JP2000111270A - Method for melting cold iron source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To melt a cold iron source with high efficiency which cannot be achieved by a conventional preheating method using exhaust gas. SOLUTION: In a method for melting a cold iron source in an arc furnace 1, a melting chamber 2 and a shaft type preheat chamber 3 directly connected to the melting chamber to preheat and melt a cold iron source 13 in the preheat chamber by generated exhaust gas. While the cold iron source is supplied to the preheat chamber so that the cold iron source is kept present continuously in the preheat chamber and the melting chamber, a projection surface area in which the cold iron source comes into contact with molten steel in the melting chamber and cold iron melting speed are controlled so as to satisfy an expression S<=2W/(T-TL) and the cold iron source in the melting chamber is melted by an arc. When the molten steel for at least one heat is stored in the melting chamber, the molten steel is supplied while the cold iron source continuously exists in the preheat chamber and the melting chamber. At that time, the difference between the molten steel supply temperature and the liquid phase line temperature of the molten steel is preferably 40 deg.C. In this case, in the expression, S is a projection surface area (m2) in which the cold iron source comes into contact with the molten steel, W is cold iron source melting speed (ton/Hr), T is molten steel supply temperature ( deg.C) and TL is the liquid phase line temperature ( deg.C) of molten steel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melting method for efficiently dissolving a cold iron source such as iron scrap and direct reduced iron.

[0002]

2. Description of the Related Art In recent years, with the increase in the amount of generated iron scrap, an arc furnace for steelmaking has been newly installed worldwide. This arc furnace heats and melts a cold iron source such as iron scrap or direct reduced iron by the arc heat generated from the arc generating electrode and refines it to produce molten steel. A number of methods have been proposed for preheating a cold iron source by using high-temperature exhaust gas generated from an arc furnace melting chamber and melting the preheated cold iron source to reduce power consumption.

For example, Japanese Patent Application Laid-Open No. 7-180975 (hereinafter referred to as “prior art 1”) discloses a shaft-type preheating chamber equipped with a grate that can be opened or closed in one or more stages.
The steel scrap held by the grate is preheated by the exhaust gas from the melting chamber, and the preheated iron scrap is dropped into the iron scrap introduction path, and is connected to the upper part of the arc furnace melting chamber via an iron scrap introduction path. A facility is disclosed in which scrap is charged into an arc furnace melting chamber by a pusher provided in an iron scrap introduction path.

[0004] Japanese Patent Application Laid-Open No. 7-332874 (hereinafter referred to as
The “prior art 2”) includes a rotary drum type first drum connected to an upper lid of an arc furnace melting chamber.
And a shaft-type second preheating chamber connected to the first preheating chamber at the bottom with the first preheating chamber, and after preheating the cold iron source with exhaust gas generated from the melting chamber in the second preheating chamber, A facility is disclosed in which a cold iron source is pushed into a first preheating chamber by a pusher, and a preheated cold iron source is charged into the melting chamber via the rotating first preheating chamber.

In addition, Japanese Patent Publication No. 6-46145 (hereinafter referred to as "Japanese Patent Publication")
In the prior art 3), a shaft-type preheating chamber directly connected to the melting chamber was provided, and a cold iron source for one heat was charged into the melting chamber and the shaft-type preheating chamber for each melting, and the exhaust gas was applied to the shaft. While preheating the cold iron source in the mold preheating chamber, the amount of the cold iron source that has been melted is freely dropped into the melting chamber, and thus all the cold iron sources charged in the melting chamber and the shaft type preheating chamber are removed. Dissolution equipment is disclosed.

[0006]

According to the above method and apparatus, if the preheating effect is high, 250 to 270
Although it is stated that a power consumption of kWh / t is achieved, the above-mentioned prior arts 1 to 3 have the following problems.

In Prior Art 1 and Prior Art 2, a device for holding and transporting a cold iron source such as a grate, a pusher, or a rotary drum is used to load a preheated cold iron source into an arc furnace melting chamber. Therefore, when preheating with the exhaust gas from the melting chamber, the preheating temperature is limited.
In other words, if a large amount of carbonaceous material such as coke and oxygen gas are blown into the melting chamber and the cold iron source is preheated with a large amount of high-temperature exhaust gas, the preheating temperature increases and the preheating effect improves,・ Equipment troubles such as thermal deformation and fusion of the transfer device occur, so that the exhaust gas temperature cannot be raised.

On the other hand, in the prior art 3, since the shaft-type preheating chamber is directly connected to the melting chamber, the above-described device for holding and transporting the cold iron source is not required, and therefore, the above-mentioned problem is also encountered. Does not occur. However, in prior art 3, 1
Each time the amount of molten steel for the heat is melted, all of the cold iron source in the preheating chamber is melted, and the molten steel is discharged without leaving the cold iron source in the preheating chamber. Since the source cannot be preheated, it cannot be said that it is sufficient in terms of effective use of exhaust gas.

The present invention has been made in view of the above circumstances,
The purpose is not to require a device for transferring the cold iron source from the preheating chamber to the melting chamber, and it is also possible to preheat the cold iron source charged at the beginning of the next heat, and An object of the present invention is to provide a method for dissolving a cold iron source with high efficiency that cannot be achieved by a preheating method using exhaust gas.

[0010]

A method for melting a cold iron source according to the present invention comprises a melting chamber provided with an electrode for arc generation, and a shaft-type preheating chamber directly connected to the melting chamber. In the method of melting a cold iron source in an arc furnace, which introduces exhaust gas into the preheating chamber and melts it while preheating the cold iron source, the cold iron source is kept in a continuous state in the preheating chamber and the melting chamber. While supplying the cold iron source to the preheating chamber continuously or intermittently.
While controlling the projected field area where the cold iron source contacts the molten steel in the melting chamber and the melting rate of the cold iron source so as to satisfy the equation (1) determined from the tapping temperature and the liquidus temperature of the molten steel, The cold iron source in the melting chamber is melted by an arc, and when at least one heat of molten steel has accumulated in the melting chamber, the molten steel is discharged while the cold iron source is continuously present in the preheating chamber and the melting chamber. It is characterized by doing. At this time, it is preferable to set the difference between the tapping temperature and the liquidus temperature of the molten steel to 40 ° C. S ≦ 2W / (T−T _L ) (1) where each symbol in the formula (1) represents the following. S: projected field area (m ² ) where cold iron source and molten steel come into contact W; cold iron source dissolution rate (ton / Hr) T: tapping temperature (° C) _TL : liquidus temperature of molten steel (° C)

In the present invention, the cold iron source preheated in the shaft-type preheating chamber directly connected to the upper part of the melting chamber falls naturally into the melting chamber according to the melting speed of the cold iron source in the melting chamber. Therefore, a device for transporting a cold iron source from the preheating chamber to the melting chamber is not required, and the preheating temperature can be increased. Then, the cold iron source in the melting chamber is melted while the supply of the cold iron source to the preheating chamber is continued so that the cold iron source is continuously present in the preheating chamber and the melting chamber. Since the molten steel is tapped in a state where the source is continuously present in the preheating chamber and the melting chamber, all the cold iron sources used for the next heating are preheated and can be melted with extremely high preheating efficiency.

On the other hand, when the cold iron source is buried in the molten steel produced in the melting chamber and melts in a coexisting state, the applied thermal energy is used for latent heat for melting the cold iron source, and the molten steel temperature rises. Hard to do. In the state where the supply and melting of the cold iron source are continuously performed as in the present invention, the transfer of heat in the region where the cold iron source is buried in the molten steel is expressed by the equation (2) macroscopically. Can be represented by However, in equation (2), Q is the latent heat of dissolution of the cold iron source (kcal / to
n), W is the dissolution rate of the cold iron source (ton / Hr), and h is the heat transfer coefficient (kcal / m ² ) at the interface between the cold iron source and the molten steel.
Hr · deg), ΔT is the superheat degree (° C.) of the molten steel, that is, the difference between the molten steel temperature and the liquidus temperature (T _L ) of the molten steel, and S ₀ is the contact interface area (m ² ) between the cold iron source and the molten steel. ). Q × W = h × ΔT × S ₀ (2)

In the case of continuous melting as in the present invention, a cold iron source
The dissolution rate (W) is constant, and the dissolution rate (W) of the cold iron source is
Under certain conditions, as expressed by equation (2),
The degree of superheat (ΔT) of molten steel is determined by the contact area (S₀Is inversely proportional to
You. That is, the contact area (S₀) Can be reduced by
It can be seen that the degree of heat (ΔT) increases. But the contact field
Area (S₀) Cannot be measured directly.
A bright person etc. has a contact area (S ₀) As a new indicator
The projected area of contact between the cold iron source and the molten steel in the melting chamber.
Test operation with various changes in the projected field area (described later)
(Described in detail in Examples). And the projection world
The area is S (m^Two), The projected field area (S) and the cold iron source
Relationship between melting speed (W) and superheat (ΔT) of molten steel during tapping
Is expressed by equation (3). In addition, tapping
The superheat degree (ΔT) of molten steel at the time is the tapping temperature (T) and the
Liquidus temperature (T_L). S = 2W / ΔT (3)

In the present invention, the degree of superheat of molten steel during tapping (ΔT)
And the melting rate of the cold iron source (W), the molten iron is melted in a range not exceeding the projected field area (S) determined by the equation (3), that is, in a range satisfying the equation (1). The heat energy decreases and the temperature of the molten steel rises, so that a predetermined degree of molten steel superheat (ΔT) can be secured during tapping. As a result, it is possible to prevent troubles caused by a drop in molten steel temperature such as blockage of a tapping port during tapping. In particular, by ensuring the molten steel superheat degree (ΔT) at the time of tapping at 40 ° C., it is possible to avoid operation troubles due to a decrease in temperature and to achieve stable operation.

The projected area (S) of the present invention where the cold iron source and the molten steel in the melting chamber are in contact with each other is defined as the interface area between the outermost peripheral portion of the cold iron source buried in the molten steel and the molten steel. Which is specifically expressed as the product of the inner peripheral length of the preheating chamber and the molten steel depth,
The molten steel for one heat according to the present invention is the amount of molten steel stored in one of the molten steel holding containers such as a ladle used for a casting operation such as continuous casting, which is a crane or the like of a building that performs the casting operation. The amount is determined by the lifting load.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings.
FIG. 1 is a schematic longitudinal sectional view of an arc furnace equipment embodying the present invention, and FIG. 2 is a schematic sectional view taken along line XX in FIG.

In the figure, a shaft-type preheating chamber 3 and a water-cooled furnace wall 4 are arranged above a melting chamber 2 having a furnace bottom electrode 6 at the bottom, which is constructed of a refractory inside. The upper opening of the furnace wall 4 that is not covered with the preheating chamber 3 is covered with a furnace lid 5 having a water cooling structure that can be freely opened and closed. An upper electrode 7 made of graphite is provided which penetrates through the furnace lid 5 and can be moved up and down into the melting chamber 2, thereby constituting the DC arc furnace 1. On the protruding part of the melting chamber 2 opposite to the part where the preheating chamber 3 is installed, the outlet of the furnace 10 is pressed against the outlet side by a door 19 and filled with sand or mud. And, on the side wall thereof, there is provided a slag port 11 in which the exit side is pressed by the door 20 and the inside is filled with sand or a mud agent.
The furnace bottom electrode 6 and the upper electrode 7, which are electrodes for arc generation, are connected to a DC power supply (not shown), and the furnace bottom electrode 6 and the upper electrode 7 are connected.
And an arc 16 is generated.

Above the preheating chamber 3, a bottom-open type cold iron source supply bucket 12 suspended from a traveling carriage 21 is provided as a cold iron source supply means. A cold iron source 13 such as iron scrap or direct reduced iron is supplied into the preheating chamber 3 through an openable / closable cold iron source supply port 17 provided at the upper part of the preheating chamber 3. And preheating chamber 3
Is connected to a dust collector (not shown), and the high-temperature exhaust gas generated in the melting chamber 2 is sucked through the preheating chamber 3 and the duct 18 in order, and the cooling air in the preheating chamber 3 is cooled. The iron source 13 is preheated. The preheated cold iron source 13
In accordance with the amount dissolved in the dissolution chamber 2, it falls freely into the dissolution chamber 2 and is charged into the dissolution chamber 2.

An oxygen blowing lance 8 and a carbon material blowing lance 9 are provided to penetrate the furnace cover 5 and move up and down in the melting chamber 2, and oxygen gas is blown into the melting chamber 2 from the oxygen blowing lance 8. Lance 9
From air and nitrogen gas as carrier gas for coke,
Charcoal such as char, coal, charcoal, graphite and the like is blown into the melting chamber 2. The injected carbon material reacts with the injected oxygen gas to generate heat of combustion and acts as an auxiliary heat source.

The method for melting the cold iron source according to the present invention in the DC arc furnace 1 will be described below. First, the melting rate (W) of the cold iron source in the DC arc furnace 1 is grasped.
The dissolution rate (W) of the cold iron source can be determined by the amount of electric power applied to the electrode for arc generation and the amount of oxygen gas blown from the oxygen blowing lance 8. However, the amount of oxygen gas to be blown may vary depending on the operating conditions. Therefore, it is preferable that the amount of oxygen gas be grasped only from the applied electric energy in consideration of the stability of the operation. When other heating means, such as a gas burner, are installed, the cold iron source dissolution rate (W) is grasped including those.

Next, the superheat degree (ΔT) of molten steel at the time of tapping,
Dispensing steel temperature (T) and liquidus temperature (T _L) And determine the difference
Overheating of molten steel determined from the cold iron source dissolution rate (W)
The degree (ΔT) is substituted into the right side of equation (1), and the right side of equation (1) is
calculate. Then, the projected field area (S) is
So that the cross-sectional area and shape of the preheating chamber 3
Defines the shape of the melting chamber 2. For example, cold iron source melting speed
Degree (W) is 150 ton / Hr, molten steel superheat degree (ΔT)
Is 40 ° C., the projected field area (S) is 7.5 m
^TwoWhat should be done is as follows.

The projected field area (S) can be calculated by the product of the molten steel depth (H) shown in FIG. 1 and the inner peripheral length (L) of the preheating chamber 3 shown in FIG. In calculating the projected field area (S), the molten steel depth (H) used the maximum molten steel depth, and the inner peripheral length of the preheating chamber 3 was obtained by projecting the preheating chamber 3 onto the melting chamber 2. Time,
The inner peripheral length of the lower part of the preheating chamber 3 projected on the bottom of the melting chamber 2 is used. Therefore, the projected field area (S) decreases as the cross-sectional area of the preheating chamber 3 decreases, and the bottom of the melting chamber 2 on the preheating chamber 3 side is raised to narrow the range in which the cold iron source 13 is buried. By making it shallow or shallow, the projection field area (S) can be made small. If the projection field (S) cannot be adjusted, increase the applied power or the amount of oxygen gas to be blown until the value satisfies the expression (1), and further provide another heating means, Increase source dissolution rate (W).

When calculating the projected field area (S) according to the equation (1), it is preferable that the superheat (ΔT) of molten steel is 40 ° C. Also, the smaller the projected field area (S), the higher the degree of superheat of molten steel (ΔT), but the degree of superheat of molten steel (ΔT)
If the temperature is too high, the furnace body refractory will be severely damaged. Therefore, the minimum value of the projected field area (S) should be in the range where the molten steel superheat (ΔT) is 150 ° C., that is, in the range of equation (4). preferable. S ≧ 2W / 150 ... (4)

After such adjustment, the operation is performed. In the operation, first, the melting chamber 2 is set in a horizontal state, and the cold iron source 13 is supplied from the cold iron source supply bucket 12 into the preheating chamber 3. The cold iron source 13 supplied into the preheating chamber 3 is also charged into the melting chamber 2 and eventually fills the inside of the preheating chamber 3. In order to uniformly load the cold iron source 13 into the melting chamber 2, the furnace lid 5 may be opened and the cold iron source 13 may be charged into the melting chamber 2 on the opposite side of the preheating chamber 3. Next, the upper electrode 7 is moved up and down while supplying a direct current between the furnace bottom electrode 6 and the upper electrode 7, and
Arc 1 between the furnace bottom electrode 6 and the inserted cold iron source 13
Generate 6. Then, the cold iron source 13 is melted by the generated arc heat, and the molten steel 14 is generated. Along with the formation of the molten steel 14, a flux such as quicklime or fluorite is charged into the melting chamber 2 to form a molten slag 15 on the molten steel 14, thereby preventing oxidation of the molten steel 14 and keeping the molten steel 14 warm.
If the amount of the molten slag 15 is too large, it can be discharged from the slag port 11 during operation.

From the time when the molten steel 14 is formed, oxygen gas and carbon material are blown into the molten steel 14 or into the molten slag 15 from the oxygen blowing lance 8 and the carbon material blowing lance 9. Carbon material or molten slag 1 blown and dissolved in molten steel 14
The carbonaceous material suspended in 5 reacts with the blown oxygen gas to generate heat of combustion, acts as an auxiliary heat source, saves electric power consumption, and the CO gas of the reaction product dissolves molten slag 15. Since the forming is performed and the arc 16 is wrapped in the molten slag 15, the heating efficiency of the arc 16 increases. In addition, the cold iron source 13 in the preheating chamber 3 is efficiently preheated by a large amount of high-temperature CO gas. As a result, the dissolution rate (W) of the cold iron source increases, and the degree of superheat (ΔT) of the molten steel increases. The amount of carbon material to be blown is determined according to the amount of oxygen gas to be blown. That is, a carbon material is added in an amount equivalent to the chemical equivalent of the oxygen gas to be blown. If the carbon material is less than the oxygen gas to be blown, the molten steel 14 is excessively oxidized, which is not preferable.

When the molten steel 14 is generated, the cold iron source 13 in the preheating chamber 3 falls freely into the melting chamber 2 in accordance with the amount melted in the melting chamber 2 and decreases. For this purpose, the cold iron source 13 is supplied from the cold iron source supply bucket 12 to the preheating chamber 3. The supply of the cold iron source 13 into the preheating chamber 3 is performed continuously or intermittently so as to keep the state where the cold iron source 13 is continuously present in the preheating chamber 3 and the melting chamber 2. At this time, it is preferable that the amount of the cold iron source 13 continuously present in the preheating chamber 3 and the melting chamber 2 be 50 wt% or more of the cold iron source 13 for one heat. The cold iron source 13 existing continuously in the preheating chamber 3 and the melting chamber 2 is always replaced with the cold iron source 13 for one heat.
By ensuring 50% by weight or more of the above, the preheating effect can be enhanced. Thus, the cold iron source 13 supplied from the preheating chamber 3 is heated and melted while being buried in the molten steel 14.

In this way, the cold iron source 13 is melted, the molten steel 14 for at least one heat is stored in the melting chamber 2 and, if necessary, refining such as decarburization is performed. 1), the melting chamber 2 is tilted to discharge the molten steel 14 from the tapping port 10 to a molten steel holding vessel (not shown). After tapping, the molten steel 14 is refined in a ladle refining furnace or the like, if necessary, and then cast by a continuous casting machine or the like. After the molten steel 14 is tapped and the molten slag 15 is drained, the melting furnace 2 is returned to a horizontal position by a tilting device, and the inside of the tapping port 10 and the tapping port 11 are filled with sand or mud material to be melted. Resume. The next heat can start melting with the preheated cold iron source 13.
At the time of tapping, several to several tens of tons of molten steel 14 is supplied to the melting chamber 2.
May be left in the chamber to resume the melting of the next heat.
By doing so, the initial dissolution is promoted, and the dissolution efficiency is further improved.

By melting in this manner, the cold iron source 13 used at the beginning of the operation is not preheated, but all the cold iron sources 13 charged after that are preheated, so that the preheating efficiency is extremely high. Operation of the arc furnace can be performed, the power consumption can be greatly reduced, and a large degree of superheat (ΔT) of molten steel can be secured. Can be prevented beforehand, and stable operation can be performed.

In the above description, the case of the DC arc furnace 1 has been described. However, the present invention can be applied without any trouble to the AC arc furnace. Further, the preheating chamber 3 and the tapping port 10 in the melting chamber 2 can be used. Is 18 relative to the center of the melting chamber 2.
The position is not limited to the position facing 0 °, but may be 90 °. Further, the sectional shape of the melting chamber 2 and the furnace bottom electrode 6
Needless to say, the structure described above and the number of upper electrodes 7 are not limited to the above.

[0030]

EXAMPLE Using a DC arc furnace as shown in FIG. 1, a total of 8 tests (test No. 1 to No. 8) were carried out in a test operation in which the cross-sectional size of the preheating chamber and the melting rate (W) of the cold iron source were changed. The cold iron source melting rate (W), projected field area (S) and molten steel superheat (Δ
T) was investigated.

In the arc furnace used, the melting chamber had a constant height of 4 m and a furnace diameter of 7.2 m, the preheating chamber had a constant height of 7 m, and the inner diameter was 2.5 m in Test Nos. 1 and 5. , Test No.
The levels were changed to 3.0 m for Test Nos. 2 and 6, 3.5 m for Tests No. 3 and No. 7, and 4.0 m for Tests No. 4 and No. 8. Maximum power capacity is 600V voltage and 100k current
A, in order to adjust the dissolution rate (W) of the cold iron source, in tests No. 1 to No. 4, the voltage was 400 V, the current was 100 kA,
In test Nos. 5 to 8, the voltage was 350 V and the current was 80 kA.
Was applied.

The furnace capacity is 180 tons, and the molten steel depth (H) at that time is 0.88 m. The inner circumference length (L) of the preheating chamber is obtained by multiplying the inner circumference of the preheating chamber by 0.8, and the projected field area (S) is 5.5 when the diameter of the preheating chamber is 2.5 m.
m ^2, 6.6 m ² when preheating chamber inner diameter of 3.0 m, if the preheating chamber inner diameter of 3.5 m 7.7 m ^2, the preheating chamber inner diameter becomes 8.8 m ² in the case of 4.0 m.

First, iron scrap 1 was placed in the melting chamber and the preheating chamber.
Fifty tons were charged, and the above-mentioned electric power was applied to start melting using a graphite upper electrode having a diameter of 28 inches. Along with the production of molten steel, quicklime and fluorite are added to form a molten slag, and then oxygen gas is supplied from an oxygen blowing lance to 950.
While blowing at 0 Nm ³ / Hr, coke was blown into the molten slag at 80 kg / min from a carbon material blowing lance. By blowing oxygen gas and coke, the molten slag formed and the tip of the upper electrode was buried in the molten slag. Then, iron scrap was supplied into the preheating chamber during melting, and the height of the iron scrap in the preheating chamber was maintained at a predetermined value or more.

As described above, melting is continued in a state in which iron scrap is continuously present in the melting chamber and the preheating chamber. When 180 tons of molten steel is accumulated in the melting chamber, the temperature of the molten steel is measured, Then, the injection of oxygen gas and the injection of carbon material were stopped, and 120 tons of molten steel for one heat was discharged to the ladle. After tapping, electricity supply, oxygen gas injection, and carbon material injection were restarted to resume operations. The dissolution rate (W) of the cold iron source when the operation is stabilized by repeating the energization to tapping is about 150 ton / H in Test Nos. 1 to 4.
r, it was about 100 ton / Hr in Test Nos. 5 to 8.

Table 1 shows the preheating chamber diameter, the projected area (S), the average value of the melting rate of the cold iron source (W) when the operation was stable, and the molten steel at the time of tapping when the operation was stable in Table 1. The average value of the degree of superheat (ΔT) is shown. As shown in Table 1, when the cold iron source melting rate (W) was constant, it was found that the smaller the projected field area (S), the greater the degree of superheat (ΔT) of the molten steel.

[0036]

[Table 1]

FIG. 3 shows the relationship between the projected area (S) shown in Table 1 and the degree of superheat (ΔT) of molten steel during tapping.
In the figure, the symbol ● indicates that the dissolution rate (W) of the cold iron source is about 150 ton / H.
In Test No. 1 to No. 4 of r, the symbol ○ indicates the dissolution rate of cold iron source (W)
Are test Nos. 5 to 8 of about 100 tom / Hr.
In the drawing, the solid line curve indicates that the dissolution rate (W) of the cold iron source is 150.
The value calculated by equation (3) when ton / Hr is shown,
The broken line curve indicates the dissolution rate (W) of the cold iron source at 100 ton / H.
The value calculated by (3) when r is shown,
It has been found that the projected field area (S) and the degree of superheat of molten steel (ΔT) are represented by the relationship of equation (3). Therefore, it was found that by controlling the projected field area (S) according to the cold iron source melting rate (W), a large molten steel superheat (ΔT) can be obtained.

[0038]

According to the present invention, since there is no need for a device for transferring a cold iron source from the preheating chamber to the melting chamber, it is possible to raise the temperature of the exhaust gas to increase the preheating temperature of the cold iron source, and to melt the iron. Since it is possible to preheat most of the cold iron source, it is possible to melt the cold iron source while maintaining extremely high preheating efficiency, and it is possible to greatly reduce the power consumption. And, since the area of contact between the molten steel and the cold iron source is heated to a predetermined value, a large degree of superheat of the molten steel can be obtained. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of an arc furnace equipment embodying the present invention.

FIG. 2 is a schematic view of a section taken along line XX in FIG.

FIG. 3 shows a projected field area (S) and a superheat degree (Δ) of molten steel during tapping.
FIG. 9 is a diagram showing a relationship with T).

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 DC arc furnace 2 Melting chamber 3 Preheating chamber 4 Furnace wall 5 Furnace lid 6 Furnace bottom electrode 7 Upper electrode 8 Oxygen blowing lance 9 Carbon material blowing lance 10 Steel tap 11 Slag tap 12 Cold iron source supply bucket 13 Cold Iron source 14 Molten steel 15 Molten slag 16 Arc

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4K001 AA10 BA22 DA05 FA10 GA16 GB10 GB11 4K014 CA00 CB01 CB02 CC01 CC04 4K056 AA02 BA01 BA02 BB08 CA02 DA02 DA33 FA04 FA12 4K063 AA04 AA12 BA02 CA01 CA06 FA53 FA73 FA78 GA07 GA09 GA33

Claims (2)

[Claims] A melting chamber provided with an arc generating electrode and a shaft-type preheating chamber directly connected to the melting chamber, wherein exhaust gas generated in the melting chamber is introduced into the preheating chamber to preheat a cold iron source. In the method of melting a cold iron source in an arc furnace that melts while supplying, the cold iron source is supplied to the preheating chamber continuously or intermittently so as to maintain the state where the cold iron source is continuously present in the preheating chamber and the melting chamber. Meanwhile, the projected field area where the cold iron source and the molten steel in the melting chamber are in contact with each other and the melting rate of the cold iron source are controlled so as to satisfy the equation (1) determined from the tapping temperature and the liquidus temperature of the molten steel. When the cold iron source in the melting chamber is melted by the arc while the molten steel for at least one heat has accumulated in the melting chamber, the molten iron source is continuously present in the preheating chamber and the melting chamber. A method for melting a cold iron source. S ≦ 2W / (T−T _L ) (1) where each symbol in the formula (1) represents the following. S: projected field area (m ² ) where cold iron source and molten steel come into contact W; cold iron source dissolution rate (ton / Hr) T: tapping temperature (° C) _TL : liquidus temperature of molten steel (° C) 2. The difference between the tapping temperature and the liquidus temperature of molten steel is 4
The method for dissolving a cold iron source according to claim 1, wherein the temperature is set to 0 ° C.