Investigation and quality control of resistance spot welding

Cross-tensile, peel and shear tests produce objective assessments of resistance spot weldability only in the case of low-carbon, normal strength steel sheet. The results of the tensile-cross and peel tests depend only on the chemical composition of the sheet, and particularly so on the contents of phosphorus and sulphur. The results of the shear test depend mainly on the strength of the welded sheet. 2 An assessment of the weldability of high-strength sheet should be made on the basis of a yield criterion, applied to a multispot welded assembly. An indicator of weldability is the number and distribution of welds that would ensure plastic deformation of the sheet in a tensile test. 3 Adaptive systems of quality control of the resistance spot welding process ensure that good quality joints are obtained. The highest degree of reliability is attained when use is made of the parameter of dynamic resistance.