Electricity + Control November 2017

round up TEMPERATURE MEASUREMENT

PreciseTemperature Control Assures High Quality Steel Information provided by Mecosa

T oday’s increasing quality standards and higher energy costs demand more ac- curate and consistent temperature control in every step of the steel making process. Steel manufacturing consists of high tem- perature manufacturing steps that use sig- nificant amounts of energy. Processes such as coke oven heating, continuous casting, furnace reheating, hot rolling, forging, sin- tering, and annealing are becoming more and more expensive. With increasing ener- gy prices at all-time highs, the cost of doing business has significantly increased. Steel facilities need the right tools to ensure they optimise energy usage across their facilities. Continuous casting is the process where the molten steel is cooled and solidified into billets or slabs. The core is still usual- ly molten with a hard outer shell. Molten metal is transferred from the ladle into a tundish, where it is slowly tapped into the casting machine. The mold in which the steel slips into is water cooled. The oper- ator’s challenge is to keep the steel within the channel and control the cooling rate. This can be difficult due to variations in the tundish temperature. In the production process of semi-fin- ished steel products in continuous casting plants, the measurement of temperatures is an ongoing daily task, however the con- trol of the secondary cooling phase is a key issue. Only exact temperature control in the cooling process enables the production of steel grades that meet high-end market requirements. The manner in which the strands are cooled in each batch is crucial to the final quality of the steel. There are different target temperatures for different types of steel, which require a control range of 600°C to 1 200°C. Ex- ceeding or undershooting the permissible temperature limits leads to a devaluation of the material and thus a lower product yield. For efficient process control, the recording of the temperature values at the outlet sec- tion of the strand is a significantly important function. Accurate cooling processes at perfectly controlled temperatures result in a high surface quality of the strands and en- sure optimally formed inner structures of the strands. In this process IMPAC pyrometers and MIKRON thermography systems meas-

ure mold temperatures and coil tempera- tures in the backbend and cooling zones.

zone and thus enable multiple temperature measurements of the individual strands at different points in the backbend zone. This allows the individual strands to be recorded on three sides.Thus the continuous casting process is monitored and controlled using the most appropriate measurement points. Using the combination of accurate hot- edge detection and temperature profile imaging, together with a very rugged stain- less steel protective housing, LumaSense MCS640-HDThermal Imaging Cameras are able to control continuous casting process- es better than any other imaging system.

Figure 1 Schematic process representation.

The surface of the material in the tundish is examined using aThermal Imaging Camera to identify any irregularities such as crack formations. In turn, this ensures that the molten material can be poured easily from the tundish with a minimum amount of ma- terial adhering to the sides of the vessel. Equipment for efficient temperature monitoring during continuous casting Lumasense Ratio Type ‘SG’-pyrometers are specially designed for continuous cast- ing processes. They are installed between the individual cooling zones, and continu- ously measure the respective strand tem- peratures. LumaSense pyrometers ISR 12- LO/GS and IGAR 12-LO/GS with protection class IP65 can withstand the harsh ambi- ent conditions, caused by high tempera- tures, cooling water mist and soiling, over many years, by employing special continu- ous casting optics.

Figure 3: LumaSense MC640-HD Thermal Imag- er with protective housing including cooling.

Steel manufacturing consists of high temperature manufacturing steps that use significant amounts of energy.

Conclusion LumaSense infrared thermometers accu- rately measure cooling requirements of slabs, billets, or blooms to ensure product uniformity and provide equipment opera- tors with immediate temperature informa- tion that is critical to the cooling process.

Figure 4: Thermal Image of a continuous casting system.

Figure 2: IMPAC ISR 12-LO/SG with special optics.

As an alternative solution to the pyrome- ters, just two LumaSenseThermal Imaging Cameras monitor the complete backbend

Enquiries: Mecosa. Henning Springer. Email henning@mecosa.co.za

34 Electricity + Control

NOVEMBER 2017