JP2009149956A - Method for producing molten steel with converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing molten steel with which a local erosion generated in an oxygen-blowing hole direction is restrained while preventing the generation of stuck scull. <P>SOLUTION: In the method for performing refining while supplying oxygen by using a top-blowing lance at the flow of 2.5 to 5.0 Nm<SP>3</SP>/min×t to molten iron in a converter; the lance has 3 to 6 pieces of the oxygen-blowing holes, forming 10° to 20° angle between the center axis of the lance and the center axes of the oxygen-blowing holes, at the tip part of the lance and also, a mechanism for rotating around the center axis of the lance, and a blowing process, in which the continuous use of the lance is regulated (to be) within 150 heats (processes), and the lance during use, is rotated in the range of θ defined with following formula (1), is provided. äm×(360°/n)+10°<θ<(m+1)×(360°/n)-10°}... (1). Wherein, m: an optional integer, n: the number of the oxygen-blowing holes arranged at the angle of ≥10° from the lance center at the tip part of the lance, the integer being 3 to 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing molten steel by a refining converter, and in particular, in order to prolong the life of the converter, the direction of the lance oxygen injection port is continuously at the maximum melting point of the refractory on the furnace wall in the converter. The present invention relates to a method for producing molten steel by a converter in which a lance is rotated so as to avoid turning to a steel.

  In order to improve the production efficiency of the converter type refining furnace, increasing the oxygen flow rate is the most effective. However, when the oxygen flow rate is increased, the amount of spitting of molten iron and slag from the fire point increases, causing troubles such as adhesion of ingots to the lance and the inability to add auxiliary materials.

  Therefore, in order to remove ingots and slag adhering to the furnace in the region from the furnace wall to the furnace port (hereinafter referred to as “attached ingots”), for example, as disclosed in Patent Documents 1 and 2, A dedicated lance cutting lance having a mechanism in which the oxygen injection port rotates around the center axis of the lance is used. As disclosed in Patent Document 3, a lance for blowing and an injection port for cutting a metal There has been proposed a technique using a lance integrated with the.

In addition, the angle formed between the central axis of the oxygen injection port at the tip of the lance and the central axis of the lance (hereinafter referred to as the “oxygen injection angle”) is increased to prevent the molten iron from being scattered in the vertical direction and to generate adhered metal. A method for suppressing the above has been proposed.
JP-A-5-320732 JP-A-5-78728 JP 2006-213940 A

  However, the method of removing the attached bullion or the like with a dedicated lance is a method that requires a large load from the standpoint of preparing a dedicated lance. Moreover, since the operation | work for removing bullion etc. will be provided separately, productivity will fall remarkably. Furthermore, in view of the recent circumstances in which increasing energy efficiency is particularly important from the viewpoint of environmental protection, this method based on the premise that the attached metal is generated is not preferable.

  Further, in the latter method, if the oxygen injection nozzle tilt angle is increased too much, the oxygen injection direction (the oxygen injected from the oxygen injection nozzle and colliding with the molten iron surface and reflected toward the converter side wall is centered on the lance central axis. The furnace wall refractory in the radial direction) melts down. The investigation of the mechanism of refractory erosion revealed that the molten iron was oxidized and the iron oxide was causing refractory erosion. In other words, when the oxygen injection port tilt angle is increased, the distance between the oxygen jet and the furnace wall is reduced, so that the amount of spitting by the oxygen jet reaches the furnace wall is particularly increased for the furnace wall in the oxygen injection direction, resulting in melting loss. It is promoted. For this reason, the life of the furnace is brought about by reducing the remaining thickness of the furnace wall in the direction of the oxygen injection port, where the melting of the furnace wall is significant, and the furnace wall far from the direction of the oxygen injection port has reached the end of its life. It became clear that there was no.

  Therefore, as a countermeasure, it is conceivable to prepare a number of refining lances with different oxygen injection port directions and replace the lances so that the injection port does not face the site where the erosion has progressed. Since the diameter of the oxygen injection port to be used is changed according to the number of furnaces, that is, the furnace volume, and there is a limit to the number of spare lances in actual operation, refining only by changing the direction of the oxygen injection port Local melting of the furnace wall of the furnace cannot be completely prevented. In addition, it is possible to make the injection port porous and make the melting loss uniform, but in order to blow a large flow of oxygen within a limited lance diameter, it is necessary to ensure an optimal injection port diameter. , Up to 6 holes is the limit. In order to further increase the porosity, it is necessary to enlarge the lance diameter, and it is difficult to realize it because enormous capital investment is required.

  In view of the above background, an object of the present invention is to provide a method for producing molten steel that suppresses local melting that occurs in the direction of an oxygen injection port while preventing the formation of attached metal.

In order to solve the above-mentioned problems of the prior art, the present inventors have performed rotation of the lance that has been performed only in the metal cutting process with a small oxygen flow rate (less than 2.5 Nm ³ / min · t) until now. Focusing on changing the direction of the oxygen injection port by performing it in the blowing process for supplying oxygen at a large flow rate of 5 Nm ³ / min · t or more, we conducted a detailed study of the possibility and obtained the following knowledge It was.

When manufacturing molten steel from hot metal using a converter, blowing is usually performed for 10 to 20 minutes per heat at an oxygen flow rate of 2.5 to 5.0 Nm ³ / min · t. This oxygen flow rate may be changed during the blowing of each heat, or may be changed between each heat. Such oxygen is mainly blown from the top blowing lance toward the hot metal, but may be supplied from a bottom blowing tuyere partly or entirely provided at the bottom of the converter.

When oxygen of 2.5 to 5.0 Nm ³ / min · t is blown from the top lance to the hot metal, about 3 to 6 oxygen injection ports are often provided concentrically at the tip of the lance. . The concentric circles are not limited to one and may be plural. For example, a lance configuration is known in which the central axes of three injection ports are arranged on a concentric circle close to the lance central axis, and the other three are arranged on a concentric circle on the outer side. In addition, another oxygen injection port may be provided on the central axis of the lance.

Moreover, the diameter of the oxygen injection port provided in each lance may not be the same in each lance.
Thus, since the usage of oxygen in the converter is not uniform, it is predicted that the refractory preventing effect of refractory due to the rotation of the lance will not be stabilized simply by rotating the lance.

  Therefore, hot metal 260-290t preliminarily dephosphorized is charged into a converter together with scrap 10-30t to obtain a low carbon steel having a carbon content of 0.03% -0.10% in the molten steel. The oxygen supply conditions are continuously operated with 40 to 50 heat fixed for each condition, and the furnace wall erosion status of the converter is measured using a laser distance meter to determine the oxygen supply conditions and the furnace wall erosion. The relationship was first investigated.

  The measurement result of the furnace wall melting loss is shown in FIG. 1 together with the oxygen supply conditions used for the measurement. In FIG. 1, the horizontal axis is a numerical value representing the oxygen flow rate per oxygen injection port as an average value in each heat. Oxygen supplied from the lance central axis is excluded.

  In this experimental investigation, the center axis of the lance and the direction of the oxygen jet ejected from the lance port are problems, so the center axis of the oxygen injection port provided in each lance is provided on one concentric circle for each lance. A certain type (= for each lance, all oxygen injection nozzles have the same oxygen injection nozzle tilt angle and the same distance from the lance bottom at the center of each oxygen injection nozzle) was used.

  On the other hand, the vertical axis in FIG. The oxygen spouted from the lance once reacts with the hot metal and then bounces off the hot metal surface toward the converter side wall. The furnace wall shape in the direction of the oxygen injection port was measured using a laser distance meter, and the minimum erosion in the cross section of the converter including the maximum erosion site was the smallest and the remaining brick thickness was the largest. The angle in the range where the difference between the partial brick residual thickness X1 and the local molten brick residual thickness X2 in the direction of the oxygen injection port becomes 10 mm or more is taken as the vertical axis of FIG.

  From the results shown in FIG. 1, the furnace wall melting inclination angle increases when the oxygen feed rate per oxygen injection port increases, and the furnace wall melting inclination angle increases even when the oxygen injection nozzle inclination angle increases. I understood.

  However, even if the relationship between the oxygen supply condition and the furnace wall melted state as shown in FIG. 1 is recognized through the investigation for the present invention, this relationship is extended in the converter life in the actual converter operation. Ingenuity is necessary to utilize it.

  This is because in an actual converter operation, the oxygen flow rate is frequently changed, and it is not uncommon for the oxygen injection port inclination angles to be mixed and not constant. In addition, it is necessary to avoid as much as possible to actually measure the melting state of the furnace wall between the blow smelting because of the time loss.

Therefore, firstly, a method of rotating the lance around the central axis can be considered so that it is surely avoided that the range in which the furnace wall melting inclination angle is narrowest in the investigated range is continuously melted. Such a condition is that the oxygen flow rate is 6 lances except for the central-axis direction jet port, and the oxygen flow rate per jet port is 0 with the lance having an oxygen jet angle of 10 °. The furnace wall melting inclination is 12 ° when blown at 42 Nm ³ / min · t. Therefore, in consideration of the existence of a progressing portion of the erosion from the inside of the furnace wall erosion inclination angle to the periphery thereof, if the lance rotation is less than 10 °, the effect of equalizing the erosion caused by the lance rotation can be sufficiently mentioned. I found it difficult. However, this oxygen injection port has an oxygen injection port every 60 ° except for the central axis direction injection port, and if the lance was rotated 60 °, the lance was not rotated. Would be the same situation. In order to avoid such a situation, the lance rotation needs to be 50 ° (60 ° -10 °) or less.

  By the way, the furnace wall melting inclination angle in FIG. 1 is in the range of “melting difference with surroundings ≧ 10 mm” obtained by the test operation of 40 to 50 heat, but it is frequently used in actual operation due to operational reasons. In many cases, the lance cannot be rotated. As a countermeasure, considering that the actual length of the converter brick is 1000 to 2000 mm, it was considered to perform the furnace wall melting equalization operation in the range of “melting difference with surroundings ≦ 25 mm”. . As a result of a separate test, it was confirmed that the condition that caused a melting loss of 10 mm with 40 to 50 heats was equivalent to the condition that caused a melting loss of 25 mm with about 150 heats. It can be said that a predetermined lance rotation may be performed. Therefore, hereinafter, the furnace wall melting inclination angle β, as shown in FIG. 2, is the minimum melted portion brick residual thickness X1 in which the melting loss is the smallest and the brick residual thickness is the thickest, and the local portion in the oxygen injection nozzle direction. It is defined as an angle in a range where the difference from the remaining brick thickness X2 is 25 mm or more. FIG. 3 shows the aforementioned oxygen injection port tilt angle α.

The results of the above studies are summarized as shown in the following formula (1).
{M × (360 ° / n) + 10 ° <θ <(m + 1) × (360 ° / n) −10 °} (1)
θ: Lance rotation angle (deg)
m: Arbitrary integer n: Number of oxygen injection nozzles provided at the tip of the lance at an angle of 10 ° or more from the center axis of the lance, and an integer of 3 to 6

  Next, the relationship of FIG. 1 showing the results of the investigated range is summarized into a quantitative empirical formula by multiple regression, and the furnace wall melting inclination angle obtained by the empirical formula is more than the lance rotation angle per time. A way to do this is conceivable. As a result of putting the results shown in FIG. 1 into an empirical formula, the following formula (2) is shown.

{M × (360 / n) + ξ} ° <θ <{(m + 1) × (360 / n) −ξ} ° (2)
ξ = 0.520xα + 31.73xV + k
m: Arbitrary integer n: Number of oxygen injection ports provided at the tip of the lance at an angle of 10 ° or more from the vertical axis, an integer of 3 to 6 α: The central axis of the lance and the central axis of the oxygen injection port Average value of angle (°) formed by V V: Average value of oxygen ejection speed per nozzle (Nm ³ / min · t) k: -6.244 (constant)

  Further, when the furnace wall melting inclination angle β can be measured relatively frequently, the lance rotation angle can be set based on the following formula (3) using the result.

{M × (360 / n) + β} ° <θ <{(m + 1) × (360 / n) −β} ° (3)
m: Arbitrary integer n: Number of oxygen injection holes provided at an angle of 10 ° or more from the vertical axis at the tip of the lance, and an integer of 3-6

The present invention has been made based on the above findings, and the gist thereof is as follows.
(1) A method for producing molten steel in which refining is performed while supplying oxygen to a hot metal in a converter at a flow rate of 2.5 to 5.0 Nm ³ / min · t using an upper blowing lance, The front end has 3 to 6 oxygen injection ports in which the central axis of the lance and the central axis of the oxygen injection port form an angle of 10 ° to 20 °, and a mechanism that can rotate around the central axis of the lance, Production of molten steel by a converter, comprising a blowing step of rotating the lance in use within the range of θ defined by the following formula (1) within 150 heat of continuous use of the lance. Method.

{M × (360 ° / n) + 10 ° <θ <(m + 1) × (360 ° / n) −10 °} (1)
m: Arbitrary integer n: Number of oxygen injection ports provided at the tip of the lance at an angle of 10 ° or more from the center of the lance, and an integer of 3 to 6

(2) A method for producing molten steel in which refining is performed while supplying oxygen to the hot metal in the converter at a flow rate of 2.5 to 5.0 Nm ³ / min · t using an upper blowing lance, The front end has 3 to 6 oxygen injection ports in which the central axis of the lance and the central axis of the oxygen injection port form an angle of 10 ° to 20 °, and a mechanism that can rotate around the central axis of the lance, A method for producing molten steel by a converter, comprising a blowing step of rotating the lance within the range of θ defined by the following formula (2) within 150 heat of continuous use of the lance. .

{M × (360 / n) + ξ} ° <θ <{(m + 1) × (360 / n) −ξ} ° (2)
ξ = 0.520xα + 31.73xV + k
m: Arbitrary integer n: Number of oxygen injection ports provided at the tip of the lance at an angle of 10 ° or more from the vertical axis, an integer of 3 to 6 α: The central axis of the lance and the central axis of the oxygen injection port Average value of angle (°) formed by V V: Average value of oxygen ejection speed per nozzle (Nm ³ / min · t) k: -6.244 (constant)

(3) A method for producing molten steel in which refining is performed while supplying oxygen to the hot metal in the converter at a flow rate of 2.5 to 5.0 Nm ³ / min · t using an upper blowing lance, The front end has 3 to 6 oxygen injection ports in which the central axis of the lance and the central axis of the oxygen injection port form an angle of 10 ° to 20 °, and a mechanism that can rotate around the central axis of the lance, Within 150 heats of continuous use of the lance, the minimum remaining brick thickness X1 with the largest remaining brick thickness X1 in the cross section including the maximum damaged portion of the converter in use and the locally damaged brick in the direction of the lance oxygen injection port It is characterized by comprising a blowing step of measuring an angle β in a range where the difference from the remaining thickness X2 is 25 mm or more and rotating the lance in use within the range of θ defined by the following formula (3). The manufacturing method of the molten steel by a converter.

{M × (360 / n) + β} ° <θ <{(m + 1) × (360 / n) −β} ° (3)
m: Arbitrary integer n: Number of oxygen injection holes provided at an angle of 10 ° or more from the vertical axis at the tip of the lance, and an integer of 3-6

  By rotating the lance at an angle according to the method of the present invention in the smelting furnace, it is possible to eliminate local melting damage that occurs in the direction of the lance oxygen injection port. As a result, the life of the smelting furnace can be extended significantly. Therefore, by adopting the method of the present invention, the frequency of repairing the furnace can be reduced, the refractory cost can be reduced, the operating efficiency of the equipment is increased, and the productivity is improved.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.
FIG. 4 is an explanatory view showing a refining rotary lance structure of the present embodiment, FIG. 4 (a) is an overall view, and FIG. 4 (b) is a refining nozzle attached to the tip of the refining rotary lance. It is an example of a shape.

  In the description of the present embodiment, the number of oxygen injection ports of the refining nozzle is six except for the vertical direction, but is not limited to this, and is 3 to 6 concentrically. Good. There may be a plurality of concentric circles.

In this embodiment, the tilt angle of the oxygen injection port of the refining nozzle is 15 ° with respect to the vertical direction of the lance center axis, but is not limited to this and may be 10 to 20 °.
Further, as shown in FIG. 4 (a), the refining lance of the present embodiment is provided with a rotary joint 1 at the upper part, and the oxygen supply pipe 2 and the inner cylinder 3 are connected through the rotary joint 1. The space between the cooling water supply pipe 4 and the inner cylinder and the intermediate cylinder 5 and the space between the cooling water drain pipe 6 and the intermediate cylinder 5 and the outer cylinder 7 communicate with each other. A lance depositing portion 9 where the lance lifting carriage 8 and the lance contact is divided into an upper portion 10 connected to the lance and a lower portion 11 that can freely rotate. Thereby, the space between the oxygen supply pipe 2 and the inner cylinder 3, the space between the cooling water supply pipe 4 and the inner cylinder and the intermediate cylinder 5, and further between the cooling water drain pipe 6 and the intermediate cylinder 5 and the outer cylinder 7 The space between the oxygen supply pipe 2, the cooling water supply pipe 4, and the intermediate cylinder 5 to the outer cylinder 7 can rotate in a state where the spaces are communicated. In other words, in a state of being overlaid on the lance lifting carriage 8, a portion existing below the rotary joint 1 can be rotated around the lance center.

  As a means for rotating the refining lance, it is desirable to install a driving device on the lance carriage 8 and rotate the lance outer cylinder 7. However, the rotary joint portion 1 may be rotated at a lance maintenance site or the like.

  The refining lance of the present embodiment is configured as described above. Next, the situation where the local melting damage of the refining furnace is made uniform using the refining lance will be described.

  FIG. 5 is an explanatory diagram showing a situation in which refining lances according to the present embodiment are arranged inside an upper bottom blown converter type refining furnace and refining is performed.

First, a refining lance is inserted into the top-bottom blowing converter type refining furnace, and then refining is performed. Refining is carried out at a large oxygen flow rate (2.5 to 5.0 Nm ³ / min · t). Except in special cases, the refining is performed at an oxygen flow rate of 2.5 to 4.0 Nm ³ / min · t in normal operation. Often. At this time, oxygen is injected from the nozzle of the smelting lance toward the hot metal, and refining is performed. Moreover, spitting generated by oxygen injection damages the furnace wall in the direction of the oxygen injection port.

6A and 6B are explanatory views showing the AA cross section in FIG. 5. FIG. 6A shows a case where the refining lance is not rotated, and FIG. 6B shows a case where the refining lance is rotated.
As shown in FIG. 6 (a), when the refining lance is not rotated, the refractory on the furnace wall in the refining furnace melts preferentially from the direction of the oxygen injection port, and oxygen injection is performed as in the present embodiment. If the number of mouths is six, melting damage proceeds preferentially from these six directions. Lance with a large oxygen flow rate (2.5 to 5.0 Nm ³ / min · t), 3 to 6 concentric oxygen injection ports installed, and an oxygen injection port tilt angle of 10 to 20 ° As described with reference to FIG. 1, the furnace wall melting inclination angle is in the range of 12 ° to 48 °.

  On the other hand, when the smelting lance is rotated by the angle θ shown in the equation (1), the local erosion site facing the oxygen injection port and the direction of the oxygen injection port are shifted from each other. The melting damage of the wall refractory is made uniform as shown in FIG.

{M × (360 ° / n) + 10 ° <θ <(m + 1) × (360 ° / n) −10 °} (1)
m: Arbitrary integer n: Number of oxygen injection ports (including non-uniform intervals) provided at an angle α of 10 ° or more from the center axis of the lance at the tip of the lance, and an integer of 3-6. Is rotated more than the actual smelting furnace furnace wall erosion angle in the direction of the oxygen injection port and completely removed from the local erosion site and the direction of the oxygen injection port, or the local erosion site before the rotation and the direction of the oxygen injection port after the rotation. Is preferable because the melting loss of the furnace wall refractory in the refining furnace becomes more uniform.

  The refining lance may be rotated during blowing or during non-steel making. However, it is desirable to rotate during non-steel making because the requirement for the sealing performance of the rotary joint portion is low, and relatively simple equipment is sufficient.

In addition, the rotation frequency of the lance is 3 to 6 concentrically, as described above, with a large oxygen flow rate (2.5 to 5.0 Nm ³ / min · t) and the number of oxygen injection ports installed in the refining nozzle. When a lance having an oxygen injection port tilt angle of 10 to 20 ° is used, the upper limit is 150 heat. If the lance rotation angle is the same and the heat exceeds 150 heat, the melting loss of the furnace wall in the direction of the oxygen injection port becomes large, and it may be difficult to realize uniform melting damage of the furnace wall even if it is rotated thereafter. . In addition, since the life of the lance is currently about 400 heat, when rotating over 150 heat, it is only rotated once or twice before the lance life, and it is difficult to enjoy the benefits of the method according to the present invention. . On the other hand, the lower limit of the rotation frequency is not particularly limited. Although rotating at a predetermined angle every time is ideal from the viewpoint of uniform melt damage, in reality, a predetermined time is required for rotation. For this reason, if it is rotated every time, there is a concern that the productivity is lowered due to the rotation work time.

  Further, dephosphorization, desulfurization, and other adjustments of the content of elements such as Si and Mn may be performed based on a commonly performed method before or after the blowing process described so far.

In order to confirm the effect of the present invention, the following tests were conducted to evaluate the state of smelting furnace furnace wall erosion.
1. Example 1
(1) Test conditions The molten iron component was [C]: 2.8 to 4.9% by mass, [Si]: 0.50% by mass or less, [P]: 0.150% by mass or less, [Mn]. : About 290 t of hot metal having a charging temperature of 1250 to 1450 ° C. of 0.35% by mass or less is poured into an upper bottom blowing converter and blown to obtain a carbon concentration of 0.03 to 0.08. A mass% molten steel was obtained.

The refining lance according to the present invention was refined under the conditions of a pre-lance pressure of 7.0 kg / cm ² and an oxygen flow rate of 2.9 Nm ³ / min · t. At that time, the distance between the lance and the molten metal surface is defined by the following formulas (4) to (6), which is a value L / L0 obtained by dividing the penetration depth L of the oxygen jet into the steel bath by the steel bath depth L0. Was set in a range of 0.05 to 0.20. When the embodiment of the present invention is applied, the distance between the lance and the molten metal surface is 3.2 to 3.4 m.

In Example 1 of the present invention, a refining lance having six oxygen injection ports concentrically with an oxygen injection port tilt angle of 15 ° except for the injection port in the central axis direction has an average oxygen flow rate of 0.1. 47 Nm ³ / min · t was blown. Further, the refining lance was rotated in the same direction (3 times) by 12 ° at intervals of 130 to 150 heat during continuous use of the same lance.

  Invention Example 2 was blown at the same average oxygen flow rate using the same refining lance as that of Invention Example 1. In addition, since the calculated value of the furnace wall melting inclination angle using the above formula (2) is 16.5 °, the same 17 ° which satisfies the requirement of the above formula (2) at intervals of 130 to 150 heats. Rotated in direction (3 times).

In addition, as Comparative Examples 1 and 2, operation was performed under the following conditions.
Comparative Example 1 was blown at the same average oxygen flow rate using the same refining lance as that of Invention Example 1 having no rotating function.

  Comparative Example 2 was blown at the same average oxygen flow rate using the same refining lance as that of Invention Example 1. The refining lance was rotated in the same direction (3 times) by 8 ° at intervals of 130 to 150 heat.

(2) Evaluation results For each of the invention examples and comparative examples, the melt damage state of the furnace wall was measured at the stage where the converter was used for 1000 heats or more, and the progress of the melt damage at the site where the progress of the melt damage was the greatest. The implementation effect was confirmed by comparing the speed (mm / heat).

As a result, it was 0.23 in Invention Example 1, 0.20 in Invention Example 2, 0.35 in Comparative Example 1, and 0.30 in Comparative Example 2, confirming the effects of the Example of the present invention.
Further, for each example, the blowing conditions including the average oxygen flow rate and the oxygen injection nozzle tilt angle, the rotation interval, and the rotation angle were kept the same until the furnace wall remaining thickness of the portion where the most erosion progressed was 100 mm. The number of heats at this time was compared as the life of the furnace. As a result, in Invention Example 1, the furnace wall of the smelting furnace can be melted uniformly, and the remaining thickness of the furnace wall refractory is large. Therefore, it is possible to extend the life of the furnace, and the furnace life is 3050 times. . Further, in Invention Example 2, the furnace wall melted more uniformly, the progress of the melting damage was slow, and the life of the furnace was prolonged as compared with Invention Example 1, resulting in 3550 times. On the other hand, in the comparative example 1, since the lance for refining cannot be rotated, the progress of the furnace wall refractory erosion in the direction of the oxygen injection port is rapid, resulting in a short life of the furnace, which is 2030 times. In Comparative Example 2, the refining lance was operated by rotating it at a temperature less than the furnace wall melting angle through one furnace. In this case, the progress of the furnace wall refractory erosion in the direction of the oxygen injection port is slower than that in Comparative Example 1, but no significant difference is observed. The lifetime was short, 2370 times.

2. Example 2
Blowing under the same conditions as in Example 1 except that the oxygen injection port excluding the central axis injection port uses three lances and the average oxygen flow rate per hole is 0.95 Nm ³ / min · t. Went. In this case, since the calculated value of the furnace wall melting inclination angle based on the above formula (2) is 31.6 °, in Example 3 of the present invention, the rotation angle at intervals of 130 to 150 heat is 14 ° in the same direction. In Example 4 of the present invention, the angle was 32 °, in Comparative Example 3 was 0 °, and in Comparative Example 4 was 8 °.

  In this case, the maximum erosion rate (mm / heat) at the time of 1000 heats is 0.34 in Invention Example 3, 0.27 in Invention Example 4, and 0.4 in Comparative Example 3, respectively. In Comparative Example 4, it was 0.38.

  From this result, even when the average oxygen flow rate per hole is large, it is possible to reduce the amount of local erosion by rotating the lance approximately 10 ° or more, and the angle can be determined based on the above equation (2). It was confirmed that the amount of erosion loss can be greatly reduced if set.

It is a graph which shows the relationship between the acid feed rate for every lance type | mold, and a furnace wall melting angle. It is sectional drawing which shows notionally the cross section of a smelting furnace containing the largest erosion site | part. It is a typical fragmentary sectional view of the tip of a lance for explaining the angle of inclination of a gas injection mouth. It is explanatory drawing which shows the rotary lance structure for refining of this Embodiment, FIG. 4 (a) is a general view, FIG.4 (b) is an example of the shape of the nozzle for refining attached to the rotation lance tip for refining. FIG. It is sectional drawing which shows notionally the blowing condition using a rotation lance. 6A and 6B are explanatory views showing a cross section AA in FIG. 5, in which FIG. 5A shows a case where the refining lance is not rotated, and FIG. 5B shows a case where the refining lance is rotated.

Explanation of symbols

1: Rotating joint 2: Oxygen supply pipe 3: Inner cylinder 4: Cooling water supply pipe 4
5: Intermediate cylinder 6: Cooling water drain pipe 7: Outer cylinder 8: Lance lifting cart 9: Lance deposit part 10: Upper part of lance deposit part 11: Lower part of lance deposit part

Claims (3)

A method for producing molten steel in which refining is performed while supplying oxygen to a hot metal in a converter using a top blowing lance at a flow rate of 2.5 to 5.0 Nm ³ / min · t,
The lance has 3 to 6 oxygen injection ports at the tip of which the central axis of the lance and the central axis of the oxygen injection port form an angle of 10 ° to 20 °, and is rotatable about the lance central axis. Equipped with a mechanism
The continuous use of the lance comprises a blowing step of rotating the lance in use within the range of θ defined by the following formula (1) within 150 heats,
A method for producing molten steel using a converter.
{M × (360 ° / n) + 10 ° <θ <(m + 1) × (360 ° / n) −10 °} (1)
m: Arbitrary integer n: Number of oxygen injection ports provided at the tip of the lance at an angle of 10 ° or more from the center of the lance, and an integer of 3 to 6 A method for producing molten steel in which refining is performed while supplying oxygen to a hot metal in a converter using a top blowing lance at a flow rate of 2.5 to 5.0 Nm ³ / min · t,
The lance has 3 to 6 oxygen injection ports at the tip of which the central axis of the lance and the central axis of the oxygen injection port form an angle of 10 ° to 20 °, and is rotatable about the lance central axis. Equipped with a mechanism
The continuous use of the lance comprises a blowing step of rotating the lance during use within the range of θ defined by the following formula (2) within 150 heat,
A method for producing molten steel using a converter.
{M × (360 / n) + ξ} ° <θ <{(m + 1) × (360 / n) −ξ} ° (2)
ξ = 0.520xα + 31.73xV + k
m: Arbitrary integer n: Number of oxygen injection ports provided at the tip of the lance at an angle of 10 ° or more from the vertical axis, an integer of 3 to 6 α: The central axis of the lance and the central axis of the oxygen injection port Average value of angle (°) formed by V V: Average value of oxygen ejection speed per nozzle (Nm ³ / min · t) k: -6.244 (constant) A method for producing molten steel in which refining is performed while supplying oxygen to a hot metal in a converter using a top blowing lance at a flow rate of 2.5 to 5.0 Nm ³ / min · t,
The lance has 3 to 6 oxygen injection ports at the tip of which the central axis of the lance and the central axis of the oxygen injection port form an angle of 10 ° to 20 °, and is rotatable about the lance central axis. Equipped with a mechanism
Within 150 heats of continuous use of the lance, the minimum remaining brick thickness X1 with the largest remaining brick thickness X1 in the cross section including the maximum damaged portion of the converter in use and the locally damaged brick in the direction of the lance oxygen injection port Measure the angle β in a range where the difference from the remaining thickness X2 is 25 mm or more,
Characterized by comprising a blowing step of rotating the lance in use within the range of θ defined by the following formula (3):
A method for producing molten steel using a converter.
{M × (360 / n) + β} ° <θ <{(m + 1) × (360 / n) −β} ° (3)
m: Arbitrary integer n: Number of oxygen injection holes provided at an angle of 10 ° or more from the vertical axis at the tip of the lance, and an integer of 3-6

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