Seamless steel pipes are widely used in many mechanical engineering fields, so how are they produced? Today will take you to understand the production method of seamless steel pipe.
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 there are many racks, but recently there is a variable roll pitch rolling mill, and the idea of a four-roll reducer is proposed. In the future, the direct connection technology of the mandrel seamless tube rolling mill, the sizing machine and the tension reducer will also attract people's attention. The development of the above-mentioned high-alloy piercing mandrels in the field of steel pipes and the development of mandrel guide grooves and billet lubricants are closely related to tribological technology. It is hoped that the long-life technology will be further developed.
2. Stretch straightening
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 sets to 4-5 sets, and the energy consumption of piercing machine and mandrel seamless steel pipe rolling can be reduced by about 20%. In the mandrel seamless tube rolling mill control technology, 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 seamless tube rolling mill tube end pre-thinning forming technology Technology, the steel pipe rolling mill adopts oil pressure reducing device for the first time.
3. Stamping and rolling
PPM (pressure roll punching machine) that uses square billets has been replaced by a diagonal roll punching machine that uses round billets. The advantage of the conical piercing machine is that it has a rotary forging effect, can suppress circumferential shear deformation, and therefore can suppress defects on the inner surface of the steel pipe, and can be used for piercing difficult-to-process materials, especially reaming and thin-wall piercing. 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 tubes with a T/D of 3.2% can be pierced.
