Predicting the hardness profile across resistance spot welds in martensitic steels

Vignier, Samuel; Biro, E.; Hervé, Mathilde

doi:10.1007/s40194-014-0116-0

Cited by 26 publications

(9 citation statements)

References 12 publications

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“…The steel materials between the fusion zone and upper-critical HAZ will be heated above the transition temperature between the austenite and delta ferrite. In the subsequent quenching at the rapid cooling stage of RSW, the carbon redistribution and decomposition of delta ferrite would be inhibited and preserved in the transition zone, which resulted in the slight decrease of the hardness [23,24]. Figure 15b shows the microstructure of zone in Figure 15a, which is the softening zone with different softening degree varying with the location, and microstructure changing with the location is observed in this figure.…”

Section: Microstructurementioning

confidence: 81%

Analysis of Fracture Modes of Resistance Spot Welded Hot-Stamped Boron Steel

Zhao

Zhang

Lai

2018

Metals

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Fracture modes of resistance spot welded ultra-high strength hot-stamped boron steel via lap-shear test are different from that of the traditional advanced high strength steel due to the difference in geometrical size and material property of the spot welds. In this paper, lap-shear fracture modes of resistance spot welding joints were analyzed and joint characteristics that affecting the fracture behavior were discussed. Three fracture modes were found to change from interfacial fracture (IF) to pull-out fracture (PF) with the increase of nugget diameter. For PF I mode, the fracture initiated at the transition zone between the fusion zone and upper-critical heat affected zone (HAZ) and propagated along the thickness of the nugget. For PF II mode, during which the failure initiated at the sub-critical HAZ where the softest zone occurred, and it propagated to the base material. Obvious hardness decrease was observed in the transition zone with the formation of the delta ferrite at the fusion boundary due to the relatively high amount of alloying element in the hot-stamped boron steel, which could provide the reason for route of PF I extending along this zone. Fluctuation in the hardness in the transition zone led to the existence of both PF I and PF II at the same welding current.

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Section: Microstructurementioning

confidence: 81%

Analysis of Fracture Modes of Resistance Spot Welded Hot-Stamped Boron Steel

Zhao

Zhang

Lai

2018

Metals

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“…Compared to other AHSS types, the welding behaviour of martensitic grades are less investigated [17][18][19][20] and therefore further clarifications on structure-properties relationships in martensitic AHSS steel RSW are required. This paper aims at understanding welding metallurgy of MS1400 martensitic AHSS during RSW.…”

Section: Introductionmentioning

confidence: 99%

Welding metallurgy of martensitic advanced high strength steels during resistance spot welding

Tamizi

Pouranvari

Movahedi

2017

Science and Technology of Welding and Joining

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The paper addresses the process-microstructure-performance relationships in resistance spot welding of a martensitic advanced high strength steel. Significant softening was observed in the heat affected zone (HAZ) due to allotriomorphic ferrite formation in the inter-critical HAZ and tempering of martensite in sub-critical HAZ (SCHAZ), with the latter plays more important role in mechanical properties of the spot welds. The strain concentration associated with the HAZ softening promotes initiation of pullout failure from the soft SCHAZ. While, the peak load in the interfacial failure mode is governed by the fusion zone size, that of the pullout mode is significantly affected by the HAZ softening. To improve weldability of martensitic steels, the HAZ softening should be minimised via modifications in welding process or steel chemistry.

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“…For conventional strength steels such as high strength low alloy (HSLA) steels, the fusion zone hardness is much harder (2-3 times harder) than base metal due to the formation of martensite [9] and so the hardness across the weldment is only a function of cooling rate [10]. However, in advanced high strength steels (AHSS) such as dual-phase (DP), transformation induced plasticity (TRIP) and martensitic steels where the base material contains metastable phases such as martensite and retained austenite, the sub-critical heat-affected zone (HAZ) tempers so its hardness is reduced from its base material hardness [11]. For Austenitic stainless steel, its austenitic microstructure is maintained at all temperature from the cryogenic region to the melting point, and its RSW fusion zone hardness is close to its base metal hardness [12].…”

Section: Introductionmentioning

confidence: 99%

Weld hardness ratio and liquid metal embrittlement crack’s detrimental effect on resistant spot weld strength

Zhang

DiGiovanni

et al. 2020

Science and Technology of Welding and Joining

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Studies on the detrimental effect of liquid metal embrittlement cracks on resistant spot weld joint strength have shown conflicting results. To help understand the cause of these discrepancies, this study will investigate the effect of liquid metal embrittlement cracks on weld strength under different hardness ratios between fusion zone and base metal. In this study, a novel methodology using finite element modelling and experimental testing reveals that the liquid metal embrittlement crack affects the weld strength differently under different weld's hardness ratio, i.e. under low hardness ratio, the cracks have a relatively big effect on weld strength while under high hardness ratio the cracks have relatively little effect. This work helps further understand when LME cracks are detrimental to strength.

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Predicting the hardness profile across resistance spot welds in martensitic steels

Cited by 26 publications

References 12 publications

Analysis of Fracture Modes of Resistance Spot Welded Hot-Stamped Boron Steel

Analysis of Fracture Modes of Resistance Spot Welded Hot-Stamped Boron Steel

Welding metallurgy of martensitic advanced high strength steels during resistance spot welding

Weld hardness ratio and liquid metal embrittlement crack’s detrimental effect on resistant spot weld strength

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