Heat treatment

Better temperature control during heat treatment

Precise temperature control is vital during heat treatment of steel. The IR pyrometer method often results in measurement errors, but Swerea has come up with a successful solution to the problem.

To influence material hardness and other properties, a heat treatment process called annealing is used. During heat treatment it is important to be able to control the temperature in the furnace, so that the desired material
properties are achieved.

Radiation shield reduced measurement errors

For temperature measurement, an infrared (IR) pyrometer, which is a type of non-contact thermometer for measuring high temperature, can be used. But with this method, reflected radiant furnace heat commonly causes measurement errors, since the surroundings are hotter than the steel surface.

To develop a successful solution to this problem, Swerea has collaborated with the steel industry. By combining a multi-wavelength IR pyrometer with a radiation shield, the effect of radiated furnace heat can be almost completely eliminated.

From pilot-scale trials to effective use at SSAB. 

Swerea has conducted pilot-scale trials in a chamber furnace and the measurement results have been very good. Temperature can be measured with greater precision, which ensures better quality and more consistent material properties in the strip steel.

The method is now used on the continuous annealing line at SSAB in Borlänge.