Production methods of seamless carbon steel pipe

The application field of seamless carbon steel pipe is very wide, many machinery and engineering will use it, so how is it produced?

1. Reducing rolling and sizing rolling

Although there is no technical development worthy of special introduction in reducing rolling and sizing rolling for final adjustment of outer diameter, many large-diameter sizing machines also use three-roll sizing machines. The disadvantage of using three rolls is that the roll pitch cannot be changed, so the number of stands is large, but rolling mills with variable roll pitches have recently appeared, and the idea of a four-roll reducer has also been proposed. In the future, the direct connection technology of the mandrel-type seamless tube rolling mill and the sizing machine and the tension reducer will also arouse people's attention. The development of mandrels for high-alloy piercing in the steel pipe field mentioned above and the development of mandrels and blank guide groove lubricants are closely related to tribological technology. Therefore, it is hoped that further development of technology for longevity will be made. 

2. Stretch rolling

The mandrel-type seamless tube rolling mill has been developed in the direction of large-scale and compact. The number of stands is reduced from 7-9 stands to 4-5 stands, and the total energy consumption required for the piercing machine and mandrel seamless tube rolling can be reduced by about 20%. In the control technology of the mandrel-type seamless tube rolling mill, in order to reduce the cutting loss of the tube end wall thickness in the tension reducer, the tube end pre-thinning forming technology was developed, that is, the mandrel-type seamless tube The rolling mill uses the forming technology of thinning the pipe ends in advance, and the hydraulic pressure reduction device is used for the first time on the steel pipe rolling mill.

3. Piercing and rolling

The PPM (pressure roll piercing machine) that uses square billets has been replaced with an oblique roll piercing machine that uses round billets. The advantage of the conical piercing machine is that it has the effect of rotary forging and the effect of restraining the shear deformation in the circumferential direction, so it can suppress the defects of the inner surface of the steel pipe, and can be used for perforating difficult-to-process materials, especially for reaming and thin-wall perforation. . When using an ordinary piercing machine, the limit of the wall thickness/outer diameter ratio (T/D) is about 6%, while when using a conical piercing machine, thin-walled pipes with a T/D of 3.2% can be pierced.

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