Welding Process for 310S Ball Valves<\/p>\n
Chemical Composition Analysis of 310S Ball Valves<\/p>\n
The primary alloying elements of 310S stainless steel are Cr, Ni, Mn, and Si, with mass percentages of 25% chromium, 19% nickel, 2% manganese, and 1% silicon; the material is typically supplied in a solution-annealed condition. Welding heat input should be neither too high nor too low; it is generally controlled within the range of 0.5\u20132.5 kJ\/cm, with the specific value selected based on the thickness of the workpiece. Preheating is generally not required; however, if the workpiece is very thick or the ambient temperature is too low, preheating measures must be taken to prevent post-weld cracking in the weld seam and heat-affected zone (HAZ) caused by excessive cooling rates. Since 310S valves are manufactured via casting, oxides and impurities (such as sand inclusions) may be present; consequently, welding operations primarily involve the repair of sand holes. Repair procedures require removing oil and grease from the weld area with acetone and preheating the sand hole site. Appropriate welding parameters must be selected. To prevent grain coarsening in the weld HAZ, interpass temperature must be controlled; for stainless steel, the interpass temperature is generally kept below 100\u00b0C.<\/p>\n
Basic Process Requirements for 310S Ball Valves<\/p>\n
310S Ball Valve Process Requirements:<\/p>\n
1. Personnel performing welding work must undergo training and examinations covering basic welding knowledge and operational skills, and must hold a welder qualification certificate issued by the quality and technical supervision department.<\/p>\n
2. Pre-welding preparations for 310S ball valves:<\/p>\n
\u2460 Inspect the welding machine, welding torch, tungsten electrode, external shielding gas shroud (or nozzle), welding wire, flux, cooling water system, etc.; welding may only proceed if all systems are functioning correctly.
\n\u2461 Verify the process routing card against the markings and details on the steel component to be welded, ensuring that the material grade, specifications, thickness, and other parameters match the information on the routing card. \u2462 Clean the longitudinal areas extending 20 mm on both sides of the weld joint. Remove contaminants such as oil and rust that could affect weld quality using alcohol, acetone, cotton waste, or wire brushes\/wheels; welding may only commence after the alcohol and acetone have completely evaporated.
\n\u2463 Verify that the welding wire is compatible with the base metal and that there is a sufficient quantity to complete the weld pass.<\/p>\n
3. Selection of welding wire for 310S ball valves
\nFor 0Cr25Ni20 (310) base metal, only ER310 (HOCr26Ni21) welding wire shall be used.<\/p>\n
4. Key points for welding 310S ball valves:<\/p>\n
\u2460 Perform welding in accordance with the process parameters specified in the Welding Procedure Specification (WPS).<\/p>\n
\u2461 Arc initiation and termination must be performed on run-on and run-off tabs; the initiation and termination points should be located within 50 mm of the outer edge of these tabs.<\/p>\n
\u2462 Plasma welding is susceptible to “double-arcing”\u2014which is prohibited\u2014if the welding current exceeds the nozzle’s maximum rated current or if the tungsten electrode is misaligned (non-concentric) with the nozzle. The standoff distance from the workpiece surface is generally set at 3\u20135 mm (excessive distance reduces penetration capability, while insufficient distance causes spatter accumulation on the nozzle). The nozzle orifice diameter determines the plasma arc diameter and should be selected based on the operating current and plasma gas flow rate.<\/p>\n
\u2463 Monitor the welding arc continuously during the process and make minor adjustments to welding parameters as necessary; interrupting the arc during welding is not permitted.<\/p>\n
5. Upon completion of welding, perform a self-inspection of the weld seam. Address any defects identified during self-inspection in accordance with relevant regulations and accurately complete all associated records. The weld seam must transition smoothly into the base metal and be free from defects such as cracks, porosity, undercut, incomplete penetration, weld spatter\/nodules, or concavity.<\/p>\n
6. After welding and prior to moving the welded pipe, the welding carriage must be relocated to a safe position.<\/p>\n