Liquid Metal Embrittlement in Resistance Spot Welding and Hot Tensile Tests of Surface-refined TWIP Steels

Automotive industry strives to reduce vehicle weight and therefore fuel consumption and carbon dioxide emissions. Especially in the auto body, material light weight construction is practiced, but the occupant safety must be ensured. These requirements demand high-strength steels with good forming an...

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Bibliographic Details
Published in:IOP conference series. Materials Science and Engineering 2016-03, Vol.118 (1), p.12002-12009
Main Authors: Barthelmie, J, Schram, A, Wesling, V
Format: Article
Language:English
Subjects:
Alloying
Automobile industry
Automotive bodies
Automotive engineering
Automotive fuels
Carbon dioxide
Crack initiation
Elongation
Ferritic stainless steels
Fracture mechanics
Fuel consumption
Heat treating
High strength steels
High temperature
Liquid metal embrittlement
Manganese
Parameter sensitivity
Resistance spot welding
Spot welds
Steel
Strain
Structural steels
Tensile tests
TWIP steels
Weight reduction
Welding parameters
Yield point
Zinc coatings
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Summary:Automotive industry strives to reduce vehicle weight and therefore fuel consumption and carbon dioxide emissions. Especially in the auto body, material light weight construction is practiced, but the occupant safety must be ensured. These requirements demand high-strength steels with good forming and crash characteristics. Such an approach is the use of high- manganese-content TWIP steels, which achieve strengths of around 1,000 MPa and fracture strains of more than 60%. Welding surface-refined TWIP steels reduces their elongation at break and produces cracks due to the contact with liquid metal and the subsequent liquid metal embrittlement (LME). The results of resistance spot welds of mixed joints of high-manganese- content steel in combination with micro-alloyed ferritic steel and hot tensile tests are presented. The influence of different welding parameters on the sensitivity to liquid metal embrittlement is investigated by means of spot welding. In a high temperature tensile testing machine, the influence of different parameters is determined regardless of the welding process. Defined strains just below or above the yield point, and at 25% of elongation at break, show the correlation between the applied strain and liquid metal crack initiation. Due to the possibility to carry out tensile tests on a wide range of temperatures, dependencies of different temperatures of the zinc coating to the steel can be identified. Furthermore, the attack time of the zinc on the base material is investigated by defined heating periods.
ISSN:1757-8981
1757-899X
DOI:10.1088/1757-899X/118/1/012002