Improving the welding process of kitchen storage racks requires focusing on reducing stress concentration at the weld joints. This process necessitates a multi-dimensional approach, encompassing welding method selection, process parameter optimization, structural design adjustments, assembly sequence planning, post-weld treatment enhancement, and upgraded quality inspection. Stress concentration occurs when localized stress in the weld area is significantly higher than the average stress due to abrupt geometric changes or welding defects. This not only reduces the load-bearing capacity of the storage rack but can also lead to fatigue cracks and shorten its service life. Therefore, systematically improving the process to reduce stress concentration is crucial for enhancing the quality and reliability of storage racks.
The choice of welding method directly impacts heat input and weld formation quality. Traditional manual arc welding, due to its large heat input and wide heat-affected zone, tends to result in coarse weld metal grains, increasing the risk of stress concentration. In contrast, TIG welding features concentrated heat input and precise molten pool control, producing narrower and deeper welds, reducing the heat-affected zone and thus lowering residual stress. For medium-thick plate welding, MIG welding is more efficient, but requires pulsed current technology to control heat input and prevent weld overheating. Furthermore, high-energy beam welding methods such as laser welding can significantly reduce deformation and stress concentration due to extremely low heat input and narrow weld seams, but the equipment cost is high, making them suitable for high-end products.
Optimizing process parameters is the core of reducing stress concentration. Parameters such as welding current, arc voltage, and welding speed must be precisely matched according to the material thickness and weld seam location. For example, excessive current can lead to overheating of the molten pool and grain coarsening; insufficient current can easily cause incomplete fusion defects. The welding sequence is equally crucial. Symmetrical structures should be welded symmetrically to avoid localized stress superposition; long weld seams should be segmented with skip welding, each segment controlled to a length of 200-300mm, and adjacent weld seams should be in opposite directions to offset shrinkage stress. For multi-layer, multi-pass welding, the thickness of each weld layer should not exceed 3mm, and each subsequent layer should cover 1/2-2/3 of the previous layer to reduce heat input per layer and minimize deformation.
Structural design adjustments can reduce stress concentration from the source. Weld seams should avoid areas with geometrical abrupt changes such as corners and sharp angles, and butt joints should be preferred over lap joints. If T-joints or corner joints must be used, full penetration welds should be employed, ensuring a smooth transition at the weld toe. For thick plate welding, arc-starting and arc-extinguishing plates can be installed on both sides of the weld to prevent stress concentration caused by defects at the arc initiation and termination points. Furthermore, reducing the number and length of welds, and using intermittent welding or spot welding instead of continuous full welding, can effectively reduce residual stress.
Planning the assembly sequence is crucial for controlling deformation. During assembly, the reference surface should be fixed first, and then other components should be assembled sequentially to avoid assembly stress caused by forced assembly. Using specialized tooling fixtures to fix the workpiece can limit the degree of freedom of shrinkage during welding and reduce deformation. For example, when splicing plates, a set of pressure irons and bolt plates should be set every 500 mm to ensure uniform pressure; when welding pipe fittings, V-blocks and locating pins should be used for fixation to prevent sagging and bending. Allowing for shrinkage allowance before welding can prevent insufficient dimensions after cooling.
Post-weld treatment is a key step in eliminating residual stress. Low-temperature stress-relief annealing involves heating the workpiece to 300-400℃, holding it at that temperature for 1-2 hours, and then slowly cooling it in the furnace to release over 80% of residual stress, preventing delayed deformation later. For large workpieces, vibration aging treatment can be used. Vibration is applied near the weld using a vibrator to induce microscopic plastic deformation within the metal, thereby reducing stress. Localized hammering is suitable for short welds; lightly tapping the weld and heat-affected zone with a round-headed hammer can eliminate surface stress, but the force must be controlled to avoid scratching the surface.
Upgraded quality inspection ensures the effectiveness of process improvements. Non-destructive testing techniques such as X-ray inspection and ultrasonic testing can detect internal weld defects, such as porosity, slag inclusions, and cracks, which are major sources of stress concentration. Magnetic particle testing and penetrant testing are suitable for surface defect detection, ensuring a smooth, crack-free weld surface. For critical welds, metallographic examination can be performed to observe the grain size and microstructure of the weld metal, ensuring compliance with quality requirements.
By optimizing welding methods, precisely controlling process parameters, improving structural design, planning assembly sequence, strengthening post-weld treatment, and upgrading quality inspection, the welding process of kitchen storage racks can significantly reduce stress concentration at weld seams, thereby improving the product's load-bearing capacity and service life. This process requires combining material properties, product structure, and usage scenarios, and through experimental verification and continuous improvement, to achieve a balance between welding quality and efficiency.
