This article describes two of the most common methods for controlling the temperature of metal melts in industrial steel production: infrared measurement and the thermoelectric force (thermo-EMF) method. Next, we will talk about the advantages and disadvantages of each method, determine the conditions for their optimal use, and evaluate the accuracy of metal temperature measurements in metallurgical production units.

Introduction

The melt temperature plays a key role in the technological process of steelmaking, determining product quality, equipment performance and process efficiency. Temperature control allows you to optimize heating modes, ensure the required physico-chemical properties of the alloy and reduce energy consumption.

Two main approaches are used to measure the temperature of liquid metal: contact and non-contact methods. Among the latter, the infrared method and the thermoelectromotive force (thermo-EMF) method have become the most widespread.

2. Infrared temperature measurement method

2.1 Operating principle

The method is based on recording the thermal radiation of an object, which is proportional to the surface temperature of the material according to the Stefan-Boltzmann law. The radiation is detected by a sensitive detector (usually a pyrometer), after which the signal is converted into a temperature value. The pyrometric sensor determines the temperature through the ratio of the intensity of the radiated heat to the surface temperature of the object.

Advantages:

Non-contact: the absence of direct contact of the sensor with molten metal reduces the likelihood of damage to the equipment and increases the safety of measurements.
High reaction speed: the instant receipt of results allows you to quickly adjust the technological parameters.
A wide range of measurements: from room temperature to high temperatures typical of metal melting processes.

Disadvantages:

Dependence on the emission properties of the surface: the accuracy depends on the emission coefficient of the material, which varies depending on the composition of the alloy, the condition of the surface and the presence of contamination.
Environmental influences: dust, smoke, and humidity affect the measurement results, causing systematic errors.

2.2 Application in metallurgical production

Infrared sensors are actively used to monitor temperatures at all stages of the process cycle, including charge loading, melting, casting, and metal solidification. The use of pyrometers is especially effective in the case of unstable geometry of the measured object or rapidly changing working area conditions.

3. Thermoelectric temperature measurement method (thermo-EMF method)

3.1 Operating principle

This approach is based on the Seebeck effect, which consists in the occurrence of an electromotive force (EMF) in a circuit of dissimilar conductors when the junction of the contacts is heated. The EMF value is determined by the composition of the materials of the pair and the temperature of the transition between them. By calibrating a pair of materials, direct temperature measurement is possible by converting voltage into degree readings.

Advantages:

Measurement accuracy: ensures high reproducibility of the results.
Low sensitivity to external conditions: minimally affected by environmental factors such as dust.

Disadvantages:

Contact nature: the need to immerse the sensors directly into the metal limits the scope of the method and increases the risk of damage to the devices.

3.2 Application in metallurgical production

Thermocouples are widely used as control elements in arc and induction furnaces, converters, providing technology monitoring.

4. Comparative characteristics of the methods

Comparing both methods, it is important to take into account the specifics of a particular production situation and the requirements for measurement quality.

The table shows that the choice of method should be based on the specific features of the production process and the available technical resources of the enterprise.

Conclusions and recommendations
Based on the above, it can be concluded that each of the considered methods has its own strengths and limitations. The choice of a specific method for measuring the temperature of liquid metal should be based on the specifics of the technology, accuracy requirements, economic considerations and the level of automation of production.
It is recommended to combine both approaches, when contact sensors provide precise control of operating parameters, and infrared devices are used for operational monitoring and emergency warning of deviations from set values.
Thus, the comprehensive implementation of modern temperature measurement technologies contributes to improving the quality of products, increasing productivity and reducing production costs.