scholarly journals Significance of cutting plane in liquid metal embrittlement severity quantification

2021 ◽  
Vol 3 (6) ◽  
Author(s):  
C. DiGiovanni ◽  
L. He ◽  
C. Hawkins ◽  
N. Y. Zhou ◽  
E. Biro
Keyword(s):  
Liquid Metal ◽  
Cross Section ◽  
Standard Procedure ◽  
Fuel Efficiency ◽  
Zinc Coating ◽  
High Strength Steels ◽  
Absolute Measurement ◽  
Cutting Plane ◽  
Liquid Metal Embrittlement ◽  
Welding Parameters

AbstractThe automotive industry is turning to advanced high strength steels (AHSS) to reduce vehicle weight and increase fuel efficiency. However, the zinc coating on AHSS can cause liquid metal embrittlement (LME) cracking during resistance spot welding. To understand the problem, the severity of the cracking must be measured. Typically, this is done from the weld cross-section. Currently, there is no standard procedure to determine which plane through the weld must be examined to gauge cracking severity, leading to a variety of practices for choosing a cutting plane. This work compares the magnitude and variability of LME severity measured from the plane of exhibiting the most severe surface cracking to arbitrarily chosen planes. The plane exhibiting the most severe cracks had more and longer cracks on the cross-section than the arbitrarily chosen plane, resulting in a higher crack severity measurement. This higher absolute measurement increased the relative accuracy of the examination, allowing for fewer welds to be examined to precisely determine the effect of LME mitigation methods on cracking severity, how welding parameters affect LME cracking severity and the predicted LME affected strength of a particular weld.

scholarly journals Liquid Metal Embrittlement of Galvanized TRIP Steels in Resistance Spot Welding

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 787 ◽  
Author(s):  
Wook-Sang Jeon ◽  
Ashutosh Sharma ◽  
Jae Pil Jung
Keyword(s):  
Liquid Metal ◽  
Resistance Spot Welding ◽  
Spot Welding ◽  
High Strength Steels ◽  
High Strength ◽  
Liquid Metal Embrittlement ◽  
Surface Cracks ◽  
Resistance Spot ◽  
Research Activities ◽  
Microscopic Features

Liquid metal embrittlement (LME) in Zn-coated steels is a serious issue in automotive design. The risk of rising LME surface cracks in resistance spot welding (RSW) of Zn-coated high strength steels has triggered significant research activities across the globe. This paper presents a state-of-the-art review of the various phenomena and issues related to LME during RSW. Various aspects of LME surface cracks have been described in this review, focusing on the macro- and microscopic features of LME, spot weld cracks, the sensitivity of the LME cracks towards surface locations, welding conditions, and susceptibility to high strength and galvanized steels. We also focus on the effects of various processing factors, such as temperature, stress, microstructure, and the nature of the galvanized layer, related to studies with actual spot welds LME cracks. Finally, we summarize the possible mechanisms of embrittlement and the remedies for minimizing LME cracks, with suitable guidelines to suppress surface cracks during RSW.

scholarly journals Effect of Severe Welding Conditions on Liquid Metal Embrittlement of a 3rd-Generation Advanced High-Strength Steel

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1166
Author(s):  
Outhmane Siar ◽  
Yacine Benlatreche ◽  
Thomas Dupuy ◽  
Sylvain Dancette ◽  
Damien Fabrègue
Keyword(s):  
Liquid Metal ◽  
High Strength Steel ◽  
Spot Welding ◽  
High Strength ◽  
Holding Time ◽  
Liquid Metal Embrittlement ◽  
Welding Parameters ◽  
Advanced High Strength Steel ◽  
Electrode Force ◽  
Influential Parameters

The occurrence of liquid metal embrittlement (LME) during the resistance spot-welding of a zinc-coated Advanced High-Strength Steel (TRIP-aided AHSS) is investigated in this work. Welds are generated using controlled degradation of the welding conditions to favor the occurrence of LME cracks in a two-sheets homogeneous configuration. Detailed inspection of the welds shows that electrode misalignment, short holding time, low electrode force and long welding time constitute a propitious environment for both inner and outer LME cracks. A statistical analysis allows weighting and interpreting of the significance of the welding parameters. Electrode misalignment and reduced holding time appear as the most influential parameters in the design of experiment. Moreover, it is worth noting that standard ISO welding conditions are prone to avoid any LME cracks in the investigated two-sheets homogeneous configuration.

scholarly journals Liquid Metal Embrittlement of Advanced High Strength Steel: Experiments and Damage Modeling

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5451
Author(s):  
Konstantin Manuel Prabitz ◽  
Mohammad Z. Asadzadeh ◽  
Marlies Pichler ◽  
Thomas Antretter ◽  
Coline Beal ◽  
...  
Keyword(s):  
Liquid Metal ◽  
Damage Model ◽  
High Strength Steels ◽  
High Strength ◽  
Liquid Metal Embrittlement ◽  
High Ductility ◽  
Resistance Spot ◽  
Advanced High Strength Steels ◽  
Strain And Strain Rate ◽  
Resistance Spot Weld

In the automotive industry, corrosion protected galvanized advanced high strength steels with high ductility (AHSS-HD) gain importance due to their good formability and their lightweight potential. Unfortunately, under specific thermomechanical loading conditions such as during resistance spot welding galvanized, AHSS-HD sheets tend to show liquid metal embrittlement (LME). LME is an intergranular decohesion phenomenon leading to a drastic loss of ductility of up to 95%. The occurrence of LME for a given galvanized material mainly depends on thermal and mechanical loading. These influences are investigated for a dual phase steel with an ultimate tensile strength of 1200 MPa, a fracture strain of 14% and high ductility (DP1200HD) by means of systematic isothermal hot tensile testing on a Gleeble® 3800 thermomechanical simulator. Based on the experimental findings, a machine learning procedure using symbolic regression is applied to calibrate an LME damage model that accounts for the governing quantities of temperature, plastic strain and strain rate. The finite element (FE) implementation of the damage model is validated based on the local damage distribution in the hot tensile tested samples and in an exemplary 2-sheet resistance spot weld. The developed LME damage model predicts the local position and the local intensity of liquid metal induced cracking in both cases very well.

Zn-Assisted Liquid Metal Embrittlement of 980MPa Grade Advanced High Strength Steels

2019 ◽  
Vol 953 ◽  
pp. 3-8
Author(s):  
Ying Hua Jiang ◽  
Jian Zhou ◽  
Can Fu ◽  
Xue Bai
Keyword(s):  
Liquid Metal ◽  
Tensile Test ◽  
High Strength Steels ◽  
High Strength ◽  
Liquid Metal Embrittlement ◽  
Dp Steel ◽  
Structural Part ◽  
Resistance Spot ◽  
Advanced High Strength Steels ◽  
Automotive Body

Recently, the weight reduction of automotive body and crash safety become much more important factors. In addition, the corrosion resistance must be ensured for any material used in a structural part of automotive components. In an effort to satisfy these requirements, zinc-coated high strength steels have been developed. However, challenges to resistance spot weldability of zinc-coated high strength steel such as liquid metal embrittlement (LME) have emerged. In this study, the high temperature tensile test was conducted for 980MPa DP steel. And resistance spot welding was conducted for 980MPa DP steel and CP steel. The results show that the fracture behavior during tensile test are influenced by the temperature and strain rate. Cracks were formed on the weld surface of the DP steel after welding.

scholarly journals LME susceptibility of galvanised welded structures of high strength steels

2011 ◽  
Vol 2 (3) ◽  
pp. 442-447
Author(s):  
M. Vermeersch ◽  
W. De Waele ◽  
N. Van Caenegem
Keyword(s):  
Liquid Metal ◽  
High Strength Steels ◽  
High Strength ◽  
Short Description ◽  
Liquid Metal Embrittlement ◽  
Zinc Bath ◽  
Master Thesis ◽  
Extensive Test ◽  
Influencing Parameters ◽  
Set Up

Hot dip galvanizing is a very popular and well known process in corrosion protection of steel.However, very occasionally, cracks appear on structures when they leave the zinc bath. The responsiblecrack phenomenon appears to be liquid metal embrittlement. This phenomenon is already known for a longtime, but it is still not yet fully understood. The lack of fundamental theoretical knowledge and the absenceof accurate models to predict liquid metal embrittlement oblige engineers to set up extensive test programsto determine an area of process parameters in which safe design is guaranteed. A qualitativeunderstanding of the various influencing parameters during galvanizing is necessary to explain theoccurrence of liquid metal embrittlement. This knowledge is also helpful to design an experimental test setup and procedure for evaluating the influence of one parameter where the effect of other parameters shouldremain constant. This master thesis deals with the occurrence of liquid metal embrittlement whengalvanizing welded high strength steels. This paper gives an overview of the most important processparameters and gives a short description of possible future experimental work.

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