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A review of current LME test methods and suggestions for developing a standardized test procedure
Welding in the World ( IF 2.1 ) Pub Date : 2021-01-11 , DOI: 10.1007/s40194-020-01050-7
C. DiGiovanni , E. Biro

To improve automotive fuel economy, automobile manufacturers are minimizing the weight of the body-in-white. To do this, they are adopting new 3rd generation advanced high strength steels that have excellent strength and ductility. However, these steels are also prone to liquid metal embrittlement (LME) cracking; intergranular cracks caused by molten zinc, from the galvanized coating, penetrating the steel substrate during the resistance spot welding (RSW) process. These cracks are not acceptable to automobile manufacturers as it is unknown how LME cracks affect joint strength during weld service. To decrease LME cracking, extensive research into understanding its governing metallurgy, optimizing welding parameters, and comparing the LME sensitivity of multiple grades has been done. Most of this work was done using hot-tension testing or RSW testing. However, as there is no standard methodology for these tests, producing results that were difficult to compare. This review examined test methodologies for hot-tension and RSW testing LME severity. It was determined that the usefulness of LME testing could be improved if test methods reflected the temperature and stress-state of the welding process, facilitated comparisons between tests, and quantified results were reported. Recommendations are provided to improve hot-tension and RSW tests to meet these goals.



中文翻译:

回顾当前的LME测试方法以及制定标准化测试程序的建议

为了提高汽车的燃油经济性,汽车制造商正在使白车身的重量最小化。为此,他们采用了具有出色强度和延展性的新型第三代高级高强度钢。但是,这些钢还容易发生液态金属脆化(LME)裂纹。在电阻点焊(RSW)过程中,由镀锌层产生的熔融锌引起的晶间裂纹会穿透钢基材。这些裂纹对于汽车制造商来说是不可接受的,因为未知LME裂纹如何影响焊接服务期间的接头强度。为了减少LME裂纹,已经进行了广泛的研究,以了解其控制冶金,优化焊接参数以及比较多个等级的LME敏感性。大部分工作是使用热张力测试或RSW测试完成的。但是,由于这些测试没有标准方法,因此产生的结果很难比较。这篇评论检查了热法和RSW测试LME严重性的测试方法。如果测试方法能够反映焊接过程的温度和应力状态,促进测试之间的比较并报告量化结果,则可以确定LME测试的有用性可以得到提高。提供了一些建议来改进热拉伸和RSW测试,以实现这些目标。如果测试方法能够反映焊接过程的温度和应力状态,便于进行测试之间的比较并报告量化结果,则可以确定LME测试的有用性可以得到提高。提供了一些建议来改进热拉伸和RSW测试,以实现这些目标。如果测试方法能够反映焊接过程的温度和应力状态,促进测试之间的比较并报告量化结果,则可以确定LME测试的有用性可以得到提高。提供了一些建议来改进热拉伸和RSW测试,以实现这些目标。

更新日期:2021-01-11
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