The welding process of stainless steel sieve plates is a core element in ensuring their structural integrity and leak-proof operation, especially in fields with extremely high requirements for sealing and durability, such as petroleum, chemical, and food processing. Welding quality directly affects the service life and filtration efficiency of the sieve plate. To ensure welding effectiveness, a comprehensive approach is needed, encompassing material selection, process design, equipment control, operational procedures, and quality inspection, forming a complete process assurance system.
Material selection is fundamental to welding quality. Stainless steel sieve plates typically use austenitic stainless steel such as 304 or 316L. These materials have good weldability and corrosion resistance, but their high coefficient of thermal expansion and poor thermal conductivity make them prone to deformation or cracking during welding. Therefore, a matching material must be selected based on the sieve plate's operating environment (such as temperature and media corrosivity), and the base material must be rigorously inspected before welding to ensure the absence of cracks, delamination, and other defects. Simultaneously, the chemical composition of the welding material must be similar to that of the base material to avoid reduced weld corrosion resistance due to compositional differences.
Process design must balance structural strength and sealing performance. Welding of stainless steel sieve plates primarily employs TIG welding or plasma arc welding. These two processes offer advantages such as stable arc, concentrated heat, and good weld formation, effectively reducing porosity and cracking. For thin-plate sieves, low current and short arc parameters are required to avoid burn-through. For thick plates or structures requiring high strength, multi-layer, multi-pass welding can be used, with each subsequent weld layer heat-treating the previous one to refine the grain and improve weld toughness. Furthermore, the sieve plate's gap design (e.g., trapezoidal cross-section) must be matched to the welding process to ensure the weld covers the gap edges and prevent media leakage.
Equipment control is crucial for ensuring welding stability. The welding power source must have precise current and voltage regulation capabilities to adapt to welding requirements of different thicknesses and materials. For automated production lines, CNC welding equipment is necessary, using preset programs to control the welding torch's trajectory and welding parameters, ensuring the repeatability and consistency of each weld pass. Simultaneously, the welding environment must be kept clean to prevent wind, dust, and other factors from interfering with arc stability; localized exhaust ventilation or protective gas hoods can be installed if necessary.
Operating procedures directly impact weld quality. Welders must undergo professional training and master stainless steel welding techniques, such as arc initiation, arc termination, and oscillation. During welding, appropriate arc length and welding speed must be maintained to avoid incomplete fusion due to excessive speed or overheating deformation due to insufficient speed. For joints in the sieve plates, tack welding is required to prevent displacement during welding. For multi-layer welding, slag and spatter must be cleaned promptly to avoid slag inclusion defects. Furthermore, the weld reinforcement must be controlled within a reasonable range; excessive reinforcement will reduce the flatness of the sieve plate, while insufficient reinforcement may affect sealing.
Quality inspection is the final line of defense in the welding process. Welds must be visually inspected, penetrant tested, or radiographically inspected to confirm the absence of cracks, porosity, incomplete fusion, and other defects. For sieve plates used with high-pressure or corrosive media, pressure testing or airtightness testing is also required to ensure the weld can withstand the design pressure without leakage. In addition, the hardness, corrosion resistance, and other properties of the welded area must be sampled and tested to verify compliance with usage requirements.
Post-processing can further improve welding quality. After welding, the weld seam needs to be pickled and passivated to remove oxide scale and form a dense passivation film, improving corrosion resistance. For screen plates requiring high flatness, mechanical grinding or laser polishing can be used to eliminate weld excess and ensure a smooth surface. Furthermore, screen plates used long-term require regular inspection of the weld condition, and timely repair of leaks caused by wear or corrosion.
Process optimization and continuous improvement are essential for ensuring long-term welding quality. By collecting data during the welding process (such as current, voltage, and welding time), the causes of weld defects can be analyzed, and process parameters can be continuously adjusted. For example, if cracks are found in the weld seams of a batch of screen plates, the carbon content of the base material or the compatibility of the welding materials can be checked; if the weld formation is poor, the welding torch angle or oscillation method can be optimized. Simultaneously, introducing new materials or processes (such as laser welding or friction stir welding) can further improve welding efficiency and quality.
