Position sensor for tandem hot rolling process
Find out how to improve the position control of the rolls in the tandem hot rolling mill with the resolution of 0.5 𝜇m with an update time of 2 kHz (every 500 𝜇s)
The hot rolling process is mainly used for the production of sheet metal or simple sections such as rails.
In the hot rolling mill the process is designed to compress the steel billets or ingots and obtain the desired shape and thickness by using rollers.
The rolling is controlled by adjusting the micrometric distance of the rollers with the use of magnestrictive transducers.
The WRA-S data refresh rate and 0.5 𝜇m resolution allows you to control laminating stations accurately and in real time.
Overview
- Product: WRA-S Magnetostrictive transducer – 550 mm stroke – inside cylinder mounting
- Customer request: 1 𝜇m of maximum error in controlling the distance between the two rollers of a rolling station, with highest sampling rate
- Result: WRA-S enabled the control of the distance to a resolution of 0,5 𝜇m with a refresh rate of 2 kHz reading (every 500 𝜇s)
The process
Hot rolling process is used mainly to produce sheet metal or simple cross-sections such as rail tracks. Other typical uses for hot-rolled metal are truck frames, automotive clutch plates, wheels and wheel rims etc
A tandem rolling line is a process where series of rolling stations are deployed one after the other to reduce the plate thickness in succession in one pass. The number of stands (rolling stations) ranges from 2 to 18.
In a tandem hot rolling process, steel billets or ingots are heated above 1000°C before passing through a series of pairs of rollers (rolling stations). The process is designed to compress the billets or ingots to obtain the desired shape and the thickness.
The position of each pair of rollers (one rolling station) is controlled by 4 hydraulic cylinders.
The challenge
- Depending on the final product to be obtained, each rolling station must control very precisely and strictly the micrometric distance between the two rollers.
- Of the four cylinders to control each pair of rollers, at least two must be equipped with position sensors.
- Any of the stations might require to make additional micro-corrections to compensate for the errors in the previous station and therefore it is important that the reaction time of the rollers is as fast as possible.
- Should be noted that the metal block/ sheet passes through the first rolling station at a temperature above 1000°C.
Product benefits
- 0,5 𝜇m resolution of WRA-S supports micrometric control required for the rolling stations
- In addition to high resolution, special SSI Gray code output allows a direct and safe data transfer to the PLC without passing through a fieldbus
- The position reading refresh rate of 2 kHz (every 500 𝜇s) ensures a real time control of the roller compression
- Operating temperature: -30°C to +85°C ( -32°F to +185° F)
Solution
Precise position control of the distance of a pair of compressing rollers (rolling station) in a tandem hot rolling mill carried out using 2 Nos of WRA-S rod transducers mounted inside the cylinders.
Precision and high sampling rate requirement of the process was met due to the following technical specifications of WRA-S transducer
- Resolution: 0,5 𝜇m
- Position reading refresh rate: 2 kHz (every 500 𝜇s)
- Output type: 25-bit SSI Gray code for prompt and precise transfer
- Working Temperature: -30 to +85 °C
