The Production Technology of Hot Rolled Seamless Steel Pipes

The hot rolled seamless steel pipe: 
The technology of hot rolling is relative to the technology of cold rolling. The technology of cold rolling is for the pipes rolled below the re-crystallization temperature. The technology of hot rolling is for the pipes rolled above the re-crystallization temperature.

The basic production process of the hot rolled seamless steel pipe includes:
Preparation and inspection of billets → heating of pipes → perforation → rolling of pipes → reheating of steel pipes→ sizing (reducing)→ heat treatment → straightening of finished pipes → finishing → inspection (non-destructive, physical and chemical, table inspection)→ storage

The manufacturing process of seamless steel pipes-PMC
There are three main deformation processes in the production of the hot rolled seamless steel pipe: perforation, rolling and sizing and reducing. The respective process objectives and requirements are as follows.

1. The perforation
The perforation is the insertion of a solid pipe into a hollow capillary. The equipment is called a puncher. The requirements of the perforation process are:

(1) Ensure that the capillary wall thickness is uniform. The ellipticity is small, and the geometric dimension accuracy is high.
(2) The inner and outer surface of the capillary is smooth, without scars, creases, cracks and other defects.
(3) There must be corresponding perforation speed and rolling period to adapt to the production rhythm of the whole unit. It makes the capillary final rolling temperature meet the requirements of the pipe mill.

2. The pipe mill
The pipe rolling is the process of pressing perforated thick-walled capillary pipes into thin-walled waste pipes to achieve the desired thermal size and uniformity of finished pipes. That is, the wall thickness of waste pipe in this process is determined according to the reduction amount of subsequent processes and the empirical formula of wall thickness treatment. This equipment is called a pipe mill.

The requirements of the rolling process are as follows:

(1) When changing the thick-walled capillary into thin-walled waste pipes (wall reduction and lengthening), the uniformity of the wall thickness of waste pipes should be high first.

(2) The waste water pipe has good internal and external surface quality. The selection of pipe mills and the reasonable matching of its deformation and perforation process are the key to the quality, output and technical and economic indexes of the mill.

3. Fix (reduce) the diameter
The main function of sizing down is to eliminate the outer diameter difference of waste pipes caused by rolling process in the previous process so as to improve the outer diameter accuracy and roundness of hot-rolled finished pipes. The reduction is to reduce the diameter of large pipes to the required size and precision of pipes. The reducing tension is to reduce the diameter under the action of front and rear frame tension. At the same time, it will reduce the wall. The equipment used for sizing and reducing is a sizing (reducing) machine. The requirements for sizing and reduction processes are as follows:

(1) Under the condition of a certain total reduction rate and a small single frame reduction rate, it can achieve the purpose of sizing.
(2) It can realize the task of producing finished pipes of various sizes from one size billet.
(3) It can further improve the outer surface quality of steel pipes.

At the end of the 1980s, there was a trend to cancel the rolling process. It only used the method of perforating and reducing the diameter to produce seamless steel pipes, CPS for short, and the factory industrial test was held in March 1990 to July 1991 in South Africa. The production of outer diameter is from φ33.4 to φ179.8mm, and the wall thickness is from 3.4 ~ 25mm. The minimum diameter of fixed diameter is 101.6mm. The quality of the steel pipe with wall thickness greater than 10mm is acceptable. However, when a steel pipe with wall thickness less than 8mm is produced, the spiral line of perforated capillary can not be completely eliminated by sizing and reducing tension, which affects the appearance of the steel pipe.

Tip: ASTM A53 covers seamless and welded steel pipes with nominal wall thickness. The surface condition is usually black and hot dip galvanized. ASTM A53 is used primarily for pressure and mechanical applications and also for conveying steam, water, and gas lines. ASTM A53 Class B is more popular than other grades. These pipes may be bare without any coating, or they may be hot-dipped or galvanized and manufactured by welding or seamless manufacturing processes.