Manufacturing Processes of Seamless Pipes And Welded Pipes
Publish Time: 2024-12-17 Origin: Site
Manufacturing Process of Seamless Pipes
Seamless pipes are pipes without welds, usually formed through processes like extrusion, drawing, and expansion. The manufacturing process generally includes the following key steps:
(1) Raw Material Preparation
The raw material is typically a steel billet or casting, which is heated in a furnace to a certain temperature, usually around 1200°C.
(2) Piercing
The heated billet is sent to a piercing machine, where rollers or forging equipment create a hollow pipe (a "pipe blank," which is a semi-finished product of seamless pipes).
(3) Shaping (Expanding)
The pipe blank, after further heating, is expanded radially to form the desired pipe shape. This process is usually carried out on various machines such as extrusion machines and expanding machines.
(4) Sizing and Cooling
After expansion, the pipe undergoes sizing to achieve the required inner and outer diameters. This is typically done during the cooling process using sizing dies.
(5) Heat Treatment
Seamless pipes undergo heat treatment, which usually involves normalizing or annealing to remove residual stress and improve the mechanical properties of the steel pipe.
(6) Cooling and Straightening
After heat treatment, the pipe is cooled and then straightened to ensure that it does not become bent.
(7) Surface Treatment
The surface may be treated as required, such as by pickling, coating with anti-rust oil, etc.
(8) Inspection and Cutting
The final step in the production of seamless pipes is quality inspection, including checking dimensions, hardness, surface defects, etc., followed by cutting and packaging as needed.
2. Manufacturing Process of Welded Pipes
Welded pipes are made by heating a strip of steel and then using welding technology to join the two edges, forming a pipe. The manufacturing process of welded pipes is relatively simpler and generally includes the following steps:
(1) Raw Material Preparation
The raw material for welded pipes is usually steel coils or strips, which are cut and uncoiled to prepare the steel strips suitable for pipe production.
(2) Pipe Forming
The steel strip is heated and then fed into a forming machine, where it is rolled into a pipe shape. The edges of the strip are bent into a cylindrical shape by rollers.
(3) Welding
The formed pipe blank is then welded, typically using high-frequency welding (ERW) or submerged arc welding (SAW). In high-frequency welding, high-frequency current heats the edges of the strip, and pressure is applied to weld them together, forming a seam.
(4) Post-Welding Treatment
After welding, the pipe undergoes cooling and various processes to remove burrs from the weld seam and to shape the pipe, ensuring a smooth appearance.
(5) Cooling and Sizing
The welded pipe is cooled and further sized to adjust its outer diameter to the required specifications.
(6) Heat Treatment (Optional)
Some welded pipes may undergo heat treatment such as annealing to relieve stresses created during welding and improve the microstructure of the weld zone.
(7) Inspection and Cutting
Welded pipes typically undergo weld quality inspections (such as ultrasonic testing, X-ray inspection, etc.) to ensure there are no defects in the weld seam. After inspection, the pipes are cut to the desired length, surface treated (such as pickling or galvanizing), and then packaged.
Key Differences Summary
| Aspect | Seamless Pipe | Welded Pipe |
|---|---|---|
| Manufacturing Process | Piercing, extrusion, and expansion without seams | Strip steel is rolled and welded to form the pipe |
| Raw Material | Steel billets | Steel strips or coils |
| Weld Seam | No weld seam | Has a weld seam |
| Strength | Higher, with no defects in the weld area | Strength may be lower in the weld zone |
| Cost | Higher production cost | Lower production cost |
| Applications | Used in high-strength and high-pressure applications | Used in low-pressure applications |
| Production Efficiency | More complex, time-consuming process | Simpler, more efficient production |
Summary
Seamless pipes generally have higher strength and uniformity, making them suitable for high-pressure and high-strength applications, but their manufacturing process is complex and costly.
Welded pipes, on the other hand, are suitable for applications with lower strength requirements, with a simpler manufacturing process, lower cost, and higher production efficiency, making them ideal for large-scale production.