Critical design parameters of the electrode for liquid metal embrittlement cracking in resistance spot welding

Murugan, Siva Prasad; Mahmud, Kaisar; Ji, Changwook; Jo, Ilguk; Park, Yeong-Do

doi:10.1007/s40194-019-00797-y

Cited by 36 publications

(9 citation statements)

References 24 publications

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“…A highly increased current, combined with a decreasing cooling capacity of the larger electrode cap is described as the assumed cause, while no information on the achieved nugget diameters as basis for a comparison of the used welding schedules is given. Murugan et al [19] study the individual effects of electrode design parameters on LME formation. They report a decreasing LME tendency for radius type electrode geometries compared to dome type electrodes.…”

Section: Introductionmentioning

confidence: 99%

Prevention of liquid metal embrittlement cracks in resistance spot welds by adaption of electrode geometry

Böhne¹,

Meschut²,

Biegler

et al. 2019

Science and Technology of Welding and Joining

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Advanced high strength steels are usually coated by a zinc layer for an increased resistance against corrosion. During the resistance spot welding of zinc coated steel grades, liquid metal embrittlement (LME) may occur. As a result, cracking inside and around the spot weld indentation is observable. The extent of LME cracks is influenced by a variety of different factors. In this study, the impact of the used electrode geometry is investigated over a stepwise varied weld time. A spot welding finite element simulation is used to analyse and explain the observed effects. Results show significant differences especially for highly increased weld times. Based on identical overall dimensions, electrode geometries with a larger working plane allow for longer weld times, while still preventing LME within the investigated material and maintaining accessibility.

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Section: Introductionmentioning

confidence: 99%

Prevention of liquid metal embrittlement cracks in resistance spot welds by adaption of electrode geometry

Böhne¹,

Meschut²,

Biegler

et al. 2019

Science and Technology of Welding and Joining

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“…Temperature distribution is an important factor for determining LME cracking in RSW; this can be inferred from the microstructure of the weldments, especially from the perspective of the fusion zone and heat-affected zone (HAZ) [7, 17]. It is evident from the nugget diameter and HAZ width in Figure 2(a–b) that the heat input in W2 is higher than that in W1.…”

Section: Resultsmentioning

confidence: 99%

“…These observations are consistent with the findings reported in previous studies [11,20]; therefore, an attempt to investigate the role of Zn coatings on LME behaviour, as mentioned above, which has not been the focus of previous studies, is presented herein. Temperature distribution is an important factor for determining LME cracking in RSW; this can be inferred from the microstructure of the weldments, especially from the perspective of the fusion zone and heataffected zone (HAZ) [7,17]. It is evident from the nugget diameter and HAZ width in Figure 2(a-b) that the heat input in W2 is higher than that in W1.…”

Section: Lme Cracks In Weldsmentioning

confidence: 99%

“…Various studies have been conducted to understand the influence of different factors, such as the steel microstructure [9, 16], welding electrode [10, 17, 18] and welding parameters [19, 20], on LME during RSW. However, the effect of Fe–Zn reaction and the resulting microstructural evolution of Zn coating have not been sufficiently studied.…”

Section: Introductionmentioning

confidence: 99%

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Liquid metal embrittlement during the resistance spot welding of galvannealed steels: synergy of liquid Zn, α-Fe(Zn) and tensile stress

Kim

Murugan

Kim

et al. 2021

Science and Technology of Welding and Joining

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In this study, the influence of the microstructural evolution of galvannealed (GA) coating and the thermomechanical characteristics of liquid metal embrittlement (LME) cracking during resistance spot welding (RSW) of steels were investigated. The analysis of LME cracks, coating microstructure and thermomechanical characteristics at various weld regions revealed a synergistic effect of liquid Zn, α-Fe(Zn), and tensile stress on LME cracking during RSW. A continuous α-Fe(Zn) layer inhibits liquid Zn from contacting the steel substrate; hence, LME was suppressed. However, a long-duration, high-magnitude tensile stress can fragment the α-Fe(Zn) layer and enable LME cracking. Conversely, α-Fe(Zn) particles allow the easy infiltration of liquid into the steel and make the crack on tensile stress development.

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“…Precisely correlating crack depth to weld strength degradation for a particular weld is unrealistic because there is large weld-to-weld variation in LME crack severity and location [10], and in a manufacturing setting, there are insufficient resources to measure crack depths from all welds. However, considering that a particular combination of welding parameters will result in a repeatable depth/quantity distribution of LME cracks in multiple welds [6,11], cracking severity may be classified based on the number and depth of the entire population of cracks found in a particular weld. This approach was used by Wintjes et al [6] to correlate an LME cracking severity index to welds strength degradation.…”

Section: Introductionmentioning

confidence: 99%

Significance of cutting plane in liquid metal embrittlement severity quantification

DiGiovanni

Hawkins

et al. 2021

SN Appl. Sci.

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The 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.

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Critical design parameters of the electrode for liquid metal embrittlement cracking in resistance spot welding

Cited by 36 publications

References 24 publications

Prevention of liquid metal embrittlement cracks in resistance spot welds by adaption of electrode geometry

Prevention of liquid metal embrittlement cracks in resistance spot welds by adaption of electrode geometry

Liquid metal embrittlement during the resistance spot welding of galvannealed steels: synergy of liquid Zn, α-Fe(Zn) and tensile stress

Significance of cutting plane in liquid metal embrittlement severity quantification

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