As the core load-bearing component of heavy machinery and equipment frames, thick plate box structures feature large plate thickness and high structural restraint. Their welding process is prone to problems such as incomplete penetration, deformation and cracking, and excessive residual stress. Standardized welding demonstrations can standardize operating procedures and stabilize forming quality.

The demonstration adopts medium and thick carbon steel box workpieces. V-groove and X-groove machining are matched according to plate thickness to ensure root penetration conditions. Strict groove cleaning, rust and oil removal are carried out before welding. Overall preheating is performed in accordance with process requirements, and interlayer temperature is controlled to avoid hidden dangers of cold cracks in thick plates. The gas metal arc welding multi-layer and multi-pass symmetrical welding process is adopted, following the step-by-step operation principle of backing welding, filler welding and cover welding. The methods of segmented backward welding and symmetrical welding are applied to balance heat input and effectively suppress box distortion and angular deformation.

Appropriate current and voltage parameters are adopted throughout the welding process, with strict control over welding speed and welding torch swing amplitude to prevent defects such as arc stop slag inclusion and porosity. Slow cooling and heat preservation treatment are implemented after welding, supplemented by stress relief processes, followed by weld grinding, shaping and non-destructive testing. The complete set of demonstrations provides replicable and implementable process references for the welding of thick plate box structures.