How seamless steel pipe is made?

Seamless steel pipes are made through a process that does not involve welding or joints, resulting in a continuous, uniform structure throughout the length of the pipe. Here’s an overview of the manufacturing process.

1. Selection of Raw Material

The process begins with selecting high-quality steel billets or solid steel bars.

2. Heating

The steel billets are heated to a high temperature (typically around 1200°C) in a rotary hearth furnace.

3. Piercing

The heated billet is then pierced using a rotary piercer or a mandrel mill. This process involves pushing a mandrel or piercing plug through the center of the billet to create a hollow shell.

4. Elongation

The hollow shell is then elongated using a series of rolling mills (such as a plug mill, a mandrel mill, or a push bench). This reduces the diameter and wall thickness while increasing the length of the pipe.

5. Sizing and Stretch Reducing

The elongated pipe is then passed through a series of sizing mills and stretch-reducing mills to achieve the desired diameter and wall thickness.

6. Heat Treatment

The pipe undergoes heat treatment (such as annealing, normalizing, quenching, and tempering) to achieve the required mechanical properties and relieve any internal stresses.

7. Straightening

After heat treatment, the pipe is straightened using a straightening machine.

8. Cutting

The pipe is cut to the desired length using a cutting machine.

9. Finishing

The pipe undergoes finishing operations, which may include beveling, threading, or other surface treatments to meet specific requirements.

10. Inspection and Testing

The final product is subjected to various inspections and tests (such as ultrasonic testing, eddy current testing, hydrostatic testing, and dimensional inspection) to ensure it meets the required quality standards.

11. Marking and Packaging

The pipes are marked with the necessary information (such as batch number, heat number, size, and grade) and then packaged for shipment.

Manufacturing Process Flow

Billet Heating: Rotary Hearth Furnace

Piercing: Rotary Piercer or Mandrel Mill

Elongation: Rolling Mills (Plug Mill, Mandrel Mill, Push Bench)

Sizing & Stretch Reducing: Sizing Mills and Stretch Reducing Mills

Heat Treatment: Annealing, Normalizing, Quenching, and Tempering

Straightening: Straightening Machine

Cutting: Cutting Machine

Finishing: Beveling, Threading, Surface Treatments

Inspection & Testing: Ultrasonic, Eddy Current, Hydrostatic, Dimensional

Marking & Packaging: Batch Number, Heat Number, Size, Grade

This seamless manufacturing process ensures that the pipes have a consistent structure, better mechanical properties, and superior strength compared to welded pipes.

Continental Steel is specialized in seamless steel pipe designing, manufacturing, stocking and exporting in China. If you have any request, please contact:sales@continental-steel.com