Overview & control in the production of long or wide flat products in the hot rolling mill
Long or wide flat products are produced in the hot rolling mill. For this purpose, the steel is first heated to temperatures of up to 1,260 °C in a walking beam, pusher-type or rotary hearth furnace and freed from scale. The product is then fed via a roller conveyor line through a rolling mill, where it is formed into sheets, rails or wire, for example. In flat steel processing, the sheet is then wound into coils on coiling machines and transported to a cold rolling mill for further processing.
OVERVIEW CAMERAS
Process monitoring, which focuses on detailed monitoring and evaluation within a production chain, should not disregard visual observation of the complete plant. For this purpose, overview cameras are installed in such a way that they provide an overall picture of the running production. The images generated in this way reach the control centre via live stream, so that emerging malfunctions can be detected at an early stage and production does not have to be interrupted.
In addition to avoiding cost-intensive production stoppages, the environment also benefits here: a defective filter system, for example, can be detected more quickly, as a change in the colour of the exhaust gas often already indicates this. The control room can thus take immediate action and counteract dangers.
At the same time, the use of overview cameras increases occupational safety for the skilled personnel working directly on the equipment: The early detection of a malfunction, which the employee on site may not even be able to perceive, reduces the risk of an accident to a minimum.
SLAB STORAGE / BARCODE CAPTURE
For a general overview and control, the slab warehouse is often monitored with the help of visual cameras. In addition, general observation of the warehouse also serves to increase occupational safety. Potential hazards, which the individual employee may have difficulty recognising on site, are recognised more quickly by the control center, which has a better overall view; accidents can be avoided.
In addition, in some cases the products are provided with barcodes instead of punch markings, which provide information for further processing about length, alloy, etc. Before charging into the walking beam or pusher furnace, the barcodes are scanned and stored. Depending on the requirements, this also serves as part of a complete documentation of the entire production process.
HEATING FURNACE
In a walking beam or pusher-type furnace, the slabs are moved continuously: from the charging device, the steel is fed to the furnace by a transport system, whereby in a walking beam furnace this is done via individual, parallel beams that lift the slab by an upward movement and transport it horizontally a certain distance before placing the slab back on the furnace floor. This is repeated on a kind of "kiln line" up to the unloading machine.
In order to avoid wedging of the slabs on their transport route, furnace probes can be used here to observe the inside of the furnace. In this way, the operator can precisely control where the steel is deposited again or when a new slab can be fed into the furnace.
ROLLING ROAD
After the steel has been heated, it is transported through several rollers and thus reduced to a desired thickness. Between the individual rolling processes, the surface of the hot strip can be observed via visual cameras to obtain indications of the quality. If material defects appear over a longer distance, this can be an indication of a damaged roll that needs to be replaced or repaired.
The most important camera positioning is at the point where the hot strip has passed through the last roller, before it is coiled. If defects are detected during the visual material inspection, the strip may be reintroduced into steel production or - in the case of minor defects - its quality may be devalued and it may be classified as structural steel, for example.
