Pre-welding quality of LSAW steel pipe

LSAW or straight seam steel pipe features a weld seam running parallel to the pipe's longitudinal direction. These pipes are commonly classified into various types, such as metric electric welded steel pipes, electric welded thin-walled pipes, and transformer cooling oil pipes. The production of straight seam steel pipes is straightforward, characterized by high production efficiency, low cost, and rapid development.

While spiral welded pipes typically offer higher strength than straight seam steel pipes, LSAW pipes have their own advantages. For instance, large-diameter welded pipes can be produced using narrower billets, and pipes of varying diameters can be made from billets of the same width. However, compared to straight seam pipes of equivalent length, spiral pipes have a weld length that is 30% to 100% longer, which can slow down production.

Pre-Welding Quality of LSAW Steel Pipes

Ensuring high pre-welding quality is crucial for LSAW steel pipes, as it directly affects the final weld integrity and overall pipe performance. The pre-welding quality involves both joint and weld quality, with the following key considerations:

- Seam Alignment:
The forming seam must have minimal or no misalignment. Typically, the misalignment should be ≤ 8% of the steel plate thickness, with a maximum limit of 1.5mm.

- Weld Penetration:
Adequate weld penetration and depth are essential. The weld must avoid cracking or burning while ensuring that the external weld’s residual height does not negatively impact the pipe.

- Seam Continuity:
The weld seam should be continuous and well-formed to ensure high-quality final welding on the pipe's exterior.

- Defect-Free Welding:
The weld’s reverse side should be free from defects like deviations, pores, cracks, slag inclusions, burn-through, and welding nodules. The weld’s center deviation must be less than 1mm.

- Surface Quality:
There should be no arc burns, minimal spatter, and no adverse impact on the pipe's groove end and surface quality.

- Material Consistency:
The weld seam should seamlessly integrate with the base metal, ensuring that the weld metal's physical and chemical properties meet the necessary quality standards.

These pre-welding quality measures are essential to achieving a reliable and durable LSAW steel pipe, ensuring its performance in various applications.