Process Differences Between SSAW Steel Pipe And LSAW Steel Pipe

In the field of welded steel pipes, SSAW steel pipe and LSAW steel pipe are two widely used types. They differ in application scenarios, quality stability, and weld seam reliability, which all originate from their fundamentally different manufacturing processes. This article provides an in-depth comparison of their process flow, welding techniques, and weld characteristics, followed by a concise comparison table for quick reference.

I. Manufacturing Process of SSAW Steel Pipe

1. Spiral Weld Seam Forming Method

SSAW steel pipe is produced by spirally forming steel strip at a specific angle and then welding the pipe internally and externally. As the strip is wound at a set spiral angle, a continuous helical weld seam is formed. This design allows better load distribution and reduces requirements for strip width, making SSAW steel pipe suitable for high-volume, long-distance pipeline products.

2. Welding Process Flow

SSAW steel pipe commonly uses double-sided submerged arc welding or high-frequency welding. The welding temperature is high and penetration depth is stable, but due to the extensive weld seam length, each pipe requires more welding passes. Typical SSAW production equipment includes uncoiling, leveling, forming, internal welding, external welding, sizing, and cutting. Although the production pace is efficient, the long weld seam and varying welding angle are critical factors that affect the final quality.

3. Process Characteristics

SSAW steel pipe offers flexible processing capability, wide diameter range, and adaptability to various wall thicknesses. However, the long weld seam exposes the weld metal to higher dynamic load risks, limiting its use in high-standard projects.

II. Manufacturing Process of LSAW Steel Pipe

1. Longitudinal Weld Seam Forming Method

LSAW steel pipe is produced by edge milling, pre-bending, and forming steel plate, followed by internal and external double-sided submerged arc welding. Its key feature is a straight longitudinal weld seam with a short welding path, which significantly enhances quality control.

2. Welding Process Flow

LSAW steel pipe typically adopts UOE or JCOE forming processes. The production sequence includes edge milling, pre-bending, forming, internal welding, external welding, expansion, hydrostatic testing, and ultrasonic flaw detection, etc. Submerged arc welding provides deep penetration, stable weld metal, and highly controllable weld quality, making it one of the most recognized welding methods in high-end industrial applications.

3. Process Characteristics

LSAW steel pipe has short weld seams and a concentrated heat-affected zone, enabling high-strength, high-quality weld formation. Its uniformity, fatigue performance, and overall weld seam stability are superior to SSAW steel pipe, making LSAW the preferred choice for high-pressure, high-strength, and large-scale structural projects.

III. Comparison Table of Process Differences

IV. Conclusion

Both SSAW steel pipe and LSAW steel pipe play important roles in engineering applications. However, from the standpoint of manufacturing processes and weld seam stability, LSAW steel pipe is better suited for projects requiring high welding strength and reliability. Its straight weld seam and double-sided submerged arc welding deliver high structural stability, making LSAW a mainstream choice for oil and gas pipelines, offshore engineering, and pressure-bearing applications.