Manufacturing process of cold drawn seamless steel pipe

Cold-drawn seamless steel pipes are long steel products with a hollow cross-section and no seams, offering significant advantages over welded steel pipes. Cold-drawn seamless pipes are produced through a series of processes such as cold drawing and cold bending at room temperature, while hot-rolled seamless pipes are formed above the recrystallization temperature. This article will outline the manufacturing process of cold-drawn seamless steel tubes.

1. Raw Material Preparation

The raw materials for cold-drawn seamless steel pipes are steel ingots or billets that must meet specific national standards for chemical composition. These materials undergo surface treatment to ensure a smooth finish and controlled surface roughness.

2. Preheating

To prevent deformation and quality issues during cold drawing, the steel must be preheated. The preheating temperature is typically around 600°C for about 30 minutes.

3. Cutting

The preheated steel is then cut into appropriately sized pipe blanks using specialized machinery.

4. Pickling

The steel pipe blanks are immersed in an acid solution to remove rust, oxide scale, and other impurities through chemical reactions. This process cleans the steel surface and reduces potential damage during cold drawing.

5. Welding

To minimize waste in long steel products, shorter steel pipe blanks can be welded together using high-frequency induction heating. This process combines the shorter sections into longer pipe blanks.

6. Cold Drawing Processing

Using a cold drawing machine, the steel pipe blanks are drawn through a die, gradually deforming the steel into seamless pipes. Key parameters such as temperature, perforation, and drawing speed must be controlled to maintain quality.

7. Heat Treatment

Post-processing heat treatment improves the mechanical properties of the cold-drawn seamless steel pipes, enhancing their ductility and toughness. The heat treatment temperature is generally around 800°C for approximately one hour.

8. Surface Treatment

The final steel pipes undergo surface treatments including rust removal, grinding, and painting to enhance appearance, corrosion resistance, and reduce surface roughness.

9. Inspection

The final step is a thorough inspection, including both appearance and performance evaluations. Appearance inspection checks surface quality and dimensional accuracy, while performance inspection tests tensile strength, impact resistance, and hardness to ensure the pipes meet mechanical standards. Strict control of inspection standards and methods ensures the final product meets customer requirements.

These steps outline the main production process for cold-drawn seamless steel pipes. Each stage demands precise control and adherence to quality standards to produce high-quality seamless steel pipes.