JPH11140526A - Converter blowing method restraining deposition of metal on furnace opening hole part and side wall in furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for melting the deposited metal which secures the productivity of a converter while restraining the erosion of refractory in the converter and the deposition of metal at the furnace opening hole part and the side wall in the furnace. SOLUTION: Raw material consisting essentially of molten iron as iron source is charged into the converter type refining furnace 1, and a lance arranging oxygen nozzles 7 for melting the deposited metal on the outer periphery is inserted from the furnace opening hole part 14 of the refining furnace and the reaching height of blowing locuses of the oxygen for melting the deposited metal to the furnace opening hole part and the side wall in the furnace, is controlled so as to become lower than the heights of the deposited metals 8 and 16. Jetting direction of the oxygen jetting from the oxygen nozzles 7 for melting the stuck metal, is made to the downward direction of 40-90 deg. in the angle θ formed with the axial line in the longitudinal direction of the lance or the horizontal direction. Further, the molten iron having P concn. by pre- dephosphorizing to the P concn. demanded in a product or lower, is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refining method in a converter type refining furnace, which suppresses the adhesion of metal at the furnace port and the inner wall of the furnace.

[0002]

2. Description of the Related Art In converter blowing, part of molten steel and slag scattered by spitting and slopping generated during the blowing adhere to a furnace port and a furnace inner wall as metal. The deposited metal grows as the heat continues, and if its size exceeds a certain limit, it not only hinders the charging of hot metal and scrap, but also greatly impedes the operation due to falling during blowing. Therefore, ingots adhering to the furnace opening and the inner wall of the furnace (hereinafter, both referred to as “inner wall ingots”) need to be removed before the metal becomes larger than the size that hinders the operation.

[0003] As a traditional method for removing the furnace slab metal, there is a method of hitting the scrap slab to the furnace slab metal and physically removing the scrap (Prior Art 1). However, since this method is carried out when the converter is not blown, it increases the non-steel making time and significantly impairs converter productivity. In addition, since the scraps are directly hit against the metal slab, the impact may cause the bricks of the furnace to fall off.

On the other hand, in addition to the physical removal method, various methods have been proposed in which exhaust gas generated during blowing is subjected to secondary combustion to dissolve and remove the furnace mouth metal. For example, there is a method (prior art 2) disclosed in JP-A-4-084346. This is an oxygen bottom blown converter.
This is a method in which slagless blowing is performed at a rate of about 1 charge, oxygen gas is introduced into the furnace from the upper blowing lance, and the metal in the vicinity of the furnace port is melted. In addition, the amount of slag generated in the furnace is 20 kg / t.
-Steel and below are said to be effective in removing ingots.

Further, for example, JP-A-6-248323 discloses that
During blowing, a secondary combustion oxygen supply nozzle mounted downward at an angle within the range of θ = 25 to 40 ° with respect to a blowing lance axis provided on a side wall of the main blowing lance, and a molten metal surface is formed. Discloses a method (prior art 3) of spraying oxygen for secondary combustion to burn the converter exhaust gas in the furnace to remove the metal that has adhered to the furnace opening.

[0006] Japanese Patent Application Laid-Open No. 61-139616 discloses that, during converter refining, a blowing lance provided with a blowing nozzle and a furnace port smelting nozzle is used to melt a furnace port smelting nozzle. Disclosed is a method (prior art 4) of melting and removing a furnace port metal by injecting air toward a converter furnace port.

[0007] Japanese Patent Application Laid-Open No. 9-3519 discloses that during converter refining, a blowing lance having a blowing oxygen nozzle, a secondary combustion nozzle and a lance metal melting nozzle is used. From the nozzle for the next combustion, oxygen is injected horizontally or downward to melt and remove the furnace mouth metal, and by injecting a small amount of oxygen from the nozzle for melting the lance metal, the metal that has adhered to the lance itself is removed. A method for dissolving and removing (Prior Art 5) is disclosed.

[0008]

However, in the prior art 1, there is a danger that the converter productivity is reduced and the furnace bricks are damaged. The prior arts 2 to 4 have a problem that the secondary combustion of the CO gas in the furnace causes not only the furnace slab metal but also the refractories in the furnace to melt significantly and shorten the furnace life extremely.

Further, the inventors of the present invention focused on the following points in order to minimize damage to the refractory at the furnace port and to carry out the processing efficiently, when developing a technique for dissolving and removing the metal at the furnace port of the converter furnace.

[0010] Oxygen gas sprayed from the nozzle for melting the ingot of the inner wall of the furnace is efficiently used for melting the ingot, and the kinetic energy of the oxygen gas applied to the ingot is reduced. It has been conceived that it is important to reduce the kinetic energy of oxygen gas given to the refractory and its surrounding refractories so that the temperature in these refractories is not overheated.

According to the above viewpoints, the above-mentioned prior arts 3 to 5 have the following problems. In the prior art 3, since the injection direction of the oxygen for secondary combustion is relatively vertically downward, the CO gas is secondary-burned while being caught in the furnace exhaust gas, and most of the secondary combustion from the furnace to the furnace port is performed. Is consumed. Therefore, the high-temperature gas of 2000 ° C. or more due to the high heat generated at that time tends to cause not only melting of the converter port metal but also significant damage to the converter port and the furnace port refractory.

According to the prior art 4, since air is used as an oxygen source for melting the furnace mouth metal, the injection amount is increased as compared with the case of injecting oxygen, and the melting of the hardware of the furnace mouth refractory is prevented. be able to. However, since the oxygen concentration in air is low, it takes time to dissolve the furnace mouth metal and the efficiency is poor.

According to the prior art 5, since oxygen for melting the furnace mouth metal is injected from the secondary combustion nozzle at an angle close to a horizontal direction or a relatively horizontal direction, the trajectory of the injected oxygen gas is determined by the furnace. Reach the bullion. Accordingly, since the furnace mouth metal is oxidized to generate a low-melting iron oxide, the furnace mouth metal is easily dissolved and removed. However, since the trajectory of the secondary combustion oxygen reaches the furnace mouth metal part, a large kinetic energy is given to this part by the oxygen gas. For this reason, a dynamic pressure is applied to the furnace port refractory, which may cause erosion of this portion. Therefore, it is necessary to adjust the dynamic pressure.

It is an object of the present invention to secure the productivity of molten steel in a converter, to suppress the adhesion of the metal at the furnace opening and the inner wall of the furnace without adversely affecting the refractory of the converter. ,
An object of the present invention is to provide a method for dissolving the metal.

[0015]

As a result of various studies, the present inventors have solved the above problems and developed the following method. A converter blowing method for suppressing the adhesion of the metal at the furnace port and the inner wall of the furnace according to claim 1 is a method of charging a raw material using molten iron as a main iron source into a converter type refining furnace and dissolving the metal on the outer periphery. In a method in which a lance provided with an oxygen nozzle is inserted from the furnace port of the refining furnace, and the raw material is blown with top-blown oxygen and / or bottom-blown oxygen, the furnace of the blowing trajectory of the ingot for melting metal ingot is used. The present invention is characterized in that the height of the arriving point to the port and the inner wall of the furnace is controlled to be lower than the height of the metal sticking to the furnace port and the inner wall of the furnace.

However, the point at which the trajectory of the oxygen for melting metal reaches the inner wall of the furnace does not necessarily mean that the trajectory reaches the inner wall of the furnace, but also indicates that the trajectory rises along the furnace wall. The converter blowing method for suppressing the adhesion of the furnace port and the furnace inner wall metal according to claim 2 is the method according to claim 1, wherein the injection direction of the oxygen injected from the metal melting oxygen nozzle is set to The angle between the lance and the longitudinal axis is in the range of 40 to 90 °, and the lance is directed downward or horizontally.

The converter blowing method for suppressing the adhesion of the metal at the furnace port and the inner wall of the furnace according to claim 3 is the method according to claim 1 or 2, wherein the P concentration of the hot metal is adjusted to the P concentration required for the product. The present invention is characterized in that it is preliminarily de-P-refined and the hot metal de-P is used as a main iron source material.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies to develop a method for efficiently suppressing the adhesion of metal at the furnace port while suppressing damage to the refractory at the furnace port, and obtained the following findings. Was.

(1) An important feature of the present invention is that the vertical height of the point where the trajectory of the injection oxygen for metal ingot adhering to the furnace inner wall reaches the furnace inner wall is the height of the metal adhering to the furnace inner wall. The control to be lower than the above will be described below.

FIG. 1 is a schematic vertical sectional view of an example of an apparatus used to carry out the present invention. Hot metal 12 and slag material 1
A blowing lance 5 is inserted into the furnace through the furnace port 14 from above the converter 1 into which the furnace 3 is charged. The blowing lance 5
An oxygen nozzle 6 for blowing is provided at a lower end, and a nozzle 7 for melting metal ingot on a furnace inner wall is provided at a predetermined position above the lower end. As the structure of the blowing lance 5, a triple pipe structure of an oxygen supply pipe, a cooling water supply pipe, and a cooling drain pipe, or an oxygen pipe for melting a furnace port metal from the triple pipe oxygen supply pipe may be used. Or a quadruple tube structure. However, a four-tube structure is more preferable because the flow rate of the oxygen for melting the metal at the furnace port can be easily controlled.

First, a curve representing the trajectory of the oxygen discharged from the nozzle 7 for melting the metal on the inner wall of the furnace was obtained by numerical calculation. In determining the trajectory of the jet oxygen, the inside radius of the converter, the discharge velocity of the top blown oxygen for blowing, the discharge velocity of the oxygen for dissolving the metal, and the mounting angle of the nozzle for dissolving the metal were varied. FIG. 2 illustrates the locus of oxygen for dissolving metal.

Based on the obtained curve, the vertical height of the trajectory of the trajectory of the ingot for dissolving the metal to the inner wall of the furnace was examined. However, the point at which the trajectory of the metal melting oxygen reaches the inner wall of the furnace does not necessarily mean that the trajectory reaches the inner wall of the furnace, but also indicates that the trajectory rises along the furnace wall. FIG. 3 shows the difference between the height position of the metal melting oxygen nozzle and the vertical height position of the trajectory of the metal melting oxygen trajectory reaching the furnace inner wall (hereinafter, Δ
and h _C at hereinafter), the vertical component of the discharge flow rate of the oxygen for bullion dissolved (hereinafter, a graph plotting the relationship between hereinafter) in U _OV. Here, R represents the inside radius of the converter.
Here, the position of the oxygen discharge port from the metal dissolution oxygen nozzle is the origin of the coordinates, the position in the height direction and the direction of the velocity are positive in the vertical upward direction, and the position in the horizontal direction and the direction of the velocity are the furnace inner diameter. The furnace wall direction was positive.

Incidentally, the trajectory of the oxygen for dissolving the metal is expressed by U _OV = 85 to 342 m / considering the operating conditions in the actual operation.
various levels in the range of s, U _Or = 346-480 m / s
(However, U _Or is a radial component in the furnace of the discharge flow rate of the metal melting oxygen in the furnace), various levels in the range of R = 1 to 3 m, and the superficial velocity in the furnace is 1 in the upward direction. .3-9m
/ S is obtained by changing to various levels within the range of / s.

The jet of oxygen discharged from the metal-dissolving oxygen nozzle has its own, that is, the horizontal velocity component of the oxygen jet is zero at the point where the trajectory of the metal-dissolving oxygen reaches the inner wall of the furnace. (Zero). An important feature of the present invention is that the vertical height of the point at which the injection oxygen trajectory for ingot melting attached to the furnace inner wall reaches the furnace inner wall is lower than the height of the metal attached to the furnace inner wall, This indicates that the above-mentioned arrival point is located at a position lower than the ingot on the inner wall of the furnace. Then, the subsequent metal-dissolving oxygen rises with the gas flow from below, thereby dissolving the metal or suppressing the adhesion of the metal. As described above, in the present invention, the kinetic energy of the injection oxygen for ingot dissolution applied to the ingot is reduced, and the kinetic energy of oxygen gas applied to the refractory in the ingot and the surrounding area is also reduced. Thus, the refractory is prevented from being overheated to suppress the erosion of the refractory. Here, it is necessary that the position of the lowest point of the injection trajectory of the oxygen for ingot melting be higher than the upper surface of the molten steel in the converter.

As described above, a major feature of the present invention is that the height of the trajectory of the injection oxygen for ingot melting to the inner wall of the furnace in the vertical direction is controlled to be lower than the height of the ingot adhering to the inner wall of the furnace. As a result, it can efficiently contact the surface of the
In addition, it is intended to suppress the erosion of the refractory.
Thus, a part of the metal for melting metal reacts with the iron in the metal to form iron oxide having a low melting point, thereby suppressing damage to the furnace port refractory 9 and quickly forming the furnace port metal 8. We found that it can be dissolved and removed.

(2) Next, as a result of various studies, the present inventors have obtained the following knowledge on the factors that cause the formation of slabs adhering to the furnace opening, and based on the findings, have found that there is a method for suppressing the adhesion of slabs. Furnace blowing method was developed.

As a method of quantitatively grasping the amount of the metal produced on the furnace port, as shown in FIG. 4, a dust concentration meter 3 is installed in a passage 2 of the converter exhaust gas generated from the converter 1, and the dust in the exhaust gas is measured. The relationship between the concentration and the removal frequency of the furnace mouth metal 4 was investigated. As a result, as shown in FIG. 5, an extremely good correlation was obtained between the amount of exhaust gas dust in the early stage of blowing and the frequency of removal of the slab metal, so that the method of quantitatively grasping the metal splatter was used. Used as one.

As shown in FIG. 6, in the conventional blowing,
Dust generation rate is high at the beginning of blowing. Therefore, a large amount of furnace mouth metal is generated in the early stage of blowing. As a result of further investigation, it was found that the influence of the Si concentration in the hot metal and the amount of residual slag in the furnace was large as shown in FIGS.

Si is more easily oxidized than carbon in hot metal,
In the early stage of decarburization blowing, the silicon removal reaction occurs preferentially. At this time, the vicinity of the free surface of the hot metal is dense, and it is considered that dust (splash) is very likely to be generated by collision or passage of oxygen gas. On the other hand, when the decarburization reaction shifts to an active period, it is considered that CO gas generated by the decarburization reaction is present in the vicinity of the free surface of the hot metal or molten steel and becomes foamy, so that dust (splash) is hardly generated.

The residual slag in the furnace is a substance once melted in the decarburization blowing process of the previous heat, and is quickly dissolved even in the early stage of the decarburization blowing. Therefore, it is considered that the free surface of the hot metal can be quickly covered at an early stage, and generation of dust can be suppressed.

As described above, in the present invention, the hot metal Si
Concentration is 0.15% or less, and heat slag is 10kg / t
It was found that by blowing the steel remaining in the furnace for more than -steel, the effect of suppressing the adhesion of ingot was further improved.

[0032] The ingots attached to the furnace mouth of the conventional blowing were collected and examined in detail, and it was found that the ingots were in a state in which the ingots and small particles of slag were mixed. If it adheres to the furnace port in this state, it is entangled with each other and adheres firmly. As a result of examining the relationship between the amount of slag present in the furnace and the frequency of metal removal, it was found that as shown in FIG. 9, the smaller the amount of slag present in the furnace, the smaller the adhesion of the furnace opening metal. This is because the smaller the amount of slag in the furnace, the smaller the percentage of slag at the time it adheres to the furnace port, and the lower the melting point, especially since the dust generated in the initial stage almost coincides with the hot metal component. It is considered that this is because of dripping from

However, if the amount of slag is too small, there is no cover for the molten iron, which leads to the scattering of the molten iron.
However, in the present invention, since the residual slag of the pre-heat exists in the furnace at least 10 kg / t-steel or more,
This problem can be avoided.

As described above, in the present invention, hot metal Si
Concentration is 0.15% or less, and heat slag is 10kg / t
It was found that by blowing the steel remaining in the furnace for more than -steel, the effect of suppressing the adhesion of ingot was further improved.

As described above, in the present invention, it was found that by blowing the slag in the furnace with the slag in the furnace being 30 kg / t-steel or less, the effect of suppressing the adhesion of the ingot was further improved. Based on the above development, the situation when blowing was continued was investigated. As a result, as shown in FIG. 10, the higher the ratio of blowing with the above conditions applied, the lower the frequency of furnace slab removal, and a remarkable effect is obtained especially when the application ratio reaches 80% or more. Was done.

In the above-mentioned development, it was found that by preliminarily setting the phosphorus concentration in the hot metal to be equal to or less than the phosphorus concentration of the product, the effect of suppressing the adhesion of the metal was further improved. In the present invention, it is desirable to use hot metal that has been preliminarily dephosphorized so that the phosphorus concentration is equal to or lower than that of the product.

Now, in the present invention, as shown in FIG. 1, a converter 1 into which a hot metal 12 and a slag material 13 are charged
From above, the blowing lance 5 is inserted into the furnace through the furnace port 14. However, the Si concentration of the hot metal 12 and the input amount of the slag-making material 13 are determined based on the standard in ordinary refining, and the slag from the previous heat is not left. The blowing lance 5 is provided with a blowing oxygen nozzle 6 at the lower end and a furnace port metal melting nozzle 7 at a predetermined position above the lower end. As the structure of the blowing lance 5, a triple pipe structure of an oxygen supply pipe, a cooling water supply pipe, and a cooling drain pipe, or an oxygen pipe for melting a furnace port metal from the triple pipe oxygen supply pipe may be used. Or a quadruple tube structure. However, a four-tube structure is more preferable because the flow rate of the oxygen for melting the metal at the furnace port can be easily controlled.

Next, oxygen gas having a predetermined flow rate a (Nm ³ / min) is injected from the oxygen nozzle 6 for blowing using the above-mentioned equipment, and during the refining of the hot metal, the relation of the following equation (1) is satisfied. Then, the oxygen gas b (Nm
³ / min).

(B / a) × 100 = 1 to 50 (%) --- (1) The converter has a furnace port 14 before the start of refining. A base metal 8 is attached and formed on the surface of the furnace port refractory 9. By performing converter blowing under the above conditions, the furnace opening metal 8 is gradually dissolved and removed. Heat to be blown under these conditions is given under unsteady working conditions in the converter operation or unsteady process operation, for example, when the time interval between the heat becomes long and the furnace heat decreases. The effect is further enhanced by appropriately performing the operation according to the conditions and the like.

On the other hand, the direction of injection of the oxygen 15 for melting the metal on the inner wall of the furnace is defined by the angle θ with respect to the longitudinal axis 10 of the lance.
However, it has been found that when the angle is in the downward direction or the horizontal direction at an angle of 40 to 90 [deg.], The effect of suppressing the adhesion of the base metal is further improved. In the present invention, the angle θ is set to 40
It is desirable to be within the range of 90 °.

In order to efficiently dissolve and remove the furnace mouth metal, in addition to the above-described conditions, the gas velocity in the furnace, the flow rate of the oxygen for melting the furnace mouth metal, and the injection are determined by the operation and equipment conditions. Factors such as the pressure, the diameter, shape, number of holes, and the mounting position of the nozzle for melting the furnace opening metal, the furnace opening, the throttle angle of the furnace opening, and the lance height are important factors.

As described above, in the present invention, the melting and removal of the furnace mouth and the inner wall metal by the oxygen injection and the suppression of the adhesion are performed by using the high heat generated mainly by the secondary combustion of the furnace exhaust gas as in the prior art. To the method of applying to gold, or to the method of combining the heat generated by the secondary combustion of the furnace exhaust gas with the direct fusion of oxygen gas to the furnace mouth metal to melt the metal. The greatest feature is that the primary focus is on removing oxygen by causing it to softly contact the metal so as not to directly collide with the metal and generate iron oxide having a low melting point.

[0043]

As described above, according to the present invention,
In addition to suppressing the adhesion of ingots on the furnace port and the inner wall of the converter type refining furnace, it is easy to dissolve the ingots. Is not required, and the productivity of the converter is greatly improved. Such a converter blowing method can be provided, and an industrially useful effect is obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an example of equipment in a case where blowing is performed using a lance having a furnace port and a nozzle for melting metal ingot on a furnace inner wall in the present invention.

FIG. 2 is a graph exemplifying a trajectory of the oxygen for dissolving metal when the discharge condition and the operating condition of the oxygen for dissolving metal are changed.

FIG. 3 shows the difference (Δh _C ) between the height position of the metal melting oxygen nozzle and the vertical height of the trajectory of the metal melting oxygen reaching the inner wall of the furnace, and the discharge of the metal melting oxygen. It is the graph which plotted the relationship with the vertical component ( _UOV ) of the flow velocity.

FIG. 4 is a schematic diagram illustrating a general form of decarburization blowing and a mode of measuring dust concentration in exhaust gas.

FIG. 5 is a graph showing a relationship between an initial dust generation amount and a furnace mouth metal removal frequency.

FIG. 6 is a graph showing a change in the amount of dust generated during one heat of decarburization blowing.

FIG. 7 is a graph showing the effect of molten iron Si concentration on the amount of dust generated during the first three minutes of decarburization blowing.

FIG. 8 is a graph showing the effect of the amount of residual slag in the furnace from the preheating on the initial dust generation rate.

FIG. 9 is a graph showing the effect of the amount of slag in the furnace during blowing on the initial dust generation rate.

FIG. 10 is a graph showing the effect of the application ratio of the conditions of the present invention on the adhesion of the slab metal when the decarburization blowing is continuously performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Converter 2 Exhaust gas passage 3 Dust densitometer 4 Furnace mouth metal 5 Blowing lance 6 Blowing oxygen nozzle 7 Furnace inner wall bullion melting nozzle 8 Furnace mouth metal 8a Surface 9 Furnace mouth refractory 10 Axle wire 11, 11 ′, 11 ″ Vertical lowest point of trajectory of injected oxygen 12 Hot metal 13 Slag making material 14 Furnace port 15 Oxygen for melting metal ingot on furnace inner wall 16 Metal ingot on furnace inner wall

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Kodaira 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Shigeru Inoue 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor, Kanji Hiji, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan

Claims (3)

[Claims] 1. A raw material containing molten iron as a main iron source is charged into a converter type refining furnace, a lance having an outer periphery provided with a metal melting oxygen nozzle is inserted from a furnace port of the refining furnace, and In the method in which the raw material is blown with top-blown oxygen and / or bottom-blown oxygen, the height of the point at which the injection trajectory of the metal infusing metal reaches the furnace port and the inner wall of the furnace is adjusted to the height of the furnace port and the inside of the furnace. A converter blowing method for controlling the adhesion of metal at the furnace port and the inner side wall of the furnace, wherein the method is controlled to be lower than the height of the metal adhered to the wall. 2. The method according to claim 1, wherein an angle of an injection direction of the oxygen injected from the oxygen nozzle for melting the metal with a longitudinal axis of the lance is 40 to 90 °.
A converter blowing method for suppressing the adhesion of the furnace opening and the inner wall of the furnace inner wall, wherein the furnace opening and the furnace inner wall are set in a downward or horizontal direction. 3. The method according to claim 1 or 2, wherein the P concentration of the hot metal is removed in advance to a P concentration or less required for the product, and the removed hot metal is used as a main iron source material. A converter blowing method for suppressing the adhesion of metal at the furnace port and the inner wall of the furnace.