Alloy cladding wear-resistant steel plates, by laminating a high-hardness alloy layer onto the surface of a base steel plate, significantly improve the wear resistance of the material and are widely used in high-wear environments such as mining machinery and construction machinery. However, improper operation during welding can easily lead to cracking, thinning, or peeling of the cladding layer, thereby affecting its wear resistance and corrosion resistance. To prevent damage to the cladding layer, comprehensive measures are needed, including selection of welding methods, control of process parameters, optimization of joint design, application of isolation layers, preheating and post-heat treatment, planning of welding sequence, and post-weld inspection and repair.
Choosing a suitable welding method is fundamental to preventing cladding layer damage. Gas-shielded welding (such as MIG/MAG welding) can reduce the heating time of the cladding layer and the size of the heat-affected zone due to concentrated heat input and high welding speed, thereby reducing the risk of cracking. For thin plates or cladding layers sensitive to heat input, high-energy beam welding methods such as laser welding or plasma welding are more suitable, as they have high energy density, small welding deformation, and can effectively protect the performance of the cladding layer. While submerged arc welding (SAW) is highly efficient, it involves significant heat input, requiring careful selection and the use of low-hydrogen flux to reduce the tendency for hydrogen-induced cracking.
Precise control of process parameters is crucial to preventing cladding damage. Welding current, voltage, and welding speed directly affect heat input and must be appropriately matched based on the cladding material and thickness. For example, high-hardness alloy claddings are sensitive to heat input, necessitating a combination of low current, high voltage, and rapid welding to shorten the molten pool time and minimize alloy element loss and dilution. Simultaneously, controlling the arc length and oscillation amplitude prevents the arc from directly impacting the cladding surface, thus preventing localized overheating and cracking.
Optimized joint design can significantly reduce the risk of cladding damage. For butt joints, U-shaped or K-shaped bevels can be used to reduce the amount of deposited metal, thereby lowering the cladding dilution rate. In corner joints, the cladding layer should be located on the non-stressed side, or the stress point should be transferred to the base alloy cladding wear-resistant steel plate by adding a transition layer, avoiding direct stress on the cladding layer. Furthermore, the joint gap and blunt edge dimensions of the alloy cladding wear-resistant steel plate must be precisely controlled. An excessively large gap can lead to excessive deposited metal, increasing the risk of dilution; an excessively small gap can easily result in incomplete fusion defects.
The application of an isolation layer is an effective means of preventing cladding layer dilution. Pre-depositing a layer of alloy with a composition similar to the cladding layer between the base steel plate and the cladding layer as an isolation layer can reduce the dilution effect of the base steel plate on the cladding layer during welding. The isolation layer material should have good metallurgical compatibility with the cladding layer and a melting point slightly lower than the cladding layer to ensure good fusion during welding. When depositing the isolation layer, the interpass temperature must be controlled to avoid overheating, which could lead to the formation of brittle phases between the isolation layer and the base steel plate.
Preheating and post-heat treatment are important measures to prevent cladding layer cracking. For high-hardness alloy cladding, the base steel plate must be preheated before welding to reduce residual welding stress and decrease the tendency for cold cracking. The preheating temperature must be appropriately selected based on the cladding material and the thickness of the alloy cladding wear-resistant steel plate; excessively high temperatures can soften the cladding, while excessively low temperatures will not effectively eliminate stress. After welding, post-heat treatment is necessary immediately, using heat preservation and slow cooling to further eliminate residual stress and prevent delayed cracking.
Planning the welding sequence can reduce the number of times the cladding is heated and stress concentration. For complex structures, symmetrical welding or segmented back-welding methods should be used to offset weld shrinkage stresses and reduce overall deformation. In multi-layer, multi-pass welding, the welding direction of each pass must be rationally arranged to avoid repeated heating in the same direction, which can degrade the cladding performance. Simultaneously, interpass temperature should be controlled to prevent overheating and interfacial reactions between the cladding and the base steel plate.
Post-weld inspection and repair are the last line of defense to ensure the performance of the cladding. After welding, the weld must undergo visual inspection, non-destructive testing (such as ultrasonic testing and radiographic testing), and hardness testing to ensure that there are no defects such as cracks and porosity, and that the hardness of the cladding layer meets the requirements. For locally damaged cladding layers, wear-resistant welding electrodes can be used for repair. The material of the repair layer should be consistent with the original cladding layer, and the welding process parameters must be strictly controlled to avoid the recurrence of defects.
