Thermal imaging & vision systems


1500 long wavelength thermal imaging camera, to measure surface temperature before and after descaling to assess descalability and heat loss based on nozzle pressure/flow and descaling speed. High pressure water (HPW) descaling is the process of removing oxide scale by spraying the hot steel surface under a range of moderate-to- high pressure water using stationary (usually flat jet nozzles) or rotary (rotor descaler) systems. The aim is to ideally remove loose to sticky, primary to tertiary scale under optimum impingement and surface chilling, as well as power-water flow rate consumption, for improving the surface quality of rolled products and minimising work roll wear. Complex solid-fluid thermal-mechanical mechanisms are acting through the scale, scale interface and sub-surface of the steel substrate depending on the descaling process parameters of impact pressure, descaling energy and temperature. The HPW descaling process is a harsh process where, in particular, measurement of temperature and surface state are difficult to achieve (in view of steam/water, oxide scale debris, confined descaling boxes). Measuring surface losses using IR technology can provide benefits to thermo-mechanical processing for difficult to roll steel grades that are prone, for example, to ductility cracking and/or surface defects, and leads to efficient descaling under robust and energy efficient regime maps.


T


ata Steel is using a thermoIMAGER TIM M-1 thermal imaging camera from Micro-Epsilon with a short 1μm wavelength, as well as a thermoIMAGER TIM 400T


To study and optimise the descaling process, Tata Steel together with the Steel Metal Institute in South Wales (SAMI) have revamped a HPW descaling rig to optimise the process. The unit can be used in two modes, static or dynamic, with hot or cold material, from steel to simulation material. Reheated samples are typically blocks of 70x70x100mm thick placed on a carriage which transports the sample at a fixed speed (up to 4m/s). Following descaling, the carriage stops and the sample is transferred to an Argon-filled container to limit further oxidation. All signals (height, pressure, flow,


temperature, etc) are logged via a Windaq data acquisition system. A sophisticated post- analysis procedure has been put in place to characterise descaling efficiency. Tata Steel is using a thermoIMAGER TIM M-1 thermal imaging camera from Micro-Epsilon with a


SAMI laboratory HPW descaling rig


Micro-Epsilon standard thermal recording with TIM 400T (left) and TIM M-1 (right) post-descaling. 34 April 2022 Instrumentation Monthly


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