JP2006274364A - Bottom-blown tuyere for use in refining vessel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bottom-blown tuyere which has excellent spalling resistance and stirring power and has variable blowing amount of refining gas over a wide range. <P>SOLUTION: The bottom-blown tuyere is disposed at the bottom part of a refining vessel for holding and refining molten metal and is used for blowing the refining gas into the refining vessel, wherein two or more flowing passage for refining gas formed of fine tubes are provided in the tuyere refractory formed in a columnar shape. The flowing passage is opened at the upper end surface of the tuyere refractory and the opening hole center points being the centers of the opening hole part of the flowing passage are evenly spaced on the circumference of a circle having the center axis of the tuyere refractory as the center, and the inclination angle α of the center axis of the flowing passage to the perpendicular line passing the opening hole center part is made to a fixed value at all opening hole center points. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tuyere (hereinafter referred to as a bottom-blown tuyere) that is disposed at the bottom of a container for containing and refining molten metal and blows a refining gas into the molten metal in the container.

When supplying refinement gas to molten metal (for example, molten steel),
(a) a refining method in which a refining gas is blown at a high speed from above the bath surface of the molten metal,
(b) a refining method in which a refining gas is blown from the bottom of a refining vessel containing molten metal,
(c) A refining method using both (a) and (b) above is widely adopted. The refining gas is not only an inert gas (eg, Ar gas, N ₂ gas, etc.) for stirring the molten metal, but an O ₂ gas, etc., for promoting the decarburization reaction when the molten metal is molten steel. Various gases are appropriately selected according to the purpose and used.

  The bottom blowing tuyere used in the above refining method (b) or (c) is disposed at the bottom of a refining vessel (for example, bottom blowing converter, top bottom blowing converter, etc.) containing molten metal. Therefore, during refining operations, it always comes into contact with the molten metal, and chemical or physical erosion easily proceeds. Further, when refining is completed and the molten metal is discharged, the bottom blowing tuyere is cooled, and if the molten metal is accommodated in the refining vessel again, the temperature of the bottom blowing tuyere rises rapidly. By repeatedly receiving such a thermal shock, physical erosion of the bottom blowing tuyere proceeds.

Therefore, in order to increase the durability of bottom-blown tuyere, suppression of chemical erosion (that is, improvement of corrosion resistance) and suppression of physical erosion (that is, improvement of spalling resistance and wear resistance) are required. . For this reason, various studies have been made on the structure of the bottom blowing tuyere as well as the components of the material constituting the bottom blowing tuyere.
For example, Patent Literature 1 discloses a bottom-blown tuyere in which an outer tube whose inside is a hollow tube and a solid inner tube whose inside is a tube are combined. This bottom blowing tuyere is for blowing a refining gas from the gap between the outer tube and the inner tube arranged with the center axes aligned. However, Patent Document 1 does not consider the dimensions of the outer tube and the inner tube. Therefore, when the gas for refining blown from the gap between the outer tube and the inner tube becomes excessively large in the molten metal, the surrounding melted into the space after the bubbles are released from the bottom blowing tuyere When the metal is filled, the impact acting on the bottom blowing tuyere increases. In other words, the technique disclosed in Patent Document 1 cannot be expected to improve the anti-spooring property.

Non-Patent Document 1 discloses a tuyere in which a large number of thin tubes are combined (hereinafter, referred to as a thin tube collective tuyere). The capillary tube type tuyere can change the amount of refining gas blown by appropriately selecting the inner diameter and the number of narrow tubes. From the viewpoint of improving the productivity of the molten metal refining process or homogenizing the components, in order to increase the stirring power of the refining gas blown through the narrow tube aggregate tuyere,
(A) Enlarging the inner diameter of the narrow tube,
(B) increase the number of tubules,
(C) Increase the source pressure of the refining gas,
(D) It is necessary to increase the flow rate of the gas for refining, for example, by disposing a large number of narrow tube aggregate tuyere in the refining vessel.

  Generally, when refining molten metal (for example, molten steel) using a refining vessel (for example, bottom blowing converter, top bottom blowing converter, etc.), the refining vessel is erected during refining. The blowing tuyere is located below the bath surface of the molten steel. However, when charging or discharging molten steel, the refining vessel is tilted, so that the bottom blowing tuyere is exposed. Therefore, it is necessary to change the amount of refining gas blown over a wide range from a small flow rate to a large flow rate.

However, in (A) above, the pressure loss in the narrow tube is reduced, so it is possible to increase the flow rate of the refining gas, but it is necessary to increase the lower limit value of the refining gas flow rate in order to prevent leakage of steel. I do not get. Therefore, the changeable range of the refining gas flow rate is narrowed.
In (B) above, since the inner diameter of the narrow tube is not changed, the lower limit of the refining gas flow rate per narrow tube is constant, but as the number of narrow tubes increases, refining as a narrow tube aggregate tuyere is performed. The lower limit of the working gas flow rate increases. Therefore, the changeable range of the refining gas flow rate is narrowed.

In (C) above, drastic remodeling of piping for refining gas, pumps, dampers, etc. is necessary, which not only requires expensive capital investment but also suspends equipment operation for a long period of time for construction. There must be.
In (D) above, as in (C), major equipment modifications such as piping, pumps and dampers for blowing refining gas are required. Moreover, since the furnace bottom structure of the refining vessel must be changed, a higher cost is required.
JP-A-57-114623 Kawasaki Steel Technical Report 17 (1985) 4,357-364

  An object of the present invention is to provide a bottom blowing tuyere that solves the above-described problems, has excellent anti-spooring properties and stirring power, and can change the amount of refining gas blown over a wide range. Further, the bottom blow tuyere of the present invention can be used without requiring significant modification of existing refining containers and peripheral equipment.

  The present invention is a bottom-blown tuyere that is disposed at the bottom of a refining vessel for containing and refining molten metal and blows a refining gas into the refining vessel. Two or more refining gas flow paths are formed into a thin tubular shape, the flow path is opened at the upper end surface of the tuyere refractory, and the flow path is formed on the circumference around the central axis of the tuyere refractory. The opening center points, which are the centers of the openings, are arranged at equal intervals, and the inclination angle α between the vertical line passing through the opening center point and the center axis of the flow path is in the range of 10 to 45 ° at all opening center points. It is a bottom blowing tuyere.

  In the bottom blow tuyere of the present invention, the twist angle β obtained by projecting the angle formed by the tangent line at the opening center point of the circle formed by the opening center point and the center axis of the flow path on the horizontal plane is at all opening center points. And preferably within ± 10 ° with respect to the tangent. Furthermore, it is preferable that the circumference at which the opening center point is arranged is two or more around the center axis of the tuyere refractory.

  According to the present invention, it is possible to improve the anti-sporing property and stirring force of the bottom blowing tuyere and to change the refining gas blowing amount over a wide range. In addition, when using the bottom blow tuyere of the present invention, it is not necessary to significantly modify the existing refining vessel and peripheral equipment, so that the capital investment can be kept low.

FIG. 1 is a perspective view schematically showing an example of the upper end surface of the bottom blowing tuyere of the present invention. The bottom blowing tuyere is disposed at the bottom of a refining vessel such as a bottom blowing converter (that is, buried in the furnace bottom refractory), but the furnace bottom refractory around the bottom blowing tuyere is shown in FIG. Is omitted.
As shown in FIG. 1, in the bottom blow tuyere of the present invention, a cylindrical tuyere refractory 1 is provided with a thin tubular refining gas flow channel 2, and the flow channel 2 is provided on the upper end surface of the bottom blow tuyere. Open. Two or more flow paths 2 are provided in the tuyere refractory 1. FIG. 1 shows an example in which six flow paths 2 are provided. The centers Cp of the openings of these flow paths 2 (hereinafter referred to as opening center points) are arranged at equal intervals on the circumference of a circle CA centered on the central axis CL1 of the tuyere refractory 1.

FIG. 2 is an enlarged side view showing the vicinity of the opening of an arbitrary channel 2 in FIG. An angle α (hereinafter referred to as an inclination angle) formed by the central axis CL2 of the flow path 2 and a vertical line passing through the opening center point Cp is 10 to 45 ° at all the opening center points.
FIG. 3 is a cross-sectional view schematically showing an example in which a refining gas is blown from the bottom blowing tuyeres of the present invention into the molten metal in the refining vessel. The bottom blowing tuyere is disposed such that the upper end surface is exposed on the upper surface of the refining vessel. The refining gas 4 is supplied from the bottom of the bottom blowing tuyere, passes through the flow path 2 and is blown into the molten metal 3 as bubbles 4a from the opening. Since the flow path 2 is inclined at a constant inclination angle α with respect to the vertical line at each opening center point Cp, the bubbles 4a of the refining gas 4 blown into the molten metal 3 form a swirling flow SE. To do. Therefore, the molten metal 3 can be sufficiently stirred by blowing the refining gas 4 using the bottom blowing tuyere of the present invention.

As already explained, in the bottom blow tuyere of the present invention, two or more refining gas flow paths 2 are provided in the cylindrical tuyere refractory 1. The number and inner diameter of the flow path 2 are appropriately set according to the size of the refining vessel, the type of molten metal, the amount of refining gas blown in, and the like.
If the inclination angle α is less than 10 °, the swirl flow SE of the molten metal 3 does not occur. On the other hand, if the inclination angle α exceeds 45 °, the hitting damage due to the expandable bubbles at the tuyere exit becomes large, so that the opening is easily lost. Therefore, it is preferable that the inclination angle α satisfies the range of 10 to 45 °.

  The central axis CL2 of the flow path 2 is preferably tangential to the circumference CA where the opening center point Cp is arranged. However, as shown in FIG. 4, an angle β (hereinafter referred to as a twist angle) projected on a horizontal plane (that is, a plan view) is an angle formed by a tangent line CB at the opening center point Cp of the circle CA and the central axis CL2 of the flow path 2. Can be within ± 10 °. Here, in FIG. 4, the twist angle β set below the tangent line CB is assumed to be plus, and the twist angle β set above the tangent line CB is assumed to be minus. When the twist angle β exceeds + 10 °, the refining gas 4 blown from the flow path 2 interferes in the circle CA, and the swirling flow SE is not formed. On the other hand, when the twist angle β exceeds −10 °, the refining gas 4 blown from the flow path 2 is dissipated in the direction of the side wall (not shown) of the refining vessel, so that the swirl flow SE is not formed. That is, in order to form the swirl flow SE of the molten metal 3, the twist angle β is preferably within ± 10 °.

FIG. 1 shows an example in which one circle CA is formed by the opening center point Cp, but two or more circles CA may be formed. FIG. 5 shows an example in which two circles CA are formed. These circles CA1 and CA2 are both concentric circles centered on the central axis CL1 of the tuyere refractory 1.
In this manner, the bottom blow tuyere of the present invention can improve the spalling resistance and the stirring power. In addition, by setting the number and the inner diameter of the flow passages 2 of the refining gas 4 to values that satisfy the preferable range, it is possible to change the refining gas blowing amount over a wide range from a small flow rate to a large flow rate. . Further, if the bottom blow tuyere of the present invention has the same dimensions (that is, outer diameter, height, etc.) as the conventional tuyere, existing refining containers and peripheral equipment can be used.

  A bottom-blown tuyere was placed at the bottom of a 500 mm diameter laboratory container. As the bottom blowing tuyere, the one in which the flow path 2 is arranged as shown in FIG. 5 was used. The outer diameter of the tuyere refractory 1 was 120 mm, and the inner diameter of the flow path 2 was 1 mm. The total number of the flow paths 2 is 30, 20 are arranged at equal intervals in the circle CA1, and 10 are arranged at equal intervals in the circle CA2. The inclination angle α at the opening center point Cp of each flow path 2 is constant, and seven types of bottom blowing tuyere with α values of 0 °, 5 °, 10 °, 20 °, 30 °, 45 °, and 60 ° are provided. used. The twist angle β was ± 0 °.

Ion exchange water (so-called pure water) is stored in this experimental vessel up to a depth of 500 mm, air is supplied from the bottom of the bottom blowing tuyere (flow rate: 0.8 m ³ (standard state) / min), Was blown into the ion exchange water. While blowing air into the ion exchange water in the experimental container, 10 cm ^{3 of an} aqueous potassium chloride solution (concentration: 1% by mass) was dropped into the center of the water surface.
The transition of electrical conductivity at this time was measured. The sensor was placed in the vicinity of the wall surface at the bottom of the experimental container. By dripping the potassium chloride aqueous solution, the electric conductivity of the ion exchange water increases, and reaches a constant value after a sufficient time has elapsed. In this transition of electrical conductivity, the time from the start of dropping of the aqueous potassium chloride solution until the electrical conductivity rose to a value within ± 5% of the finally reached electrical conductivity was defined as the uniform mixing time. .

  The measurement of the uniform mixing time was performed three times for each of the seven types of bottom blowing tuyeres with different inclination angles α, and the average value was calculated. FIG. 6 shows the relationship between the inclination angle α and the average value of the uniform mixing time. However, in FIG. 6, uniform mixing time is shown as a stirring index. The stirring index is an index that is relatively evaluated with the average value of the uniform mixing time of the bottom blowing tuyere having an inclination angle α = 0 ° as a reference value (= 1). That is, the smaller the stirring index, the shorter the uniform mixing time (that is, the stronger the stirring power). As is clear from FIG. 6, the stirring index decreases in the range where the inclination angle α is 10 ° or more.

  Next, molten steel was accommodated in a test converter (capacity 5 tons) provided with a bottom blow tuyere and refined, and the yield of Mn and the wear amount of the bottom blow tuyere were investigated. As the bottom blowing tuyere, the one in which the flow path 2 is arranged as shown in FIG. 1 was used. However, in the bottom blowing tuyere used in the test converter, the number of the flow paths 2 was 10 and 10 were arranged at equal intervals in a circle CA. The inner diameter of the flow path 2 was 2 mm. The inclination angle α at the opening center point Cp of each channel 2 was constant, and three types of bottom blowing tuyere whose α values were 0 °, 10 °, 20 °, and 60 ° were used. The twist angle β was ± 0 °.

In this test converter, 5 tons of molten steel was accommodated, N ₂ gas was supplied from the bottom of the bottom blowing tuyere (flow rate: 1.0 m ³ (standard state) / min), and blown into the molten steel through the flow path 2. While N ₂ gas was blown into the molten steel in the test converter, 100 kg of Mn ore was poured into the molten steel bath surface. After 15 minutes have passed since the Mn ore was charged, the N ₂ gas blowing was stopped. The temperature of the molten steel was 1650 ° C.
Measure the Mn content (mass%) of the molten steel after stopping the N ₂ gas blowing, and calculate the Mn content (kg) in the molten steel from the molten steel amount (= 5 tons) and the Mn content in the steel before and after blowing. The Mn yield was calculated by the following formula.

Mn Yield (%) = 100 x M _STEEL / M _ORE
M _STEEL : Mn content in molten steel (kg)
M _ORE : Mn content in Mn ore (kg)
FIG. 7 shows the relationship between the inclination angle α and the Mn yield. However, in FIG. 7, the Mn yield is shown as a yield index. The yield index is an index that is relatively evaluated with the Mn yield at an inclination angle α = 0 ° as a reference value (= 1). That is, the larger the yield index, the stronger the stirring force. As is apparent from FIG. 7, the yield index increases in the range where the inclination angle α is 10 ° or more.

Further, after stopping the N ₂ gas blowing, the molten steel was discharged from the test converter, the bottom blowing tuyere was collected, and the length (mm) of the bottom blowing tuyere was measured. The difference between the length measured in advance before the N ₂ gas blowing was started and the length measured after the blowing was stopped was obtained, and the value was used as the amount of wear of the bottom blowing tuyere. FIG. 8 shows the relationship between the inclination angle α and the amount of wear of the bottom blowing tuyere. However, in FIG. 8, the amount of wear of the bottom blowing tuyere is shown as a wear index. The wear index is an index that is relatively evaluated with a wear amount at an inclination angle α = 0 ° as a reference value (= 1). That is, the larger the wear index, the greater the wear amount. As is apparent from FIG. 8, the wear index decreased when the inclination angle α was 45 ° or less.

It is a perspective view which shows typically the example of the upper end surface of the bottom blowing tuyere of this invention. It is a side view which expands and shows the opening part vicinity of the flow path in FIG. It is sectional drawing which shows typically the example which blows the gas for refining from the bottom blowing tuyere of this invention to the molten metal in the container for refining. It is a top view which expands and shows the opening part vicinity of the flow path in FIG. It is a top view which shows typically the other example of the upper end surface of the bottom blowing tuyere of this invention. It is a graph which shows the relationship between inclination-angle (alpha) and a stirring index. It is a graph which shows the relationship between inclination-angle (alpha) and a yield index. It is a graph which shows the relationship between inclination-angle (alpha) and a wear index.

Explanation of symbols

1 Tuyere refractory 2 Refining gas flow path 3 Molten metal 4 Refining gas
4a Bubble 5 Furnace bottom refractory
SE swirl flow
CL1 Center axis of tuyere refractories
Center axis of CL2 flow path
Cp Opening center point
CA A circle formed by the center point of the opening
The tangent of the circle formed by the CB opening center point

Claims (3)

  A bottom-blown tuyere that is disposed at the bottom of a refining vessel for containing and refining molten metal, and blows a refining gas into the refining vessel. Two or more gas flow paths are formed in a thin tubular shape, the flow path is opened at the upper end surface of the tuyere refractory, and on the circumference centered on the central axis of the tuyere refractory, The opening center points that are the centers of the openings of the flow paths are arranged at equal intervals, and an inclination angle α formed by a vertical line passing through the opening center point and the central axis of the flow path is 10 to 10 at all opening center points. Bottom blowing tuyere characterized by being in the range of 45 °.   A twist angle β obtained by projecting an angle formed between a tangent line at the opening center point of the circle formed by the opening center point and the center axis of the flow path onto the horizontal plane is ± with respect to the tangent line at all opening center points. The bottom-blown tuyere according to claim 1, wherein the bottom-blown tuyere is within 10 °. 3. The bottom-blown tuyere according to claim 1, wherein the circumference at which the opening center point is arranged is two or more around the central axis of the tuyere refractory.

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