The rolling mill for sections and profiles basically consists of alternating lamination in the so-called Roughing Mill (also known as blooming), usually composed by a Two High or Three High Stand - between three and thirteen different passes. The later phase is also performed alternately - up to three passes - in the Tandem group (composed by up to three different stands alternated between universal stands–H/V-and edging one’s. Finally, in the Finishing group, a simple final calibration pass is performed.
The proposed control system for a Sections, classifies these into three different categories: Master Control System, Sequential Control Systems and Technological Control Systems.
In a section mill there will be at least three Master Control Systems. These will be in charge of the generation and control of speed and torque set-points of the main Edger & Roughing, Tandem and Finishing drives. It will also manage the speed set-points of certain auxiliaries, mainly roller tables.
Master Control System by means of the dedicated HMI’s also manages the mill pass schedule program, calculating the main rolling parameters, giving pass to pass roll settings, helping the operator in their supervisory task.
Regarding Sequential Control Systems, the number of them will be given by the program load to be managed, by the number of inputs-outputs to be treated, by the different nature of the elements to be controlled or for any other reason.
Basically in a large Section Mill there are the following - not including those related to the continuous casting machine and reheating furnace:
- Edger and Roughing, sequential control system, including fast roll change,
- Tandem and Finishing, sequential control system, including fast roll change,
- Cooling, sequential control system,
- Straightener, sequential control system,
- Saws for cutting-to length, sequential control system,
- Evacuation and Stacking, sequential control system,
Finally the Technological Control Systems deal with the tasks related to the process: The regulation of the Heating Furnace will be controlled by one of these systems (the kinematics of the Furnace is managed by a Sequential Control System).
Likewise, the use of hydraulic stand capsules for Tandem and Finishing stands adjustment is managed by the TCS’s, controlling each one of the hydraulic axes appertaining to the above mentioned sections – Hydraulic Gap Control, HGC - either in force or position mode, both in closed loop regulation.