Spatter generated during welding with a used high-frequency welded tube mill is primarily due to process control failures caused by aging equipment, abnormal material conditions, and the combined effects of high-frequency welding characteristics. Long-term use of used equipment reduces the energy conversion efficiency of the high-frequency power supply, deteriorating the stability of welding heat input, and prolonging the time the molten pool remains in a semi-solidified state. This allows metal droplets to escape from the molten pool under electromagnetic forces, forming spatter. Furthermore, aging insulation in the induction coil of used equipment can cause localized magnetic flux leakage, disrupting the flow of the molten metal and forming eddies at the V-shaped junction, which can eject metal droplets from the molten pool and exacerbate spatter.
Abnormal material conditions are another key factor in spatter generation. The surface of the strip processed by a used high-frequency welded tube mill often contains residual oil, oxide layers, or cooling water stains. These impurities rapidly vaporize or decompose under high-frequency heating during welding, generating explosive impact forces that tear the molten metal into spatter particles. For example, water stains on the strip accumulate at the V-shaped junction, forming small droplets. High-frequency welding heats these droplets, which instantly burst and carry tension, propel the molten metal in all directions, ultimately solidifying as spatter. Furthermore, excessive wire extension reduces current stability, increases the risk of arc drift, and leads to uncontrolled droplet transfer, further exacerbating spattering.
Degradation in the accuracy of the equipment control system is a unique problem for used high-frequency welded tube mills. Older equipment's high-frequency power supply has slow dynamic response speed, resulting in large fluctuations in welding heat input, leading to unstable weld pool volume and the tendency for metal droplets to fall off during solidification due to uneven shrinkage. Aging in the induction coil's insulation can also cause localized overheating, accelerating the degradation of electrical components and creating a vicious cycle. For example, reduced cooling system circulation efficiency can cause the equipment to operate at high temperatures for extended periods, leading to welding parameter drift and a significant increase in spatter rate.
A dynamic adjustment mechanism is required to optimize process parameters. Used high-frequency welded tube mills should first determine a base welding current range based on the pipe material characteristics, then gradually adjust voltage parameters through experimental methods to stabilize the arc length within a reasonable range. For pipes of varying wall thicknesses, a segmented control strategy is required: When welding thin-walled pipes, reduce the wire feed speed and use a short-arc welding mode to minimize the droplet transfer distance. When welding thick-walled pipes, use a pulsed current waveform, periodically inputting energy to control the molten pool volume and avoid metal overfill. Furthermore, the wire extension should be shortened to minimize interference from resistance heat on droplet transfer.
Standardizing the material pretreatment process is fundamental to spatter control. Strip material processed by a high-frequency welded pipe mill undergoes multi-stage cleaning before entering the welding process: first, a high-pressure spray is used to remove surface dust, then an electrolytic cleaning tank is used to remove oil, and finally, a hot air circulation system is used for thorough drying. For heavily oxidized pipes, an additional pickling and passivation step is required to form a dense oxide film on the strip surface, minimizing metallurgical reactions during welding. Welding wire should be stored in a constant-temperature warehouse with a humidity below 60%. Before use, it should be polished with a wire wheel to remove surface rust.
Upgrades and modifications to the equipment control system should focus on key modules. The high-frequency power supply module of a used high-frequency tube welder should be replaced with an IGBT inverter structure. This significantly improves energy conversion efficiency over traditional thyristor-based systems and offers faster dynamic response. The induction coil should be rewound and insulated with multiple layers of mica tape to ensure that the magnetic flux leakage coefficient meets standards. The welding control system should integrate an expert database module to automatically generate an optimal process curve by collecting real-time data on parameters such as welding current, voltage, and wire feed speed, thereby reducing operator error.
Improving the use of auxiliary equipment can significantly improve spatter control. A high-pressure airflow shielding device should be installed inside the welding box of a used high-frequency tube welder to direct spatter away from the weld pool. The contact nozzle should be made of copper-plated ceramic, which offers several times greater wear resistance than ordinary copper nozzles and maintains a stable arc shape. The nozzle structure should be optimized to a convergent-divergent design to achieve laminar shielding of the shielding gas, effectively isolating nitrogen and oxygen from the air. Furthermore, applying an anti-clogging agent to the nozzle prevents spatter from clogging the nozzle and extends the equipment's service life.
