RAPID ANALYSIS OF METAL

Accuracy and rapidity of getting, processing and reproducing results are particular qualities of systems for molten metal parameters determination provided by the NORDINKRAFT-SENSOR Company. Such results are reached due to the use of the most reliable and efficient measuring method – probe method (immersion of a probe direct into the medium which is to be measured). It enables the steelmaker to master a new level of smelting control technique due to getting the precise parameters of melt on-line. The systems are widely used for intermediate control of melts parameters in advanced enterprises of metallurgical complex (ferrous and non-ferrous metallurgy). Operating these systems doesn’t require special training. Reliable and available systems of the NORDINKRAFT-SENSOR Company provide steelmakers with reliable parameters at work with molten metals.

Performance capabilities of these systems:

1. Determination of melt temperature.
2. Determination of:

· oxygen activity

· hydrogen content

· nitrogen content

3. Determination of FeO content in slag.
4. Determination of sulphur content in iron.
5. Use of combined control systems significantly optimising the process of smelting due to combination of several operations, such as:

· temperature measurement;

· oxygen activity measurement;

· carbon content determination;

· sampling.

6. Sampling of molten metal (steel, iron), slag.

FUNCTIONING OF DEVICES AND SYSTEMS FOR CONTROL OF MOLTEN METAL PROPERTIES


1. Measuring probes (thermocouples).
2. Secondary devices.
3. Samplers.

1. Measuring probes

Thermocouples and probes of various types are consumable parts of system for direct measurement of molten metal properties.
Thermocouples belong to the class of thermoelectric transducers and are meant for one use only, intended for temperature measurement in hostile environment. Their action is based on thermoelectric effect: if alloys of two dissimilar metals forming a closed circuit, have different temperatures, - then, this creates voltage in the circuit. Thermoelectric effect is generating of thermo electromotive force (EMF) which appears due to the temperature difference between two junctions of different metals and alloys.

Disposable oxygen probes are complex devices allowing the conduct of temperature determination (together with secondary device), as well as determination of oxygen percentage (oxidability) and aluminium quantity needed for introduction into molten metal.

The system is used to monitor the condition of liquid steel and coating slag. The ceramic tip of a disposable probe contains sensitive elements – a galvanic cell and a thermocouple.

Functioning of the system is based on interaction of high temperature electrochemical cell with solid electrolyte. Two galvanically isolated measuring inputs (temperature and EMF) give the possibility to exclude their interaction and effect of other circuits on them. Thus, equilibrium is established between the standard electrode, the solid electrolyte and the analysed melt. As a result of processing of signals from galvanic cell and thermocouple, secondary device marks out the “areas” on the measurement curves, according to the given scheme, showing metal temperature and EMF (MV).

According to the given readings a report on oxygen percentage (oxydability, ppm) is made, as well as recommendation on aluminium quantity necessary for introduction into the mass (kg). In the unkilled steel the device shows data on carbon mass concentration (%).

The probes for hydrogen content determination are complex disposable devices.
Operating principle of such device is based on determination of equilibrium partial hydrogen pressure for melt by means of carrier gas (nitrogen) blowing through metal with subsequent recovery of it by the porous tip of a probe.

Pneumatic block carries out continuous circulation of the carrier gas in the system. Contacting with liquid metal the carrier gas absorbs the hydrogen dissolved in the melt. On getting into the pneumatic block this gas is cyclically analysed by means of thermal conductivity detector. As the partial pressure stabilizes, the measurement ends, and the processor records the results.
Time consumption – not longer than 1 minute.
Combined probes are complex devices with a number of built-in thermoelectric sensors and sampling devices inside. This type of disposable probes is used with the purpose of combining of several operations in the technological cycle of metal smelting, particularly for use in converter.

2. Secondary measuring devices

Secondary devices carry out processing, registration and indication of data based upon functioning of thermocouples and other measuring blocks. As a matter of fact, most of them are industrialised computers which allow using a wide range of possibilities of the system for visual, convenient and responsible application.

3. Samplers

It is necessary to use the up-to-date specialised samplers in order to quickly get a qualitative metal sample to render it to the laboratory. Nordinkraft-Sensor produces wide range of such devices for liquid iron sampling, steel sampling, non-ferrous sampling as well as slag sampling which allow getting representative samples of different forms.

A disposable device is a cardboard tube with a sectional crystalliser body inside.


The following types of samplers can be distinguished depending on specific character and place of use:
1. Immersion samplers.
The sampler is immersed into metal by means of the probe holder. The filling of the receptacle chamber of a sampler with liquid metal is provided due to ferrostatic pressure.

2. Vacuum suction samplers.
The filling with liquid metal is provided due to the vacuum created with a manual pump.

The use of deoxidant metals provides the filling of crystalliser chamber with molten steel with high oxygen content and low carbon content. As a result, a representative sample is ready in no time (sampling process 6-8 sec.).

 
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