Achieving accurate temperature measurement in metal production

Bestech Australia Pty Ltd
Monday, 17 August, 2020


Achieving accurate temperature measurement in metal production

Temperature monitoring and control are crucial steps in almost every industrial manufacturing process, particularly metals. Temperature needs to be strictly controlled to ensure the quality of the finished products in the metals industry. Many existing metal processing industries also need to consistently monitor the process temperature for surveillance purposes — to ensure workplace safety and process optimization — in areas such as blast furnaces, rolling mills, die forming and hardening processes.

Non-contact sensors such as infrared thermometers and thermal imaging cameras are suitable for this type of industry due to the limitations in using contact-type sensors. They also have the capability to measure the wide temperature ranges from 400°C to 3000°C that are commonly encountered in metal processing industries, and they can provide reliable measurement at high temperatures.

The Micro-Epsilon thermoIMAGER TIM M1 is a compact thermal imaging camera with an extremely short wavelength of 0.85–1.1 µm for reliable non-contact temperature measurement on hot metal surfaces. The emissivity error due to the higher radiation intensity from metals at very high temperatures, and temperature differences due to metal oxides, are minimised when measured in this wavelength band.

The TIM M1 also has a very large measurement range from 400°C to 1800°C and a real-time output rate of 1 kHz to monitor fast industrial processes. The camera is also equipped with a jacketed cooling system to withstand hot ambient temperatures up to 315°C.

The fast sampling rate enables the detailed analysis of fast thermodynamic processes that occur during metal processing, as well as temperature adjustments in real-time processes. The system can be configured to output temperature values or alarm values via the process interface.

In real-world applications, this online thermal imager can be permanently installed for early detection of wear in the refractory lining of torpedo cars, slag cars and ladles. It can also be programmed to send an automated alarm whenever hot spots are detected on the outer walls of furnaces. Maintenance can then be effectively scheduled to reduce and eliminate the risk of shutdown.

Thermal imagers can also be used for continuous measurement to monitor the forming temperature in rolling mills or within die forming processes. However, there are more cost-effective solutions, such as using a high speed infrared thermometer with a short wavelength, as it does not require the detection of hot spots.

The thermoMETER CTRatio M1 is a high-speed ratio pyrometer specifically designed for the measurement of red-hot and glowing metal objects with an operating wavelength of 0.7–1.1 µm. It is a more suitable sensor for the measurement of moving objects in the production line due to its fast response time. This glass-fibre ratio pyrometer is not affected by interference such as smoke, fog or dust that may partially or fully conceal the moving object.

As an example, the CTRatio high speed pyrometer has been previously installed in rolling mills to continuously measure forming temperature between individual rolls. This allows the optimisation of the process parameters and resulting product quality, since temperature shifts directly affect the quality of the finished product. It is also suitable for measuring temperature during die forming processes, as the temperature of the blank needs to be precise before it is hot formed. It can also be used to measure the temperature after forming and before being sent for storage.

In induction hardening processes, an optimum temperature-time profile is essential to produce metals with the desired microstructure. For easy control and monitoring, the CTRatio high speed pyrometer can be permanently installed for continuous monitoring or alternatively, a handheld pyrometer can be used for sporadic measurement.

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