CN111136253B - Plasma heating method and plasma heating system for tundish molten steel - Google Patents
Plasma heating method and plasma heating system for tundish molten steel Download PDFInfo
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- CN111136253B CN111136253B CN202010032011.3A CN202010032011A CN111136253B CN 111136253 B CN111136253 B CN 111136253B CN 202010032011 A CN202010032011 A CN 202010032011A CN 111136253 B CN111136253 B CN 111136253B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
- B22D41/005—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like with heating or cooling means
- B22D41/01—Heating means
- B22D41/015—Heating means with external heating, i.e. the heat source not being a part of the ladle
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Abstract
The invention provides a plasma heating method and a plasma heating system for tundish molten steel, and relates to the technical field of ferrous metallurgy continuous casting. The heating method comprises the following steps: and during heating, the heating electrode group is positioned at the preset height of the upper surface of the molten steel, and the arc starting heating is carried out by firstly heating for 5-8min at the power of 700-. The heating method enables the heating temperature to be easily regulated and controlled, constant-temperature pouring is achieved within a short time, stability is maintained, macrostructure of a casting blank is effectively improved, the center isometric crystal rate of the casting blank is increased, casting blank defects are reduced, the number density of inclusions in the casting blank is reduced, the isometric crystal rate of the casting blank is increased, and the quality of the casting blank is improved.
Description
Technical Field
The invention relates to the technical field of ferrous metallurgy continuous casting, in particular to a plasma heating method and a plasma heating system for tundish molten steel.
Background
With the continuous development of the metallurgical technology of the tundish, the main functions of the tundish are gradually developed from initial transition, buffering and molten steel distribution to have the functions of promoting inclusion floating, blowing operation and alloying, temperature control and the like. With the progress of continuous casting technology, the content of non-metallic inclusions in steel is reduced, and the cleanliness of steel is higher and higher. The temperature of molten steel in the tundish has important influence on the quality of a casting blank, the temperature of the molten steel is required to be controlled to be close to a stable target value, but in an abnormal casting period, heat loss with different degrees exists in the tundish, the temperature drop of the molten steel in the tundish seriously influences the quality of the casting blank, a temperature field and a flow field in the tundish influence each other, the change of the temperature field can cause the change of the flow field, and a good flow field can influence the movement behavior of impurities in the tundish and influence the characteristics of the impurities. The traditional tundish metallurgy improves the removal rate of inclusions in the tundish by changing the internal structure of the tundish, and although the flowing state of molten steel is improved to a certain extent, the internal temperature of the molten steel is not uniform, and the quality of a casting blank is finally influenced. At present, for the problem of temperature drop, an external heat source is usually adopted to heat molten steel, an induction heating method is commonly used, but an induction heater, a channel and an air cooling pipe are required to be installed on a tundish in the process of induction heating, a certain space in the tundish needs to be occupied, the effective volume of the tundish can be reduced, and the investment cost of a steel mill is increased.
In view of this, the invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a plasma heating method for tundish molten steel, which not only ensures that the temperature of the molten steel in a tundish is uniform, but also can improve the purity of the molten steel.
The invention aims to provide a plasma heating system for tundish molten steel, which is simple to install, does not need to transform a tundish type, and has adjustable power and strong controllability.
The invention is realized by the following steps:
in a first aspect, embodiments provide a method of plasma heating of tundish molten steel,
the plasma heating device outside the tundish is used for heating the molten steel in the tundish, the plasma heating device comprises a heating electrode group,
and during heating, the heating electrode group is positioned at the preset height of the upper surface of the molten steel, and the arc starting heating is carried out by firstly heating for 5-8min at the power of 700-.
In an optional embodiment, during heating, the heating electrode group is inserted into the molten steel in the tundish, so that the lower surface of the heating electrode group is 50-100mm below the upper surface of the molten steel, and then the heating electrode is pulled up to the preset height.
In an optional embodiment, the preset height is 140 mm and 250mm above the upper surface of the molten steel on the lower surface of the heating electrode group.
In an alternative embodiment, the set of heating electrodes is heated by dc plasma.
In an alternative embodiment, the holder holding the heating electrode group is water-cooled during heating.
In a second aspect, embodiments provide a plasma heating system for a tundish molten steel, which is suitable for heating the molten steel in the plasma heating method for the tundish molten steel according to any one of the preceding embodiments, and comprises a tundish and a plasma heating device for heating the tundish;
plasma heating device includes heating electrode group, air feed mechanism and heating operation dish, heating electrode group optionally inserts in the middle package or hang in the middle package top, air feed mechanism with heating electrode group intercommunication, heating operation dish with the middle package is connected in order to detect the temperature of middle package, heating operation dish with heating electrode group connects in order to control heating electrode group's power.
In an alternative embodiment, the heating electrode group comprises a plurality of electrodes, wherein one ends of the electrodes are provided with internal threads, and the other ends of the electrodes are provided with external threads;
preferably, the diameter of the electrode is 130-150mm, and the length of the electrode is 800-1200 mm;
preferably, the middle part of the electrode is provided with an inner hole, the inner hole is communicated with the gas supply mechanism, and the diameter of the inner hole is 6-10 mm.
In an optional embodiment, the plurality of electrodes include a graphite anode and a plurality of graphite cathodes, the plurality of graphite cathodes are respectively connected to a cathode of a power supply, the graphite anode is connected to an anode of the power supply, and the plurality of graphite cathodes are uniformly distributed around or on two sides of the graphite anode; and the graphite cathodes are communicated with the gas supply mechanism.
In an alternative embodiment, the plasma heating apparatus includes a lifting mechanism for inserting or pulling the heating electrode group into or onto the upper surface of the molten steel;
preferably, elevating system includes supporting platform, stand, arm and holder, the stand install in supporting platform, the one end liftable of arm install in the stand, the arm keep away from the one end of stand with the holder is connected, the holder with heating electrode group connects.
In an alternative embodiment, the plasma heating apparatus further comprises a water supply mechanism for water-cooling the holder;
preferably, the mechanical arm and the gripper are communicated and provided with an inner pipe for installing a line and an outer pipe sleeved outside the inner pipe, the outer pipe is provided with a water inlet and a water outlet, and the water supply mechanism is communicated with the water inlet.
The invention has the following beneficial effects:
according to the method, an external plasma heating device is used for heating molten steel in a tundish, and particularly, the molten steel is heated for 5-8min at the power of 700 plus-800 kw, the power is high at the moment, the molten steel can be heated rapidly, then the molten steel is heated for 3-6min at the power of 400 plus-500 kw, supplementary heating is achieved by reducing the power, the heating temperature can be adjusted and controlled more easily, constant-temperature pouring is achieved within a short time and is kept stable, the macrostructure of a casting blank can be improved by constant-temperature pouring, the isometric crystal rate of the center of the casting blank is improved, the defects of the casting blank are reduced, the number density of inclusions in the casting blank before and after heating is reduced obviously, the size change of the inclusions is small, meanwhile, the isometric crystal rate of the casting blank is improved, and the quality of the casting blank is. In addition, the plasma heating device that this application provided, its installation is simple, need not reform transform the tundish type, utilizes the heating operation panel to carry out real-time detection to the temperature of molten steel in the tundish to judge whether need the heating, can also adjust power simultaneously, and set for the heat time according to the temperature variation of molten steel, realize heating stage by stage, the controllability is strong.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is a schematic structural diagram of a plasma heating apparatus provided in the present application;
FIG. 2 is a schematic structural diagram of an electrode provided herein;
FIG. 3 is a schematic structural diagram of a lifting mechanism provided herein;
fig. 4 is a schematic structural diagram of the robot arm and the gripper of the lifting mechanism provided by the present application when they are water-cooled.
Icon: 100-plasma heating means; 110-heating electrode group; 111-electrodes; 112-inner hole; 113-a graphite anode; 114-graphite cathode; 115-internal threads; 116-external threads; 120-a gas supply mechanism; 130-heating the operating panel; 140-a lifting mechanism; 141-a support platform; 142-a column; 143-a robotic arm; 144-a gripper; 145-a water inlet; 146-a water outlet; 147-an inner tube; 148-an outer tube; 150-a water supply mechanism; 160-a power supply mechanism; 161-PLC main control cabinet; 162-motor control cabinet; 163-dc power cabinet; 200-a steel ladle; 201-ladle long nozzle; 202-tundish.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The present application provides a plasma heating method of tundish molten steel and a plasma heating system of tundish molten steel, in which the plasma heating method of tundish molten steel is heated by the plasma heating apparatus 100, so that in order to introduce the plasma heating method of tundish molten steel, the structure of the plasma heating apparatus 100 is introduced first.
Referring to fig. 1, the present application provides a plasma heating system for tundish molten steel, which includes a plasma heating apparatus 100 and a tundish 202. The plasma heating apparatus 100 includes a heating electrode assembly 110, a gas supply mechanism 120, a heating operation panel 130, a power supply mechanism 160, a lifting mechanism 140, and a water supply mechanism 150.
The heating electrode group 110 is used for heating the molten steel in the tundish 202, wherein the molten steel enters the tundish 202 through the ladle nozzle 201 of the ladle 200. In the present application, the heating electrode assembly 110 includes a plurality of electrodes 111, wherein one end of each electrode 111 is provided with an internal thread 115, and the other end of each electrode 111 is provided with an external thread 116 (see fig. 2). When the electrode 111 consumes approximately two thirds, the electrode 111 can be replaced. The specific operation is as follows: the new electrode 111 is screwed in from the other end of the electrode 111, and the new and old electrodes 111 are combined into a new electrode 111 to be continuously used, so that waste in replacing the electrode 111 is avoided.
Further, in the present application, the diameter of the electrode 111 is 150mm, and the length of the electrode 111 is 1200 mm; the middle part of the electrode 111 is provided with an inner hole 112, and the diameter of the inner hole 112 is 6-10 mm. The inner hole 112 is communicated with the gas supply mechanism 120 and the power supply mechanism 160, and the gas supply mechanism 120 is used for supplying gas to the heating electrode group 110 so as to realize gas ionization and form an electric circuit, form a plasma arc and heat molten steel.
Further, the plurality of electrodes 111 in the present application include a graphite anode 113 and a plurality of graphite cathodes 114, the plurality of graphite cathodes 114 are respectively connected to cathodes of a power supply, and the graphite anode 113 is connected to an anode of the power supply. That is, in the present application, the graphite anode 113 is a common anode and forms a circuit with the plurality of graphite cathodes 114. A plurality of graphite cathodes 114 are uniformly distributed around or on both sides of the graphite anode 113; the plurality of graphite cathodes 114 are all in communication with a gas supply 120. In the application, the plurality of graphite cathodes 114 are arranged, so that heating can be simultaneously performed at multiple points in the tundish 202, and the heating is more uniform.
The heating panel 130 is connected to the tundish 202 to detect the temperature of molten steel in the tundish 202, and the heating panel 130 is connected to the heating electrode group 110 to control the power of the heating electrode group 110. Realize the temperature of molten steel in the real-time detection tundish 202 through heating operation panel 130 in this application to judge whether need the heating, can also adjust power simultaneously, and set for the heat time according to the temperature variation of molten steel, realize heating stage by stage, the heating effect is better, can make the molten steel temperature realize the constant temperature pouring in the short time, and maintain stably.
In this application, power supply mechanism 160 includes PLC main control cabinet 161, motor control cabinet 162 and DC power supply cabinet 163, PLC main control cabinet 161 communicates with motor control cabinet 162 and DC power supply cabinet 163 respectively, in order to control motor control cabinet 162 and DC power supply cabinet 163 respectively, this motor control cabinet 162 is connected with elevating system 140, go up and down in order to control elevating system 140, in addition, this motor control cabinet 162 still communicates with water supply mechanism 150, make its holder 144 that is elevating system 140 carry out the water-cooling in order to realize the control to water supply mechanism 150. The dc power supply cabinet 163 in this application is connected to the heating electrode assembly 110, so as to provide dc power to the heating electrode assembly 110, thereby implementing dc plasma heating. Direct current is more stable than alternating current, thus reducing consumption of the graphite electrode 111, the direct current power supply is easy to strike arcs, and the stability of the ionization state in the plasma region is maintained once arcs are struck.
Further, the electrode 111 is connected to a lifting mechanism 140, and the lifting mechanism 140 controls the heating electrode assembly 110 to move up and down, thereby performing arc starting heating. Specifically, referring to fig. 3, the lifting mechanism 140 includes a supporting platform 141, a column 142, a mechanical arm 143, and a holder 144, wherein the column 142 is mounted on the supporting platform 141, one end of the mechanical arm 143 is mounted on the column 142 in a liftable manner, one end of the mechanical arm 143 away from the column 142 is connected to the holder 144, and the holder 144 is connected to the heating electrode assembly 110. In this application, utilize holder 144 centre gripping heating electrode group 110, realize holder 144 and drive heating electrode group 110 up-and-down motion to heat the molten steel.
In addition, referring to fig. 4, the water supply mechanism 150 in the present application is used for cooling the holder 144, an inner pipe 147 for installing a line and an outer pipe 148 sleeved outside the inner pipe 147 are opened on the mechanical arm 143 and the holder 144 in the present application, a water inlet 145 and a water outlet 146 are opened on the outer pipe 148, and the water supply mechanism 150 is communicated with the water inlet 145. The water supply mechanism 150 is communicated with the water inlet 145 to realize water inlet, water entering the outer pipe 148 flows in the outer pipe 148 and is discharged from the water outlet 146, the circuit in the inner pipe 147 is cooled, and the phenomenon that the clamp 144 damages the internal circuit due to overhigh temperature is effectively avoided.
The plasma heating device 100 provided by the application is simple to install, is located in the outer side of the middle package 202, has no influence on the overall structure of the middle package 202, does not need to transform the package type of the middle package 202, and has adjustable power and strong controllability.
Next, a plasma heating method of the tundish molten steel provided by the present application is introduced, which includes the steps of:
when heating, the heating electrode group 110 is positioned at the preset height of the upper surface of the molten steel, and the arc starting heating is carried out, wherein the heating is firstly carried out for 5-8min at the power of 700-.
Specifically, during heating, the heating electrode assembly 110 is inserted into the molten steel of the tundish 202 by a predetermined depth, the gas supply mechanism 120 supplies gas to the heating electrode assembly 110 to generate plasma, the heating electrode assembly 110 is pulled to be located at a predetermined height on the upper surface of the molten steel, the arc is ignited for heating, the power of the heating electrode assembly 110 is adjusted by the heating operation panel 130, the heating is performed for 5-8min at the power of 700-.
Specifically, in the present application, the lifting mechanism 140 is used to insert or lift the heating electrode group 110 above the molten steel, and the lifting mechanism 140 can start heating and stop heating at any time, and at the same time, the heating electrode group 110 does not need to be fixed at a specific heating position in advance, so that the operating space during pouring of the tundish 202 is not damaged, and the obstruction to the field space and the influence on the production process are reduced. The arc starting heating is to supply gas to the heating electrode group 110 through the gas supply mechanism 120, and realize the dc plasma heating under the energizing effect of the dc power supply of the power supply mechanism 160. The arc is more stable in dc heating than in ac heating, reducing the consumption of graphite electrode 111, the dc power source is easy to strike, and once striking, the stability of the ionization state in the plasma is maintained. The power of the heating electrode group 110 is then adjusted by using the operation panel, so that staged heating is realized. Particularly, the casting blank is heated for 5-8min at the power of 700 plus 800kw, the power is high at this moment, the heating temperature can be rapidly increased, then the casting blank is continuously heated to the target temperature at the power of 400 plus 500kw, the supplementary heating is realized by reducing the power, the heating temperature can be more easily regulated and controlled, further, the constant-temperature casting is realized in a shorter time and is kept stable, the macrostructure of the casting blank can be improved by the constant-temperature casting, the isometric crystal rate of the center of the casting blank is improved, the generation of defects of the casting blank is reduced, the number density of inclusions in the casting blank before and after heating is obviously reduced, the size change of the inclusions is not large, and the quality. And when the temperature of the molten steel rises to be close to the target value, closing the plasma heating device 100 and returning the heating electrode group 110.
Wherein the preset depth is 50-100mm below the upper surface of the molten steel on the lower surface of the heating electrode group 110. The predetermined height is 140 mm and 250mm above the upper surface of the molten steel on the lower surface of the heating electrode assembly 110. In the present application, by controlling the lowering position and the lifting position of the heating electrode group 110, a better arcing heating effect can be ensured.
For the tundish 202 with determined heating positions in some factories, holes can be formed in the cover of the tundish 202 according to the heating positions, then the heating electrode group 110 is moved to the preset position by the lifting mechanism 140, preparation before heating can be completed in a short time, a heating signal can be quickly started, the graphite anode 113 is lowered into slag to serve as a current loop during work, and the graphite cathodes 114 are subjected to arc starting and heating.
Therefore, the plasma heating method for the tundish molten steel provided by the application is not only applicable to the tundish 202 without a fixed heating position, but also applicable to the tundish 202 with a specific heating position, and has a wide application range.
According to the heating method, the molten steel can be effectively heated, the cleanliness of the molten steel is improved, and the characteristics of inclusions in the casting blank are improved. The temperature field and the flow field are mutually influenced, and further the movement behavior of the inclusions is influenced. The number density of the inclusions in the casting blank is obviously reduced before and after heating, and the size change of the inclusions is not large. The constant temperature pouring can improve the macrostructure of a casting blank, improve the center isometric crystal rate of the casting blank, reduce the defects of the casting blank and improve the quality of the casting blank. According to the method, the molten steel is poured at constant temperature, the tissue structure of the casting blank can be controlled, the macrostructure of the continuous casting blank is controlled, namely, the columnar crystal area at the center of the casting blank is reduced, the equiaxial crystal area is enlarged, the equiaxial crystal area at the center can effectively prevent the defects of shrinkage cavity and central crack, and the quality of the casting blank is improved. The method of plasma heating the tundish not only enables the temperature of the molten steel in the tundish 202 to be uniform, but also can improve the purity of the molten steel. And plasma heating device 100 installs simply, need not transform the package type of middle package 202, and power is adjustable, and controllability is strong.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
The low-carbon steel smelting is carried out in a certain steel plant by the process route of 'converter smelting → LF refining → RH refining → continuous casting', wherein the converter smelting period is 40min, the oxygen level is less than 600ppm, 400kg of top slag and 50kg of fluorite are added into the converter steel discharged, the temperature in the LF furnace is 1610 ℃, the treatment period in the LF furnace is 30min, the temperature in RH molten steel is 1625 ℃, the treatment period in the LF furnace is 35min, the temperature in molten steel is 1588 ℃ at the end of RH refining, the temperature in the middle and later periods of pouring in a tundish 202 is 1552 ℃, when the heating electrode group 110 is inserted into the molten steel and the lower surface of the heating electrode group 110 is 70mm below the upper surface of the molten steel, the plasma heating is started, and the heating electrode group 110 is lifted so that the lower surface of the heating electrode group. The heating power is adjusted to 750KW, the heating time is 5min, the temperature is raised by 7 ℃, and the average heating rate is 1.4 ℃/min. Then, the power is adjusted to 500kw, the heating is carried out for 4min, and the temperature is increased by 4 ℃ on the basis of the original temperature.
Sampling and analyzing the casting blank sample before and after heating, wherein the number density of inclusions before heating is 96.56/mm2Average size 2.33 μm; the number density after heating is 73.59 pieces/mm2Average size of 2.58 μm; the size of the inclusions does not vary much. The equiaxed crystal ratio of the cast slab before heating was 43.15%, and the equiaxed crystal ratio of the cast slab after heating was 52.93%.
Example 2
A certain steel mill performs low-carbon steel smelting, the process route is 'converter smelting → argon station → RH refining → continuous casting', the converter smelting period is 40min, the oxygen level is less than 600ppm, the LF treatment period is 28min, the RH treatment time is 35min, the carbon content is reduced, and the component fine adjustment is performed. After the RH refining is finished, the temperature of the molten steel is 1585 ℃, the temperature of the tundish 202 in the middle and later casting periods is 1549 ℃, the heating electrode group 110 is inserted into the molten steel, when the lower surface of the heating electrode group 110 is 80mm below the upper surface of the molten steel, the plasma heating is started, and the heating electrode group 110 is lifted to enable the lower surface of the heating electrode group 110 to be 200mm above the upper surface of the molten steel. The heating power is adjusted to 780KW, the heating time is 5min, the temperature is increased by 7 ℃, the heating rate is 1.4 ℃/min, then the power is adjusted to 480KW, the heating is carried out for 6min, and the temperature is increased by 6 ℃ on the original basis.
Sampling and analyzing the casting blank before and after heating, and counting the number of inclusions before heatingThe density is 78.52 pieces/mm2Average size 1.91 μm; the number density of the inclusions after heating was 56.36 pieces/mm2The average size was 2.06. mu.m, and the size of the inclusions was not greatly changed. The equiaxed crystal ratio of the cast slab before heating was 37.82%, and the equiaxed crystal ratio of the cast slab after heating was 46.05%.
Example 3
The modification of "the heating electrode group 110 is inserted into the molten steel with the lower surface of the heating electrode group 110 positioned 70mm below the upper surface of the molten steel" in example 1 was: "the heating electrode group 110 is inserted into the molten steel with the lower surface of the heating electrode group 110 positioned 60mm below the upper surface of the molten steel", "lifting the heating electrode group 110 with the lower surface of the heating electrode group 110 positioned 160mm above the upper surface of the molten steel" is modified to "the heating electrode group 110 is lifted with the lower surface of the heating electrode group 110 positioned 150mm above the upper surface of the molten steel".
Comparative example 1
The staged heating (adjusting the heating power to 750KW, the heating time to 5min, the temperature to rise by 7 ℃, the average heating rate to 1.4 ℃/min, then adjusting the power to 500KW, heating for 4min, the temperature to rise by 4 ℃ on the original basis) in the embodiment 1 is modified into one-time heating, specifically: the heating power is adjusted to 750KW, the heating time is 8min, and the temperature is increased by 11 ℃.
Comparative example 2
The staged heating (adjusting the heating power to 750KW, the heating time to 5min, the temperature to rise by 7 ℃, the average heating rate to 1.4 ℃/min, then adjusting the power to 500KW, heating for 4min, the temperature to rise by 4 ℃ on the original basis) in the embodiment 1 is modified into one-time heating, specifically: the heating power is adjusted to 500KW, the heating time is 12min, and the temperature is increased by 11 ℃.
Comparative example 3
The modification of "the heating electrode group 110 is inserted into the molten steel with the lower surface of the heating electrode group 110 positioned 70mm below the upper surface of the molten steel" in example 1 was: "the heating electrode group 110 is inserted into the molten steel with the lower surface of the heating electrode group 110 positioned 200mm below the upper surface of the molten steel".
Comparative example 4
The modification of "the heating electrode group 110 is inserted into the molten steel with the lower surface of the heating electrode group 110 positioned 70mm below the upper surface of the molten steel" in example 1 was: "the heating electrode group 110 is inserted into the molten steel and the lower surface of the heating electrode group 110 is 20mm below the upper surface of the molten steel. "
Comparative example 5
The modification of "lifting the heating electrode group 110 such that the lower surface of the heating electrode group 110 is positioned 160mm above the upper surface of the molten steel" in example 1 was "lifting the heating electrode group 110 such that the lower surface of the heating electrode group 110 is positioned 100mm above the upper surface of the molten steel".
Comparative example 6
The modification of "lifting the heating electrode group 110 such that the lower surface of the heating electrode group 110 is positioned 160mm above the upper surface of the molten steel" in example 1 was "lifting the heating electrode group 110 such that the lower surface of the heating electrode group 110 is positioned 300mm above the upper surface of the molten steel".
The cast slabs before and after heating were sampled and analyzed in examples 1 to 3 and comparative examples 1 to 6, and the analysis results were as follows:
as can be seen from the above table, the arcing heating effect becomes weaker when the difference between the electrode lowering and raising distances in example 3 is smaller than that in example 1, while the arcing and heating effects can be significantly improved by the staged heating in the present application as seen from comparative examples 1-2, and the rate of decrease in the number density of inclusions is decreased and the rate of increase in the equiaxed crystal ratio is also lower by the conventional one-time heating. Further, as can be seen from comparative examples 3 to 6, when the distance of descent and ascent of the electrode is greater or less than the value of the range claimed in the present application, there is a significant influence on the arcing and heating effects, and particularly, the arcing and heating effects are significantly reduced as the ascent distance becomes greater or smaller.
In summary, in the present application, the external plasma heating device 100 is used to heat the molten steel in the tundish 202, the heating operation panel 130 is used to detect the temperature of the molten steel in the tundish 202 in real time, so as to determine whether heating is needed, and simultaneously, the power can be adjusted, and the heating time is set according to the temperature change of the molten steel, so as to achieve staged heating, especially, the heating is performed at a power of 700-, the number density of the inclusions in the casting blank is obviously reduced before and after heating, the size change of the inclusions is small, and meanwhile, the isometric crystal rate of the casting blank is favorably improved, so that the quality of the casting blank is improved. In addition, the plasma heating apparatus 100 provided by the present application is simple to install, does not need to transform the package type of the tundish 202, and has adjustable power and strong controllability. The heating method provided by the application can be applied to the continuous casting stage of the low-carbon steel smelting method, the purity of molten steel is finally improved, and the quality of a casting blank is improved.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A plasma heating method of tundish molten steel is characterized in that the molten steel in a tundish is heated by a plasma heating device outside the tundish, the plasma heating device comprises a heating electrode group,
during heating, the heating electrode group is firstly inserted into the molten steel of the tundish, the lower surface of the heating electrode group is positioned 50-100mm below the upper surface of the molten steel, then the heating electrode group is lifted and positioned at the preset height of the upper surface of the molten steel, arc starting and heating are carried out, firstly heating is carried out for 5-8min at the power of 700-;
the preset height is 140 mm and 250mm, wherein the lower surface of the heating electrode group is positioned above the upper surface of the molten steel.
2. The method of claim 1, wherein the set of heating electrodes is heated by direct current plasma.
3. The method of claim 1, wherein the holder holding the heating electrode group is water cooled during heating.
4. A plasma heating system of a tundish molten steel, which is suitable for heating the molten steel in the plasma heating method of the tundish molten steel according to any one of claims 1 to 3, characterized by comprising a tundish and a plasma heating device for heating the tundish;
the plasma heating device comprises a heating electrode group, an air supply mechanism and a heating operation panel, wherein the heating electrode group can be selectively inserted into the tundish or hung above the tundish, the air supply mechanism is communicated with the heating electrode group, the heating operation panel is connected with the tundish to detect the temperature of the tundish, and the heating operation panel is connected with the heating electrode group to control the power of the heating electrode group;
the plasma heating device comprises a lifting mechanism for inserting the heating electrode group into the molten steel or lifting the heating electrode group to the upper surface of the molten steel; the lifting mechanism comprises a supporting platform, a stand column, a mechanical arm and a clamp holder, wherein the stand column is installed on the supporting platform, one end of the mechanical arm is installed on the stand column in a lifting mode, one end of the mechanical arm, which is far away from the stand column, is connected with the clamp holder, and the clamp holder is connected with the heating electrode group.
5. The plasma heating system of tundish molten steel of claim 4, wherein the set of heating electrodes comprises a plurality of electrodes, one end of each electrode is provided with an internal thread, and the other end of each electrode is provided with an external thread.
6. The plasma heating system for tundish molten steel of claim 5, wherein the diameter of the electrode is 130-150mm, and the length of the electrode is 800-1200 mm.
7. The plasma heating system of tundish molten steel of claim 5, wherein the middle of the electrode is provided with an inner hole, the inner hole is communicated with the gas supply mechanism, and the diameter of the inner hole is 6-10 mm.
8. The plasma heating system for tundish molten steel of claim 5, wherein the plurality of electrodes comprise a graphite anode and a plurality of graphite cathodes, the plurality of graphite cathodes are respectively connected with a cathode of a power supply, the graphite anode is connected with an anode of the power supply, and the plurality of graphite cathodes are uniformly distributed around or on two sides of the graphite anode; and the graphite cathodes are communicated with the gas supply mechanism.
9. The plasma heating system of tundish molten steel of claim 4, further comprising a water supply mechanism for water cooling the holder.
10. The plasma heating system of tundish molten steel of claim 9, wherein the mechanical arm is in communication with the holder and is provided with an inner tube for installing a line and an outer tube sleeved outside the inner tube, the outer tube is provided with a water inlet and a water outlet, and the water supply mechanism is in communication with the water inlet.
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| CN111931392B (en) * | 2020-10-16 | 2021-02-12 | 北京科技大学 | Method and device for optimizing argon blowing parameters of plasma heating tundish bottom |
| CN114449723A (en) * | 2022-04-08 | 2022-05-06 | 北京奥邦新材料有限公司 | Device and method for improving power factor of tundish plasma heating system |
| CN114433806B (en) * | 2022-04-08 | 2022-06-10 | 北京奥邦新材料有限公司 | Method and system for preventing molten steel of tundish from being carbureted |
| CN117683968B (en) * | 2024-02-02 | 2024-04-23 | 北京科技大学 | Tundish plasma heating desulfurization method |
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| GB9008833D0 (en) * | 1990-04-19 | 1990-06-13 | Boc Group Plc | Heating |
| JPH0740011A (en) * | 1993-08-02 | 1995-02-10 | Nippon Steel Corp | Plasma heating device for molten steel in tundish |
| JP3268235B2 (en) * | 1997-07-09 | 2002-03-25 | 三菱重工業株式会社 | Molten steel heating tundish |
| JP2002143991A (en) * | 2000-11-09 | 2002-05-21 | Nippon Steel Corp | Method of heating molten steel in tundish |
| JP3849471B2 (en) * | 2001-08-02 | 2006-11-22 | 住友金属工業株式会社 | Uniform heating method for molten steel in tundish |
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| CN203304546U (en) * | 2012-10-18 | 2013-11-27 | 上海万恒基热能技术有限公司 | Continuous casting middle ladle liquid steel heating device |
| CN205834205U (en) * | 2016-07-13 | 2016-12-28 | 北京麦特尔科技有限公司 | The continuous casting production direct current plasma heater of electrode is made by many graphite hollow stick |
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