Product category:
Rolling mills and equipment
News Release from: Donix | Subject: Bar and wire mills - avoiding 'cobbles'
Edited by the Manufacturingtalk Editorial
Team on 29 January 2007
Bar and wire mills - avoiding 'cobbles'
Controling the kinematic parameters of continuous rolling mill trains, described by the authors, features measurement of angular speeds of the rollers using magnetic field sensors.
On modern bar and wire mills the rotation of entry guide rollers of the working stands is controlled visually As there are no devices for automated control over the rotation it is impossible to control the rollers availability during rolling
This article was originally published on Manufacturingtalk on 11 Apr 2006 at 8.00am (UK)
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Thus, if one or both rollers stop, for example, due to the damage of the bearing, the metal pickup by the rollers or due to any other causes, it results in 'cobbles'.
It is especially important to control the guide rollers availability during rolling on wire mills, equipped with finishing blocks.
There are no devices for automated control over the guide rollers availability, besides, the visual control over the finishing block is impossible as the stands are covered with a housing, and the rolling speeds are high, up to 80-110m/s.
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Therefore any 'cobbles' at this section of the mill result in severe problems.
It is possible to avoid emergency situations provided that the condition of the guide rollers is under continuous control, the speed of their rotation is recorded, its value is displayed on the monitor and the deviation of the rollers speed is estimated.
Periodical press provides some information about the application of automated systems for diagnostics of the condition of guide rollers in the finishing blocks at Belarussian and Moldavian metallurgical works.
The systems' application results in complete elimination of any 'cobbles' due to the guide rollers jamming.
RPC 'Donix' has developed a new method of control over the kinematic parameters of the rolling mill.
The method includes control over the rotation of guide rollers with the sensors mounted on the guides as well as control over the kinematic parameters of the mill.
Kinematic parameters are controlled through the measurement of angular speeds of the rollers which is carried out by magnetic field sensors.
After that, linear speeds are derived from the known diameters of the rollers and the relations of linear speeds of the stock in the adjacent stands or trains.
The obtained relations are compared with the reference values, corresponding to the speed schedule with minimal interstand tensions.
The suggested method makes it possible to control the kinematic parameters on a continuous rolling mill by comparing the measured values with the reference values.
Control over the kinematic parameters includes control over the relation of linear speeds which ensures minimal interstand tensions on the continuous mill, and hence the required accuracy of the stock cross-section along the length of the rolled stock.
The suggested method was implemented by the experts of RPC 'Donix' on the finishing block of wire mill 150 of CJSC 'Makeevka Metallurgical Works' ('CJSC MMW').
Magnetic field sensors were placed in immediate proximity to the magnetized entry guide rollers.
The sensors generated the electric signal which is proportional to the rotation speed of the roller.
The signal converter together with the program unit generate the current and archive data about the rollers' speeds and their changes on each stand with the further data storage in the computer.
Thus the operator can control and correct the rolling process, if necessary.
We studied different methods of magnetizing the rollers, conditions of the rollers operation and of their change during short scheduled downtimes.
As a result we developed and constructed a simple and reliable device for marking the rollers.
From August 2005 till October 2005 the system of control over the entry guide rollers of the finishing wire block was tested on wire mill 150 of CJSC 'MMW'.
The system's interface includes two windows for the speed schedule presentation.
Virtual speeds of the rollers for each controlled stand and rotations of the main drive of the block are presented in the first window as bar graphs.
Virtual linear speeds of each roller are presented in the second window as line diagrams (graphs).
During the testing period speed graphs of the rollers' rotation for every rolled billet were saved to the computer.
To analyze the accuracy of the rollers' speed measurement we used a mathematical model of the kinematic conditions of rolling in the block developed by RPC 'Donix'.
During the testing period the system ensured the following control functions.
* - The pre-emergency condition of the rollers' bearings is monitored by speed graphs of the rollers' rotation; that is achieved by means of recording the speed deviation exceeding the allowable value.
* The roller jamming due to different causes is detected by means of analyzing the roller stop 'prehistory'.
* The compliance of the gaps setup in the roller guides with the roll gaps setup in the stands with oval passes is checked by means of comparing the speeds of a pair of rollers in the controlled stand.
* Kinematic conditions of the block operation are controlled by means of comparing the actual relations of the linear speeds of the stock for a pair of adjacent stands with the optimal ones.
* Speed graphs are saved to the computer in case if the actual speeds deviate from the rated speeds for further analysis.
The developed system of control over the rotation of entry guide rollers of the finishing block may be used to avoid 'cobbles' due to the roller jamming.
That is achieved by means of the visual and program monitoring of speed deviations.
To facilitate the operator's work the system is provided with the function of logical analysis and voice signals generation, characterizing the location and the cause of the guide deviation from the normal operation conditions.
The system of control over the kinematic parameters will increase the mill efficiency by means of reducing the downtimes, rejects due to the entry guide rollers jamming in the mill blocks, and by means of reducing the bad quality wire rod production.
* The authors are V S Solod, Y S Dmitriev, D N Novikov and S N Rudskoy are at RPC 'Donix', Ukraine.
The full version of the paper, 'System of Control over the Kinematic Parameters of Continuous Trains of a Rolling Mill', can be found at
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