JP4003133B2 - Apparatus and method for charging additive into molten steel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to an additive device for adding molten steel to a molten steel by adding and melting a granular additive containing a free-cutting element in the molten steel in a ladle, and a method for charging the additive. Additive feeding device for molten steel to produce free-cutting steel by adding granular additives such as lead (Pb) particles temporarily stored in the hopper to the molten steel in the ladle through a rotary valve And a method for charging the additive.
[0002]
[Prior art]
For the purpose of improving the machinability of steel materials, free-cutting steel to which elements (free-cutting elements) such as sulfur (S), calcium (Ca), lead (Pb), bismuth (Bi) are added is widely used. Among these free-cutting elements, in particular, Pb and Bi are uniformly distributed in the base material, so that the chip crushability is improved and the influence on the base material strength is small. Therefore, steel materials to which Pb and Bi are added are widely used. It is used for
[0003]
Free-cutting elements are introduced into molten steel using additives made of or containing free-cutting elements. As a method of adding and adding such additives to steel materials, For example, the CAS method (Composition Adjusting Process by Sealed Argon Bubbling) is used. FIG. 3 is a schematic diagram showing an outline of a charging apparatus for charging Pb grains as an additive by the CAS method. As shown in the figure, the charging device is for storing Pb grains, and is provided with a Pb hopper 1 having a gate 2 that can be opened and closed at the bottom thereof, and disposed below the Pb hopper 1. Weighing hopper 3 for temporarily storing Pb particles 24 supplied from, an open / close valve 51 disposed at the bottom of the weighing hopper 3, and an air cylinder 50 as a power source for operating the open / close valve 51. A turning chute 15 disposed on the discharge side of the on-off valve 51 and configured to be rotatable about the center line 23 in the direction of the arrow b, for example, and a dip tube 16 connected to the tip of the turning chute 15 With.
[0004]
Then, the Pb grains 24 are supplied from the Pb hopper 1 to the weighing hopper 3 through the gate 2, and then are put into the molten steel through the opening / closing valve 51, the turning chute 15, and the dip pipe 16 at the bottom of the Pb hopper 3. At this time, by repeatedly opening and closing the on-off valve 51 disposed at the bottom of the weighing hopper 3, the charging unit is charged at a predetermined amount per unit time (hereinafter referred to as charging rate) and the tip of the dip tube 16 is molten steel. The slag 22 floating on the surface of the molten steel 19 is cut by immersing it into the molten steel 19 so that the Pb grains are directly charged into the bare bath exposed. Further, during the charging operation, the turning chute 15 is rotated, and Ar gas is blown from the porous plug 18 provided at the bottom of the ladle 17 and the molten steel 19 is stirred by the bubbles 20 so that the concentration of the charged Pb is uniform. It is intended to be
[0005]
According to such a configuration, Pb grains can be introduced with simple equipment, and thus there is an advantage that lead free cutting steel can be manufactured at a low manufacturing cost. However, since Pb has a large specific gravity and low solubility in molten steel, Pb remaining without melting and diffusing in the molten steel settles and aggregates to form large Pb grains. It is mixed in the lump and becomes a defective product. In order to prevent this, the molten steel in the vicinity of the bottom of the ladle 17 needs to be extracted from the extraction hole 21 after the addition, and the yield decreases accordingly.
[0006]
As a result of researches aimed at improving the yield of lead-free-cutting steel manufactured by a method in which inexpensive Pb grains are added as an additive, the present inventors have used Pb grains of a certain size as an additive. Even if it exists, it was discovered that the yield of Pb free-cutting steel can be improved by keeping the charging speed of Pb grains low and constant. However, in the configuration in which the air cylinder and the open / close gate described above are combined, the Pb input speed is adjusted by the open / close cycle of the open / close gate, but it is difficult to make fine adjustments to maintain the speed at a low speed. Variation will occur. Further, in the configuration using the open / close gate, there is a problem that the Pb grains are crushed by the gate and combined to form huge Pb grains and put into the molten steel.
[0007]
As a method for improving the yield without increasing the production cost of the lead free cutting steel, for example, commercially available granules of suboxide Pb having a particle size of 1 to 5 μm and a particle size of 0.5 to 5.0 mm are used. As the additive, Ar gas was blown from a porous plug provided at the bottom of the ladle containing the molten steel, and the molten metal surface slag was pushed away by the Ar gas bubbles and appeared in the bare water A method has been proposed in which a mixed powder prepared by mixing calcium carbonate in a range of 2 to 8% by weight with the granular suboxide Pb stored in a Pb hopper is introduced from a Pb chute by a natural fall method (Patent Document 1). reference).
[0008]
According to this method, by mixing calcium carbonate with granular sub-oxide Pb, uniform dissolution of Pb in molten steel can be promoted, and the yield can be improved. Since the Pb free-cutting steel can be manufactured using the simple charging equipment as it is, an increase in manufacturing cost can be suppressed. However, in the natural fall method, it is difficult to make the Pb charging speed constant, and it is difficult to stabilize the yield. Moreover, there is a concern that calcium carbonate may adversely affect the base material when the content is increased.
[0009]
On the other hand, methods that do not use granular Pb as an additive include a wire feeder method and a powder injection method. The wire feeder method is a method in which Pb is charged by charging and adding a wire filled with Pb powder in a sheath tube into molten steel at a predetermined speed. In addition, the powder injection method is a method in which Pb is introduced and added to molten steel by blowing a mixed powder obtained by mixing CaO as a carrier into PbO powder into the molten steel with a carrier gas (for example, a wire feeder method or a powder injection method). For details, see Non-Patent Document 1.) However, although the method described in Non-Patent Document 1 can improve the yield, the manufacturing cost is significantly increased because an expensive Pb powder or PbO powder is used as compared with the above method and configuration.
[0010]
For this reason, there has been a demand for an apparatus for adding an additive to molten steel that can uniformly increase the molten steel and stably improve the yield while suppressing an increase in manufacturing cost of free-cutting steel and the like.
[0011]
[Patent Document 1]
JP 2000-178632 A
[Non-Patent Document 1]
Hiroyuki Sasaoka Iron and Steel Technology Flow 2 Ladle Refining Method Jinjinkan
[0012]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to use inexpensive Pb grains as an additive for free-cutting elements, particularly to molten steel, to obtain free-cutting steel with a uniform composition and at the same time without increasing the production cost. It is an object of the present invention to provide an addition device and an introduction method for an additive composed of Pb grains that can be improved and stabilized.
[0013]
[Means for Solving the Problems]
In order to solve such a problem, the invention according to claim 1 is an apparatus for adding an additive to be introduced into the molten steel in the ladle, and includes an element having a low solubility in the molten steel and a higher specific gravity than the molten steel. A hopper in which the granular additive is stored, a rotary valve that sends out the additive temporarily stored in the hopper, and a path of the additive that is disposed below the rotary valve and is sent out from the rotary valve. A switchable butterfly valve, wherein the gap between the tip of the rotor blade of the rotary valve and the inner surface of the casing housing the rotor is 2 to 10 times the particle size of the additive. is there.
[0014]
According to such a configuration, for example, a granular additive containing an element having a low solubility in molten steel such as Pb and a high specific gravity as a free-cutting element is temporarily stored in the weighing hopper, and the rotor of the rotary valve When the rotational speed is adjusted and the butterfly valve is opened, the granular additive is charged into the molten steel in the ladle while the charging speed is kept low and constant. Since the gap between the tip of the rotor blade of the rotary valve and the inner surface of the casing is about 2 to 10 times the particle size of the additive, prevent the additive from inadvertently flowing out from this gap. The addition of the additive at a constant charging speed is achieved, and the additive is prevented from being inadvertently caught in the inner surfaces of the rotor and the casing and generating enormous additive particles.
[0015]
In this case, as described in claim 2, if the additive is Pb, Bi or a compound thereof, the homogeneity as free-cutting steel is good, and a commercially available inexpensive additive is used as it is. Therefore, the manufacturing cost can be reduced.
[0016]
According to a third aspect of the present invention, the butterfly valve includes a valve shaft installed in a direction perpendicular to the additive path therein, and is integrally fixed to the valve shaft so as to be centered on an axis of the valve shaft. A rotatable valve body, the valve body having a portion that opens downward by rotating about the valve shaft, and the path of the additive from the rotary valve to the butterfly valve is substantially vertical. A part of the cross section of the pipe line is closed above the one side including the part where the valve body of the butterfly valve does not open downward. When the closing member is disposed, and the upper surface of the closing member is formed with an inclined surface that descends toward one side that is not closed, the butterfly valve is sent from the rotary valve in a closed state, Or the rotary valve low The additive that has flowed out of the gap between the tip of the blade and the inner surface of the casing can be biased and deposited on one side that rotates downward of the valve body of the butterfly valve, so that the additive is deposited on the valve body. Even when it is deposited, the valve element can be operated with a small force.
[0017]
Furthermore, the invention described in claim 4 is a method for charging an additive to molten steel in a ladle, wherein the molten steel in the ladle is a granular additive containing an element having a low solubility in the molten steel and a higher specific gravity than the molten steel The gap formed between the tip of the rotor blade and the inner surface of the casing housing the rotor is 2 to 10 times the particle size of the additive. The rotary valve rotor is rotated and sent out, and the butterfly valve provided below the rotary valve is opened and put into molten steel in the ladle.
[0018]
Although the object of the present invention can be achieved, the charging rate of the additive can be reduced when the additive is charged by rotating the rotary valve. If the swirl chute is rotated when the additive is added to the molten steel and the molten steel is stirred by blowing an inert gas, even an additive having low solubility in the molten steel can be uniformly dissolved. In addition, since the additive drops and accumulates biased to one side that opens below the butterfly valve, it can be opened with a small force when the butterfly valve is opened, and the additive can be introduced into the stable molten steel. It will be.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. As a result of studying the application of a rotary valve as a configuration in which inexpensive Pb particles are used as an additive and the charging speed is kept low and constant, the inventors of the present invention have studied the tip of the rotor blade and the casing of the rotary valve. Stable improvement in yield at low cost by optimizing according to the Pb particle size using the gap with the inner surface (hereinafter referred to as the casing gap) and adding a structure to prevent Pb particle leakage The charging device and the charging method are invented. In addition, the same code | symbol is attached | subjected and used about the same part as the conventional structure.
[0020]
FIG. 1 is a schematic diagram showing a configuration of an additive charging apparatus composed of Pb grains according to an embodiment of the present invention. FIG. 1 is a schematic diagram, and the dimensions of each part do not indicate the ratio of actual dimensions. As shown in FIG. 1, the additive charging apparatus according to the present embodiment is for storing Pb grains 24 and includes a Pb hopper 1 having an open / close gate 2 at the bottom, and a lower part of the Pb hopper 1. The weighing hopper 3 that is disposed and temporarily stores the Pb particles 24 supplied from the Pb hopper 1, and the rotary valve for sending out the Pb particles 24 temporarily stored in the weighing hopper 3 at a predetermined charging speed. 8, a butterfly valve 11 connected to the discharge pipe 7 side of the rotary valve 8 and intermittently passing the path of the Pb grains 24, and a path for guiding the Pb grains 24 passing through the butterfly valve 11 to the dip pipe 16, The upper end of the swirl chute 15 is disposed on the lower end side of the butterfly valve 11 and is configured to be rotatable so that the lower end of the butterfly moves. Provided. Further, a closing member 10 that closes a part of the path is provided in the pipe line 9 between the rotary valve 8 and the butterfly valve 11.
[0021]
When describing each part in detail, the Pb hopper 1 is a container for storing a large amount of Pb particles 24 as an additive, and has a discharge port at the bottom, and an open / close gate 2 is provided at the discharge port. And is normally kept closed. The bottom surface of the Pb hopper 1 is inclined toward the discharge port (opening / closing gate 2), and the Pb particles 24 stored in the Pb hopper 1 are discharged through the discharge port (opening / closing gate 2), and the weighing hopper 3 It is comprised so that the Pb grain 24 can be supplied to. The structure of the open / close gate 2 is not limited as long as the opening / closing of the discharge port can be switched, and various gates such as a slide type and a butterfly type can be used.
[0022]
The weighing hopper 3 is a container for receiving and temporarily storing the Pb particles 24 from the Pb hopper 1 in order to weigh the Pb particles 24, and a Pb particle discharge port is formed at the bottom thereof. An inclined surface is formed toward the discharge port so that the Pb particles are discharged from the discharge port. A rotary valve 8 is connected to the discharge port so that the Pb particles in the weighing hopper 3 are sent out. It is desirable that the weighing hopper 3 has a capacity sufficient to store an amount of Pb grains to be charged by at least one charging operation.
[0023]
The rotary valve 8 disposed at the discharge port of the weighing hopper 3 basically has the same structure as a rotary valve that is generally used for conveying powdery and granular materials. Specifically, the rotor 6 has a plurality of blades and rotates so as to scrape out the Pb particles, and the casing 4 that houses the rotor 6 so as to surround the rotor 6, and extends from the casing 4, Pb An introduction pipe 5 for introducing the grains 24 into the rotor 6 and a discharge pipe 7 for discharging the Pb grains sent out from the rotor 6 are provided. The introduction pipe 5 of the rotary valve 8 is connected to the discharge port of the weighing hopper 3, and the discharge pipe 7 is connected to the pipe line 9 on the butterfly valve 11 side.
[0024]
The gap between the casings of the rotary valve 8 is preferably configured to be 2 to 10 times the particle size of the Pb particles as the additive.
[0025]
That is, since Pb is an extremely soft material, when the gap between the casings is small, when the rotor 6 rotates, the Pb grains are caught in the gap between the casings, and a plurality of Pb grains are combined to form huge Pb grains. May generate. When such huge Pb grains are put into the molten steel, it settles at a high speed and is difficult to melt and diffuse, so that it accumulates at the bottom of the ladle 17 and causes a decrease in yield and variation. . Further, the biting Pb may cause clogging and cause malfunction of the rotary valve 8.
[0026]
On the other hand, when the gap between the casings is large, when temporarily stored in the weighing hopper 3, the Pb particles 24 flow out of the gap between the casings to cause leakage of the Pb particles, and as a result, the charging speed of the Pb particles is reduced. In addition, it is difficult to maintain a constant value, which also causes a decrease in yield and variation.
[0027]
When applying the rotary valve, the inventors of the present invention desirably have a casing gap of at least twice the particle size of the Pb particles in order to prevent the formation of huge Pb particles due to the bonding of the Pb particles. In order to prevent the Pb particles from flowing out of the gaps in the casing, it has been found that it is desirable that the particle size of the Pb particles be 10 times or less, and thus the gaps in the casing are reduced to the particle size of the additive. Of 2 to 10 times.
[0028]
A pipe line 9 erected substantially vertically is connected to the lower end of the discharge pipe 7 of the rotary valve 8, and a butterfly 11 valve is disposed at the lower end of the pipe line 9. According to such a configuration, the Pb particles sent out from the rotary valve 8 are sent to the butterfly valve 11 through the pipe line 9 by natural fall.
[0029]
This butterfly valve 11 is for switching the opening and closing of the pipeline 14, and can apply a butterfly valve having a general structure. The outline of the structure will be described. The valve rod 13 is installed in the pipeline 14 at a right angle to the direction of the pipeline, and is rotatable about the axis thereof. And a plate-like valve body 12 that rotates in the pipe line 14 as it rotates, and the valve body 12 is rotated by a power source (not shown) so that the opening and closing of the pipe line 14 can be switched. When the valve body 12 is in a horizontal state in a vertically installed pipe line, the pipe line 14 is closed, one side of the valve body 12 is directed upward with the valve rod 13 as the center, and the other side is downward. The pipe 14 is opened by rotating in the direction of the arrow a toward The butterfly valve 11 is maintained in a state in which the pipe line 14 is closed when the Pb particles are not charged.
[0030]
With this configuration, when the Pb particles 24 in the Pb hopper 1 are supplied to the weighing hopper 3, the butterfly valve 11 prevents the Pb particles from flowing out of the casing. Therefore, the Pb particles are prevented from inadvertently leaking outside through the swivel chute 15 and the dip tube 16.
[0031]
Moreover, a closing member 10 that closes a part of the cross section in the pipe line is disposed in the pipe line 9 that is provided substantially vertically between the rotary valve 8 and the butterfly valve 11. When the valve body 12 of the butterfly valve 11 rotates in the direction of the arrow a by rotating the valve body 12 of the butterfly valve 11 around the valve shaft 13 in the direction of arrow a toward the lower side, the other side is opened. It arrange | positions so that the one side opened toward the upper side may be obstruct | occluded. With such a configuration, the Pb particles dropped from the rotary valve 8 are collected on the non-blocked side of the pipe line 9 by the closing member 10 and opened to the lower side of the valve body 12 of the butterfly valve 11. Will fall to the side. For this reason, when the butterfly valve 11 is closed, the Pb particles are accumulated in a biased direction toward the lower side of the valve body 12 and the Pb particles are deposited on the valve body 12. The butterfly valve 11 can be opened by rotating the valve body 12 with a small force compared with the case where the particles are uniformly deposited, and the rotational power source of the butterfly valve 11 can be reduced in size.
[0032]
The closing member 10 is also configured so that the upper surface side, that is, the surface on the rotary valve 8 side is an inclined surface, and the Pb particles falling from the rotary valve 8 flow down on the inclined surface and do not accumulate. It is desirable.
[0033]
In addition, the structure which arrange | positions the said obstruction | occlusion member 10 as a structure which accumulates the Pb grain 24 in the one side which the valve body 12 of the butterfly valve 11 opens toward the downward direction, and reduces force required for operation | movement of a butterfly valve. In addition, a configuration in which a small-diameter pipe is partially incorporated, and the center of the small-diameter pipe is arranged so as to be biased to one side that opens to the lower side of the valve body 12 of the butterfly valve 11, or in the middle of the pipe It is possible to apply a configuration in which a funnel-shaped member is provided on the upper side of the butterfly valve 11 so that the discharge port at the lower portion of the funnel is located above one side that opens to the lower side of the valve body 12 of the butterfly valve 11. The point is that the Pb particles fed from the rotary valve 8 can be deposited on the valve body 12 of the butterfly valve 11 so that the center of gravity is located at least on the side opening toward the lower side. Structure for disposing the blocking member Not limited to the structure using a thin pipe having or diameter.
[0034]
The dosing device can be downsized by integrally configuring the weighing hopper 3, the rotary valve 8, the butterfly valve 11, and the conduit 9 between the rotary valve 8 and the butterfly valve 11.
[0035]
The swivel chute 15 is a path for sending the Pb grains that have passed through the butterfly valve 11 to the dip tube 16, and the upper end side of the swivel chute 15 is disposed so that the opening extends in a funnel shape and is positioned on the lower end side of the butterfly valve 11. The Pb grains that have passed through the butterfly valve 11 are received without leaking. Further, the lower end side is connected to the upper end of the dip tube 16, and the path between the upper end and the lower end is disposed inclined from the upper end side toward the lower end side. For this reason, the Pb particles that have passed through the butterfly valve 11 flow down the inclined surface of the turning chute 15 and are guided to the dip tube 15. And the upper end which receives Pb grain which passed the butterfly valve 11 is made into the rotation center (center line 23), and a lower end side is comprised so that it may carry out the circumferential motion (movement rotating in the direction of arrow b) within a horizontal surface. The inclined portion of the turning chute 15 may be a pipe line or a path having an open upper surface.
[0036]
The upper end of the dip tube 16 is connected to the lower end of the turning chute 15, and the lower end is immersed in the molten steel when Pb grains are introduced. Then, along with the circumferential motion of the turning chute 15, the circumferential motion is performed.
[0037]
The operation procedure for introducing Pb grains into molten steel using the Pb grain introduction apparatus having such a configuration is as follows.
[0038]
First, in order to weigh the Pb particles 24, the open / close gate 2 provided at the bottom of the Pb hopper is opened to drop the Pb particles 24. The particle size of the Pb particles is preferably in the range of 0.05 to 3.0 mm, and more preferably 0.7 mm or less.
[0039]
The dropped Pb grains are temporarily stored above the rotor 6 of the rotary valve 8 and in the weighing hopper 3. At this time, a part of the temporarily stored Pb particles may leak from the gap in the casing of the rotary valve 8 and flow out to the discharge pipe 7 side. Since the amount is less than double, the amount of Pb particles flowing out is suppressed to be small, and a large amount of Pb particles is prevented from being deposited on the valve body 12 of the butterfly valve 11. Therefore, when the butterfly valve 11 is opened in the charging operation, it is possible to prevent a large amount of Pb particles from being charged at a time and make the charging speed non-uniform, thereby improving the yield. Further, since the butterfly valve 11 connected to the discharge pipe 7 side is closed before the closing operation, it does not leak to the outside through the turning chute 15 and the dip pipe 16.
[0040]
When the rotor 6 of the rotary valve 8 is rotated at a predetermined speed and the butterfly valve 11 is opened, the Pb particles above the rotor of the rotary valve 8 are moved to the discharge pipe 7 side at a charging speed corresponding to the rotational speed of the rotor 6. It is fed into the molten steel through the released butterfly valve 11, the turning chute 15 and the dip pipe 16. In addition, the Pb particles are prevented from flowing out of the gap between the casings even during the charging operation, so that the charging speed is not uniform, and in particular, the charging speed is prevented from increasing due to the addition of the outflow from the casing gap. Thus, the yield can be improved and uniformized. At this time, as in the conventional example, the Pb grains are directly poured into the bare bath exposed by immersing the tip of the dip tube 16 in molten steel, and the turning chute is rotated and the ladle of the ladle is rotated during the Pb grain charging operation. An inert gas such as Ar gas is blown from the porous plug 18 provided at the bottom, and the molten steel is stirred by the bubbles 20 so that Pb is uniformly diffused and melted in the molten steel.
[0041]
【Example】
Finally, an experiment carried out to confirm the effect of the additive charging apparatus according to the present invention will be described. The experiment is to produce 0.08 wt% Pb lead free cutting steel in S45C. The Pb grains to be charged were those having a particle size in the range of 0.3 to 0.7 mm, and were charged at a charging speed of 25 kg per minute. The gap between the casings is set to about 2 mm.
[0042]
FIG. 2 is a graph showing the frequency rate (%) of the experimental results. This frequency rate (%) is the percentage of the frequency (number of times) of the Pb yield appearing in each section among the number of times the experiment was performed. It is shown. As shown in the figure, the Pb yield is distributed between 60% and 95% when the conventional charging device is used, whereas the Pb yield is 70% to 95% according to the device of the present invention. It is confirmed that the variation in the Pb yield is small. In addition, according to the conventional charging device, the Pb yield appears most frequently in the 75 to 80% section, whereas when the charging device according to the present invention is used, the Pb yield appears most frequently in the 80 to 85% section. The yield is improved as a whole.
[0043]
As described above, according to the charging device according to the present invention, it is possible to prevent the variation in the Pb yield as compared with the conventional charging device, and to improve it.
[0044]
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and examples, and various modifications can be made without departing from the spirit of the present invention. For example, the additive to be applied is not limited to the Pb grains, and can be applied to the addition of various other known additives. There are various types of rotary valves, but any type such as open type, pocket type, and helical type may be used as long as the gap of the casing is configured within a predetermined range, and the type is not limited. Absent. In this embodiment, an example in which an additive (free cutting element) is added / added for the purpose of producing free-cutting steel is shown. Is also possible.
[0045]
【The invention's effect】
According to the first aspect of the present invention, since the Pb particles in the weighing hopper are sent out by the rotation of the rotor of the rotary valve, the charging speed of the Pb particles is low and constant compared to the combination of the air cylinder and the open / close gate. In addition, the gap between the tip of the rotor blade of the rotary valve and the inner surface of the casing is optimized according to the particle size of the additive, so that the additive leaks from this gap. It is possible to prevent variation in the charging rate of the additive. Furthermore, the additive is less likely to bite into the gap between the tip of the rotor blade of the rotary valve and the inner surface of the casing to form huge additive particles, and the additive does not dissolve and the ladle is not dissolved. To prevent the yield from falling to the bottom. For this reason, the stable improvement of the yield of free-cutting steel can be aimed at.
[0046]
In addition, as described in claim 2, if Pb, Bi and a compound thereof are used as additives, for example, when producing lead free-cutting steel using Pb as a free-cutting element, commercially available inexpensive Pb grains Can be used as an additive as it is, and an increase in raw material cost can be suppressed.
[0047]
According to the third aspect of the present invention, in a state where the butterfly valve closes the route of the additive, it is fed from the rotary valve or from the gap between the tip of the rotor blade of the rotary valve and the inner surface of the casing. The additive that has flowed out is accumulated while being biased toward one side rotating downward of the valve body of the butterfly valve. For this reason, for example, even when an additive made of heavy Pb is deposited on the valve body, the butterfly valve can be opened with a small force, and the power source of the butterfly valve can be reduced in size.
[0048]
According to the invention described in claim 4, since the rotary valve is used for charging the additive stored in the weighing hopper, when the additive is charged by rotating the rotary valve when the additive is charged. In addition, the additive charging speed can be reduced. Then, when the additive is added to the molten steel, the swivel chute is rotated and the inert steel is blown to stir the molten steel. Therefore, even an additive having low solubility in the molten steel can be uniformly dissolved. Further, since the additive falls and accumulates biased to one side that opens below the butterfly valve, the butterfly valve can be opened with a small force.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the configuration of an additive charging apparatus according to an embodiment of the present invention.
FIG. 2 is a graph showing a comparison of the yield of lead free-cutting steel when using the charging device of the present invention and when using a conventional method.
FIG. 3 is a schematic diagram showing a configuration of an additive charging apparatus according to a conventional CAS method.
[Explanation of symbols]
3 Weighing hopper
6 Rotor
8 Rotary valve
11 Butterfly valve
17 Ladle
19 Molten steel
24 Pb grains

Claims (4)

A device for adding an additive to be introduced into molten steel in a ladle, and a hopper in which a granular additive containing an element having a low solubility in molten steel and a higher specific gravity than molten steel is stored, and temporarily stored in the hopper A rotary valve that sends out the added additive, and a butterfly valve that is disposed below the rotary valve and can be switched to open and close the path of the additive sent from the rotary valve. An apparatus for adding an additive to molten steel, characterized in that the gap between the tip and the inner surface of a casing housing the rotor is 2 to 10 times the particle size of the additive. The said additive is Pb, Bi, and its compound, The injection | throwing-in apparatus of the additive to molten steel of Claim 1 characterized by the above-mentioned. The butterfly valve includes therein a valve shaft that is installed in a direction perpendicular to the additive path, and a valve body that is integrally fixed to the valve shaft and is rotatable about the axis of the valve shaft. The body has a portion that opens downward by rotating about the valve shaft, and the path of the additive from the rotary valve to the butterfly valve is constituted by a pipe that is erected substantially vertically, A closing member that closes a part of the cross section of the pipe line is disposed above the one side including the part where the valve element of the butterfly valve does not open downward in the pipe line. The apparatus for feeding additive to molten steel according to claim 1 or 2, wherein the upper surface of the member is formed with an inclined surface that descends toward one side that is not closed. When a granular additive containing an element having a low specific gravity and a higher specific gravity than the molten steel is added to the molten steel in the ladle, the granular additive temporarily stored in the hopper is added to the tip of the rotor blade and the rotor. Rotate the rotor of the rotary valve whose gap formed between the inner surface of the casing and the casing is 2 to 10 times the particle size of the additive, and send out the butterfly valve provided below the rotary valve. A method for adding an additive to molten steel, characterized in that the molten steel is introduced into the ladle in a ladle.

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