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

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.