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Manufacturing method of steel pipe

Dec. 18, 2019

1. Marking, cutting and beveling

(1) The marking of the steel plate is based on the construction drawing, and factors such as cutting loss and welding shrinkage are considered. After marking, use steel stamps and paint to mark the steel pipe section, section number, water flow direction, horizontal and vertical center line, bevel angle and cutting line.

(2) The blanking and beveling of steel plates are processed by CNC cutting machines or semi-automatic cutting machines. The overall dimensions and cutting quality of the steel plates meet the requirements of the specification. The slag, burrs and defects on the groove surface are cleaned by an angle grinder. Immediately after the bevel processing, the non-toxic anti-rust coating that does not affect the welding performance and quality is sprayed.

Sprial Steel Pipe

Sprial Steel Pipe

2. Coil

The steel pipe is rolled by cold rolling. The direction of the coil is the same as the rolling direction of the steel plate. It is not allowed to bend and shape the steel pipe by hammering at the port of the steel plate. The rolled steel pipe is erected on the platform in a free state, and the arc of the steel pipe is checked with a template.

3. Welding

The longitudinal seam of the steel pipe is welded with X-shaped grooves on both sides. The longitudinal seam welding of the same section of steel pipe is submerged arc automatic welding. Generally, the inner seam is welded first. After the appearance inspection of the inner seam is qualified, the back of the carbon arc gouging is used to clean the root. Welding procedure qualification: The butt weld test piece is used, and the welding procedure qualification is completed before welding. Before the assessment, according to the product standard and design technical requirements, draw up a technical plan for the steel plate grade, thickness, welding method, welding material grade and groove type used. Welded steel pipes’ process plan includes bevel processing, group alignment, cleaning, preheating temperature, inter-layer temperature, post-heating temperature and time, welding parameters, welding position, number of welding layers and tracks, line energy range, stress relief after welding, heat treatment Items and procedures for specification and inspection and testing.

4. Rounding

The round adjustment of the seamless carbon steel pipe is performed on the round platform. After rounding, it is supported symmetrically at the steel pipe port to prevent the steel pipe from deforming during welding or lifting.

5. Assembly and welding of pipe joints

The steel pipe is rounded on the round platform. The rounded single pipe sections are integrated into the number sequence, and the manufacturing tolerances of the steel pipe are checked to make the manufacturing tolerances meet the relevant provisions of the code. In order to ensure uniform and consistent shrinkage during the welding of steel pipes, each ring seam is welded by four welders at the same time, and symmetrical, segmented, multi-layer, multi-pass, retrogressive welding is used, and hammering is used to eliminate welding residual stress. Each layer of welding joint is staggered by 50mm, and the cover seam is formed at one time. After all the welds have been welded, they shall be visually inspected, and after passing the non-destructive inspection of the welds.

6. Anticorrosive coating for anti-corrosion steel pipes

(1) After the fabrication of each section of steel pipe is checked and confirmed by the engineer, the anticorrosive coating operation can be performed in accordance with the specifications and the requirements of the engineer.

(2) Anti-corrosion process: preparation of rust removal tools and tools removal of welding slag, spatter, etc. surface treatment quality inspection coating application inspection and acceptance.

(3) Anti-corrosion coating of steel pipes in accordance with the technical provisions of the bidding documents and the requirements of the engineers.