WO2019203096A1

WO2019203096A1 - Top-bottom-combined blown converter-type refining vessel

Info

Publication number: WO2019203096A1
Application number: PCT/JP2019/015675
Authority: WO
Inventors: 鉄平田村; 真広坪井; 紀史浅原
Original assignee: 日本製鉄株式会社
Priority date: 2018-04-20
Filing date: 2019-04-10
Publication date: 2019-10-24
Also published as: TW202003863A; JP6874904B2; JPWO2019203096A1; CN111278996A

Abstract

A top-bottom-combined blown converter-type refining vessel characterized in that: in the shape of a throat as viewed in the direction of a furnace body central axis, the outline of the throat comprises an arc and a line segment, wherein the line segment is parallel to a trunnion axis and present on the opposite side to a tapping outlet across the trunnion axis; when a straight line connecting two intersection points at which a straight line obtained by projecting the trunnion axis at the throat overlaps the arc has a length D0 and the line segment has a length D1, the ratio D1/D0 is not less than 0.2 and not more than 0.8; and when, in the shape of a cross section perpendicular to the trunnion axis and including the furnace body central axis, the tangent at an arbitrary point on a furnace inner surface on the opposite side to the tapping outlet across the furnace body central axis and the furnace body central axis form an angle θ, the angle θ has a maximum angle of less than or equal to 70°.

Description

Top-bottom converter type refining vessel

The present invention particularly relates to an upper bottom blown converter type refining vessel suitable for intermediate slag removal.

Steel refining is performed by forming molten slag in the upper layer of the hot metal contained in the refining furnace, and moving impurities contained in the hot metal to the molten slag. The refining furnace has a furnace port at the top of the furnace, and hot metal and slag raw material are charged from the furnace port for refining. After finishing the refining, the refining furnace is tilted and only the molten steel is discharged from the outlet hole, and then the refining furnace is tilted to the opposite side and the molten slag is discharged from the furnace port.

Recently, in steel refining using a converter, a method of performing dephosphorization refining and decarburization refining separately in the same converter is widely used. In this method, first, hot metal is charged into a converter, and further, a slag raw material for dephosphorization is charged, and dephosphorization refining is performed at a low temperature that is thermodynamically advantageous for dephosphorization. And after completion | finish of dephosphorization refining, a converter is inclined to the opposite side to a steel outlet hole, and dephosphorization slag is discharged | emitted out of a furnace from a furnace port. After that, decarburization and refining is performed in the same converter while leaving the hot metal to produce molten steel at a high temperature. After decarburization and refining, the converter is tilted to discharge only the molten steel from the outlet hole, and then tilted to the opposite side and decarburized slag is discharged from the furnace port. In addition, the process of tilting the converter to the opposite side to the outlet hole after the dephosphorization is completed and discharging the dephosphorization slag out of the furnace from the furnace port is called intermediate waste. Moreover, the ratio of the weight of the slag discharged by the intermediate waste to the weight of the dephosphorization slag generated in the converter after completion of the dephosphorization refining is called an intermediate waste rate.

When the converter is tilted and the dephosphorization slag is discharged from the furnace port, the intermediate discharge rate is low, and a large amount of dephosphorization slag remains in the converter after the intermediate discharge. Phosphorus that has moved to (5) is restored to the hot metal during decarburization and the dephosphorization effect due to dephosphorization at low temperatures is reduced. Therefore, it is very important to increase the intermediate rejection rate.

For example, when the tilt angle is increased in order to improve the intermediate waste rate, dephosphorization slag is discharged more, but the molten iron is also discharged from the furnace port together with the dephosphorization slag. The dephosphorization slag discharged from the furnace port is received by a discharge pan waiting under the converter. At this time, when the hot metal is discharged together with the dephosphorization slag, the dephosphorization slag and the hot metal are stirred in the discharge pan, react with each other to generate gas, and the dephosphorization slag forms. If the amount of hot metal outflow is small, slag discharge work can be continued by putting foaming sedative into the ladle. However, if the amount of hot metal outflow is excessive, the formed dephosphorization slag overflows from the waste pan, resulting in equipment damage and deterioration of productivity associated with the damage. Also, even if the slag pan is made larger and slag overflow due to forming becomes possible, the yield of iron will decrease due to the outflow of molten iron. It is not preferable to improve it.

As described above, it is not easy to remove most of the dephosphorization slag only by the tilting operation of the converter, and the development of a method capable of improving the intermediate rejection rate is required. Therefore, Patent Document 1 discloses a technique for improving the intermediate rejection rate by providing a weir at the furnace port.

However, the method described in Patent Document 1 has a problem that it is not technically easy to construct a weir at the furnace port. Furthermore, when weirs are constructed with refractories, it is necessary to maintain the same life as the refractories that form the inside of the converter, but there is a problem in durability because the load is applied to the weirs during intermediate discharge. It will occur.

JP 2005-264210 A

In view of the above-mentioned problems, the present invention provides a top-bottom blower that is durable, has a high durability, has a high intermediate waste rate, and can reduce the amount of molten iron outflow when no intermediate weir is provided. An object is to provide a converter-type refining vessel.

The present invention is as follows.
(1) In the shape of the furnace port as viewed in the direction of the center axis of the furnace body, the outline of the furnace port is composed of an arc and a line segment, the line segment is parallel to the trunnion axis, and the steel exit hole is the trunnion D _{0 is} the length of the straight line connecting two intersecting points where the straight line projected on the furnace port and the circular arc is present on the opposite side across the axis, and the length of the line segment is D ₁ The ratio D ₁ / D ₀ is 0.2 or more and 0.8 or less,
In the shape of a cross section perpendicular to the trunnion axis and including the furnace body central axis, the lead-out hole is a tangent at an arbitrary point on the inner surface of the furnace opposite to the furnace body central axis, and the An upper bottom blown converter type refining vessel, wherein the maximum angle of the angle θ is 70 ° or less, where θ is an angle formed with the furnace body central axis.
(2) The iron shell of the throttle part of the top bottom blown converter type refining vessel is a truncated cone, and the angle θ is the maximum angle in the top bottom blown converter type refining vessel inside the iron skin of the throttle part. The top-bottom blown converter type refining vessel according to (1) above, which is constructed of a refractory material, including the points that are present.

According to the present invention, an upper bottom blown converter type refining that is durable, has a high intermediate waste rate and can reduce the outflow amount of hot metal, without providing a weir. A container can be provided.

FIG. 1A is a diagram showing an example of a refining vessel having a general circular furnace opening. FIG. 1B is a diagram showing an example of a refining vessel having a shape in which a weir is provided at the furnace port. FIG. 1C is a diagram illustrating an example of a refining vessel having a shape in which a part of the furnace port is flattened. FIG. 2A is a diagram for explaining a state in which simulated slag flows from the furnace port when the furnace port has a general circular shape. FIG. 2B is a diagram for explaining a state in which simulated slag flows from the furnace port when the weir is provided in the furnace port. FIG. 2C is a diagram for explaining a state in which simulated slag flows from the furnace port in a case where a part of the furnace port is flattened. FIG. 3A is a diagram showing the relationship between the ratio D ₁ / D ₂ and the intermediate rejection rate. FIG. 3B is a diagram showing the relationship between the ratio D ₁ / D ₂ and the furnace port cross-sectional area ratio. FIG. 4A is a view for explaining the shape of the furnace port viewed from the direction of the furnace body central axis. FIG. 4B is a view for explaining a cross section of the upper bottom blowing converter type refining vessel as seen from the direction of the trunnion axis.

In order to examine the shape of the furnace port so that the intermediate waste rate is high and the molten iron outflow amount is reduced during the intermediate waste, the present inventors have made an acrylic product of about 1/10 scale of a 300-ton converter. A water model experiment was conducted using a converter type water model test vessel. The converter type water model test vessel is prepared with three types of vessels with different shapes of the furnace mouth. Each furnace mouth has a general circular shape shown in FIG. 1A and a weir in the discharge direction shown in FIG. 1B. The installed shape and the furnace port in the discharge direction shown in FIG. 1C were made flat. In the examples shown in FIGS. 1B and 1C, the shape at the furnace port height is the same in the direction of the central axis of the furnace body, the length of the flat part of the furnace port is D ₁ , and the arc part of the furnace port is The diameter was D ₀ and the ratio D ₁ / D ₀ was both 0.5. Moreover, water was used as a model metal for simulating hot metal, and silicone oil was used as a slag for simulating molten slag.

First, 44 L of water for simulating molten iron and 10 liter of silicone oil for simulating dephosphorization slag were poured in an empty converter-type water model vessel upright at an inclination angle of 0 °. After the water and silicone oil are completely separated from each other in the vertical direction, the water is tilted in the direction of drainage at a tilt rate of 0.5 ° / sec until the water surface reaches the furnace port, and is stopped until the drainage of the silicone oil stops. did. Thereafter, the amount of discharged silicone oil was measured, and the model intermediate rejection rate was calculated. The model intermediate rejection rate was calculated by the mass of discharged silicone oil relative to the mass of silicone oil poured into the converter type water model container. As a result, the model intermediate rejection rate of the shape shown in FIG. 1A was 60%, but the model intermediate rejection rate of the shape shown in FIGS. 1B and 1C was equal to 70%.

In the shapes shown in FIGS. 1B and 1C, the furnace port in the direction of discharge is both flat, and the example of FIG. 1B is provided with a weir, whereas the example of FIG. 1C is not provided with a weir. Is different. However, the model intermediate rejection rates of the shapes shown in FIGS. 1B and 1C are both higher than the model intermediate rejection rates of the shapes shown in FIG. 1A, and there is no difference in the shapes shown in FIGS. 1B and 1C. From this, it was found that whether it is a weir contributes little to the improvement of the model intermediate rejection rate. Although the shape shown in FIG. 1C has no weir, the furnace outlet in the direction of evacuation was flat as in the shape shown in FIG. 1B, so the model intermediate evacuation rate in FIG. 1C was considered to be equivalent to that in FIG. 1B. It is done.

From the observation results of this water model experiment, the model intermediate rejection rate improved when the furnace outlet in the discharge direction was flat.The simulated slag furnace outlet in the state where the water surface reached the furnace opening and tilting stopped. It is presumed to be caused by a nearby state.

2A to 2C are diagrams for explaining the state near the furnace port at the time of intermediate evacuation in the water model experiment.
In the case of the general circular shape of the furnace port in FIG. 1A, at the end of the evacuation, as shown in FIG. 2A, the thickness of the simulated slag remaining in the furnace becomes thin, and the thickness from the lowest end of the circular furnace port decreases. Simulated slag is now discharged in a narrow flow. At that time, when observing the bath surface of the simulated slag remaining in the furnace, the flow of the simulated slag adhering to the vicinity of the furnace wall is slow in the vicinity of the furnace mouth, and the slow flow near the furnace wall should be discharged from the furnace mouth. It was observed that the tendency of the slag to be suppressed was promoted because the furnace wall became closer to the furnace opening.

On the other hand, when the simulated slag is discharged from the flat part of the furnace port, as shown in FIG. 2B and FIG. 2C, the flatness of the furnace port is maintained even when the thickness of the simulated slag remaining in the furnace is reduced. The simulated slag could be discharged from the part with a wide flow. At that time, when the bath surface of the simulated slag remaining in the furnace is observed, the flow of the simulated slag adhering to the vicinity of the furnace wall is slow in the vicinity of the furnace port, but the flow in the flat part of the furnace port is wide. The effect of the slow flow of the simulated slag near the wall was smaller than in the case of FIG. 2A, and the discharge of the simulated slag was smooth.

As a result of the water model experiment described above, the effect of the furnace opening being flatter than the effect of the weir was observed. It was found that the model intermediate rejection rate can be improved by the effect of reducing the influence of slag flow suppression by the furnace wall by flattening the furnace port even at the end of the rejection period. Accordingly, it has been found that even if the weir is not provided as in FIGS. 1B and 2B, the furnace port in the discharge direction should be flat as in the shape shown in FIGS. 1C and 2C.

Next, it was confirmed whether the same effect was expressed using a test converter. First, hot metal used for the experiment was prepared. Hot metal components include [C] = 4.5 mass%, [Si] = 0.4 mass%, [Mn] = 0.3 mass%, [P] = 0.1 mass%, [S] = 0.01 mass% To do. Then, the shape of the furnace port of the test converter was set to a flat shape with a mortar or the like without the weir as shown in FIG. 1C, and the ratio D ₁ / D ₀ was changed. went.

The experimental procedure was as follows. Hot metal having the above components was charged into a 2.0 t test converter, 17.0 kg of quick lime was added, and Ar gas was blown in at 0.4 Nm ³ / min from the bottom blowing tuyere. However, oxygen was blown in from the top blow 4-hole lance at 4.0 Nm ³ / min for 8 min to perform desiliconization and dephosphorization blowing. After that, the blowing was stopped, the test converter was tilted to the opposite side of the steel hole, and the intermediate slag was performed, and the test was conducted at 1 ° / sec until the tilt angle at which the hot metal was predicted in advance was calculated. The converter was tilted, and then the tilting was stopped, and when the slag discharge stopped, the furnace body was returned to an upright state.

The intermediate waste slag is received by the waste pan, and the waste CaO mass is calculated from the amount of slag discharged there and the CaO concentration, and the waste CaO mass / initial charge CaO mass (initial charge quick lime mass) The intermediate rejection rate was determined at x100. The result is shown in FIG. 3A.

From the results shown in FIG. 3A, it was found that the intermediate rejection rate increases as the ratio D ₁ / D ₀ is increased. In particular, when the ratio D ₁ / D ₀ is 0.2 or more, the intermediate rejection rate may be increased by 10% or more compared to a normal circular furnace port shape where the ratio D ₁ / D ₀ is 0. It could be confirmed.

However, as shown in FIG. 3B, when the ratio D ₁ / D ₀ is 0.87 or more, the furnace port cross-sectional area is 20% or more compared to the normal circular furnace port shape with the ratio D ₁ / D ₀ of 0. It gets smaller. When the cross-sectional area of the furnace port becomes small, the superficial velocity of exhaust gas at the furnace port increases during dephosphorization blowing, and spitting and slopping occur greatly. Therefore, the ratio D ₁ / D ₀ is up to about 0.8. It turned out that it is better to suppress it.

From the above experimental results, in order to increase the intermediate rejection rate, it is better to flatten the furnace port in the direction of discharge, and it is not necessary to be a weir, refractory construction, and furnace port refractory In order to ensure the durability, the present inventors have found that a shape in which the furnace port is flat without providing a weir is good.

Next, a specific shape of the upper bottom blowing converter type refining vessel of the present invention will be described with reference to FIGS. 4A and 4B. First, the shape of the furnace port viewed from the outside will be described. FIG. 4A is a view for explaining the shape of the furnace port viewed from the direction of the furnace body central axis.
In FIG. 4A, a straight line S indicates a straight line obtained by projecting a trunnion shaft, which serves as an axis for tilting the furnace body, onto the furnace port. Line segment AB is line segment corresponding to the length D ₁ shown in FIG. 1C, the tapping hole is formed on the opposite sides of the trunnion shaft. The line segment AB is parallel to the straight line S projected on the trunnion axis. That is, it is parallel to the trunnion axis. The arc C corresponds to a part of a circle having a diameter D ₀ that forms the furnace port. That is, the length of the straight line connecting the two intersections of the arc C and the straight line S corresponds to the diameter D ₀ .

The experimental results described above, the ratio D ₁ / D ₀ of the length D ₁ of the line segment AB to the length D ₀ is 0.2 to 0.8. If the ratio D ₁ / D ₀ is less than 0.2, the intermediate rejection rate is not sufficiently improved, and the effect is insufficient. On the other hand, if the ratio D ₁ / D ₀ exceeds 0.8, spitting and slopping will occur greatly during blowing.

Next, the internal shape of the top-bottom converter type refining vessel will be described. FIG. 4B is a view for explaining a cross section of the upper bottom blowing converter type refining vessel as seen from the direction of the trunnion axis. The cross section shown in FIG. 4B represents a plane that is perpendicular to the trunnion axis and includes the furnace body central axis 45.

In FIG. 4B, the throttle part 41 which is in the vicinity of the furnace port 40 and its vicinity and gradually decreases in the cross-sectional area of the container from the lower part of the container toward the furnace port 40 is constructed by a refractory material 42 such as a brick. The outside is covered with an iron skin 44. In the cross section shown in FIG. 4B, a tangent line at an arbitrary point P on the furnace inner surface on the opposite side (intermediate exhaust side) across the furnace body central axis 45 and the furnace body central axis 45 Is θ, the angle θ is always 70 ° or less at an arbitrary point P in order to ensure the durability of the refractory. That is, the maximum angle of the angle θ is set to 70 ° or less. Here, the arbitrary point P is mainly a point of the throttle portion 41 on the furnace inner surface, and at least the bottom surface is excluded. Since the refractory on the upper side gradually protrudes toward the furnace body central shaft 45 side in the throttle part 41, if the maximum angle exceeds 70 °, the durability decreases as in the case where the weir is provided. Because it will end up. Although the furnace surface is a smooth curved surface, the furnace surface was originally formed by stacking multiple refractories, and before the refining furnace was used for the first time, there was a slight gap between the refractories. However, there are cases where unevenness is formed, but such unevenness is ignored. In addition, although the lower limit of the maximum angle of the angle θ is not particularly limited, it is preferable that the maximum angle of the angle θ is substantially 20 ° or more as a range in which the inner wall of the refractory can be formed in a normal converter.

In order to obtain the converter vessel shape as described above, it is not always necessary to change the shape of the iron shell 44 significantly. The iron skin 44 of the throttle part 41 is also a truncated cone shape that is normally used, and can be realized by using a refractory 42 having a shape different from the usual one. Changing the shape of the iron skin of the smelting furnace requires a great deal of cost and work time, but the present invention can be realized at low cost mainly by changing the shape of the refractory. In the present invention, it is necessary to change the holding metal fitting for the refractory of the furnace port to a shape matching the shape of the furnace port.

Next, examples of the present invention will be described. The conditions in the examples are one condition example adopted to confirm the feasibility and effects of the present invention, and the present invention is based on this one condition example. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

First, [C] = 4.3 to 4.4 mass%, [Si] = 0.4 to 0.5 mass%, [Mn] = 0.3 to 0.4 mass%, [P] = 0.10 to 0 A hot metal containing .11 mass% and [S] = 0.010 to 0.015 mass% was prepared. Then, in a 300 t / heat top bottom blowing converter, 290 to 300 t of scrap and hot metal having the above components were charged, 2.8 to 2.9 t of quick lime was added, and oxygen gas was then supplied from the bottom blowing tuyere. while watching blowing at 40Nm ³ / min, between the top-blown 800Nm from the lance ³ / min at 4.0 ~ 5.0min, blowing on the oxygen to desiliconization, the dephosphorization blowing was carried out. After that, the converter was tilted at a tilt angle of 85 ° to 88 ° at which the molten iron appeared at a rate of 0.15 to 0.30 ° / sec to perform intermediate waste, and then returned to the original upright state and removed again. After adding 3.6 to 4.0 t of quick lime for charcoal blowing, decarburization blowing was performed by blowing up oxygen from the top blowing lance at 1200 Nm ³ / min for 11.0 to 12.0 min. .

After carrying out decarburization blowing, decarburized slag is collected and subjected to chemical analysis, and the basicity B (CaO mass) / (SiO ₂ mass) of the decarburized blown slag is determined from the analysis results. Asked. Here, the basicity B of the slag can also be obtained by the following equation (1).
B = (W _{CaO, blow1} × R / 100 + W _{CaO, blow2} ) / (W _M × [Si] / 100 / M _Si × M _{SiO 2} × R / 100) (1)
Here, W _{CaO, blow1} : amount of CaO in quicklime added by desiliconization and dephosphorization blowing, W _{CaO, blow2} : amount of CaO in quicklime added by decarburization blowing, R: Intermediate waste rate (%), W _M : Hot metal amount (t), [Si]: Si concentration in molten iron (mass%), M _Si : Atomic weight of Si (g / mol), M _SiO2 : Molecular weight of SiO ₂ ( g / mol).

In this example, it was difficult to directly measure the weight of the slag that was intermediately rejected as in the experiment in the test converter described above. It calculated | required by the following formula | equation (2).
R = 10000 × W _{CaO, blow2} / (B × W _M × [Si] / M _Si × M _SiO2 −100 × W _{CaO, blow1} ) (2)

The above operation was repeated, and the average intermediate rejection rate R of the first 10 Ch was calculated. The results are shown in Table 1. Table 1 also shows the number of charges until the intermediate rejection rate is reduced to 60% or less due to wear near the furnace port after 10 Ch. In this example, the case where the average intermediate rejection rate of the first 10 Ch was 60% or more and the number of charges until the intermediate rejection rate was less than 60% was 40 or more was regarded as a pass line.

In the inventive examples 1 to 3, the shape of the furnace port in the discharge direction is made flat without installing a weir at the furnace port, and the length of the flat part (the length of the part corresponding to the line segment AB in FIG. 4A) the D _1, the diameter of the circular arc portion of the furnace opening when the D _0, 0.3,0.6,0.8 the ratio D ₁ / D ₀ respectively, the maximum angle of the angle theta 35 °, This is an example of 40 ° and 70 °. In the inventive examples 1 to 3, the intermediate rejection rate R could be improved by 10% or more compared with the comparative example 1 having a normal circular furnace opening shape. In Comparative Example 2, a weir with a ratio D ₁ / D ₀ of 0.2 was installed, and the intermediate rejection rate was improved by 10%, but the life of the weir constructed with refractory was short and 10 charges As a result, the intermediate rejection rate decreased to 60% or less, and it could not be put into practical use by repeating the operation. In Comparative Example 3, an attempt was made to install a weir having a ratio D ₁ / D ₀ of 0.3, but construction of the refractory was difficult, and the installation of the weir was abandoned.

According to the present invention, an upper bottom blown converter type refining that is durable, has a high intermediate waste rate and can reduce the outflow amount of hot metal, without providing a weir. Containers can be provided and the industrial value is great.

Claims

In the shape of the furnace port in the direction of the center axis of the furnace body, the outline of the furnace port consists of an arc and a line segment, the line segment is parallel to the trunnion axis, and the steel outlet hole sandwiches the trunnion axis And D 0 is the length of the straight line connecting the two intersections where the straight line projecting the trunnion axis onto the furnace port and the arc overlaps, and the length of the line segment is D 1 The ratio D 1 / D 0 is 0.2 or more and 0.8 or less,
In the shape of a cross section perpendicular to the trunnion axis and including the furnace body central axis, the lead-out hole is a tangent at an arbitrary point on the inner surface of the furnace opposite to the furnace body central axis, and the An upper bottom blown converter type refining vessel, wherein the maximum angle of the angle θ is 70 ° or less, where θ is an angle formed with the furnace body central axis.
The iron skin of the throttle part of the upper bottom blown converter type refining vessel is a truncated cone, and the angle θ forms the maximum angle in the upper bottom blown converter type refining vessel inside the iron skin of the throttle part. The top bottom blown converter type refining vessel according to claim 1, which is constructed of a refractory material including points.