Thick-wire GMAW for fusion welding of high-strength steels

Abstract

The paper describes a high-current Gas Metal Arc Welding (GMAW) process using wire electrodes with diameters up to 4.0 mm for single-pass full penetration butt joint welding of 20 mm thick steel plates. Fundamental research aims to develop thick-wire GMAW into a high-efficiency method by identifying the limits of welding performance and achievable deposition rates. Current gaps in understanding include equipment requirements, process properties, application fields, and weld quality. The research project addresses these gaps through systematic investigations of basic technological analyses, application sample welding, and quality evaluations. The objective was to create a robust, cost-efficient gas-shielded high-performance welding technology with deposition rates comparable to Submerged Arc Welding. The fully mechanized, automatic welding setup included two parallel-connected welding power sources, one wire feeder and one high-power welding torch. Welding parameters and conditions were evaluated with the aim of achieving a high-quality weld. Optimal parameters were identified for one-sided single-pass welding on 20 mm thick plates. Validation of thick-wire GMAW for 20 mm thick high-strength steels was conducted via two-sided single-pass welding on S690Q grade plates. Testing of the weld joint included static tensile strength test (3x tensile specimen), a Charpy impact test at −40 °C (6x Charpy V-notch specimens respectively with notch position in weld metal, base material and heat-affected zone (HAZ)), microstructure examination and a hardness test. The lowest recorded impact energy was observed to be 50 J within the weld metal, in combination with hardness peaks in the HAZ reaching 415 HV1, and all tensile specimens failing outside the HAZ within the base material. The process achieved reliable, reproducible, and economical joint welding, meeting necessary mechanical-technological quality standards. The paper enhances the understanding of selected welding techniques tor thick plate joining and offers valuable industrial insights, demonstrating the technique's applicability and feasibility for high-strength applications.