How can the fatigue resistance of sheet metal parts in general machinery be enhanced through material treatment?
Publish Time: 2025-12-11
In general machinery equipment, sheet metal parts, while not always subjected to extreme loads, are frequently at risk of fatigue failure due to vibration, alternating stress, or frequent start-stop cycles—manifesting as the initiation and propagation of microcracks, ultimately leading to fracture or deformation. Unlike castings or forgings, sheet metal parts are cold-formed from thin plates, and their edges, bends, and holes are prone to stress concentration areas, becoming "weak points" for fatigue failure.1. Optimize base material selection: Improve fatigue strength from the sourceFatigue resistance primarily depends on the material itself. General sheet metal parts often use carbon steel or stainless steel, but if the operating conditions involve high-frequency vibration or heavy-load cycles, high fatigue strength plates should be prioritized, such as high-strength low-alloy steel, duplex stainless steel, or cold-rolled plates that have undergone controlled rolling and cooling treatment. These materials have finer grains and more uniform microstructure, effectively delaying crack initiation. Furthermore, the surface quality of the sheet metal is crucial—surface scratches, oxide scale, or inclusions can become the starting point for fatigue cracks. Therefore, high-quality coils with smooth, defect-free surfaces should be selected.2. Eliminating Residual Stress: The Key Role of Heat TreatmentCold stamping, bending, laser cutting, and other sheet metal forming processes introduce residual tensile stress in localized areas, significantly reducing the fatigue limit. Stress-relieving annealing is the most common and effective heat treatment method for this. Heating the sheet metal to 550–650℃, holding it at that temperature, and then slowly cooling it can significantly relax internal stresses, especially suitable for complex bending parts or welded assemblies. For stainless steel sheet metal parts, solution treatment can also be used, which not only eliminates stress but also restores corrosion resistance, indirectly improving serviceability in corrosion-fatigue coupled environments.3. Surface Strengthening Treatment: Building a "Crack-Resistant Barrier"Fatigue cracks often originate on the surface; therefore, surface modification technology is a core strategy for improving fatigue resistance:Shot Peening: High-speed shot bombardment of the surface forms a uniform compressive stress layer, effectively inhibiting crack initiation and propagation. Widely used in high-reliability brackets and aerospace sheet metal parts;Rolling/Tilting: Local rolling of edges or around holes refines surface grains and introduces compressive stress, significantly improving the fatigue strength of hole edges;Surface Coating: Such as electroplated zinc-nickel alloy and Dacromet coating, which not only provide corrosion protection but also fill micropores, smooth the surface, and reduce stress concentration sources.4. Refined Edge Treatment: Blocking Fatigue Initiation Points from DetailsThe cuts and punched edges of sheet metal parts often contain microcracks or burrs, which are typical high-stress areas. Post-treatment such as deburring, chamfering, and polishing can significantly improve stress distribution. For example, after laser cutting, vibratory grinding or chemical deburring is used to create smooth edges; flanging or riveting reinforcing rings are applied to critical stress-bearing holes to improve rigidity and distribute loads. Studies have shown that proper chamfering can increase fatigue life by 2–3 times.5. Collaborative Design and Process Control: Systematic Fatigue Resistance ThinkingMaterial treatment needs to be coordinated with structural design. Avoid sharp corners and use large radius transitions; rationally arrange reinforcing ribs to reduce local deflection; reserve mounting positions for vibration damping pads in vibration-sensitive areas, etc. At the same time, strictly controlling bending radius and welding heat input during manufacturing is also a crucial aspect of ensuring fatigue resistance.Improving the fatigue resistance of sheet metal parts in general machinery is not achieved by a single process, but rather a systematic engineering project involving material selection, heat treatment, surface strengthening, and precision manufacturing. Through scientific material treatment methods, the fatigue life of sheet metal structures can be significantly extended without significantly increasing cost and weight, improving the overall reliability of the machine. In today's industrial equipment development towards high efficiency, long life, and low maintenance, this "invisible" material wisdom is becoming a key support for the leap in quality of general machinery.
