Molten metal temperature measurement system

01

Choose dip, continuous or optical-fibre measurement

Heraeus Electro-Nite describes fast, accurate liquid-metal temperature readings as essential for cost-effective temperature control in steelmaking, offering expendable temperature sensors with a wide choice of thermocouple types, probe lengths and immersion lances for all process applications, plus non-splash and multi-immersion designs for critical applications and foundries. For continuous casting it offers a robust permanent sensor to control temperature profiles, with precision the same as dip measurements and a range of holding devices and cable lengths. [2] [1]

MINKON explains that thermocouples are quick, precise and inexpensive but cannot give an instantaneous continuous reading, while contactless optical measurement needs a free view, reads only the surface and suffers large errors because surface emissivity is unknown. Its DynTemp approach continuously immerses an optical fibre into the melt to transmit thermal radiation without emissivity losses or slag influence, for use by hand lance, manipulator, stirring lance or bottom tuyere. [3]

Give the supplier the metal and process stage (furnace, ladle, degasser, tundish, mould), temperature range, spot or continuous measurement, deployment (hand lance, automatic manipulator, permanent mount), required accuracy and repeatability, probe consumption per heat, instrument and data interface, and plant safety requirements.

02

Set accuracy expectations and deployment

MINKON gives a maximum thermocouple wire tolerance of ±1.5 °C (0.1%) at the palladium point and a tolerance of ±3.5 °C for the total measuring chain; in a 100 t ladle furnace, continuous measurement detected the required tapping temperature about two minutes earlier than interpolating manual thermocouple readings, and showed temperature homogenisation about 50 s after arc power-off without bottom stirring against about 10 s with stirring. For RH degassing it describes a manual lance with heavy-duty probes measuring for 4–6 minutes. [3]

Editorial calculation: the ±3.5 °C chain tolerance is a little over twice (2.3×) the ±1.5 °C wire tolerance, so specifications should state which of the two is meant. [3]

03

Weigh a non-contact tapping-stream pyrometer against dip thermocouples

AMETEK Land's SPOT+ MM (MeltMaster) is an infrared pyrometer for liquid iron and steel in foundry tapping, aimed at the pouring stream as it runs into each mould instead of dipping thermocouples into the ladle, which its application sheet calls dangerous and dependent on operator technique and dip depth. The product page lists a measurement range of 600 to 1,800 °C, accuracy in application of ±0.5% of the reading in kelvin, 0.1 °C resolution, 0.5 °C noise, detection in selected near-infrared bands, IP65 sealing, response time adjustable from 1 ms to 10 s, 0/4–20 mA analogue outputs plus Ethernet with Modbus TCP, and power over Ethernet or 19–30 V DC at 8 W maximum. Its application mode is designed to read through the thin oxide layers that form and re-form on the stream, it holds the tapping temperature until the next pour, and an integrated camera lets the operator watch the stream. [4] [5]

Editorial calculation: at 1,600 °C (1,873 K), ±0.5% K is about ±9.4 °C, wider than the ±3.5 °C measuring-chain tolerance MINKON gives for dip thermocouples, but the pyrometer reads every pour without consumables or a person at the ladle. Specify which you need: per-mould continuous readings for documentation, or ladle reference readings for heat control. [4] [3]

04

Questions to put to a probe or pyrometer supplier

Ask any supplier for the thermocouple type and calibration, stated accuracy of the probe and complete measuring chain, measuring time per dip, probe lengths and lance or manipulator compatibility, continuous-sensor life, instrument outputs and data integration, and references in similar melt shops.

05

Probes, lances, permanent sensors and the optical fibre route

The expendable probe and lance rows apply to dip readings; the permanent sensor and optical fibre rows are the continuous options. [2] [3]

06

Which accuracy figure: wire, measuring chain or pyrometer?

State whether accuracy means the thermocouple wire, the whole measuring chain or a pyrometer reading in kelvin, since the sources quote all three. [3] [4]

07

Send the process, method and accuracy data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Process: [furnace; ladle; degasser; tundish]
Method: [expendable dip; continuous; optical fibre]
Deployment: [hand lance; manipulator; permanent]
Accuracy: [±°C; repeatability]
Probes: [type; length; consumption]
Integration: [instrument; level 2 system]

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