Comprehensive Evaluation of Double-Wire Narrow Gap GMAW Process and Dissimilar Joint for Chute Structure

Abstract Chute structures are critical components for transporting mined coal in coal machinery, and their manufacturing involves welding dissimilar thick-plate materials. To achieve efficient and high-quality fabrication of chute structures, double-wire narrow gap gas metal arc welding (GMAW) was utilized to join 40-mm-thick wear-resistant steel NM450 and cast steel ZG30SiMn. A comprehensive evaluation was conducted on the welding process, microstructure, and mechanical properties of the welded joint. Additionally, temperature field simulations were performed to investigate the impact of multi-layer welding thermal cycles on microstructural evolution. The double-wire narrow gap GMAW process demonstrated high stability, yielding a defect-free welded joint. The weld metal (WM) microstructure comprised proeutectoid ferrite, polygonal ferrite, and acicular ferrite, which endowed the WM with better ductility and toughness. Due to the welding-induced multiple thermal cycles, a white band formed between filling layers. In the heat-affected zone (HAZ), the microstructure consisted of martensite and bainite, achieving higher strength and 86-110% toughness values of the base metals. This study successfully implemented double-wire narrow gap GMAW for chute fabrication, enabling high-quality welding of thick-plate dissimilar joint while enhancing welding efficiency without compromising performance. The findings provide actionable insights for optimizing chute manufacturing in heavy machinery industries.