How Is The Seamless Precision Tube Produced?

Seamless precision tube is a type of high-precision steel tube material obtained by cold drawing or hot rolling. They have no oxide layer on the inner and outer walls, can withstand high pressure without leakage, and have the remarkable characteristics of high precision, high finish, no deformation during cold bending, and no cracks during expansion and flattening.

The production process of seamless precision tubes is a complex and delicate process. It not only requires high precision and stability of production equipment, but also requires strict control of multiple links such as raw materials, processing technology, and quality control. From the selection of raw materials to the inspection of the final product, every step is crucial. Seamless precision tubes are widely used in aerospace, automotive energy, machinery and other industries, carrying an indispensable mission, especially under high pressure, high temperature and high strength. It shows extremely excellent performance. How are seamless precision tubes produced?

The production processes of seamless precision steel tubes mainly include the following:

1. Hot rolling method

It is one of the main methods for producing seamless precision steel tubes. First, the round tube billet is threaded into a rough tube, and then rolled through a series of rollers for multiple times, so that the rough tube gradually becomes thinner, longer and has uniform wall thickness, and then it is made into a seamless precision steel tube through sizing, cooling and other processes.

This process has high production efficiency and can produce steel tubes with larger diameters, but the surface quality is relatively poor and the dimensional accuracy is slightly lower.

2. Cold rolling method

It is generally carried out on the basis of hot-rolled steel tubes. The hot-rolled steel tube is first pre-treated by pickling and other pretreatments to remove impurities such as surface oxide scale, and then rolled through multiple cold rolling mills to further reduce the wall and diameter of the steel tube, and improve the dimensional accuracy and surface quality.

The seamless precision steel tube produced by the cold rolling method has high dimensional accuracy and good surface finish, but it is difficult to produce and has high cost. It is mainly used to produce high-precision and high-surface quality steel tubes, such as some precision tube and heat exchanger tube.

3. Extrusion method

The heated tube billet is extruded through the die hole by an extruder to change its cross-sectional shape, thereby obtaining a seamless precision steel tube of the required shape and size.

The extrusion method can produce steel pipes of various complex cross-sections, with high material utilization and high production efficiency, but it has high requirements for equipment and high mold costs.

4. Pipe jacking method

The pipe billet is pushed into the prepared hole through a special pipe jacking machine, so that it gradually extends and forms a seamless steel pipe.

The pipe jacking method is suitable for the production of long-distance large-diameter seamless precision steel pipe, casing pipe and large-diameter boiler tube. The precision control of the steel pipe is good during the production process, but the construction is difficult and requires professional equipment and technology.

5. Spinning method

The pipe billet is rotated around the central axis by a spin rolling machine and rolled by a roller at the same time.

This process can produce thin-walled, high-precision seamless precision steel pipes with high production efficiency and good control of the size and shape accuracy of the steel pipe, but it has high requirements for equipment and process.

The following are the main production process steps of seamless precision tubes:

1. Raw material preparation

Material selection: Select high-quality steel billets as raw materials. These steel billets need to undergo strict chemical composition analysis and physical property tests to ensure that they meet the requirements for the production of precision steel pipes. High-quality carbon steel pipe, alloy steel pipe, etc. are usually used as raw materials to ensure that the mechanical properties and chemical composition of the steel pipes are excellent.

Billet processing: Cut the selected raw materials into billets of suitable length and perform surface treatment, such as grinding and cleaning, to ensure that the surface of the steel pipe is smooth and pollution-free.

2. Heating and piercing

Heating: The billet is sent to the heating furnace and heated to a suitable temperature, which is about 1200 degrees Celsius. The fuel is hydrogen or acetylene. The temperature control in the furnace is a key issue.

Perforation: The perforator is used to perforate to form the initial shape of the seamless steel pipe, that is, the rough pipe. During the perforation process, a cavity is gradually formed inside the billet, and a continuous steel pipe wall is formed outside. Common perforators include tapered roller perforators, which have high production efficiency, good product quality, large perforation diameter expansion, and can perforate a variety of steel grades.

3. Rolling

Cold rolling and finishing: The perforated rough pipe enters the cold rolling unit for multiple rolling. Cold rolling is usually carried out on a two-roll or three-roll mill. By gradually reducing the gap between the rolls, the steel pipe gradually reaches the required size and accuracy. During the cold rolling process, the surface finish and dimensional accuracy of the steel pipe are significantly improved.

Hot rolling: The rolling process of some precision seamless steel pipes may also include hot rolling. Hot rolling is rolling at high temperature to quickly form the steel pipe and achieve a certain dimensional accuracy.

4. Heat treatment

The steel pipe after cold rolling or hot rolling is heat treated to eliminate internal stress, improve the organizational structure and improve performance. The heat treatment process includes annealing, normalizing, etc. The specific process parameters need to be determined according to the material and purpose of the steel pipe.

5. Pickling and surface treatment

In order to remove the oxide scale and impurities on the surface of the steel pipe and improve the surface quality, precision seamless steel pipes usually need to be pickled after rolling. After pickling, surface treatments such as passivation and oiling are also required to prevent corrosion.

6. Finishing and inspection

Finishing: After heat treatment, the steel pipe is cut, polished and other finishing treatments are carried out to ensure that its dimensional accuracy and surface quality meet the standards.

Inspection: The appearance, size and performance of the produced precision steel pipe are inspected. The inspection content includes appearance inspection, size measurement, mechanical property test, etc. Qualified steel pipes will be marked with numbers, specifications, production batch numbers, etc., and hoisted into the warehouse by crane.

7. Packaging and delivery

The steel pipes that have passed the inspection are packaged to protect the surface of the pipes from damage. The packaged steel pipes can be shipped out of the factory for sale.

Summary

The above are the main production processes and production steps of seamless precision steel pipes. Different processes have their own advantages and disadvantages. In actual production, the appropriate process is selected according to different needs and conditions.

Read more: Seamless Steel Pipe Sizes