHSS) grades with an ultimate tensile strength above 1000 MPa are necessary to facilitate lightweight design concepts. These high strength steel grades exhibit LME cracks both inside and outside the electrode indentation area, which is critical for the joint strength. Additionally, they show a significantly higher penetration depth of LME cracks. A comprehensive characterization of LME crack types is necessary to improve confidence and security in processing AHSS. A precise classification of different crack sizes and geometries shall be established, enabling the determination of tolerable/critical LME intensities regarding effects on the load bearing capacity of crack-afflicted spot welds. Numerical simulations of temperature, stress and strain fields and their interactions support the experimental investigations. These values are not accessible with conventional measurement techniques. The simulation thereby improves the process understanding, and extends experimentally tested parameter ranges. It allows the reproducible replication of different crack types in fine increments. The absence of experimental scattering, as well as a high grade of flexibility in terms of crack position and size, provide possibilities beyond any experimental setup. The described approach is suitable for evaluation of different MTCs, and development of potential LME prevention strategies.

直到今天，对液态金属脆化（LME）的研究主要集中在现象的单个方面，或者分析特定的影响因素、材料厚度组合（MTC）或裂纹强度。因此，现有的一些研究结果存在争议。因此，不可能确定各种调查之间的主要相关性。迄今为止，缺乏一种整体的方法，即系统地研究LME的影响因素，采用一致的方法。研究极限抗拉强度在1000 MPa以上的高级高强度钢（AHSS）等级对于促进轻量化设计概念是必要的。这些高强度钢种在电极压痕区域的内部和外部都表现出LME裂纹，这对接头强度至关重要。此外，它们显示出LME裂纹的显著更高的穿透深度。全面表征LME裂纹类型对于提高加工AHSS的置信度和安全性是必要的。应建立不同裂纹尺寸和几何形状的精确分类，以便确定与受裂纹影响的点焊的承载能力有关的容许/临界LME强度。数值模拟的温度，应力和应变场及其相互作用支持的实验研究。这些值是无法用传统的测量技术获得的。模拟从而提高了工艺理解，并扩展了实验测试的参数范围。它允许以精细增量再现不同裂纹类型。实验散射的情况下，以及在裂纹的位置和大小方面的高等级的灵活性，提供了超越任何实验设置的可能性。所描述的方法是适合于不同的MTCs的评价，并制定潜在的LME预防策略。