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Aluminum Rolling Mills

Temperature Control in the Hot Rolling Mill

Aluminum sheet and plate products are used for a wide range of applications, including can stock, brazing, automotive and aerospace. These industries demand exacting tolerances and precise mechanical properties, particularly for new, technically challenging high-strength alloys. As a result, modern aluminum rolling mills demand previously unobtainable levels of aluminum infrared temperature sensor accuracy for the control of rolling mill bite, pressure, speed, and coolant. To meet this need, Williamson offers two multi-wavelength infrared technologies able to provide the unprecedented accuracy this industry now demands for temperature readings throughout the hot rolling process.

Williamson Multi-Wavelength Technologies

Williamson offers two multi-wavelength technologies for aluminum rolling mills. Each technology includes application-specific ESP algorithms for optimal performance.

  • The Williamson MW pyrometer includes ESP Algorithms to compensate for different surface texture characteristics of an aluminum rolled surface or the side of a coil. The MW pyrometer provides a high degree of accuracy when the aluminum surface characters are relatively consistent. It can also measure the lower temperature values that are required at the coiler.
  • The Williamson MWx pyrometer includes Dynamic ESP Technology to compensate for the significant variation in surface character associated with the ingot measurement and during the reversing mill process. This dynamic technology completely eliminates any need to define and make adjustments for alloy, pass number or thickness that is so often associated with the reversing mill application.

Download the Complete Set of Rolling Mill Application Notes

Williamson Multi-Wavelength Technologies


Pyrometer Type MWx-AS MW-20
  • Multi-wavelength with Dynamic ESP Technology
  • Automatically compensates for changing surface character conditions*
  • Multi-wavelength with Static ESP Technology
  • Assumes reasonably predictable surface character conditions
Temperature Range 550-1200 °F / 285-650 °C 300-1200 °F / 150-650 °C
Measurement Locations
  • Ingots
  • Reversing/Roughing Mill
  • Finishing Mill*
  • Coiler

*Temperature Footnote:
The need for a MWx pyrometer v. a MW pyrometer is determined by changes in surface characteristics not temperature range.

*Finishing Mill Footnote: The MWx-AS is preferred for Finishing Mills, however, the MW can be used under certain circumstances.


Application Overview

Before heading to the rolling stands, a large ingot of aluminum is heated in a furnace for hours to days. Ingots need to be heated for this long of a time so they are completely heated through to the core so that the ingot can be rolled out into a longer strip without being reheated.

Overview of heated Aluminum Ingot in a Rolling Mill
Williamson Wavelength Advantage

The ingot is soaked for such a long time to assure uniform temperature prior to rolling, and the soaking time is often extended due to process downtime. These extended soaking times often alter the emissive character of the aluminum even when the surface texture is reasonably consistent, and this is the primary reason why the Dynamic ESP Technology associated with the MWx pyrometer is required.

Pyrometer Benefits
  • Conserve Energy
  • Assure Desired Aluminum Properties
  • Optimize Rolling Mill Speed
Wavelength Technology
  • MWx – Dynamic ESP Technology automatically corrects for variation of alloy, oxidation, elemental migration to the surface, and surface texture

Roughing/Reversing Mill

Application Overview

At the reversing mill, rolling speed, roll bite, and coolant flow may be optimized only with a precise real-time knowledge of metal temperature. The low and highly variable non-greybody emissivity character associated with this complex aluminum process dictates the use of the most sophisticated multi-wavelength infrared pyrometers as the material converts from a coarse ingot to a smooth strip.

Overview of Aluminum Rolling and Reversing Mill
Williamson Wavelength Advantage

The Williamson model MWx, designed specifically for the demanding aluminum hot reversing rolling mill application, uses the most advanced Multi-Wavelength Dynamic ESP Technology available for unequaled accuracy under all operating conditions.

Pyrometer Benefits
  • Improved Product Properties
  • Improved Process Consistency
  • Faster Rolling Speeds
  • No need for real-time interaction with the pyrometer
Wavelength Technology
  • MWx Dynamic ESP Technology corrects for the non-greybody emissivity variation associated with aluminum.
  • Williamson’s exclusive Dynamic ESP technology automatically corrects for variations in alloy and thickness.

Finishing Mill

Application Overview

Tight control of finishing temperature assures the desired mechanical properties and a blemish-free surface. The low and highly variable non-greybody emissivity character associated with this aluminum process dictates the use of multi-wavelength infrared pyrometers.

Overview of Aluminum finishing mill
Williamson Wavelength Advantage

The traditional multi-wavelength (MW) technology works well at the finishing mill where the process is highly repeatable. While the temperature may vary from alloy to alloy, this variation is repeatable. For exceptional accuracy and repeatability across alloys, the MWx technology is required.

Pyrometer Benefits
  • Assures Desired Mechanical Properties
  • Prevents Surface Blemishes
  • Optimizes Line Speed
Wavelength Technology
  • Williamson multi-wavelength technology automatically corrects for the non-greybody emissivity variation associated with this application.
  • The MWx Dynamic ESP Technology and the original MW Technology both produce repeatable temperature readings at this location across all alloys, with the Dynamic ESP Technology producing more absolutely accurate values.


Application Overview

The temperature at the coiler is an important process parameter. If the temperature is too hot, then the metal may soften and stick. If the temperature is too cool, then the material may become too hard and crack. Hand-held thermocouple probes are notoriously inaccurate and are prone to misuse and interpretation.

Close view of Aluminum Coiler
Williamson Wavelength Advantage

The multi-wavelength pyrometer produces a much more repeatable and accurate temperature value than the traditional thermocouple. The pyrometer can be used to measure the temperature of the strip as it enters the coiler and/or measure the side of the coil while it is being wound or after it has been removed from the coiler.

Pyrometer Benefits
  • Assures Desired Mechanical Properties
  • Automates Temperature Measurement
  • Eliminates Thermocouple Maintenance
  • Provides Consistency
  • Measures the Same Spot Each Time
Wavelength Technology
  • Multi-Wavelength Technology assures accurate readings when viewing the non-greybody aluminum material.

Consult With One of Williamson’s Temperature Experts

We would love to discuss your temperature measurement application with you.

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