In the processing of alloy cladding wear-resistant steel plates, heat input control is the core factor determining the metallurgical bonding quality between the cladding layer and the substrate. Excessive heat input may lead to crack initiation due to thermal stress concentration in the cladding layer; insufficient heat input may result in spalling defects due to insufficient bonding strength. Therefore, precise control of heat input requires multi-dimensional process optimization.
Matching welding current and voltage is fundamental to heat input control. Current directly affects arc energy density, while voltage determines arc length and energy distribution. In the cladding welding of alloy cladding wear-resistant steel plates, appropriate parameters must be selected based on the characteristics of the cladding material. For example, when using Inconel 625 alloy, excessive current increases the molten pool depth, significantly increasing the proportion of iron elements diffused from the substrate into the cladding layer, leading to decreased corrosion resistance; insufficient current easily causes incomplete fusion defects due to insufficient energy. Pulsed TIG technology can achieve instantaneous high-energy input of peak current at low average current, ensuring molten pool fluidity while avoiding excessive overall heat input, thereby reducing the risk of cracking. Dynamic adjustment of welding speed is crucial for balancing heat input. Excessive speed leads to shortened solidification time, insufficient gas escape, and the formation of porosity or cracks; excessive speed causes the heat-affected zone to expand, resulting in residual stress accumulation. In multi-layer welding, the speed must be adjusted in real-time according to inter-layer temperature changes. For example, the first layer requires a slower speed to increase heat input due to the lower substrate temperature; subsequent layers can gradually increase the speed due to the substrate preheating effect, avoiding excessive heat accumulation. Furthermore, coordinated control of wire feed speed and welding speed is essential, ensuring that the wire melting rate matches the molten pool filling requirements to prevent bonding defects caused by insufficient filling.
Preheating and post-heat treatment are effective means of mitigating thermal stress. Preheating reduces the temperature difference between the substrate and the cladding layer, minimizing shrinkage stress during cooling. For high-carbon equivalent or thick-section alloy cladding wear-resistant steel plates, the preheating temperature needs to be determined based on the material's hardening tendency, generally controlled between 150-300℃. Post-heat treatment promotes hydrogen diffusion through slow cooling and heat preservation, preventing hydrogen-induced cracking. For example, after welding, placing the workpiece in a holding furnace and cooling it to below 200℃ at a rate of 50-100℃/h can significantly reduce residual stress levels. For easily cracked materials, post-weld low-temperature tempering can further eliminate stress and optimize the microstructure.
Welding sequence and interpass temperature control are crucial for reducing heat accumulation. In multi-layer welding, if the same area is welded continuously, heat cannot dissipate in time, easily leading to localized overheating. Therefore, segmented skip welding or symmetrical welding sequences should be used to ensure uniform heat distribution. Simultaneously, interpass temperature must be strictly controlled within a reasonable range. Excessive temperature will exacerbate grain coarsening and reduce toughness; excessively low temperature may cause cracks due to sudden changes in thermal stress. For example, when welding Inconel 625 alloy, the interpass temperature is recommended to be controlled at 100-150℃ to ensure interpass bonding quality while avoiding performance degradation in the heat-affected zone.
The selection of shielding gas and welding materials has an indirect impact on heat input. Argon shielding reduces oxidation and nitriding during welding, preventing crack initiation caused by inclusions. For highly reactive alloys, an argon-helium mixture can be used to improve arc stability and energy density. The welding consumable composition must match the cladding material to minimize dilution. For example, when using ERNiCrMo-3 welding wire to clad Inconel 625, the iron content in the wire must be controlled below 5% to maintain the corrosion resistance of the cladding. Furthermore, the choice of welding consumable diameter must be compatible with welding parameters to avoid process defects caused by mismatched melting rates.
Real-time monitoring and feedback adjustment of process parameters are crucial for ensuring stable heat input. A heat input model is constructed by real-time monitoring of the molten pool temperature using an infrared thermometer or thermocouple, combined with welding current and voltage data. When the monitored value deviates from the preset range, the system automatically adjusts the parameters to achieve closed-loop control. For example, in an automated cladding production line, a PLC control system can be used to adjust the welding speed and current in a coordinated manner to ensure that heat input fluctuations are controlled within ±5%, thereby guaranteeing the stability of the cladding quality.
Heat input control in the processing of alloy cladding wear-resistant steel plates requires a multi-dimensional collaborative approach, encompassing parameter matching, temperature management, sequence optimization, material selection, and intelligent monitoring. By precisely controlling core parameters such as welding current, voltage, and speed, combined with preheating, post-heating, and interpass temperature control, cladding layer cracks and spalling defects can be effectively avoided, thereby improving the overall performance and service life of the material.
