TPT January 2011

A rticle

New technology introduced for continuous rolling mill in Taiyuan Tongze Chief engineer, Guo Jibao, Taiyuan Tongze Heavy Industry Co Ltd, Taiwan

The application of a hydraulic press down system in MPM Compared to mechanical press down technology, hydraulic press down technology possesses advantages in the area of performance, precision and response. With the application of hydraulic press down technology in MPM, it helps reveal whether the MPM has good integral rigidity and the roll-gap deviation caused by the stand bounce and bearing clearance can be eliminated through the dynamic compensation of hydraulic servo system. The roll-dap dynamic adjustment can also be carried out in the rolling process, the reducing of wall thickness of tube’s top-and-end can be achieved by the adjustment of roll-gap and roller rotate speed to reduce the loss of crop loss by gradual end reduction. The distribution for each stand load of MPM can be accomplished by the test of rolling force and adjustment of roll-gap to ensure the rolling stability.

quality and tool life. And the two roll structure is more simple and the maintenance is more convenient. Tongze developed the two-roll MPM 140 and MPM180 mill unit, while mill stand main drive adopted top-drive technology and acquired the innovation patent: • The six-stand for MPM consist of three horizontal-rolling stands and three vertical-rolling stands with horizontal-vertical interlacing. The top-drive mode is adopted by the vertical- stand, which protects the vertical main gear box in a better way. It is very different from the X-mode rolling form of other manufactures since it takes up less space, is a lower cost and benefits from fast tool alteration.

• The lateral roller change is adopted by roller to enable the convenient maintenance and compact structure and so on. • The combination of 4-roughing stands and 2-finishing stands ensures the absolute diameter reduction of wall thickness of up to 12mm, the relative wall thickness reduction rate close to 70% and the maximum elongation extend to 4.6mm, which is the largest one among mill units of the same standard. • Tongze provides pass-design software to the customer and the parameter design of each pass stand can be automoatically achieved by inputting the specification of shell and finished. The curvilinear equation of metal outline for roller-gap is constructed through the analysis of the test billet for the metal outline in the gap-roller area, in accordance to the different pass-pattern of rough-rolling and finish-rolling stands, which attain the least outlet deviation of the continuous rolling pipe. • The mandrel-design software is provided to the customer, the mandrel class interval and the most reasonable limit of tolerance margin for wall thickness of shell billet is divided in consideration of the different limit of tolerance demand for thin and thick wall thickness.

Self-directed development of hydraulic press down system is equipped in the unit of MPM114 and MPM180, this system includes the mathematical model of rolling process roll-gap control and the rolling speed, temperature, wall thickness and rolling force control strategy.

Six-stands two-roller MPM For the existing two-roll production state, two-rolls have no differences compared with three-roll rolling when rolling small size pipe in terms of the field of accuracy, wall thickness, internal and external surface

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J anuary 2011

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