First, what are the raw material preparations for Q420C straight seam welded pipe production?
(a) Steel plate selection: Select steel plates that meet the Q420C material standard, ensuring that their chemical composition and mechanical properties meet the requirements. The thickness, width, and other dimensions of the steel plate should be selected according to the required specifications of the Q420C straight seam welded pipe.
(b) Steel plate inspection: Conduct a comprehensive quality inspection of the steel plate, including visual inspection to check for defects such as cracks, scratches, and dents; at the same time, perform non-destructive testing such as ultrasonic testing to ensure that there are no internal defects such as inclusions and delamination inside the steel plate.
Second, what are the steel plate pretreatments for Q420C straight seam welded pipes?
(a) Rust removal: Use methods such as sandblasting or shot blasting to remove impurities such as rust, oil, and oxide scale from the surface of the steel plate, improving the surface quality and weldability of the steel plate.
(b) Leveling: A leveling machine is used to level the steel plate, eliminating bending, twisting, and other deformations to ensure flatness for subsequent processing.
Forming:
(a) Milling: A milling machine is used to mill both edges of the steel plate on both sides to achieve the specified width, edge parallelism, and bevel shape. Beveling facilitates subsequent welding and ensures weld quality.
(b) Pre-bending: A pre-bending machine is used to pre-bend the edges of the milled steel plate, giving them the required curvature to prepare for subsequent forming.
(c) Forming Process: The steel plate is bent into a tubular shape using methods such as JCOE forming or high-frequency straight seam forming. JCOE forming involves first pressing one half of a pre-bent steel plate into a “J” shape through multiple step-by-step stamping, then bending the other half into a “C” shape, ultimately forming an open “O” shape. High-frequency straight seam forming utilizes the resistance heat generated by high-frequency current at the edge of the steel plate to rapidly melt and extrude the steel into shape.
Third, what are the welding steps for Q420C straight seam welded pipe?
(a) Pre-welding: The formed Q420C straight seam welded pipe is joined together using gas shielded welding (MAG) for continuous welding, initially shaping the Q420C straight seam welded pipe. During welding, parameters such as welding current, voltage, and welding speed must be carefully controlled to ensure weld quality.
(b) Inner welding: Longitudinal multi-wire submerged arc welding is used to weld the inside of the Q420C straight seam welded pipe. Multi-wire submerged arc welding improves welding efficiency and weld quality. Care must be taken in selecting the welding wire and matching welding parameters during welding.
(c) External Welding: Similar to internal welding, longitudinal multi-wire submerged arc welding is used to weld on the outside of the Q420C straight seam welded pipe to ensure the overall welding strength and sealing performance of the Q420C straight seam welded pipe.
Fourth, what are the requirements for weld inspection of Q420C straight seam welded pipe?
(a) Visual Inspection: Inspect the appearance of the weld to check for surface defects such as undercut, porosity, slag inclusions, and cracks.
(b) Non-destructive Testing: Use methods such as ultrasonic testing and X-ray testing to inspect the internal quality of the weld to ensure that there are no defects inside the weld. Ultrasonic testing can detect defects such as incomplete penetration and slag inclusions inside the weld; X-ray testing can visually observe the internal condition of the weld and detect defects such as porosity and cracks.
(c) Heat Treatment (as needed): If the Q420C straight seam welded pipe has special performance requirements, heat treatment may be required. Common heat treatment methods include quenching and tempering to improve the strength, toughness, and other properties of Q420C straight seam welded pipes.
Fifth, what are the finishing processes for Q420C straight seam welded pipes?
(a) Diameter Expansion: The Q420C straight seam welded pipe is expanded along its entire length after welding to improve its dimensional accuracy and the distribution of internal stress.
(b) Straightening: A straightening machine is used to straighten the Q420C straight seam welded pipe, eliminating bending deformations generated during forming and welding, and ensuring its straightness.
(c) Beveling: The ends of the Q420C straight seam welded pipe are processed to achieve the required bevel dimensions for easy connection and installation.
Sixth, what are the final inspection and packaging procedures for Q420C straight seam welded pipes?
(a) Final Inspection: A comprehensive quality inspection is conducted on the finished Q420C straight seam welded pipes, including testing of dimensions, appearance, and mechanical properties, to ensure that the Q420C straight seam welded pipes meet relevant standards and customer requirements.
(b) Packaging: The inspected and qualified Q420C straight seam welded pipes are packaged. Appropriate packaging materials and methods, such as bundling and boxing, are selected according to customer requirements and transportation methods to protect the Q420C straight seam welded pipes from damage during transportation and storage.
Post time: Jan-23-2026