Double-pass loading cabinets are core equipment in industrial storage and logistics. The welding process for their 304 stainless steel panels directly determines the cabinet's structural strength, corrosion resistance, and service life. The austenitic structure of 304 stainless steel provides excellent ductility and resistance to intergranular corrosion. However, improper heat input during welding can easily lead to intergranular corrosion and thermal cracking, necessitating strict control of process parameters.
When welding double-pass loading cabinet panels, the welding method must balance efficiency and quality. TIG welding (argon arc welding) offers high shielding gas purity and aesthetically pleasing welds, making it commonly used for precision welding of thin plates (≤3mm) and particularly well-suited for decorative welds in double-pass loading cabinets. MIG welding (gas shielded welding) offers high productivity and is suitable for rapid welding of medium-thick plates, meeting the welding requirements of double-pass loading cabinet main frames. Manual arc welding, while flexible, suffers from low electrode deposition efficiency and is primarily used for local repairs or small-scale production.
Preheating and interpass temperature control are key to avoiding welding defects in double-pass loading cabinets. 304 stainless steel has poor thermal conductivity, so the interpass temperature must be controlled to no more than 200°C during welding to prevent grain coarsening in the heat-affected zone (HAZ). For thicker double-pass loading cabinet components, the preheat temperature can be set between 50-100°C to reduce welding stress and the risk of cold cracking. When performing multi-layer, multi-pass welding, ensure that each weld is fully fused to avoid incomplete fusion defects.
The choice of welding consumables directly impacts the corrosion resistance of double-pass loading cabinets. The welding wire composition should match the base material. ER308L welding wire containing titanium and niobium stabilizers is preferred to inhibit chromium carbide precipitation during welding and reduce the tendency to intergranular corrosion. For food-grade applications of double-pass loading cabinets, low-carbon welding consumables are required to ensure a weld metal carbon content of 0.03% or less to meet hygiene standards.
Optimizing welding parameters requires consideration of the structural characteristics of the double-pass loading cabinet. Excessive welding current leads to excessive heat input, which can cause intergranular corrosion; too low a current can easily result in incomplete penetration defects. Typically, the welding current for thin plates is controlled between 80-120A, and for medium and thick plates, 150-200A. The welding speed must be matched to the current, reaching 30-50cm/min for thin plates and 15-25cm/min for medium and thick plates. The shielding gas flow rate should be controlled at 15-20L/min to ensure that the weld area is isolated from the atmosphere.
Welding quality inspection for double-pass loading cabinets requires comprehensive inspection. Before welding, the base metal surface cleanliness must be checked to remove impurities such as oil, scale, and other impurities. During welding, arc stability must be monitored to prevent arc deviation that could lead to poor weld formation. Post-weld, visual inspection, non-destructive testing, and corrosion resistance testing are required. Visual inspection focuses on weld reinforcement, undercut, and surface porosity. Non-destructive testing uses penetrant testing or X-rays to ensure the weld is free of cracks and slag inclusions. Corrosion resistance testing involves salt spray testing to verify the weld's corrosion resistance.
Post-weld treatment is the final step in improving the performance of double-pass loading cabinets. After welding, slag must be removed immediately to prevent residual corrosion of the base material. Decorative welds require polishing to ensure the weld and base material finish match. If the double-pass loading cabinet is used in a humid or corrosive environment, the welds must be passivated to form a dense oxide film, further enhancing corrosion resistance. Strict quality control ensures that the weld joints in the double-pass loading cabinet have a lifespan comparable to that of the base material, ensuring long-term use.
