TPT July 2007

4. Technical profile of the FQM™ retained mandrel mill The FQM™ mill is mainly comprised of rolling units and cartridges – each one with 3 driven rolls – supported by chocks and mounted in a shifting slide inside the cartridge. Each cartridge is comprised of two cast shells. The design of the cartridge allows the radial extraction of the shifting slides, containing chocks and rolls, without the necessity to open the cartridges into two halves. Due to the geometry of the mill the required adjustment to roll position before

› Figure 6 : Advantages of the FQM process: comparison between 2-roll RMM (left) and 3-roll FQM (right)

sizes and steel grades. There is also a better yield, with improved quality in the shape of the tube end leading to a reduction in cropping. Because of a wider wall thickness range capability on the same mandrel, the total number of mandrels required to cover the complete size range is reduced. Consequently, there is a reduced mandrel inventory and less frequent mandrel size changeover. There is also a significantly reduced consumption of mandrels and rolls because of lower average and peak pressures. There is a higher degree of stability of the material flow during rolling, which reduces accidents and the losses for cobbles. This increase in efficiency leads to better productivity and yield.

or after profile redressing can be undertaken directly with the hydraulic capsule. The hydraulic capsules are mounted outside the container and engaged/disengaged to the roll during the roll changeover procedure. The mandrel supporting units are installed inside the container. These units guarantee optimum operation, by means of three self- centring rolls, with adjustable positioning in accordance to mandrel size, and oil-hydraulically operated for opening/closing the mandrel centring and support during rolling. The number and position of mandrel supporting stands depends on the mill configuration. For example, on a 5-stand mill the mandrel supporting stands are installed at the inlet and outlet of the first rolling unit, between the third and the fourth rolling unit and at the outlet of the last rolling unit. The roll cartridges and the mandrel supporting units are inserted in a fixed and rigid cylindrical container and sit on side supports inside the container. Due to his geometry the container is designed to react uniformly to the three separating forces acting in radial direction. For the roll changeover all the rolling units and the mandrel supporting units are pushed along the rolling axis toward the mill exit. The changeover is performed with a side-shifting type car. 5. FQM™ process control Seamless tube plants are configured as distinct technological areas in which different jobs can take place at the same time. Each technological area has its own process control system that is integrated with the others via level 3 automation. The following goals can be achieved with this process control system: • Enhanced dimensional quality of the final product • Improved operator independence for better production quality • Improved consistency of production quality • Maximised yield of the plant • Simplified start-up for new production configurations A suitable integration and process automation system is essential to match the high quality performance and results gained from 3-roll pass design. The Danieli automation system is supported by ‘fast’ data collection of the main process variables. During the rolling process all data is gathered from level 1 and used for process tracking, process tuning and input for level 2 models.

fi Figure 7 : A mandrel supporting stand from the FQM container

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J uly /A ugust 2007