How is welded steel pipe made?

How is welded steel pipe made?

The production process of welded steel pipes involves bending steel plates or steel strips into pipe blanks with the required cross-sectional shape and size through various methods, and then welding the weld seams with different welding methods to obtain the steel pipes. Compared with seamless steel pipes, welded steel pipes have advantages such as high product precision, small floor space and continuous operation during the production process.

From the production process, the welded steel pipe is divided into three kinds: SSAW (spiral submerged arc welding), LSAW (straight seam submerged arc welding), ERW (resistance welding).

ERW steel pipe: high frequency straight seam resistance welded steel pipe, it uses hot rolled wide rolled material as raw materials, through pre-bending, continuous forming, welding, heat treatment, sizing, straightening, cutting and other processes made, compared with spiral pipe, it has short weld, high precision, uniform wall thickness, good surface quality, high pressure grade characteristics. However, the defect is that only small and medium caliber thin-walled pipes can be produced, and the weld is prone to defects. Generally used for urban gas and crude oil transportation.

SSAW steel pipe: spiral submerged arc welded steel pipe, is a kind of steel pipe with a spiral weld. Its weld can avoid the main stress, the force is good. The disadvantage is that the weld is easy to crack, and the welding may have defects. Generally used for oil and gas pipelines.

LSAW steel pipe: straight seam submerged arc welded steel pipe, using a single medium thick steel pipe as raw material, pressed in the mold or forming machine, using double-sided submerged arc welding method of expanding production. Its product standard specifications, good fineness of the weld, with large caliber, pipe wall thickness, high pressure resistance, corrosion resistance and other advantages. When high strength and high quality long oil and gas pipelines are needed, the steel pipes required are mostly LSAW steel pipes.

Weld detection
The inspection of welds is usually hydraulic method, ultrasonic and X-ray, which is used to check whether there are cracks or pores inside the weld to ensure that the quality of the welding meets the standard.

Surface treatment
Correction: Through the straightening machine to correct the roundness and flatness of the steel pipe to ensure that the size of the steel pipe meets the requirements.

Surface anti-corrosion: Usually galvanized, spray paint or spray anti-corrosion coating is used to increase the corrosion resistance of the pipeline and extend the service life of the steel pipe.

In summary, the manufacturing process of welded steel pipes involves multiple steps such as steel plate rolling, forming, welding, heat treatment, inspection and coating protection. Through advanced welding technology and strict quality control, welded steel pipes not only ensure good strength and sealing performance, but also meet the usage requirements under different pressures and environments. For this reason, welded steel pipes are widely used in fields such as petroleum, natural gas, water conservancy, construction and industry, and have become indispensable important materials in modern pipeline engineering.