Noncontact Infrared Temperature Control in Aluminum Rolling Process

Challenges in Infrared Temperature Measurement for Aluminum Rolling Processes

The aluminum rolling process is critical to the aluminum manufacturing industry, where precise temperature measurement is essential for ensuring high-quality product output and protecting equipment. This process, which produces aluminum coils through various methods, including cold rolling, direct casting, and continuous casting, plays a fundamental role in determining the final properties of the material.

During this process, aluminum slabs or billets undergo either cold working or hot working, depending on the desired material characteristics. Cold rolling increases the strength and hardness of the aluminum by altering its microstructure, though it also makes the material more brittle. Conversely, hot working, conducted at temperatures between 260 °C and 510 °C depending on the alloy, maintains the aluminum’s ductility by preventing work hardening. As the aluminum passes through the rolling mill, its temperature varies significantly—from an initial preheating stage at around 200 °C, rising to approximately 450 °C upon entering the rolling mill, and then dropping below 100 °C as it exits.

One of the key challenges in this process is the accurate temperature measurement of aluminum, particularly due to its highly reflective surface. Aluminum is notoriously difficult to measure with infrared cameras because of its low emissivity and high reflectivity in the infrared spectrum. Especially when polished or bright, aluminum’s emissivity is very low, typically ranging from 0.02 to 0.1 for long-wavelength infrared devices. This low emissivity means that aluminum emits very little infrared radiation compared to other materials, making it challenging for long-wavelength infrared cameras to provide accurate temperature readings. Additionally, aluminum’s emissivity can vary with temperature, further complicating precise measurement. Short-wavelength infrared cameras, which typically have a higher evaluated temperature range, are often incompatible with the temperatures used in aluminum processing, making them less suitable for these applications.

Achieving Optimal Aluminum Cold Rolling with Affordable Temperature Monitoring Using Wedge Measurement Techniques

To roll high-grade products the decisive difference is the precise temperature control. If the required temperatures are precisely maintained, the product quality can be assured and damages to the roll stand will be avoided. This application is suitable for the wedge measurement technique used at the coiler or between the roll and the product during the rolling process, which eliminates the challenges posed by low temperatures and variable emissivity, and also eliminates background reflection influences. This allows the manufacturer to implement continuous process temperature monitoring. It ensures that the system consistently tracks temperature variations throughout the production process, allowing for real-time adjustments and supporting the documentation of process and tool temperatures, providing insights into the production process, and enabling closed-loop control for automated adjustments that maintain optimal conditions and prevent deviations.

Any Optris long wavelength camera can exhibit the wedge effect to accurately measure the strip temperatures in cold rolling and coiling applications. In this application, the autonomous thermal imager from the Xi Series provides multiple interface options, enabling the camera to be easily integrated into new or existing process control systems. Unlike other solutions from the competition, there is no need for special software or unique sets of wavelengths in this challenging application, as Optris infrared cameras will measure the wedge effect at an affordable price.