To control the steelmaking process, namely, to accurately calculate the required amount of deoxidizers and alloying additives, a method of express determination of steel oxidation using oxygen probes is used. The EURAZOXY oxidation probe (similar to the Celox oxygen probes manufactured by Heraeus Electro-Nite) allows determining the melt temperature and the content of active (unbound) oxygen. Based on these data, it is possible to calculate the required addition of aluminum for steel deoxidation and alloying, as well as control the aluminum content in the melt (for steel grades of type 08U), eliminating the need to wait for the results of metal sample analysis.

This probe is disposable and is a paper sleeve, at one end of which a head is fixed with sensitive elements located in it, generating EMF: a hot junction of a thermocouple (which is located in a U-shaped quartz tube) and a solid electrolyte made of zirconium dioxide, which upon contact with the melt forms a galvanic cell (Mo / Cr + Cr2O3 // ZrO2 (MgO) // a (O) Fe / Fe (+) ). Oxidation probes with thermocouples of the "S" and "R" types have become widespread abroad. In our country, preference is given to oxygen probes of the "B" type.

Operating principle

The oxygen probe is connected to a secondary device (for example, Multi-Lab III Celox by Heraeus Electro-Nite) when connected to the contact block by putting the oxidation probe on the rod (for manual immersion) or on the manipulator (for automatic immersion). This contact block has a coaxial connector with four outputs for connecting to the rod. Therefore, the rod for measuring steel oxidation can also be used to measure the melt temperature with replaceable EVRAZTEMP blocks (PTPR-91, POSITHERM) without any alterations. A compensation wire is used as a conductor in the rod (for type "B", ordinary copper wires can be used as a compensation wire). After connecting the oxygen probe to the rod, the secondary device sends a signal about the circuit closing and readiness for use.

1 – current terminal (negative electrode); 2 – external sand body; 3 – internal sand filler; 4 – mastic; 5 – bath current collector (positive electrode); 6 – rolled cardboard (additional impact protection); 7 – protective cap.

To take measurements, lower the probe into the metal melt (to a depth of no more than half the cardboard sleeve) for several seconds (no more than 10). As a result of immersion of the probe into the melt, the steel protective cap on the head melts (which protects the sensitive elements from damage during storage and immersion of the probe through slag). Then, the molten metal directly with the quartz tube heats the thermocouple and interacts with the solid electrolyte. The secondary device begins to record the EMF generated by the sensitive elements until the readings reach a stable platform (after which the probe is removed from the melt). The secondary device converts the EMF into the temperature of the metal melt (in degrees Celsius) and into the activity of unbound oxygen (in ppm - concentration in parts per million). Based on these data, the secondary device is able to calculate the content of sulfur and silicon in cast iron, as well as carbon and aluminum in steel.

There are several types of EURAZOXY oxidation probes:

1. for high oxidation of steel (from 1 to 1500 ppm)
- used mainly to determine oxidation in converters;
2. for low oxidation of steel (from 1 to 1000 ppm)
- used mainly to determine oxidation during secondary steel treatment;
3. to determine the aluminum content (from 1 to 1000 ppm)
- used to determine oxidation at all stages of steelmaking
- used for steel grades containing aluminum (type 08U)
- measures the content of molten aluminum in steel