Thermal Cameras for Reliable Steel Billet Monitoring

Why Single-Point Pyrometers Struggle with Steel Billet Temperature Measurement

Steel billets are semi-finished cast products, usually with square cross-sections of about 130 to 160 mm. Before hot working, they need to be reheated evenly to around 1100 to 1250 °C. Keeping a precise temperature is vital. Too much heat or too long exposure can roughen the grain structure. This can lead to brittleness or even serious overburn. If billets get too hot, they might crack during rolling or forging, which can damage rolls or dies. On the other hand, if they are not heated enough, they resist deformation. This can cause structural flaws and wear out equipment more quickly.

Heating billets comes with challenges. Oxide scale that forms in the furnace acts like an insulating layer, causing temperature differences on the surface. Typical measurement methods, like single-point infrared pyrometers or contact thermocouples, only provide isolated snapshots, missing the complete thermal picture. In reality, significant temperature gradients often exist between the billet’s surface and its core or between the center and corners, especially as it exits the furnace. Corners heat up faster because of a higher surface-to-volume ratio and cool down quickly when exposed to air. Measurements taken right at the furnace exit can be misleading due to these “hot corner” effects. Allowing about 30 seconds for corners to cool gives a better average temperature, but it’s often too late to adjust the process.

In flame-fired furnaces, cold oxide patches make readings even more difficult, often leading to underestimation unless a large surface area is examined. These challenges make it hard to ensure uniform heating of billets using single-point methods. This increases the risk of uneven deformation, cracks, higher scrap rates, and damage to equipment downstream.

How Thermal Imaging Reduces Scrap and Improves Consistency in Steel Mills

Implementing the Xi 1M thermal imaging system for monitoring billets brought noticeable benefits in production quality, efficiency, and cost savings. First, steel quality improved significantly. With each billet heated to the right range and checked by the camera, downstream processes like rolling faced fewer defects. The camera ensured temperature uniformity and nearly eliminated issues caused by thermal gradients. The risk of billets cracking from cold spots or becoming brittle from overheating dropped dramatically. As a result, the scrap rate fell, and product consistency increased, leading to higher customer satisfaction.

Another major benefit was the reduced stress on equipment and less downtime. By keeping under-heated billets from entering the mill, the plant avoided situations where excessive force or repeated passes were necessary. This protected the rolls and presses from unnecessary wear. Similarly, avoiding overheating prevented damage to roll surfaces and guide equipment from burnt material. Continuous monitoring also allowed for diverting or correcting any billets trending out of specifications before halting production. Over time, the facility saw less unscheduled downtime and lower maintenance costs for the furnace and mill because the process stayed closer to design temperatures.

From an operational view, the automation and data from the Optris system improved efficiency. The camera replaced the need for multiple pyrometers and operators, reducing the need for manual measurements on the hot line. This improved worker safety and allowed staff to focus on other tasks. Human error in temperature readings was almost eliminated since the system measures and alerts on its own. Integration with control systems meant the furnace could operate more efficiently. For example, heat output could be adjusted in real time to prevent over-firing billets that were already at temperature, saving energy and fuel costs. Better control over furnace conditions also led to fewer incidents of excessive scale formation since billets were not overheated, directly improving yield and reducing maintenance for scale removal.

A key advantage of the Xi 1M camera over traditional solutions is the detailed temperature information it provides. It automatically records the hottest and coolest parts of each billet, ensuring no anomalies are missed. This gave operators new confidence; they no longer had to guess internal billet temperatures from a single surface spot but could see a complete thermal map. The thorough logging of thermal images also supports the plant’s quality assurance and reporting.

Finally, the cost-benefit of the Optris thermal camera has been very positive. The investment in the Xi 1M camera and its accessories was balanced by savings in various areas: lower scrap rates, less fuel usage, reduced downtime, and delaying equipment replacement due to gentler operation. Compared to disposable sensors, like dip thermocouples used in some forging operations, or even multiple high-end pyrometers, the single-camera solution proved to be very cost-effective, achieving full return on investment in a short time.