Seamless Steel Pipe Production Process

### Seamless Steel Pipe Production Process

The general production process of seamless steel pipes can be categorized into **cold drawing** and **hot rolling**. The production process of cold-rolled seamless steel pipes is generally more complex than that of hot-rolled pipes. The pipe billet first undergoes three-roll continuous rolling. After extrusion, a sizing test is performed. If there are no surface cracks, the round pipe is cut into billets about one meter long. The billets then undergo an annealing process. During annealing, the pipes are acid-washed with acidic solutions. It is important to observe whether there are many bubbles on the surface during acid washing, as excessive bubbling indicates that the steel pipe does not meet the quality standards.

In terms of appearance, cold-rolled seamless steel pipes are shorter than hot-rolled seamless steel pipes, and the wall thickness of cold-rolled pipes is generally thinner. However, cold-rolled seamless steel pipes have a brighter surface, with less roughness and fewer burrs on the inner and outer diameters compared to thick-walled seamless pipes. Hot-rolled seamless steel pipes are typically delivered in the hot-rolled state or after heat treatment. After quality inspection, hot-rolled seamless steel pipes undergo strict manual selection. Following inspection, the surface is oiled, and multiple cold drawing experiments are conducted. After hot rolling, perforation tests are performed. If the perforation expansion is too large, straightening is required. After straightening, the pipes are sent to a flaw detection machine for inspection, labeled, sorted by specifications, and finally stored in the warehouse.

### Hot-Rolling Process

The general process for hot-rolled seamless steel pipes is as follows:
1. **Round billet** →
2. **Heating** →
3. **Perforation** →
4. **Three-roll skew rolling, continuous rolling, or extrusion** →
5. **Pipe removal** →
6. **Sizing (or reduction)** →
7. **Cooling** →
8. **Straightening** →
9. **Hydrostatic test (or flaw detection)** →
10. **Marking** →
11. **Storage**

Seamless steel pipes are made from steel ingots or solid billets, which are perforated to form hollow pipes. These pipes are then processed through **hot rolling**, **cold rolling**, or **cold drawing**. The specifications of seamless steel pipes are expressed in terms of outer diameter and wall thickness (in millimeters). Seamless steel pipes are divided into **hot-rolled** and **cold-rolled (drawn)** categories.

Hot-rolled seamless steel pipes are classified into general steel pipes, low and medium-pressure boiler steel pipes, high-pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes, and other types. Cold-rolled (drawn) seamless pipes, in addition to general steel pipes, low and medium-pressure boiler pipes, high-pressure boiler pipes, alloy steel pipes, stainless steel pipes, and petroleum cracking pipes, also include **carbon thin-walled pipes**, **alloy thin-walled pipes**, **stainless thin-walled pipes**, and **shaped steel pipes**.

Hot-rolled seamless pipes generally have an outer diameter greater than 32mm, with a wall thickness of 2.5mm to 200mm. Cold-rolled seamless steel pipes can have an outer diameter as small as 6mm, with wall thicknesses as thin as 0.25mm. Thin-walled pipes can have outer diameters as small as 5mm, with wall thicknesses less than 0.25mm. Cold-rolled pipes have higher dimensional accuracy than hot-rolled pipes.

### General Seamless Steel Pipes

Seamless steel pipes are typically made from high-quality carbon structural steels such as 10, 20, 30, 35, and 45, low-alloy structural steels such as 16Mn and 5MnV, or alloy steels such as 40Cr, 30CrMnSi, 45Mn2, and 40MnB, through either hot rolling or cold rolling. Seamless pipes made from low-carbon steel like 10 and 20 are mainly used for fluid transportation pipelines, while medium-carbon steels like 45 and 40Cr are used for manufacturing mechanical parts, such as load-bearing components in automobiles and tractors. General seamless steel pipes must meet strength and flattening test requirements. Hot-rolled steel pipes are delivered in the hot-rolled state or after heat treatment, while cold-rolled pipes are delivered only after heat treatment.

### Hot Rolling Process Characteristics

As the name suggests, **hot rolling** involves rolling the material at high temperatures, which reduces the deformation resistance and allows for large deformations. For example, in steel plate rolling, the thickness of the continuous casting billet is usually around 230mm, and after rough rolling and finish rolling, the final thickness is 1 to 20mm. Additionally, because the width-to-thickness ratio of steel plates is low, the dimensional accuracy requirements are relatively low, and issues with plate shape are less likely to occur. The primary concern in hot rolling is controlling the crown. For materials with specific structural requirements, controlled rolling and cooling are used, which involves controlling the **start rolling temperature** and **finish rolling temperature** in the finishing mill.

### Typical Cold-Rolling Process

1. **Round billet** →
2. **Heating** →
3. **Perforation** →
4. **Heading** →
5. **Annealing** →
6. **Acid washing** →
7. **Oiling (copper coating)** →
8. **Multiple cold drawing (cold rolling) passes** →
9. **Pipe billet** →
10. **Heat treatment** →
11. **Straightening** →
12. **Hydrostatic test (or flaw detection)** →
13. **Marking** →
14. **Storage**

### Seamless Steel Pipe Manufacturer Example

The seamless steel pipe manufacturer **Changzhou Tongxing Steel Pipe Co., Ltd.**, located in Jiangsu Province, near the mid-section of the Shanghai-Nanjing Railway and Shanghai-Nanjing Expressway, enjoys convenient transportation. The factory integrates industry expertise, new equipment, complete inspection measures, strict management, excellent service, and a high-quality workforce to produce seamless steel pipes, which serve as essential components across various industries.

### Detailed Production Process

1. **Billet** →
2. **Inspection** →
3. **Peeling** →
4. **Inspection** →
5. **Heating** →
6. **Perforation** →
7. **Acid washing** →
8. **Grinding** →
9. **Lubrication and drying** →
10. **Welding head** →
11. **Cold drawing** →
12. **Solution treatment** →
13. **Acid washing** →
14. **Pickling and passivation** →
15. **Inspection** →
16. **Cold rolling** →
17. **Degreasing** →
18. **Cutting head** →
19. **Drying** →
20. **Internal polishing** →
21. **External polishing** →
22. **Inspection** →
23. **Marking** →
24. **Final product packaging**

### Industrial Pipe Production Process

By admin|2024-09-14T08:06:45+00:00September 14th, 2024|Categories: BLOG|0 Comments

Seamless Steel Pipe Production Process