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

Böhne, Christoph; Meschut, Gerson; Biegler, Max; Frei, Julian; Rethmeier, Michael

doi:10.1080/13621718.2019.1693731

Cited by 35 publications

(20 citation statements)

References 17 publications

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“…Electrode caps of the types A0-16-20-100 (hereinafter called A0-100), as specified in ISO 5821 were used [22]. This cap type has been chosen based on the results presented in [21] as, it was shown to allow for crack free RSWs even under adverse welding conditions (i.e. elongated weld times and high heat input), by reducing the degree of plastic deformation at the indentation area.…”

Section: Welding Equipment and Experimental Designmentioning

confidence: 99%

Avoidance of liquid metal embrittlement during resistance spot welding by heat input dependent hold time adaption

Böhne¹,

Meschut²,

Biegler

et al. 2020

Science and Technology of Welding and Joining

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Christoph Böhne (M.Sc.) studied mechanical engineering at the University of Paderborn and graduated in 2017. Currently he is working as a research assistant in the work group thermal joining with focus on resistance welding processes. Prof. Dr.-Ing. Gerson Meschut, graduated in 1998 at the University of Paderborn in Mechanical Engineering. After continuing research as chief-engineer, he joined the research and development department of Volkswagen AG in Wolfsburg in 2000. From 2005 to 2011 he was the technical managing director of Wilhelm Böllhoff GmbH & Co. KG in Bielefeld. Currently, he is the head of the Laboratory for Materials and Joining Technology (LWF) of the University of Paderborn. Max Biegler (M.Sc.) finished his studies in mechanical engineering at Technical University of Munich in 2015. He is currently working as a research associate at Fraunhofer IPK with focus on numerical modelling of welding processes. Univ.-Prof. Dr.-Ing. Michael Rethmeier graduated in 2003 at the Technical University Carolo Wilhelmina Braunschweig in Mechanical Engineering. Before joining the Technical University of Berlin (TUB) and the Federal Institute for Materials Research and Testing (BAM) in 2007, he worked at the Volkswagen AG. Currently, he is head of department 'Welding Technologies' (BAM), the field of 'Joining Technologies' at the Institute for Machine Tools and Factory Management (TUB) and the department of 'Joining and Coating Technology' (Fraunhofer IPK). Avoidance of liquid metal embrittlement during resistance spot welding by heat input dependent hold time adaptionLiquid metal embrittlement (LME) cracking can occur during resistance spot welding (RSW) in zinc coated advanced high strength steels (AHSS) for automotive production. In this study, a methodological variation of hold time is performed to investigate the process-related crack influence factors. A combination of numerical and experimental investigations confirms, that the extent of heat dissipation and re-heating of the sheet surface can be influenced and thus the degree of crack formation can be controlled in a targeted manner by the parameterisation of the hold time. The temperature and stress history of crack-free and crack-afflicted spot welds are analysed and a conclusion on the borders defining the LME active region is derived.

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Section: Welding Equipment and Experimental Designmentioning

confidence: 99%

Avoidance of liquid metal embrittlement during resistance spot welding by heat input dependent hold time adaption

Böhne¹,

Meschut²,

Biegler

et al. 2020

Science and Technology of Welding and Joining

Self Cite

View full text Add to dashboard Cite

show abstract

“…So far, the only viable approach that allows monitoring of these transient fields is a numerical process simulation by means of the finite element (FE) method. The literature reports on a number of FE models of RSW processes [12][13][14][15][16]. In most of those publications only the electrical-thermal-mechanical coupling is considered, whereas the metallurgical and mechanical effects of phase transformations are not covered [17] or only dealt with by applying some simplifications [18,19].…”

Section: Introductionmentioning

confidence: 99%

“…The work of [20] considers the temperature path in a reasonable way, but phase dependent material properties were not fully investigated and were therefore only partially implemented. Other publications [14,21] base their model merely on material properties gathered from the literature. In the literature, modelling of residual stresses can be found for, e.g., butt welded plates [22], thermal-vibratory stress relief processes [23], laser-magnetic welding [24], as well as steel tubes [25].…”

Section: Introductionmentioning

confidence: 99%

Validated Multi-Physical Finite Element Modelling of the Spot Welding Process of the Advanced High Strength Steel DP1200HD

et al. 2021

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Resistance spot welding (RSW) is a common joining technique in the production of car bodies in white for example, because of its high degree of automation, its short process time, and its reliability. While different steel grades and even dissimilar metals can be joined with this method, the current paper focuses on similar joints of galvanized advanced high strength steel (AHSS), namely dual phase steel with a yield strength of 1200 MPa and high ductility (DP1200HD). This material offers potential for light-weight design. The current work presents a multi-physical finite element (FE) model of the RSW process which gives insights into the local loading and material state, and which forms the basis for future investigations of the local risk of liquid metal assisted cracking and the effect of different process parameters on this risk. The model covers the evolution of the electrical, thermal, mechanical, and metallurgical fields during the complete spot welding process. Phase transformations like base material to austenite and further to steel melt during heating and all relevant transformations while cooling are considered. The model was fully parametrized based on lab scale material testing, accompanying model-based parameter determination, and literature data, and was validated against a large variety of optically inspected burst opened spot welds and micrographs of the welds.

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“…Implementing this knowledge into a finite element (FE) code allows to predict LME and to ultimately optimize the RSW process. This will serve as the basis for suggesting LME prevention measures, e.g., modification of the electrode tip geometry [ 23 ] or the welding conditions [ 24 ].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

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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.

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

Cited by 35 publications

References 17 publications

Avoidance of liquid metal embrittlement during resistance spot welding by heat input dependent hold time adaption

Avoidance of liquid metal embrittlement during resistance spot welding by heat input dependent hold time adaption

Validated Multi-Physical Finite Element Modelling of the Spot Welding Process of the Advanced High Strength Steel DP1200HD

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

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