Liquid Metal Embrittlement Cracking During Resistance Spot Welding of Galvanized Q&amp;P980 Steel

Ling, Zhang; Chen, Ting; Kong, Liang; Wang, Min; Pan, Hongyan; Lei, Ming

doi:10.1007/s11661-019-05388-6

Cited by 40 publications

(17 citation statements)

References 34 publications

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“…Excluding volumetric cracking measurement means that planar measurement is the only viable option to characterize cracking distribution. Many studies have assessed cracking susceptibility from plan view (as seen from the top of the weld) using methods such as optical microscopy [1,15,16], liquid dye penetrant [2,17], radiography [18], fluorescent magnetic particle detection [19] and pulsed eddy current thermography [20]. However, using these techniques only views the weld surface.…”

Section: Introductionmentioning

confidence: 99%

“…For the reasons stated above, many studies have measured LME cracking severity from the weld cross-section. However, in the literature there seems to be two major philosophies on choosing the cross-section plane; these are the plane intersecting the most severe cracks [ 1 , 6 , 19 , 21 – 23 ], and a plane with a fixed orientation to the welding coupon [ 16 , 24 , 25 ]. In the above cases the cross-section plane intersected the center of the weld (lying along the weld diameter).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 99%

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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“…After the current stops passing, the sheets are cooled using water-cooled copper electrodes, and a weld nugget is formed [5][6][7]. Therefore, the necessary conditions of high temperature and stresses are met during the RSW process, creating suitable conditions for LME [8,9]. LME is a phenomenon known for decades, and it has been observed for specific solid/liquid metal couples, e.g., Al/Ga, Ni/Bi, Cu/Bi, and Fe/Zn couples.…”

Section: Introductionmentioning

confidence: 99%

“…This causes a weakening and loss of material ductility, which results in decohesion and crack nucleation due to tensile stresses during RSW [13,21,22]. Despite the low melting point of Zn, the decrease in ductility that occurs in LME, called the ductility trough, has been observed in the temperature range of 700 to 950 • C [8,13,14].…”

Section: Introductionmentioning

confidence: 99%

Investigation of Liquid Metal Embrittlement during Resistance Spot Welding of Martensitic Steel with Zn Jet Vapor-Deposited Coating

Kučera

Žofková

DiGiovanni

et al. 2021

Metals

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Advanced high-strength steels protected by zinc coatings have contributed to a reduction in CO2 emissions in the automotive industry. However, the liquid metal embrittlement (LME) of the Fe/Zn couple induced by simultaneously acting stresses and high temperatures during resistance spot welding could be the cause of unexpected failure. We investigated the possible risk of LME in spot-welded martensitic steel with Zn jet vapor-deposited coating and its influence on weld strength. The weld nugget cross-sections were analyzed (optical microscopy, SEM-EDS), and their tensile shear strengths were compared with their uncoated counterparts. LME cracks were observed in all samples meeting the process window (6, 6.5, 7 kA) located at the edge of the sheet/electrode indentation area. The frequency and length of cracks increased with current, and the occurrence of Zn within cracks indicated the LME mechanism. The shear tests showed the Zn-coated sample underwent a decrease in tensile shear strength that was most evident at a welding current of 7 kA (13.2%). However, LME was excluded as a cause of lower strength. The decrease was attributed to the smaller nugget diameter and the thin slit of Zn coating remaining in the weld notch.

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“…(1) Martensite formation in the fusion zone and coarse-grain heat-affected zone due to the extremely high cooling rate of RSW and the high hardenability of the AHSS: The brittleness of the hard martensite can provide a preferred path for interfacial failure (i.e., weld nugget failure along the sheet/sheet interface) during some loading conditions (e.g., peel and cross-tension tests). [9][10][11][12][13][14][15][16] (2) Heat-affected zone (HAZ) softening due to martensite tempering in the sub-critical HAZ during welding of martensite-containing AHSS (e.g., dual-phase steels and martensitic steels) [16][17][18][19][20][21] : This softening can promote pullout failure mode, but it may affect the joint strength.…”

mentioning

confidence: 99%

The Role of HAZ Softening on Cross-Tension Mechanical Performance of Martensitic Advanced High Strength Steel Resistance Spot Welds

Tamizi

Pouranvari

Movahedi

2021

Metall Mater Trans A

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Giga-grade martensitic advanced high-strength steels are prone to sub-critical heat-affected zone (SCHAZ) softening during resistance spot welding. The article aims at understanding the role of HAZ softening on the fracture mode, load-bearing capacity, and energy absorption capability of MS1400 resistance spot welds during the cross-tension test. The highest load-bearing capacity was obtained when pullout failure was initiated from the martensitic coarse-grained HAZ. However, more severe HAZ softening and formation of a wider softened zone, promoted at high heat input conditions, encourages strain localization in SCHAZ, promoting transition in failure location to sub-critical HAZ. This change in pullout failure location is responsible for the observed reduction in the weld peak load at high welding currents. Therefore, control of martensite tempering in the HAZ is critical to obtain strong and reliable resistance spot welds in martensitic advanced high-strength steel sheets. To preclude the detrimental effect of the martensite tempering on the weld strength, the minimum welding current, which enables pullout failure mode, should be used for resistance spot welding of MS1400 advanced martensitic steel.

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Liquid Metal Embrittlement Cracking During Resistance Spot Welding of Galvanized Q&P980 Steel

Cited by 40 publications

References 34 publications

Significance of cutting plane in liquid metal embrittlement severity quantification

Significance of cutting plane in liquid metal embrittlement severity quantification

Investigation of Liquid Metal Embrittlement during Resistance Spot Welding of Martensitic Steel with Zn Jet Vapor-Deposited Coating

The Role of HAZ Softening on Cross-Tension Mechanical Performance of Martensitic Advanced High Strength Steel Resistance Spot Welds

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