The Application of Temperature Sensors in the Steel and Metallurgy Industry

1.Introduction: Temperature - The "Lifeline" of Steel Metallurgy

Steel metallurgy is a physicochemical process under extremely high temperatures, and temperature is the most core process parameter running through it throughout. From iron ore to high-performance steel, the temperature at each stage directly determines the quality of the final product, the energy consumption of the production process, the safe lifespan of equipment, as well as production efficiency and cost. It can be said that without precise temperature measurement and control, there would be no modern steel industry. The Temperature Sensor is precisely the "eyes" and "skin" that sense this "lifeline". The progress and application level of its technology directly reflect the degree of automation and intelligence in the steel industry.

2. Core Temperature Sensing Technology and Its Principles

In the extremely harsh environments of the steel industry (high temperatures, dust, corrosion, and melt erosion), two major types of temperature sensing technologies are mainly applied:

·Contact temperature measurement: thermocouple

Working principle: Based on the Seebeck effect, two conductors of different materials are connected to form a circuit. When there is a temperature difference at both ends, a thermoelectric potential will be generated in the circuit.

Industry application features

Advantages: High measurement accuracy, can be directly inserted into the melt to obtain true and reliable temperature values.

Disadvantage: It is a consumable, especially when measuring molten steel and molten iron, and is used only once.

Common types

Type S (Platinum-rhodium 10-platinum) : Suitable for oxidizing atmospheres, with a long-term service temperature up to 1300 ° C and a short-term temperature of 1600 ° C. It is the absolute main force in steelmaking and refining.

Type B (Platinum-rhodium 30- platinum-rhodium 6) : Suitable for oxidizing atmospheres, with a higher upper limit of measurement. Long-term use can reach 1600 ° C, and short-term use can reach 1800 ° C. It is often used for measuring high-temperature molten steel.

Type K (nickel-chromium - nickel-silicon) : High cost performance, wide range (-200 to 1300℃), widely used in relatively low-temperature areas such as heating furnaces, flue gas, and steel rolling.

3. Specific Applications of Temperature Sensors in the Entire Steel Production Process

·Ironmaking process: The "thermometer" of the blast furnace

Application points: Blast furnace iron water channel, iron water tank, hot blast stove.

Requirement: Monitor the temperature of molten iron when it comes out of the furnace to ensure the stability of the blast furnace condition and prevent the furnace cylinder from freezing or overburning.

Solution

Contact type: Consumable S-type or B-type thermocouples are adopted, which are regularly inserted into the molten iron to obtain precise temperatures, serving as the key basis for process control.

 
·Steelmaking and Refining Process: The "Decisive Point" of Quality Control

Application points: Converter/electric furnace steel outlet, ladle, LF furnace, RH refining unit.

Requirement: "Terminal temperature" control is the soul of the steelmaking process, directly related to the quality of molten steel and the yield of alloys.

Solution

Absolute main force: Fast-consumable thermocouple (with temperature gun and paper tube probe). The operator inserts and measures multiple times at the end of the blowing process, before steel tapping, and at the refining station, obtaining an accurate and reliable core temperature of the molten steel within seconds. This is the gold standard for production operations and quality determination.

 
·Continuous casting stage: The "Guardian" of the Solidification Process

Application points: Ladle/tundish, secondary cooling zone, billet outlet.

Requirement: Control the superheat of molten steel to ensure stable drawing speed; Monitor the surface temperature of the cast billet in the secondary cooling zone, optimize the cooling strategy, and prevent defects such as cracks.

Solution

The temperature of molten steel: Consumable thermocouples are used for fixed-point measurement in the ladle and tundish.

4. Selection and Maintenance: The Key to Ensuring Measurement Reliability

Correct selection: Based on the measurement object (melt, solid, gas), temperature range, environmental atmosphere (oxidation/reduction), accuracy requirements, response speed and budget, comprehensively choose contact or non-contact sensors.

Maintenance and calibration: Regularly calibrate thermocouples and temperature measuring instruments to ensure system accuracy.

To address challenges: For interference from dust and water vapor, an infrared thermometer with a dust-blowing function can be selected. For high-temperature melts, select high-quality protective tube materials that are resistant to thermal shock.

Although the temperature sensor is small, it is a key technological cornerstone that supports the colossal modern steel industry. From molten iron at a thousand degrees to fiery red billets, precise temperature perception and control run through the entire process of steel production, and it is the core for ensuring safety, improving quality, and reducing costs and increasing efficiency. A thorough understanding of its application and the rational selection and maintenance of sensors are of vital significance for promoting the intelligent upgrade and high-quality development of the steel industry.