Cause analysis of slag inclusion in welded steel pipe

　Spiral welded steel pipe is a kind of low carbon structural steel or low alloy structural steel strip coiled into billet according to a certain helix angle, and then welded together to make the pipe seam. It can produce large diameter spiral welded steel pipe with narrow strip. Spiral welded steel pipe is mainly used for oil and natural gas pipeline, and its specification is expressed by outer diameter and wall thickness.

　　Spiral welded steel pipes with one-side welding and two-side welding, welded steel pipes should ensure that the hydraulic test, weld tensile strength and cold bending performance to meet the requirements.

　　Slag inclusion in welded steel pipe is slag left in the weld seam. Theoretically, there are three main reasons for slag inclusion in submerged arc automatic welding seam: (1) more inclusions in raw materials; (2) interlayer cleaning is not clean during multi-layer welding; (3) improper selection of welding parameters is not conducive to slag floating.