Production and manufacturing methods of seamless carbon steel pipe

Seamless carbon steel pipes are produced using various methods, including hot-rolling, cold-rolling, cold-drawing, and extrusion. The primary difference between cold-drawn and hot-rolled seamless steel pipes is their precision. Cold-drawn pipes typically offer higher precision compared to hot-rolled pipes, with cold-drawn pipes generally having an accuracy of around 20 wires, while hot-rolled pipes have an accuracy of around 100 wires. As a result, cold-drawn seamless steel pipes are preferred for mechanical processing and parts manufacturing due to their superior precision.

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Hot-Rolled Seamless Pipes

Hot-rolled seamless pipes are typically produced using automatic pipe rolling units. The process involves several key steps:

The solid tube blank is first inspected, and surface defects are removed.

It is then cut into the required length, with the perforated end centered before being sent to the heating furnace.

After heating, the tube blank is pierced on a punching machine, where it rotates and advances during the piercing process. Under the influence of rollers, the tube blank gradually forms a hollow structure, which is called a "gross pipe."

The pipe then continues through the automatic pipe rolling machine for further rolling.

The wall thickness is evenly distributed by a leveling machine, and the pipe’s diameter is adjusted to specification using a sizing or reducing machine.

The use of continuous pipe rolling units to produce hot-rolled seamless pipes is considered an advanced and efficient production method.

Cold-Rolled and Cold-Drawn Seamless Pipes

To obtain seamless pipes with smaller diameters and improved quality, the cold-rolling and cold-drawing methods are preferred. These processes offer superior precision and surface finish compared to hot-rolled pipes. Cold-drawing, in particular, enables the production of pipes with tighter tolerances and finer finishes.

Extrusion Method

The extrusion method involves placing a heated tube blank inside a closed extrusion cylinder. Both the perforation rod and the extrusion rod move together, causing the material to extrude through a smaller die hole. This process is suitable for producing seamless steel pipes with smaller diameters, offering high precision and the ability to work with various materials.