SU969485A1 - Device for controlling level of metal bath - Google Patents

Description

(54) DEVICE FOR MONITORING THE METAL BATHROOM LEVEL

one

The invention relates to equipment for electroslag welding, surfacing and ingot production by electroslag remelting.

A known sensor for monitoring the level of a metal bath consists of two oppositely connected (differential) thermocouples, which are mounted in slider 1.

The disadvantages of this sensor are that the difference of two thermoelectromotive forces in the differential circuit is very small and requires the use of amplifiers with a very high gain / volume ratio, and the measurement results depend on the cooling water consumption and the thickness of the slag crust under the slider. This regulator is not reliable enough, since thermocouples in the slider can easily be damaged.

An electrical probe is known that is mounted in one of the sliders and used to control the level of the metal bath. The probe is a cooled copper rod that is attached to the slide and electrically isolated from it.

The probe is powered from a source of welding current through an additional choke, which limits the current when the probe is closed on a metal bath. Power supply to the electric probe is necessary

 to maintain the microslag bath in the area of the probe so that no skull is formed on it that would prevent the metal bath from directly contacting the probe. When the metal of the bath is in contact with the probe, the voltage drop across the probe - workpiece section is zero and is different from zero when the metal bath does not touch the probe 1.

A disadvantage of the known probe is a small voltage drop, since the electric current flows along the path with the least resistance; probe - liquid slag bath - crista1 (1izator - blank. The magnitude of the voltage drop does not depend on the location of the metal bath. So

20, destruction of the probe and the mold in the probe area is observed. When the probe is fed with a constant current in the slag bath, electrolysis takes place, which leads to deposition on the electrodes (in this

the case of the probe rod and the mold) of various elements and substances, which in turn leads to a short circuit of the electrical circuit of the probe - mold when electrically conductive substances settle or the circuit of the probe - mold is broken due to the termination of the electroslag process in the probe area due to subsidence non-conductive substances.

The purpose of the invention is to improve the quality control of the metal bath level, as well as the durability of the device.

This goal is achieved by the fact that in a device for controlling the level of a metal bath containing an electrolytic probe-rod cooled, mounted on the crystallizer and electrically insulated from it, and a power source connected to the probe-rod and the crystallizer are electrically insulated from each other from the probe and crystallizer metal cooled rings-screens located concentrically relative to the probe-rod and relative to each other. The thickness of the rings-screens is chosen from the conditions:

& SV- t, where 6 - mm screen ring thickness;

V is the rate of welding (smelting) mm / s t is the response time of the actuator, s.

At the same time, in order to improve the quality control of the metal bath, the ring-screen closest to the probe rod is electrically connected to the negative pole of a separate additional source of power with high internal ohmic resistance, plus of which is connected to the crystallizer.

The drawing shows a diagram of the device and its structural features.

A device for measuring the level of a metal bath 2 is built into the mold or slider 1, which consists of an electric contact probe 3 and intermediate rings screens 4, which are electrically isolated from the probe, from each other and the mold, and are located concentrically relative to the probe and to each other. The probe rod and ring screens are cooled through the cooling system 5.

The contact probe rod is supplied with the voltage oi of the welding or special power source (CIP), and the other end of the source is connected to the weld billet or mold.

The ring-screen nearest to the probe-rod is connected to the negative pole of the additional power source (DIP) with high internal ohmic resistance, and the plus is connected to the crystallizer. When the molten metal 2 is below the device for measuring the level of the metal bath, the voltmeter V indicates the magnitude of the voltage drop across the electrical contact probe - mold, while the current passes through the molten slag bath 6 and the ring screens. As we approach. liquid metal bath to the device for control and as the contact between the metal bath and the screen rings is formed, the drop in the pressure at the probe-crystallizer section detected by the voltmeter decreases discretely, and when the contact is formed, the probe and the liquid metal are equal

zero.I

An ammeter A is also included in the circuit for monitoring open circuit. The discreteness of the change in voltage drop is caused by the fact that changes occur only when the insulating gaps pass through the liquid metal bath. The moment when the voltage drop is zero or any non-zero value corresponding to a certain level of presence of the liquid metal bath can serve as a signal for controlling the speed, the relative movement of the liquid metal bath and the mold (slider).

The thickness of the ring screen is a function of the welding speed (surfacing, smelting) and the inertia of the actuator (its response time), which reacts to changes in the level of the metal bath.

Practically, the response time of the actuator does not exceed 2 s., And the welding (smelting) speed is 15 m / h, therefore, the thickness of the shielding rings, sufficient for accurate operation of the device, may be 9 mm or less. In general, the thickness of the ring-screens can be chosen from the condition

where & is the thickness of the ring-screen, mm;

V is the welding (smelting) speed, mm / s t — the time of the actuator actuation, s.

Currently, an electrical insulating material is unknown, which can withstand for a long time the effects of high temperatures (up to 2500 ° C) and chemically active media consisting of fluoride and chloride compounds, which is a liquid slag bath.

But liquid slags, having a certain viscosity, cannot penetrate into the gap with a width of less than 2 mm, therefore insulation rings are shown conditionally in the device, since it is sufficient to have an air gap between the probe and the rings less than 2 mm.

To increase the potential difference between the probe rod and the liquid metal bath, the probe is powered by

direct current, with the minus connected to the probe-rod, plus a plus - with the weld (welded) workpiece, the ring-screen closest to the probe is closed (briefly) with the plus source. At the same time, on the positive electrode (ring), the anolyte is enriched with silica, which, under intense cooling, forms a poorly conducting layer at the ring surface, and the current between the probe and the ring does not pass, which creates an additional voltage drop across the probe - crystallizer section and improves the accuracy of determination level of liquid metal bath. This is equivalent to simply increasing the outer diameter of the insulating ring located between the probe and the first ring of the screen.

To increase the voltage drop between the probe and the second ring-screen of the ring-screen next to the probe with a negative pole, a separate additional power source with high internal ohmic resistance, the specified ring will be charged with the same charge with the probe, which will cause the movement of charged particles and electric current on a longer path than in the case of an electrically neutral ring. This increases the voltage drop, which increases the quality of the metal bath level control.

The economic effect from the introduction of the invention only in the production of a two-layer metal will be approximately 90 rubles. on 1 ton of metal.

Claims (2)

Invention Formula A device for controlling the level of a metal bath containing a cooled An electro-contact probe rod mounted on the mold and electrically isolated from it, and a power source connected to the probe and mold, characterized in that it is electrically insulated from the probe rod and the mold metal cooled to improve the performance of the device rings-screens located concentrically relative to the probe-rod and relative to each other. 2. A device according to claim 1, characterized in that the thickness of the screen rings is selected from the condition where 5 is the thickness of the screen ring, mm; V - welding speed (melting), mm / s; I time actuator actuating, p. H. The device according to claim 1, characterized in that, in order to improve the quality control of the metal bath, the ring screen closest to the probe rod is electrically connected to the negative pole of the additional power source with high internal ohmic resistance, and the positive pole of the source crystallizer. Sources of information taken into account in the examination I. Electroslag welding. Ed. B.Ye. Paton, M., Kyiv, “Mechanical Engineering, 1959, p. 233. 2. Electroshlakova welding and surfacing. Ed. B. E. Paton. M., “Mechanical Engineering, 1980, p. 143 (prototype).