LSAW steel pipe, full name Longitudinal Submerged Arc Welded steel pipe, is a mature type of welded steel pipe widely used in large-scale engineering projects such as oil and gas transmission, urban pipeline networks, water conservancy projects, bridge construction, and infrastructure development. Its core advantages stem from a complete, rigorous, and highly controllable production process.
Combined with the actual production technology of longitudinal submerged arc welded steel pipes, the following is a systematic interpretation of the entire process of LSAW steel pipes from raw materials to finished products in accordance with the standard production flow.
I. Raw Material Preparation and Preliminary Inspection
1. Raw Material Warehousing and Inspection
LSAW steel pipes usually use medium and thick steel plates as raw materials. After the steel plates arrive at the factory, checks and inspections are first conducted on their appearance, dimensions, steel grade, chemical composition, and mechanical properties to ensure the raw materials meet project and relevant standard requirements.
2. Loading and Steel Plate Inspection
Before formally entering the production line, the steel plates undergo loading inspection, focusing on checking for defects such as delamination, cracks, and inclusions on the plate surface, laying a foundation for subsequent welding quality.
II. Steel Plate Pre-treatment and Forming Preparation
1. Welding of Weld Stubs and Ultrasonic Testing
Weld stubs are welded at both ends of the steel plate to stabilize the arc striking and extinguishing quality during subsequent welding. After completion, ultrasonic flaw detection is performed on the steel plate to identify internal defects in advance.
2. Edge Milling and Rust Removal of Plate Edges
The edges of the steel plate are precision-processed through edge milling to make the groove angle and root face dimension more accurate. At the same time, rust removal is carried out on the plate edges to avoid slag inclusion or porosity during welding.
III. Steel Pipe Forming Process
1. Pre-bending and JCO Forming
The steel plate first undergoes pre-bending to form an initial curvature at the edges, then is gradually pressed into an open pipe blank through the JCO forming process. This forming method ensures uniform stress distribution, which helps guarantee the overall roundness and dimensional accuracy of the steel pipe.
2. Pre-welding and Weld Inspection & Repair
The formed pipe blank is first pre-welded to fix the pipe shape. After pre-welding, the weld is inspected, and any defects found are repaired in a timely manner to ensure the weld is in good condition before entering the formal welding stage.
IV. Internal and External Submerged Arc Welding Process
1. Internal Welding and External Welding
LSAW steel pipes adopt the double-sided submerged arc welding process, with internal welding performed first, followed by external welding. During welding, the arc burns under the flux layer, ensuring stable welding heat input, full and dense weld formation, and high consistency in welding quality.
2. Removal of Weld Stubs
After welding, the weld stubs are removed to avoid redundant welds affecting the quality of the pipe ends.
V. Weld and Overall Quality Inspection
1. Radiographic and Ultrasonic Testing
The weld undergoes multiple non-destructive testing (NDT) procedures, including radiographic testing and ultrasonic testing, to comprehensively evaluate internal weld defects and overall welding quality, ensuring the weld meets relevant technical standards.
2. Hydrostatic Test
Each steel pipe undergoes a hydrostatic test to verify its sealing performance and structural safety under pressure by simulating actual working pressure.
VI. Post-treatment and Finishing Process
1. Mechanical Expanding and Roundness Correction
Through mechanical expanding, the outer diameter, roundness, and straightness of the steel pipe are further stabilized, while the residual stress distribution is improved, enhancing the overall performance of the steel pipe.
2. Pipe End Processing and Weld Grinding
According to usage requirements, groove processing is performed on the pipe ends, and the weld reinforcement is ground to meet subsequent butt welding or installation requirements.
3. Appearance, Dimension, and Weight Inspection
The steel pipe undergoes appearance inspection, dimension review, and weight measurement to ensure each pipe meets order and standard requirements.
VII. Finished Product Inspection and Warehousing & Shipment
1. Magnetic and Final Inspection
Residual magnetism detection and final quality inspection are conducted on the steel pipe to ensure no potential hazards in performance and safety of the finished product.
2. Marking, Pipe End Protection, and Storage & Transportation
After completing marking and installing pipe end protectors, the steel pipes are transferred to the finished product storage area, awaiting shipment to the project site.
Conclusion
From the warehousing of steel plates to the delivery of finished products, the production process of LSAW steel pipes covers multiple key steps such as forming, welding, inspection, and finishing. Each process directly affects the final quality and service safety of the steel pipe. It is this rigorous and controllable production system that enables longitudinal submerged arc welded steel pipes to be widely used in high-standard engineering fields.
About Huayang Steel Pipe
As a professional steel pipe manufacturer, Huayang Steel Pipe has mature LSAW steel pipe production capabilities, with products covering an outer diameter range of 406–1422mm. We have long focused on the manufacturing and engineering application of high-quality longitudinal submerged arc welded steel pipes, providing stable and reliable product support for various large-scale projects.
