φ720mm cross-rolling expansion unit produces thin-walled P11 seamless pipe

The production process of thin-walled P11 seamless steel pipe by φ720mm slant rolling and diameter expanding unit refers to the process of producing the steel pipe by slant rolling and expanding the diameter with a φ720mm unit. The slant rolling process is a new method developed for pipe rolling, which increases the production efficiency and product quality of the steel pipe, reduces the production cost and achives a higher production rate. According to the standards of seamless steel pipes, the steel grade of P11 is X80, which is a low-carbon alloy steel with low yield strength and high transverse direction fracture toughness. Therefore, when producing the thin-walled P11 seamless steel pipe, special attention should be paid to the selection of slant rolling parameters, the design of the expansion device, etc., to ensure the production process and product quality requirements.
    
Introduction of the Production Process:
The production process of thin-walled P11 seamless steel pipe by φ720mm slant rolling and diameter expanding unit can be divided into three stages: slant rolling, expansion and sizing, and finishing. In the slant rolling process, the round billet is heated and placed in the slant rolling machine, and then subjected to an angled main rolling. By controlling the rolling parameters, the required pipe blank can be obtained after two passes of slant rolling. Subsequently, the diameter of the pipe blank is expanded by a diameter expanding unit, and then subjected to timely adjustment of the diameter and wall thickness, so as to obtain the nominal size of the thin-walled P11 seamless steel pipe. At the same time, the surface of the pipe blank is inspected, and the defective parts are cut off. Finally, the decorative surface outside the steel pipe is processed by a sizing machine to make it meet the required quality standards.
    
Table 1. Main Process Parameters of Slant Rolling
    
    | Process Parameter | Unit | Technical Requirement |
    |----------|-------|----------------------|
    | Rolling Temperature | °C | 1120-740 |
    | Rolling Force | KN | 26-41 |
    | Line Speed | m/s | 2.5-20 |
    | Angle of Slant Rolling | degree | 9.5-24.5 |
    
    Table 1. shows the main process parameters of slant rolling when producing thin-walled P11 seamless steel pipe. It can be seen that the rolling temperature should be controlled in the range of 1120-740°C, the rolling force in the range of 26-41KN, the line speed in the range of 2.5-20m/s, and the angle of slant rolling in the range of 9.5-24.5 degree.
    
Design Features of Diameter Expanding Unit
    
The diameter expanding unit is one of the most important parts of the production process of thin-walled P11 seamless steel pipe. In order to ensure that the product meets the requirements, the device should have the following design features:
    
1) The piston stroke needs to be flexible and adjustable to meet the requirements of different sizes of thin-walled P11 seamless steel pipes.
    
2) High-precision synchronous and eccentric wheel devices should be used, and the diametrical deviation should be kept within 0.2mm.
    
3) The automatic compensation mechanism for the deformation in the wall thickness and diameter should be considered to ensure the accurate adjustment of wall thickness.
    
4) There should be good guiding mechanism for the pipe blank throughout the expansion to reduce the scratch and wrinkle caused by the expanding force.

In conclusion, the production process of thin-walled P11 seamless steel pipe by φ720mm slant rolling and diameter expanding unit is important in the production of steel pipes. In the slant rolling process, attention should be paid to the selection of the rolling parameters, such as the rolling temperature, rolling force, line speed and angle of slant rolling. In addition, in order to ensure product quality, the design of the diameter expanding unit should take into account its flexibility, accurancy of the diametrical deviation, automatic compensation mechanism and good guiding mechanism.

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