1. Material Procurement: Carbon steel raw materials are sourced from major steel companies.
2. Material Technical Requirements: Raw material quality must comply with the standards for the corresponding grade of pipe fittings being bid, and the quality of the final product must be determined in accordance with the requirements of the bidding documents.
3. Manufacturing and Inspection: The wall thickness of the raw materials used to manufacture pipe fittings-steel pipes and steel plates-should be selected within positive tolerances. Carbon steel seamless elbows are formed using medium-frequency hot-pushing, using medium-frequency induction heating. Carbon steel seamed elbows are formed by pressing steel plates into two half-shells and then butt-welding them. Carbon steel seamless tees are formed using a hot-drawing process using electric furnace heating. Carbon steel seamed tees are formed by coiling steel plates into pipes and then hot-drawing them. All caps are die-formed from steel plates. All seamed pipe fittings are welded using manual metal arc welding (SMAW). Prior to welding, a welding procedure specification (WPS) and welding procedure qualification record (PQR) covering all seamed pipe fittings must be provided to the buyer for the appropriate material.
4. Heat Treatment: Carbon steel pipe fittings are heat treated by normalizing at 890°C to 920°C. Cooling is by air cooling, with a holding time of 2.5 minutes per mm of wall thickness, not less than 30 minutes.
5. Machining and Pipe Fitting Dimensions: Pipe fitting beveling is performed by machining according to standard requirements. Dimensions, tolerances, and connection types must comply with ASME B16.9, ASME B16.11, and MSS SP-97.
6. Surface Treatment: All ASME B16.9 pipe fittings are polished to remove internal and external surface defects and oxides, followed by shot blasting to achieve a Sa 2.5 surface finish. Two coats of inorganic zinc-rich primer are applied, with a total thickness of 75 microns.
The above is the general process for carbon steel pipe fitting manufacturing. The specific manufacturing process may vary depending on the specific product specifications and requirements.
