Double-electrode direct-current fused magnesia furnace system capable of monitoring molten pool depth and monitoring method

Abstract

The present invention belongs to the technical field of electrofused magnesia, and particularly relates to a double-electrode direct-current electrofused magnesia furnace system capable of monitoring the depth of a molten bath and a monitoring method. The system of the present invention is small in size and easy to build, and the layout parameters of the furnace body and the electrodes are convenient to change; it can measure and record electrical parameters at different moments during smelting; obtaining the corresponding relationship between the molten bath resistance and the molten bath morphology helps to optimize the electrofused magnesia control method; the measurement method of the melt resistance can be extended to the measurement of the load characteristics of various refractory melt.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrofused magnesia, and particularly relates to a double-electrode direct-current electrofused magnesia furnace system capable of monitoring the depth of a molten pool and a monitoring method therefor. Background Art

[0002] Single-crystal magnesium oxide is formed by using high-purity magnesium oxide powder and other raw materials and melting them to a molten state in an electric arc furnace by the arc melting method and then cooling. It has high and low temperature resistance, high pressure resistance, corrosion resistance, strong insulation performance, good thermal conductivity and optical properties, and is often used for making high-grade magnesia bricks, magnetic films, high-temperature superconducting films, high-temperature crucible materials, high-temperature insulation materials, etc.

[0003] At present, the electrofused magnesia industry in China still uses three-phase alternating-current submerged arc furnaces. However, the alternating-current arc furnace has problems such as continuous extinguishing and reignition of the arc, poor arc stability, unstable heat source, large voltage fluctuation and serious impact on the power grid, and the crystal yield is relatively low. By using a direct-current arc furnace, a steadily burning arc can be obtained, and the power factor of the direct-current furnace can generally reach more than 0.9. Since magnesium oxide has a high melting point and is easy to ablate the furnace bottom, the single-electrode method with the furnace bottom as the anode is not advisable, and only the double-electrode method can be used. The direct-current arc furnace has long been applied in the metallurgical industry, but it has not been widely used industrially in the electrofused magnesia industry.

[0004] In actual production, operators mainly rely on measuring the furnace shell temperature and voltage and current to judge the temperature state and molten pool state in the furnace, and determine the operating parameters based on experience. If the corresponding relationship between the molten pool resistance and the molten pool depth in the refining stage can be obtained, the molten pool depth can be predicted through real-time current and voltage parameters, which is helpful for more accurate control of the electrofused magnesia process and has guiding significance for optimizing the electrofused magnesia control process. Summary of the Invention

[0005] In order to better smelt magnesium oxide, the present invention provides a double-electrode direct-current electrofused magnesia furnace system and proposes a method for predicting the molten pool depth according to the load characteristics of the molten pool.

[0006] The technical solution adopted by the present invention to achieve the above object is as follows:

[0007] A double-electrode direct-current electrofused magnesia furnace system capable of monitoring the molten pool depth, comprising a furnace body, a pair of graphite electrodes, an electrode clamping device, an electrode joint, a water cooling device, an electrode height adjusting device, a direct-current welding power supply, a dust removal device, a data acquisition system based on a virtual instrument platform, and a remote control shooting system.

[0008] The furnace body is built by refractory bricks and is a cavity structure with a straight notch opened on the top wall. An observation window is opened on the side wall of the furnace body, and a high-temperature resistant glass is inlaid in the observation window.

[0009] The pair of graphite electrodes are one positive and one negative, and are vertically inserted into the furnace body through the vertical slot at the top of the furnace body, and are fixed on the electrode height adjustment device through the electrode clamping device. The distance between the two electrode axes can be adjusted by the electrode clamping device.

[0010] The electrode height adjustment device is a hydraulic device that can closed-loop control the lifting of the electrode and is located outside the furnace body.

[0011] The DC welding power supply is connected to the graphite electrode through a cable to provide stable direct current for melting in the furnace body.

[0012] The electrode joint is a copper structural part that connects the cable and the graphite electrode.

[0013] The water cooling device is immersion water cooling, which completely immerses the electrode joint in water to prevent poor contact caused by rapid oxidation of the surface of the electrode joint at high temperature during the melting process.

[0014] The dust removal device is a welding fume purifier. The suction hood covers the opening at the top of the furnace body, and the flue gas flows through the filter element through the suction pipe to reduce the pollution of dust to the air.

[0015] The data acquisition system based on the virtual instrument platform collects the output current and voltage data of the DC welding power supply through the Hall current sensor and the Hall voltage sensor, transmits the data to the data acquisition card for processing, storage, and real-time waveform display on the upper computer.

[0016] The remote control shooting system uses a remote camera and a welding lens to shoot the inside of the furnace body through the observation window on the side wall of the furnace body, and displays the image on the upper computer in real time for observing the arc.

[0017] The monitoring method of the molten pool depth in the above double-electrode DC fused magnesia furnace system that can monitor the molten pool depth is as follows: conduct an open arc experiment. When entering the refining stage, lower a pair of graphite electrodes until they contact the molten pool. At this moment, the arc disappears, and the operating resistance only includes the short circuit resistance and the melt resistance; then quickly change the power supply voltage, and the data acquisition system based on the virtual instrument platform records the voltage and current changes to obtain the melt load characteristic, that is, the molten pool resistance; stop the furnace, wait for the melt lump to cool completely, and then take out the melt lump to measure the molten pool depth; change the melting time, and repeat the experiment multiple times to obtain the corresponding relationship between the molten pool resistance and the molten pool depth; in subsequent experiments, according to the current and voltage data obtained in real time by the data acquisition system based on the virtual instrument platform, calculate the resistance, and then obtain the real-time molten pool depth according to the corresponding relationship between the molten pool resistance and the molten pool depth.

[0018] The beneficial effects of the present invention:

[0019] The present invention provides an electrofused magnesia furnace system and a method for predicting the depth of a molten pool according to the load characteristics of the melt. This system is small in size and easy to build, and the layout parameters of the furnace body and electrodes can be conveniently changed; it can measure and record the electrical parameters at different melting times; obtaining the corresponding relationship between the molten pool resistance and the molten pool shape helps to optimize the electrofused magnesia control method; the melt resistance measurement method can be extended to the measurement of the load characteristics of various refractory melts. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FIG. is a schematic diagram of a double-electrode direct-current electrofused magnesia furnace system capable of monitoring the depth of a molten pool according to the present invention.

[0021] Figure 2 FIG. is a structural diagram of an electrode chuck.

[0022] Figure 3 FIG. is a flow chart for measuring the load characteristics and characteristic dimensions of a melt.

[0023] Figure 4 FIG. is a molten pool resistance-characteristic dimension curve obtained from an embodiment.

[0024] In the figure: 1 furnace body, 2 a pair of graphite electrodes, 3 electrode clamping device, 4 electrode joint and its water cooling device, 5 electrode height adjusting device, 6 DC welding power supply, 7 dust removal device, 8 data measurement and control system based on a virtual instrument platform, 9 remote control shooting system. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following further describes the specific embodiments of the present invention in conjunction with the drawings and technical solutions.

[0026] The double-electrode direct-current electrofused magnesia furnace system capable of monitoring the depth of a molten pool in this embodiment, as Figure 1 shown, includes a furnace body 1, a pair of graphite electrodes 2, an electrode clamping device 3, an electrode joint and its water cooling device 4, an electrode height adjusting device 5, a DC welding power supply 6, a dust removal device 7, a data measurement and control system 8 based on a virtual instrument platform, and a remote control shooting system 9.

[0027] The electrode height adjusting device 5 is implemented by a hydraulic forklift, which is connected to the upper part of the electrode through the electrode clamping device 3. The lower ends of a pair of graphite electrodes 2 extend into the furnace body 1, and their axial spacing is adjusted by the electrode clamping device 3.

[0028] The electrode clamping device 3 is composed of a light axis fixing seat SK50 and a bracket. A pair of graphite electrodes 2 have a diameter of 50 mm and an axial spacing of 100 mm. A pair of graphite electrodes 2 pass through the light axis fixing seat and are clamped.

[0029] The electrode joint and its water cooling device 4 are located below the electrode clamping position, as Figure 2As shown in the figure, the electrode joint is a copper structural block fixed by a pipe clamp. The inner side of the copper structural block can closely fit the graphite electrode, and there are screw holes on one side for fixing the cable. Copper sheets are placed inside the pipe clamp to connect the two copper blocks, which makes the current distribution more uniform. The water-cooling device is sleeved outside the electrode joint. The top of it is the water inlet, and the side wall is provided with a water outlet. The water level can completely submerge the electrode joint. A spherical valve is used to adjust the water flow rate of the cooling water, which improves the service life of the electrode and the joint.

[0030] The DC welding power supply 6 can output up to 30KW at most, can provide a maximum current of 630A and can adjust the current / voltage.

[0031] The dust removal device 7 uses a welding fume purifier, which can effectively reduce the soot emission.

[0032] The data measurement and control system 8 based on the virtual instrument platform can collect the real-time voltage and current output by the DC welding power supply through the Hall voltage sensor CHV-25P / * and the Hall current sensor FXBY35, and save and process the data through MYRIO, and display the waveform on the computer.

[0033] The remote control shooting system 9 uses the AirDroid software to remotely control the mobile phone camera to shoot, uses a welding lens for light filtering, and displays the image on the computer in real time.

[0034] As Figure 3 shown, the method for monitoring the molten pool depth in the above-mentioned double-electrode DC electrofused magnesia furnace system capable of monitoring the molten pool depth: conduct an open-arc experiment, that is, do not fill the furnace with materials to ensure that the operating resistance in the refining stage only includes the short-circuit resistance, the arc resistance and the melt resistance. After melting to the refining period, control the electrode height adjustment device 5 to lower the height of a pair of graphite electrodes 2 until the bottom of the electrode is completely in contact with the surface of the molten pool. At this time, the arc disappears, and the operating resistance only contains the short-circuit resistance and the melt resistance. In the remote control shooting system 9, it can be observed that the bright arc disappears, and the upper computer display waveform can be observed to be stable in the current and voltage waveforms. At this time, control the change of the terminal voltage of the DC welding power supply 6, and record the current and voltage data to calculate the molten pool resistance. Wait for the molten mass to cool completely, take out the molten mass and measure its depth as the characteristic dimension. Conduct experiments multiple times at the same electrode spacing to obtain the characteristic curve of the molten pool resistance corresponding to different molten pool depths.

[0035] In this embodiment, the double-electrode axial spacing is 100mm, the electrode diameter is 50mm, and the experiment is repeated 4 times. The obtained molten pool resistances are 0.027Ω, 0.014Ω, 0.011Ω, and 0.009Ω respectively, and the corresponding molten pool depths are 32mm, 51mm, 69mm, and 90mm respectively. It can be Figure 4 seen that the smaller the molten pool resistance, the deeper the molten pool depth, and the smaller the resistance, the faster the change of the molten pool depth.

Claims

1. A double-electrode direct-current fused magnesia furnace system capable of monitoring the depth of the molten bath, characterized in that, The described double-electrode direct-current fused magnesia furnace system includes a furnace body, a pair of graphite electrodes, an electrode clamping device, an electrode joint, a water-cooling device, an electrode height adjustment device, a direct-current welding power supply, a dust removal device, a data acquisition system based on a virtual instrument platform, and a remote shooting system; The furnace body is built with refractory bricks and has a cavity structure with a straight notch on the top wall. An observation window is opened on the side wall of the furnace body, and a high-temperature resistant glass is inlaid in the observation window; The pair of graphite electrodes, one positive and one negative, are vertically inserted into the furnace body from the straight notch at the top of the furnace body, fixed on the electrode height adjustment device through the electrode clamping device, and the axial distance between the two electrodes is regulated by the electrode clamping device; The electrode height adjustment device is a hydraulic device that can closed-loop control the lifting of the electrode and is located outside the furnace body; The direct-current welding power supply is connected to the graphite electrode through a cable to provide stable direct current for melting in the furnace body; The electrode joint is a copper structural part connecting the cable and the graphite electrode; The water-cooling device is immersion water-cooling, completely immersing the electrode joint in water; The dust removal device is a fume purifier, and a smoke suction hood covers the opening at the top of the furnace body; The data acquisition system based on the virtual instrument platform collects the output current and voltage data of the direct-current welding power supply through a Hall current sensor and a Hall voltage sensor, transmits the data to a data acquisition card for processing, storage, and real-time waveform display on the upper computer; The remote shooting system uses a remote camera and an electric welding lens to shoot the inside of the furnace body through the observation window on the side wall of the furnace body and displays the image on the upper computer in real time for observing the arc; An open-arc experiment is carried out. When entering the refining stage, a pair of graphite electrodes are lowered until they contact the molten pool. At this moment, the arc disappears, and the operating resistance only includes the short-circuit resistance and the melt resistance; then the power supply voltage is quickly changed, and the data acquisition system based on the virtual instrument platform records the voltage and current changes to obtain the melt load characteristic, that is, the melt resistance; the furnace is stopped, and the melt is taken out after it is completely cooled to measure the depth of the molten pool; the melting time is changed, and the experiment is repeated multiple times to obtain the corresponding relationship between the melt resistance and the depth of the molten pool; during subsequent experiments, according to the current and voltage data obtained in real time by the data acquisition system based on the virtual instrument platform, the resistance is calculated, and then the real-time depth of the molten pool can be obtained according to the corresponding relationship between the melt resistance and the depth of the molten pool.

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