The role of non-contact temperature monitoring in liquid steel and metal applications

The temperature of a metal at the point of casting can significantly affect the quality, strength, and other properties of the resulting part or product. Temperature monitoring of the liquid metal, therefore, plays an essential role in the production process.

However, achieving an accurate and reliable measurement of the metal – one that is unaffected by the hot, dirty, and smoky environment, or by layers of oxide and slag forming on the surface of the metal – can prove challenging.

The traditional method for these measurements is to use thermocouples, typically dipping thermocouples that make contact with the liquid metal. Measuring the metal stream itself is not possible, so the reading is taken in the ladle or converter, at the point where the metal runs out into the mould or another vessel or ladle.

The thermocouple dips into the metal, avoiding any surface deposits that could affect the result, and within a few seconds provides an average temperature for the liquid metal at the depth and position it is dipped in. This is usually a manual process, so the operator is required to be in a hot, dirty, and smoky atmosphere during the measurement, which can be a safety risk.

Accuracy is an issue for this method: different thermocouples plus several repeated measurements are likely to produce inconsistent results. Additionally, the dipping tips for each thermocouple need to be replaced after only a few measurements, so there is an ongoing cost.