KR100340570B1 - Manufacturing method of molten steel using twin shell electric furnace - Google Patents

Abstract

The present invention relates to a method for manufacturing molten steel using a twin cell electric furnace consisting of one power supply device and two furnaces. In a furnace in which power is not input from a twin shell electric furnace, a solid iron source is used by using heat of oxidation of oxygen and carbon. In order to provide a method for manufacturing molten steel in a twin-shell electric furnace that can secure the quality of the steel by preheating the molten steel and shortening the dissolution time of the electric furnace, as well as appropriately adjusting the blowing rate of oxygen and carbon source, thereby raising the quality of the steel. There is a purpose.

The present invention provides a method for manufacturing molten steel using a twin shell electric furnace consisting of one power supply and two furnaces,

In the first furnace, preheating the solid iron source by the heat of oxidation reaction by the reaction of carbon and oxygen, and simultaneously in the second furnace, supplying power to the electrode to generate an arc to dissolve and refine the solid iron source;

After the dissolution and refining work in the second furnace is completed, arc is generated in the first furnace to dissolve and refine the solid iron source, and at the same time, the second furnace converts the power to the first furnace and injects oxygen and carbon source to refine the powder. And warming up and down, leaving the hot heel and ending the tapping, preparing for operation, putting a carbon source on the hot heel, putting a solid iron source thereon and blowing oxygen to preheat the scrap iron source; and

After the dissolution and refining operations in the first furnace are completed, arc is generated in the second furnace to dissolve and refine the solid iron source, and at the same time, the first furnace converts power to the second furnace and supplies oxygen and carbon source to refine. And warming up and down, leaving the hot heel and ending the tapping, preparing for operation, putting a carbon source on the hot heel, putting a solid iron source thereon and blowing oxygen to preheat the solid iron source. The manufacturing method of molten steel using a shell electric furnace is made into the summary.

Description

Manufacturing method of molten steel using twin shell electric furnace

The present invention relates to a method of manufacturing molten steel using an electric furnace, and more particularly, to a method of manufacturing molten steel using a twin cell electric furnace consisting of one power supply device and two furnace bodies.

Generally, an electric furnace consists of one power supply 11 and one furnace body 12 (also referred to as a "monoshell electric furnace"), as shown in FIG. 1, to manufacture molten steel using such a monoshell electric furnace. The method is a step of charging an iron source such as scrap iron into an electric furnace (hereinafter referred to as "charger"), the step of generating an arc using the electrode 13 to dissolve the iron source (hereinafter referred to as "melter") Adjusting molten molten steel to an appropriate temperature and composition (hereinafter referred to as "refining machine"), and tapping the manufactured molten steel into a ladle in an electric furnace (hereinafter referred to as "elasticizer"), The process is divided into stages (hereinafter referred to as "preparators") to prepare for work in the furnace again.

In Fig. 1, reference numeral 14 denotes a hopper, 15 denotes an oxygen lance, 16 denotes a carbon lance, 17 denotes a maniplate, 18 denotes a lower electrode, and 121 denotes a tap hole.

As described above, in the case of manufacturing molten steel using a monoshell electric furnace, the power supply is always connected to the electric furnace to supply power to the melter and refiner, but does not require arcing. Since the device does not operate, there is a problem that the operation rate of the power device is low.

In order to supplement the problems of the above-mentioned monoshell furnace operation, a twin shell furnace 20 in which two furnaces 22 are formed in one power supply device 21 as shown in FIG. The spread of twin shell furnace operation, which improves the operation rate of the power supply device, is being increased by supplying electric power to the other side of the charging, tapping, and preparing equipment which does not require arcing at one side. .

In Fig. 2, reference numeral 23 denotes an electrode, 24 denotes a hopper, 25 denotes an oxygen lance, 26 denotes a carbon lance, 27 denotes a manifold, 28 denotes a lower electrode, and 221 denotes a tap hole.

The time required for each operation step for the monoshell furnace operation method and the twin shell furnace operation method is as shown in Table 1 below.

division Monoshell furnace Twin Shell Furnace Difference in time Charge (minute) 6 3 -3 Dissolution (min) 32 32 0 Refiner (min) 15 15 0 Faucet (minutes) 3 0 -3 Preparatory minute 4 0 -4 Total processing time (minutes) 60 50 -10

As shown in Table 1, the twin shell furnace operation method is superior to the monoshell furnace operation method in terms of productivity since the work time per charge is reduced by about 10 minutes compared to the monoshell furnace operation method.

As a typical method of manufacturing molten steel using a twin cell electric furnace as described above, Japanese Patent Application Laid-Open No. 9-31521 may be mentioned.

The Japanese Laid-Open Patent Publication discloses a one-power supply apparatus having one power supply device and two furnaces and an electric furnace operation method of a two-role method. Next, one power supply device is configured to perform decarburization heating by oxygen injection and at the same time to avoid overlapping operation timings between A and B, while the other furnace conducts decarburization heating by oxygen injection when one furnace is energized. And a method of manufacturing molten steel in an electric furnace in a two-role method.

However, the method of heating and decarburizing by blowing oxygen as in the above method has a problem in that when the carbon concentration is lower than 0.1%, the oxygen concentration in the molten steel and the slab is increased to lower the quality of the steel and increase the amount of deoxidizer used.

Accordingly, the present inventors have conducted research and experiments to improve the problems of the conventional methods described above, and based on the results, the present invention proposes the present invention. Twin shell that can secure the quality of steel by heating the molten steel by appropriately adjusting the blowing speed of oxygen and carbon source by preheating solid iron source by using carbon oxidation reaction heat. An object of the present invention is to provide a method for manufacturing molten steel in an electric furnace.

1 is a schematic diagram of a conventional monoshell electric furnace consisting of one power supply and one furnace;

2 is a schematic diagram of a twin shell electric furnace consisting of one power supply and two furnaces;

Figure 3 is a schematic diagram showing a process for producing molten steel according to the present invention using a twin-shell electric furnace.

Figure 4 is a schematic diagram showing the generation of splash according to the oxygen injection

5 is a correlation diagram showing a change in the carbon concentration in the molten steel and the oxygen concentration in the slag according to the change of the carbon injection amount and the oxygen injection flow rate

6 is a graph showing a change in scrap temperature according to the oxygen injection amount

7 is a graph showing the temperature change of molten steel according to the oxygen injection amount

8 is a graph showing the change of carbon concentration in molten steel and T.Fe concentration in slag according to the oxygen injection amount

Explanation of symbols on the main parts of the drawings

11, and 21 ... power supplies, 12, 22a and 22b, 13, and 23 electrodes, 15, and 25 oxygen lances, 16, And 26 ...... carbon lance

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention comprises an oxygen lance to inject oxygen, a carbon lance to supply a carbon source, two furnaces provided with electrodes to generate arc by receiving power, and one power supply device to supply power to the electrodes. In the method of manufacturing molten steel using a twin-shell electric furnace,

In the first furnace, a carbon source is put on a hot heel loaded in the furnace, and a solid iron source is put thereon, and oxygen is blown through an oxygen lance to preheat the solid iron source. Discharging and refining the solid iron source by generating arc by supplying electric power to the electrode provided in the second furnace in the second furnace;

After dissolving and refining in the second furnace is finished, stopping power supply to the electrode provided in the second furnace in the power supply device and supplying power to the electrode provided in the first furnace;

Arc is generated in the first furnace by electric power supplied from the power supply to the electrode provided in the first furnace to dissolve and refine the solid iron source, and at the same time, the power is converted to the first furnace in the second furnace, and then oxygen lance and Oxygen and carbon source are blown through carbon lance, refined and warmed up, and the tapping is finished with the hot heel left. After preparation, the carbon source is put on the hot heel, the solid iron source is put on it, and the oxygen is blown. Preheating the scrap iron source;

After dissolving and refining in the first furnace is finished, cutting off power supply to the electrode provided in the first furnace and supplying power to the electrode provided in the second furnace; And

Arc is generated in the second furnace by the electric power supplied from the power supply to the electrode provided in the second furnace to dissolve and refine the solid iron source, and at the same time, the power is converted to the second furnace and oxygen lance and Oxygen and carbon source are blown through carbon lance, refined and warmed up, and the tap is finished with the hot heel left. After preparation, the carbon source is put on the hot heel, and the solid iron source is put on it. It relates to a method for producing molten steel using a twin-shell electric furnace comprising the step of preheating the solid iron source.

Hereinafter, the present invention will be described in detail.

As shown in FIG. 2, the present invention provides two furnaces, each provided with an oxygen lance 25 for blowing oxygen, a carbon lance 26 for supplying carbon, and an electrode 23 for generating arc by receiving power. Molten steel using the twin-shell electric furnace 20 including the first furnace 22a and the second furnace 22b and one power supply device 21 for supplying power to the electrode 23. It is applied to the manufacturing method.

3 shows an example of a process for manufacturing molten steel according to the present invention using a twin-shell electric furnace, which will be described below in detail with reference to FIGS. 2 and 3.

In FIG. 3, "1" represents a hot heel, "2" represents a carbon source, "3" represents a solid iron source, and "4" represents slag.

In the present invention, as shown in (a) of FIG. 3 (A), in the first furnace 22a, the carbon source 2 is put on the hot heel 1 charged in the furnace, and the solid iron source 3 is put thereon and the oxygen lance Oxygen is blown in through the (25) to preheat the solid iron source (3) and at the same time in the second furnace (22) of FIG. 3 (B), the second furnace (22b) of the power supply device (21). ), The arc is generated by supplying electric power to the electrode 23 provided in the) to dissolve and refine the solid iron source 4.

Next, after the refining operation is completed in the second furnace 22b, the power supply from the power supply device 21 to the electrode 23 provided in the second furnace 22b is cut off and the first furnace ( Power is supplied to the electrode 23 provided in 22b).

Next, as shown in (b) and (c) of FIG. 3A, the first power is supplied from the power supply device 21 to the electrode 23 provided in the first path 22a. Arcs are generated in the furnace 22a to dissolve and refine the solid iron source 4, and at the same time, the power is returned to the first furnace in the second furnace 22b as shown in FIGS. 3B and 3B. After converting to (22a), the oxygen and carbon source is blown through the oxygen lance 25 and the carbon lance 26, respectively, refined and warmed up and down, and the tapping is finished with the hot heel 1 remaining. After that, a carbon source is put on the hot heel 1, a solid iron source 4 is put thereon, and oxygen is blown to preheat the scrap iron source 4.

The tapping in the second furnace 22b is performed after confirming the temperature and the molten steel component. In this case, when the molten steel temperature is lower than the target temperature, oxygen and carbon sources are supplied into the slag through oxygen lance and carbon lance, respectively. The molten carbon source is oxidized and the molten steel is heated up to the target temperature using the heat of oxidation, and the tapping is performed after oxidizing and refining the impurities in the molten steel.

In addition, the preheating of the solid iron source in the second furnace (22b) is the reaction of the carbon in the carbon source and the injected oxygen, that is, the heat of oxidation reaction of the C + O → CO reaction or C + 1/2 O ₂ → CO reaction Is done by.

Next, after the refining operation is completed in the first furnace (22a), the power supply from the power supply device 21 to the electrode 23 provided in the first furnace (22a) is cut off and the second furnace ( Power is supplied to the electrode 23 provided in 22b).

Next, as shown in (f) to (g) of FIG. 3B, the power is supplied from the power supply device 21 to the electrode 23 provided in the second furnace 22b. Arc is generated in the second furnace (22b) to dissolve and refine the solid iron source (4), and at the same time, as shown in (d) to (g) of FIG. After converting to the furnace 22b, the oxygen and carbon source is blown through the oxygen lance 25 and the carbon lance 26, respectively, refined and warmed up and down, and the tapping is finished with the hot heel 1 remaining. After that, the carbon source is put on the hot hill, the solid iron source is put thereon, and the oxygen is blown to preheat the solid iron source.

The tapping in the first furnace 22a is also performed after checking the temperature and molten steel components as when tapping in the second furnace 22b. In this case, when the molten steel temperature is lower than the target temperature, the oxygen lance and the carbon lance Oxygen and carbon source are blown into the slag through oxidizing the supplied carbon source, and using the heat of oxidation reaction generated at this time, the molten steel is heated up to the target temperature, and the impurities in the molten steel are oxidized and refined and the tapping is performed.

The preheating of the solid iron source in the first furnace 22a is also the reaction of carbon in the charged carbon source with the injected oxygen, such as the preheating in the second furnace 22b, that is, C + O → CO reaction or C + 1 / ₂ O 2 → carried out by the oxidation reaction heat of CO reaction.

In the case where the twin-shell electric furnace is a refiner, it is preferable to dissolve and refine the solid iron source by generating arc while blowing oxygen and a carbon source for forming the slag in the first furnace and the second furnace.

In the present invention, the molten steel is manufactured by supplying power alternately to the first and second furnaces in the power supply device.

Examples of the solid iron source include scrap iron and scrap.

In the present invention, the power conversion from the first furnace to the second furnace and the second furnace to the first furnace is preferably performed after the time when the solid iron source charged in the electric furnace is dissolved in the whole amount and is present in the liquid phase. Is more than 1550 ℃. The reason is that if the molten steel temperature is less than 1550 ℃ during the power conversion after completion of melting, there is a solid iron source which is not dissolved in the electric furnace, which delays the heating operation of the molten steel and blocks the tap hole during the tapping. This is because the incidence of accidents increases.

In addition, the oxygen blown through the oxygen lance inevitably generates a splash, so it must be adjusted appropriately and can be immersed in the molten steel and blown or blown from the upper portion of the molten steel. The angle is preferably within 25 to 90 degrees.

In the above process, the oxygen blowing speed is closely related to the stirring force of the molten steel, and it is preferable to adjust the oxygen blowing rate as close as possible to the molten steel bath surface as much as possible by adjusting it to 1.0 (Mach 1.0) of the speed of sound and 3.0 (Mach 3.0) of the speed of sound. Do.

As shown in Fig. 4, the oxygen blowing angle is represented by the inclination angle α of the lance + the inclination angle β of the nozzle.

When the oxygen injection angle is less than 25 degrees, slag and molten steel are splashed by the injected oxygen, which makes it difficult to maintain the facility because it is attached to the wall of the furnace. It is preferable to select the oxygen injection angle of 25 to 90 degrees because it may be damaged.

In addition, the oxygen blowing rate is closely related to the stirring force of the furnace steel, and the heat transfer is not smooth at the sound wall at less than 1.0 at the speed of sound, and when it is greater than the speed of sound, the splash is increased and the oxygen supply amount is greater than 3.0. In addition, it is difficult to manage the equipment, and the iron recovery rate is lowered, thereby making the work inefficient. Therefore, the oxygen blowing rate is preferably set at a sound speed of 1.0 to 3.0.

In addition, the blowing flow rate of the oxygen is operated in consideration of the nominal capacity of the electric furnace, it is preferable to supply at 10 ~ 150N ㎥ per ton molten steel.

Meanwhile, the carbon source to be blown should be blown in such a way that it can easily come into contact with the blown oxygen. For this purpose, it is preferable to immerse it in molten steel and blow it or to impinge on the blown oxygen flow to infiltrate the molten steel and slag depending on the oxygen flow. Do.

At this time, the temperature of molten steel must be raised by the heat generated by the reaction between oxygen and carbon source, so the reaction place is important, and the reaction place of oxygen and carbon must proceed in molten steel and slag. Coal, coke, graphite, etc. having good reactivity are appropriate. The carbon concentration in the carbon source is more than 70%, and the smaller the carbon source is, the better the reactivity is, and less than 5 millimeters is preferable.

However, when the carbon concentration of the molten steel already dissolved is sufficiently high that the final component can hit the target component by electricity without blowing the carbon source, the carbon source injection may be omitted.

In addition, when the working time with only the oxygen and carbon source is excessively long, the productivity may decrease, so it is preferable to finish the work in consideration of the working time to the other side.

When the size of the carbon source is larger than 5 millimeters, the reaction time with oxygen becomes longer, and even though it is blown in the slag and molten steel, it floats and reacts to the upper part of the slag, thereby reducing the heat transfer efficiency of the generated heat to the molten steel, thus the size of the carbon source. It is preferable to select less than 5 millimeters.

In order to prevent the iron from being oxidized in the molten steel, it is important to maintain a proper relationship with the oxygen supply flow rate. The supply amount of the carbon source does not increase the oxygen concentration in the slag and does not increase the carbon concentration in the molten steel. The blowing amount of is preferably in the range of 1/2 to 2 times the oxygen blowing flow rate as shown in FIG.

That is, as shown in FIG. 5, the oxygen concentration in the slag is increased when the amount of carbon source blown is 1/2 times or less of the oxygen injection flow rate, but the carbon concentration in the molten steel is increased when it is 2 times or more. In the range of 1/2 to 2 times, the oxygen concentration in the slag and the carbon concentration in the molten steel are kept substantially constant.

However, when the carbon concentration in the molten steel is higher than the target carbon concentration or the oxygen concentration in the slag is lower than the target concentration at the time of power conversion, the blowing rate of the carbon source can be adjusted.

As described above, in order to preheat the solid iron source, a carbon source must be added to the top of the hot hill, and oxygen must be blown into the hot hill to complex.

In this case, the amount of carbon injected is preferably 0.5 to 2 kg / hr per 1 Nm 3 / hr of oxygen by calculating the amount of oxygen injectable, and when the carbon supply is too small, Fe in the hot hill is oxidized to increase iron loss.

As described above, if the power supply device performs the first furnace process and the second furnace process while supplying power alternately to the first and second furnaces, the power supply can always be kept in operation and power is supplied. In the non-furnace furnace, the preheating of the solid iron source and the molten steel as the heat of reaction of carbon and oxygen not only reduces the power consumption but also reduces the power input time.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

In a 130-ton DC-type twin-shell electric furnace, tap the first furnace with 30 tons of hot heels left, then add 2 tons of coke, load 85 tons of scrap metal, and blow oxygen at 80N㎥ / min for 20 minutes to preheat the scrap. Then, as soon as melting and refining work in the second furnace is finished, immediately connect the power supply to the first furnace and supply 15MWH of electricity to generate arc to dissolve the scrap iron, and then charge 60 tons of scrap iron to inject oxygen and carbon sources. An additional 31 MWH of electric power was added to generate arc to dissolve scrap metal, and then the electric power was converted to the second.

After switching power to the second furnace, in the first furnace, while blowing oxygen at a rate of 100 Nm 3 per minute, coal was blown at 100 kg per minute into slag to raise the molten steel.

At this time, oxygen is blown from the slag and molten steel at an angle of 46 degrees to the molten steel surface through an oxygen lance, and the carbon lance is blown at the same time by installing a carbon lance under the oxygen lance while the sound velocity is 1.0 to 2.0. The level of 1-3 mm was maintained.

In addition, in the second furnace, as in the first furnace, 2 tons of coke is charged, and then 85 tons of scrap iron is charged, and oxygen is blown at 80 Nm3 / min to preheat the scrap metal, and oxygen is immediately converted from the first furnace. Arc was generated while blowing the carbon source to dissolve scrap metal.

In the first furnace, 2 tons of coke and scrap iron were added, oxygen was blown, and then the temperature of the scrap iron in the electric furnace was measured, and the results are shown in FIG.

In addition, as a result of measuring the molten steel temperature of the first furnace before power conversion, the molten steel temperature was measured according to oxygen injection, and the results are shown in FIG. 7.

In addition, after switching the electric power in the first furnace, samples of molten steel and slag are taken while blowing oxygen and powdered coal, and changes in carbon concentration in molten steel and T.Fe concentration in slag are investigated. Indicated.

As shown in FIG. 6, it can be seen that the scrap temperature is increased as the oxygen injection amount is increased, and as shown in FIG. 7, the molten steel temperature is increased as the oxygen injection amount is increased.

That is, it can be seen that the present invention obtains the effect of preheating the solid iron source and the temperature raising effect of the molten steel.

In addition, as shown in Figure 8, even if the oxygen uptake changes, it can be seen that the carbon concentration in the molten steel and the concentration of T.Fe in the slag is almost unchanged, which is according to the present invention preheating and molten steel Even if the temperature is increased, the composition of the molten steel and the slag hardly changes.

On the other hand, in this embodiment, the time required per charge was 45 minutes, which is 15 minutes shorter than the previous 60 minutes, resulting in an hourly productivity increase of 30% or more, while oxygen consumption increased slightly, while power consumption was about 28%. Energy costs were reduced.

As described above, the present invention not only increases productivity without changing the conventional twin-shell electric furnace equipment, but also uses an oxygen and carbon source to preheat the solid iron source and to raise the molten steel, thereby increasing the amount of expensive power consumption. There is an effect that can be saved.

Claims (11)

A twin shell comprising an oxygen lance for injecting oxygen, a carbon lance for supplying a carbon source, two furnaces having an electrode for generating arc, and a power supply for supplying power to the electrode. In the method of manufacturing molten steel using an electric furnace, In the first furnace, a carbon source is put on a hot heel loaded in the furnace, and a solid iron source is put thereon, and oxygen is blown through an oxygen lance to preheat the solid iron source. Discharging and refining the solid iron source by generating arc by supplying electric power to the electrode provided in the second furnace in the second furnace; After dissolving and refining in the second furnace is finished, stopping power supply to the electrode provided in the second furnace in the power supply device and supplying power to the electrode provided in the first furnace; Arc is generated in the first furnace by electric power supplied from the power supply to the electrode provided in the first furnace to dissolve and refine the solid iron source, and at the same time, the power is converted to the first furnace in the second furnace, and then oxygen lance and Oxygen and carbon source are blown through carbon lance, refined and warmed up to start tapping, and the tapping is finished with the hot heel left, and after preparation for operation, a carbon source is put on the hot heel, and a solid iron source is put on it. Blowing to preheat the scrap iron source; After dissolving and refining in the first furnace is finished, cutting off power supply to the electrode provided in the first furnace and supplying power to the electrode provided in the second furnace; And Arc is generated in the second furnace by the electric power supplied from the power supply to the electrode provided in the second furnace to dissolve and refine the solid iron source, and at the same time, the power is converted to the second furnace and oxygen lance and Oxygen and carbon source are blown through carbon lance, refined and warmed up to start tapping, and the tapping is finished with the hot heel remaining. After preparation, the carbon source is put on the hot heel and the solid iron source is put on it. Preheating the solid iron source by blowing In the first and second furnaces, the oxygen blowing rate at the time of heating up the molten steel is 1.0 to 3.0 times the speed of sound, the blowing rate of oxygen is 10 to 150 Nm3 / min per ton of molten steel, and the blowing amount of carbon source is oxygen blowing. Method for producing molten steel using a twin shell electric furnace, characterized in that 0.5 to 2 times the flow rate The method of claim 1, wherein the oxygen is heated in the first furnace and the second furnace when the temperature of the molten steel is immersed in the molten steel and blown or blown from the upper portion of the molten steel. 3. The molten steel using a twin-shell electric furnace according to claim 2, wherein the oxygen blowing angle is 25 to 90 degrees with respect to the molten steel when oxygen is blown from the upper part of the molten steel when the molten steel is heated in the first and second furnaces. Manufacturing Method The power conversion from the first furnace to the second furnace and from the second furnace to the first furnace is after the point where the solid iron source charged in the furnace is completely dissolved and present in the liquid phase. Method for producing molten steel using a twin-shell electric furnace, characterized in that The method for producing molten steel using a twin-shell electric furnace according to any one of claims 1 to 3, wherein the carbon concentration in the carbon source is 70% or more, and the size of the carbon source is less than 5 millimeters. The method for producing molten steel using a twin-shell electric furnace according to claim 4, wherein the carbon concentration in the carbon source is 70% or more, and the size of the carbon source is less than 5 millimeters. The method of manufacturing molten steel using a twin-shell electric furnace according to claim 5, wherein the carbon source is any one selected from the group consisting of coal, coke and graphite. The method of manufacturing molten steel using a twin-shell electric furnace according to claim 6, wherein the carbon source is any one selected from the group consisting of coal, coke, and graphite. The method according to any one of claims 1, 2, 3, 6, 7, and 8, wherein when the furnace is a refiner, oxygen and a carbon source are blown into the furnace for forming slag. Method for producing molten steel using a twin-shell electric furnace, characterized in that while generating arc The method of claim 4, wherein when the furnace is a refiner, arc is generated while blowing oxygen and a carbon source into the furnace for forming the slag. The method of claim 5, wherein when the furnace is a refiner, arc is generated while blowing oxygen and a carbon source into the furnace for forming the slag.