JP6818980B2 - Bottom pouring ingot equipment - Google Patents

Description

The present invention relates to a bottom pouring ingot making facility for casting a steel ingot in which the entrainment of an in-mold agent is prevented and the occurrence of inclusion defects is suppressed.

Conventionally, there are two types of ingots for producing steel ingots using a mold, "bottom-pouring ingots" and "top-pouring ingots", depending on the difference in the injection direction of molten steel. "Top pouring ingot" is to pour the molten steel of the ladle directly into the mold from the top of the mold. On the other hand, in the "bottom pouring ingot", the molten steel of the ladle is passed through a runner formed in the horizontal direction and an injection pipe or a pouring pipe provided vertically along the vertical direction. Then, it is poured into the mold from the injection port provided at the bottom of the mold, that is, from the lower side of the ladle.

By the way, in the above-mentioned "bottom-pouring ingot", a powder-like in-mold agent is usually used in a mold for the purpose of preventing oxidation of molten steel and improving the surface of slabs. At this time, the molten steel ejected upward from the injection port at the bottom of the mold generates an injection flow in the mold. In particular, in the initial stage of casting, the in-mold agent added to the mold by this injection flow may be caught in the molten steel and trapped in the ingot. When the in-mold agent is involved in such molten steel, the in-mold agent trapped in the solidified shell on the side surface of the ingot may cause inclusion defects.

In order to prevent such entrainment of the in-mold agent, the conventional under-injection mass-forming method is provided with means as shown in Patent Documents 1 to 3 below.
For example, Patent Document 1 describes an invention relating to a pouring pipe used in a pouring method of a bottom pouring method in which molten metal is discharged into a mold from a discharge port provided at the bottom of the mold, wherein the tip portion is described above. In the pouring pipe communicating with the discharge hole, the shape of the inner hole of the pouring pipe in the region from the discharge port to the length L downward is a cross section (a cross section in the direction perpendicular to the molten metal advancing direction). ) Is gradually reduced in diameter from the starting point of the discharge port downward, and the gradually reduced diameter curve is formed by a predetermined formula in the vertical cross section passing through the central axis of the pouring pipe. Those characterized by having the represented shape are disclosed. If the pouring pipe of Patent Document 1 is used, in the pouring method of the molten metal bottom pouring method, productivity and cost increase such as installation of a complicated device are caused without lowering the pouring speed. It is possible to reduce the flow velocity of the molten metal in the mold during pouring in the direction of the molten metal surface (directly above) and reduce the deterioration of the quality of the metal ingot due to non-metal inclusions and oxidation by a simple method that does not require any work. It is said that.

Further, Patent Document 2 discloses a technique of bottom pouring ingot that reduces the discharge pressure and reduces the entrainment of the inner material in the mold without changing the casting flow rate by changing the shape of the runner. .. In other words, when the discharge pressure is large in the bottom pouring ingot, the inner material of the mold on the surface of the molten steel is driven to the outer periphery, and a bare water zone called the centerpiece is formed, which causes reoxidation, hydrogen pickup, lowering of the molten steel temperature, etc. Problems occur. Therefore, it is necessary to add a large amount of the inner material in the mold so as to suppress the formation of the bare hot water zone, but the large amount of the inner material in the mold increases the entrainment of the inner material in the mold. Although the discharge pressure can be reduced to reduce the entrainment of the inner material in the mold, the reduction in the discharge pressure cannot reduce the casting flow rate from the viewpoint of manufacturing efficiency.

Further, in Patent Document 3, when pouring and ingoting into two or more side-by-side molds, this casting defect is opposed to a casting defect that has been often observed in a mold near the injection pipe. The ingot-forming technology that can prevent the occurrence of In other words, when pouring ingots into two or more molds arranged side by side, the hydrostatic pressure resistance in the mold is small at the initial stage of molten steel injection, so the mold closer to the injection pipe is more vigorous and the molten steel flows into the mold. There are problems that the turbulence becomes large, the surface of the molten steel is not completely covered with the molten steel coating agent, reoxidation occurs due to atmospheric contact, and the molten steel coating agent is caught in the molten steel. Therefore, in the technique of Patent Document 3, the discharge pressure is reduced by forming the runner cross-sectional area formed in the lower part of the mold larger toward the upstream side, and the casting defect often observed in the mold near the injection pipe is prevented. It makes it possible to save molten steel coating.

Japanese Unexamined Patent Publication No. 2012-086233 Japanese Unexamined Patent Publication No. 9-239494 Japanese Unexamined Patent Publication No. 61-023555

By the way, conventionally, in order to improve productivity in ingot making, a ingot making facility for pouring hot water from one runner into a plurality of molds has been adopted. In such an ingot making facility that pours hot water from one runner into a plurality of molds, a part of the molten steel of the runner is divided into a T-shaped branch with respect to the runner, and the branch is formed. Hot water is poured into each mold via.
However, if a T-shaped branch is provided in the middle of the runner, the flow of molten steel tends to be biased at the branch, and this bias in the flow of molten steel (hereinafter referred to as drift) occurs at the injection port. It will also cause a large bias in the flow of molten steel. Whether or not the above-mentioned drift becomes large depends on the inflow rate of molten steel flowing from the runner into the branch path, and the inflow rate of molten steel flowing into the branch path increases as the mold is closer to the ladle, so that the drift occurs. The state also differs depending on the mold.

That is, the techniques of Patent Document 1 and Patent Document 2 described above do not take into consideration the state of occurrence of drift that differs for each mold, and a structure in which hot water is poured into a plurality of molds from one runner. It is not compatible with mass equipment. Of course, even if the techniques of Patent Document 1 and Patent Document 2 are used, it is unlikely that a sufficient discharge pressure lowering effect can be obtained.
Further, the ingot-forming technique of Patent Document 3 uses a runner that is chipped from the upstream side to the downstream side and the cross-sectional area is gradually reduced. If such a runner is provided, the flow velocity of the molten steel in the runner on the upstream side near the ladle can be reduced, the occurrence of large drift in the mold on the upstream side can be suppressed, and the molten steel coating agent can be used. Entrainment can also be reduced. However, if the above-mentioned runner whose cross-sectional area is gradually reduced is provided, the configuration of the ingot making facility becomes complicated, and the initial installation cost and the running cost become large.

The present invention has been made in view of the above-mentioned problems, and when pouring water from one runner into a plurality of molds by pouring underneath, the occurrence of drift at the injection port of the mold and the material inside the mold. It is an object of the present invention to provide a bottom pouring ingot making facility capable of effectively suppressing the entrainment of steel and producing a healthy and highly clean steel ingot at a low cost by using a simple facility configuration.

In order to solve the above problems, the bottom pouring ingot making facility of the present invention takes the following technical measures.
That is, in the bottom pouring ingot making facility of the present invention, molten steel is introduced into a branch path branched into a T shape from a runner, and molten steel is injected into a mold at the end of the branch path to ingot. In the equipment, the branching part where the branching path branches upward from the runner in a T-shape has a square box part in which the upper corner of the branching part is recessed upward in a square box shape. , A round chamfered portion with rounded corners between the square box portion and the branch path is formed, the dimension of the square box portion along the runner is X, and the radius of curvature of the round chamfered portion is When R, the inner diameter on the discharge port side of the runner and the branch path is d, the following formula is formed between the dimension X of the square box portion, the radius of curvature R of the round chamfered portion, and the inner diameter d. The feature is that the relationship (2) is established.
[Number 2]
d × 0.2 ≦ X ≦ d × 0.7
d × 0.1 ≦ R ≦ d × 0.5 ... (2)
Preferably, at least two or more molds are arranged side by side in the runner along the flow direction of the molten steel in the runner, and the square box portion and the round chamfer portion form the flow of the molten steel. It is preferable that it is formed at a branch portion where molten steel is branched into a mold arranged on the upstream side in the direction.

Preferably, the square box portion and the round chamfered portion are formed on the downstream side of the flow direction of the branch portion with respect to the flow direction of the molten steel in the runner.

According to the bottom-pouring ingot-making equipment of the present invention, when pouring hot water from one runner into a plurality of molds by pouring, it is effective to generate drift at the injection port of the mold and entrain the inner material of the mold. It is possible to produce a healthy and highly clean steel ingot at low cost by using a simple equipment configuration.

It is a figure which showed typically the underpouring ingot making equipment of 1st Embodiment. It is a figure which showed the runner arrangement of the bottom pouring mass-forming equipment of the 1st Embodiment. It is sectional drawing which showed the part A of FIG. 2 enlarged. It is a figure which showed the flow state of molten steel generated in the branch pipe by comparison with the conventional branch pipe and the branch pipe of 1st Embodiment. It is an enlarged view of FIG. The relationship between the average flow velocity of the runner and the maximum flow velocity of the discharge port in the bottom pouring ingot mass equipment of the first embodiment is shown as a graph. It is a figure which showed the flow of molten steel generated in the mold of the conventional bottom pouring ingot making equipment. It is a figure which showed the bottom pouring mass-forming equipment of the 2nd Embodiment. It is an enlarged view which showed the branch part of the bottom pouring ingot mass production facility of 2nd Embodiment. It is a figure which showed the flow state of molten steel generated in the branch pipe provided in the conventional bottom pouring ingot building equipment. It is a figure which showed the flow state of the molten steel generated in the branch pipe which formed only the square box part in the branch part. It is a figure which showed the flow state of the molten steel generated in the branch pipe of the 2nd Embodiment which formed the square box part and the round chamfer part in the branch part. It is a graph which showed the relationship between the average flow velocity of a runner and the maximum flow velocity of a discharge port in the bottom pouring ingot mass equipment of 2nd Embodiment by comparison for each dimension of the square box part. It is a graph which showed the relationship between the average flow velocity of a runway and the maximum flow velocity of a discharge port in the bottom pouring ingot mass equipment of 2nd Embodiment by comparison for each radius of curvature of a round chamfering part.

[First Embodiment]
Hereinafter, an embodiment of the bottom pouring ingot making facility 1 of the present invention will be described in detail with reference to the drawings.
Generally, there are two known methods for ingot steel, one is bottom pouring and the other is top pouring, depending on the method of injecting molten steel when solidifying molten steel in a mold to produce steel pieces. There is. In the top pouring ingot, the molten steel of the ladle is poured directly into the mold through the opening at the top of the mold and cast, whereas in the bottom pouring ingot, the injection pipe 2 having a funnel-shaped spout at the upper end Molten steel is poured into a vertical pipe called, molten steel is circulated in the horizontal direction through a runner 3 connected to the lower end of the injection pipe 2, and molten steel is poured from the lower side of the mold 5 from the runner 3 through the pouring pipe. You can pour hot water. The bottom-pouring ingot has the advantage of obtaining a better casting surface than the top-pouring ingot, and is applied to the production of high-grade steel where quality is important. In addition, compared to the top-pouring ingot, which can produce only one piece of steel (steel ingot) at one time, the bottom-pouring ingot is made of molten steel from one injection pipe 2 via a runner 3 (runner 3). By branching, steel pieces (steel ingots) can be cast at the same time with a plurality of molds 5. Therefore, the bottom pouring ingot, which has higher productivity than the top pouring ingot, is widely used in the production of steel types and large cross-section steel ingots that cannot be cast by the continuous casting method. The bottom-pouring ingot-forming equipment 1 of the first embodiment and the second embodiment is intended for the under-pouring ingot-forming method of the above-mentioned two ingot-forming methods.

As shown in FIG. 1, the underpouring ingot making facility 1 of the present embodiment for performing the above-mentioned underpouring ingot is provided in the ladle 6 in which the molten steel used for casting is charged and below the ladle 6. It includes an injection pipe 2 that stands vertically along the vertical direction. The upper end of the injection pipe 2 is connected to the ladle 6, and the molten steel in the ladle 6 can be guided downward through the inside of the injection pipe 2. Further, a runner 3 for sending molten steel in the horizontal direction is provided on the lower side of the injection pipe 2, and a plurality of branch paths 4 are provided on the middle side of the runner 3, and the runner 3 and Molten steel can be injected into each of the plurality of molds 5 via the branch path 4.

Specifically, in the bottom-pouring ingot-forming facility 1 of the first embodiment, the base plate 7 is arranged on a surface plate that can be moved in the horizontal direction with respect to the floor surface or the like, and the base plate 7 is described above. A mold 5 (mold) is arranged. Further, a through hole 8 for the runner 3 is formed so as to penetrate both the surface plate and the base plate 7 in the vertical direction. Refractory bricks are lined on the inner wall of the through hole 8 to form a round hole-shaped runner 3. Further, an injection nozzle 9 is installed in the lower part of the ladle 6, and molten steel is poured from the injection nozzle 9 into the funnel-shaped spout of the injection pipe 2 described above, and a runner connected to the lower side of the injection pipe 2. The molten steel is sent to the mold 5 side via 3. The molten steel sent to the mold 5 side in this way is poured into the mold 5 from below through the injection port at the bottom of the mold 5, and the molten steel poured is solidified to produce steel pieces (steel ingots). Ru.

In the above-mentioned bottom pouring ingot method, the surface of the molten steel in the mold 5 is covered with an inner mold material (molten steel coating agent) in order to prevent atmospheric oxidation of the molten steel and a decrease in the molten steel temperature during casting. Is done.
Further, as shown in FIG. 2, the above-mentioned runway 3 is formed along the horizontal direction from the lower end of the injection pipe 2 toward the outside, and faces from the lower end of the injection pipe 2 in multiple directions of left and right or front and back. The molten steel of the ladle 6 is distributed via the runner 3 branched into a plurality of branches. Then, the molten steel of the plurality of runners 3 is guided to each mold 5 through the branch passage 4 provided in each runner 3, and the molten steel is poured into the mold 5 from the injection port at the bottom of each mold 5. Will be done. In the case of the lower pouring ingot mass equipment 1 of the first embodiment, four runners 3 are formed at the lower end of one injection pipe 2 so as to extend radially from the lower end of the injection pipe 2. That is, each of these four runners 3 is also called a runner 3, and each runner 3 is provided with five molds 5, and the bottom pouring incubator 1 of the first embodiment is four. It has a total of 20 molds 5 together with the book runner 3.

The bottom pouring ingot equipment 1 of the first embodiment transports the cast steel pieces together with the mold 5, the injection pipe 2, and the runner 3 in order to efficiently carry out a large amount of steel pieces (ingots) from the casting factory. It is configured to be loaded and moved on a train bogie. Further, from the viewpoint of saving space in the foundry, the runners 3 are arranged along the longitudinal direction of the carriage, that is, the left-right direction on the paper surface of FIG.

A plurality of molds 5 are provided in each of the plurality of runners 3 described above. For example, FIG. 3 is an enlarged view of the runner 3 located at the upper right (the portion indicated by A) in FIG. As shown in FIG. 3, a plurality of molds 5 (five in the example) are arranged side by side in one runner 3 (runner) along the extension direction of the runner 3. These plurality of molds 5 are arranged at a distance such that adjacent molds 5 do not come into contact with each other. Further, these molds 5 are provided in an upright state on a base plate 7 located above the runner 3.

A branch path 4 extending in the vertical direction is formed between the runner 3 and the mold 5 described above, and the molten steel of the runner 3 can be distributed to the mold 5 through each branch path 4. ing. The lower ends of the branch paths 4 intersect with the runner 3 in a T-shape when viewed from the front, and each branch path 4 has a flow direction of molten steel flowing along the runner 3. Can be distributed to the mold 5 by switching 90 °. The molten steel poured into the branch path 4 in this way is sent to the mold 5 through the branch path 4 and is injected into the mold 5 from an injection port provided at the bottom of the mold 5.

By the way, at the portion where the above-mentioned branch path 4 intersects the runner 3, that is, at the branch portion 10 of the runner 3, the direction of the molten steel flowing through the runner 3 changes greatly, so that the molten steel inevitably changes at the entrance side of the branch path 4. There is a bias in the flow. Since such a biased flow of molten steel remains at the end of the branch path 4, in other words, at the injection port of the mold 5, the flow velocity of the molten steel in the mold 5 is not smooth, and the hot water in the mold 5 is not smooth. The surface is disturbed (ramp) and the inner material of the mold is likely to get caught. The mold inner material (molten steel coating agent) caught in this way is captured by the solidification interface of the ingot and remains in the ingot. Therefore, it may be detected as a defect by ultrasonic flaw detection (UT) inspection or magnetic particle flaw detection inspection after forging and machining, and the defective part is cut off, so the entrainment of the inner material of the mold is the yield of the steel ingot. It is the main factor that makes it worse.

In particular, when molten steel is injected from one runner 3 into a plurality of molds 5 as shown in FIG. 2, the mold inner material is very entangled in the mold 5 on the side close to the injection pipe 2 (ladle 6). I knew there were many. As a result of diligent research, the inventors have conducted diligent research, and the reason why the mold inner material is involved in the mold 5 mold is that the branch path 4 is branched into the branch path 4 at the branch portion 10 where the branch path 4 branches from the runner 3 (runner 3). It was found that the uneven flow of molten steel that occurs at that time leads to the runaway of the molten metal surface in the mold 5, which in turn causes the inner material of the mold to be caught. Further, among the plurality of molds 5 provided on the runner 3, the unevenness of the flow of molten steel becomes large especially at the branch portion 10 of the mold 5 (mold) on the side closer to the injection pipe 2 (ladle 6), and the inner material of the mold. I learned that it is easy for people to get involved.

That is, the entrainment of the inner material of the mold occurs when the flow velocity at the molten steel interface in the mold 5 exceeds a certain critical value. Here, the flow velocity at the molten steel interface correlates with the discharge flow velocity of the molten steel discharged from the injection port at the bottom of the mold 5, and the casting speed, that is, the larger the discharge flow velocity, the larger the flow velocity at the molten steel interface, and the entrainment of the inner material in the mold. Is also easy to get up.
Further, in the conventional bottom pouring ingot method, the average discharge flow rate of molten steel discharged from the injection port at the bottom of the mold (the flow rate obtained by dividing the casting flow rate from the injection pipe 2 by the cross-sectional area of the runner) is used as the inner material of the mold. It was judged whether or not the involvement of However, when casting from one runner into a plurality of molds, the molten steel flow may be biased at the above-mentioned branch portion, and the bias of the molten steel flow causes a locally strong flow of molten steel at the injection port. Even when it occurred, it was found that the in-mold material was involved. That is, it is necessary to consider the maximum discharge flow velocity of the molten steel for the entrainment of the inner material of the mold.

It is possible to reduce the maximum discharge flow velocity of the molten steel by reducing the discharge rate of the molten steel during casting. However, if the discharge rate of molten steel is reduced too much, the casting nozzle of the ladle 6 will be blocked, the molten steel will be solidified in the runner 3, the productivity will decrease due to the casting time becoming too long, and the temperature at the end of casting. It can also pose a risk that the temperature will drop too much and sedimentation inclusions will be more likely to occur.

Therefore, the bottom pouring ingot-forming facility 1 of the present invention provides a concave portion 11 recessed upward in a curved shape in the branch portion 10 in which the branch path 4 branches upward in a T-shape from the runner 3. Is forming. The curved surface of the recess 11 has the following equation (1) between the radius of curvature X and the inner diameter d when the radius of curvature is X and the inner diameter of the runner 3 is d. There is. In the case of the first embodiment, the radius of curvature X is the side of the inner peripheral surface of the branch path where the recess 11 is provided, and the line connecting the uppermost portion of the inner peripheral surface of the runner. The starting point of the curvature is the intersection (the point indicated by the point "S" in FIG. 5) where the line connecting the inner peripheral surfaces of the branch roads above and below intersects. The recess 11 provided in the bottom pouring ingot mass equipment 1 of the first embodiment does not necessarily have to have the above-mentioned intersection S as the starting point of curvature. For example, the radius of curvature may be set starting from a point slightly distant from the intersection S. That is, the bottom pouring ingot equipment 1 of the first embodiment has the above-mentioned recess 11 formed on the entrance side of the branch path 4 in order to eliminate the bias of the flow of molten steel generated at the branch portion 10. There is.
[Number 3]
d × 0.1 ≦ X ≦ d × 0.7 ・ ・ ・ (1)
When the above-mentioned branch portion 10 is recessed upward in a curved shape and a recess 11 satisfying the relationship of the formula (1) is provided, the branch path 4 from the branch portion 10 to the injection port at the bottom of the mold 5 It is possible to disperse the flow of molten steel that has been biased. That is, since the drift is less likely to occur at the injection port, the discharge flow rate does not increase locally, and the maximum discharge flow rate can be reduced. Therefore, when the lower pouring ingot mass equipment 1 of the first embodiment is used, the entrainment of the inner material in the mold can be effectively suppressed.

Next, the branch portion 10 provided in the ingot-forming facility of the first embodiment and the recess 11 formed in the branch portion 10 will be described.
As shown in FIG. 3, the above-mentioned branch portion 10 is a portion where the runner 3 arranged along the horizontal direction and the branch path 4 for feeding molten steel to the mold 5 intersect in a T shape when viewed from the front. Is. As shown in the figure, when five molds 5 are provided from the side (inside) where the ladle 6 is provided to the outside, the side farthest from the ladle 6 (counter ladle 6 side or outside). Except for the mold 5 located in, the intersections with the branch paths 4 in which the molten steel is distributed to the four inner molds 5 are all T-shaped and can be considered as the branch portion 10 of the present invention. .. In such a branch portion 10, the runway 3 and the branch path 4 intersect in a T-shape in a lateral view, and the above-mentioned bias in the flow of molten steel may occur.

It should be noted that it is not necessary to provide the above-mentioned recesses 11 in all the branch portions 10 by setting all the portions where the runway 3 and the branch path 4 intersect in a T shape in the front view as the branch portion 10. The recess 11 may be formed only in the branch portion 10 on the side closest to the ladle 6 where the inner material of the mold is most noticeably involved.
Further, in the example of FIG. 3, the intersection of the mold 5 and the runner 3 located on the farthest side from the ladle 6 is not treated as the “branch portion 10”. This is because the runway 3 and the branch road 4 intersect in an L-shape at the intersection on the farthest side from the ladle 6 (because they do not intersect in a T-shape). However, even at the intersection on the farthest side from the ladle 6, if the runway 3 and the branch road 4 intersect in a T shape in front view, it is treated as the branch portion 10 of the present invention. A recess 11 may be formed in the branch portion 10.

Further, the runway 3 and the branch passage 4 described above have a diameter of 40 mm to 80 mm. In the first embodiment, the runway 3 and the branch path 4 may have the same inner diameter, but may be formed to have different inner diameters within the above-mentioned inner diameter range.
In the following description, the ingot-forming equipment of the first embodiment will be described with reference to an example in which the recess 11 is provided only in the branch portion 10 for feeding molten steel from the runner 3 to the mold 5 closest to the ladle 6.

4 and 5 show the distribution of the flow direction and flow velocity of the molten steel generated at the branch portion 10 described above in the case of the lower pouring ingot building equipment 1 of the first embodiment and the case of the conventional lower pouring ingot making equipment. It is the result of comparison with. The left side of FIGS. 4 and 5 is the result of the conventional bottom-pouring ingot-forming equipment 1, and the right side is the result of the in-pouring ingot-forming equipment 1 of the first embodiment.
As shown in FIGS. 4 and 5, the recess 11 provided in the ingot-forming facility of the first embodiment is a portion (shaped portion in which the bowl is turned down) in which the surface of the refractory is recessed upward in a curved shape. There is a portion formed in a deficient state in a state of being recessed upward, and the molten steel is inverted at this recessed portion to separate and disperse the uneven flow along the inner peripheral surface of the branch path 4. This makes it possible to suppress the occurrence of bias in the flow of molten steel.

That is, in the branch portion 10 of the conventional bottom pouring ingot building facility 1 shown on the left side of FIGS. 4 and 5, the molten steel flowing from the runner 3 into the branch path 4 is first of the inner peripheral surface of the branch path 4. , Collides with a portion of the molten steel located on the downstream side in the flow direction, then moves upward along the inner peripheral surface of the branch path 4 and is poured into the mold 5. At this time, the molten steel that has collided with the inner peripheral surface on the downstream side of the branch road 4 moves upward while being attached to the inner peripheral surface of the branch road 4 and is carried to the injection port.

However, since the branch portion 10 of the bottom pouring ingot building facility 1 of the first embodiment is provided with the recess 11, the molten steel flowing from the runner 3 into the branch path 4 collides with the inner peripheral surface of the recess 11. Then, it is inverted at the recess 11 and enters the branch road 4 at an angle intersecting the inner peripheral surface of the branch road 4. As a result, the molten steel is separated from the inner peripheral surface inside the branch path 4, and a flow is formed on the central side of the branch path 4 away from the inner peripheral surface. Further, the flow formed on the central side of the branch path 4 is dispersed by the time it reaches the mold 5, and when the hot water is poured into the mold 5 from the discharge port, the flow of the molten steel is hardly biased. Therefore, in the ingot forming facility of the first embodiment, the drift is suppressed, and the uniform flow of the molten steel in the mold 5 can be realized.

The recess 11 described above needs to be formed at least on the downstream side of the branch portion 10 in the flow direction of the molten steel in the runner 3. That is, as shown in FIGS. 4 and 5, recesses 11 may be formed on both the upstream side and the downstream side in the flow direction, but at least the recess 11 (semi-bowl-shaped portion) is formed on the downstream side in the flow direction. If it is set, a sufficient effect of suppressing drift flow can be obtained.

Further, regarding the recess 11 described above, as shown in the above equation (1), when the radius of curvature of the curved surface of the recess 11 is X and the inner diameter of the runner 3 or the branch path 4 is d, the radius of curvature X The shape should be such that the relationship of the following equation (1) holds between the inner diameter d and the inner diameter d. If the recess 11 having a shape that holds the relationship of the formula (1) is provided, a flow of molten steel can be formed on the central side separated from the inner peripheral surface of the branch path 4, and the molten steel can be evenly distributed in the mold 5. It becomes possible to pour hot water into.

The relationship of the above formula (1) is established for the runner 3 or the branch path 4 having an inner diameter of φ40 to 80 mm. Further, it is established when the casting flow rate per runner 3 is 0.3 t / min to 2 t / min and the weight range of the ingot is 0.5 ton to 50 ton.
[Second Embodiment]
Next, a second embodiment of the bottom pouring ingot making facility 1 of the present invention will be described.

As shown in FIGS. 8 and 9, in the bottom pouring mass lumping equipment 1 of the second embodiment, the bottom pouring mass lumping equipment 1 of the first embodiment formed the recess 11 in the branch portion 10. The branch portion 10 includes a square box portion 12 in which the upper corner of the branch portion 10 is recessed upward in a square box shape, and a round chamfered portion 13 in which the corners of the square box portion 12 and the branch path 4 are rounded. Instead of the concave portion 11 of the first embodiment, the square box portion 12 and the round chamfered portion 13 are used to suppress the drift. That is, in the bottom pouring ingot mass equipment 1 of the second embodiment, the square box portion 12 and the round chamfer portion 13 are used in combination, and the effect of suppressing the drift flow can be obtained only by using both of them. There is.

Specifically, the square box portion 12 is a portion formed so as to scoop upward in a square box shape with respect to the branch portion 10 in which the branch path 4 and the runway 3 intersect in an inverted T shape. is there. The square box portion 12 is formed of wall surfaces arranged in five directions, front, back, left, right, and upper side. Of these five wall surfaces, the side surfaces (side wall surfaces) formed on the front, back, left and right are all formed as flat surfaces along the vertical direction. The front and rear side surfaces and the left and right side surfaces are arranged substantially in parallel with a horizontal distance, and it is possible to form a space in which molten steel can be stored inside surrounded by these four side surfaces. Further, of these five wall surfaces, the upper surface (upper wall surface) formed on the upper side is arranged so as to cover the upper part of the internal space surrounded by the four front, rear, left and right side surfaces. A branch path 4 is vertically arranged in the center of the upper surface so as to communicate with the square box portion.

That is, in the square box portion 12 formed of the above-mentioned five wall surfaces, only the lower side where the runner 3 is present is open downward, and the molten steel flowing through the runner 3 is drawn in from below. be able to.
The round chamfered portion 13 described above is a curved surface portion formed at a portion where the upper surface of the square box portion 12 and the lower end portion of the branch path 4 intersect with each other, and the molten steel flowing into the square box portion 12 can be smoothly flowed. It can be introduced (guided) to the branch road 4. Specifically, the round chamfered portion 13 is formed into a rounded curved surface having no corners at the intersection with respect to the portion where the upper surface of the square box portion 12 and the branch path 4 are orthogonal to each other. There is.

By the way, the size of the square box portion 12 and the round chamfer portion 13 described above is important for effectively suppressing the drift. For example, if the dimension X of the square box portion 12 and the radius of curvature R of the round chamfered portion 13 are relatively small compared to the inner diameters of the branch path 4 and the runner 3, the effect of suppressing drift flow will be small. That is, the dimension X of the square box portion 12 and the radius of curvature R of the round chamfered portion 13 have optimum values for effectively and efficiently suppressing the drift.

Specifically, in the bottom pouring inflatable equipment 1 of the second embodiment, the dimension X of the square box portion 12 and the radius of curvature R of the round chamfered portion 13 are set to the inner diameter of the runner 3 and the branch path 4 on the discharge port side. When d is set, the setting is as shown in the following equation (2).
[Number 4]
d × 0.2 ≦ X ≦ d × 0.7
d × 0.1 ≦ R ≦ d × 0.5 ... (2)
As shown in FIG. 9, the “dimension X of the square box portion 12” refers to the side surface of the square box portion 12 separated from the inner wall surface of the branch path 4 along the left-right direction (formation direction of the runner 3). Is the distance. Further, the "radius of curvature R of the round chamfered portion 13" is the center of the radius of curvature of the curved surface constituting the round chamfered portion 13, and in the case of the round chamfered portion 13 in the figure, the round surface on the right side. It is located further to the upper right of the chamfer 13.

If the square box portion 12 and the round chamfered portion 13 having a shape such that the relationship of the above equation (2) is established are provided, a flow of molten steel is formed on the central side separated from the inner peripheral surface inside the branch path 4. This makes it possible to evenly pour molten steel into the mold 5. Regarding the thickness of the square box in the width direction (width along the direction orthogonal to the extension direction of the runner), the diameter of the runner is basically the same, and the diameter of the runner is φ40 to 80 mm. On the other hand, the thickness of the square box in the width direction is 40 to 80 mm, which basically corresponds to each runner diameter. Therefore, the thickness of the square box portion in the width direction does not become larger than the diameter of the runner, but even if it becomes smaller, there is no change in the manifestation of the action and effect of the present invention.

The relationship of the above-mentioned equation (2) is also established for the runner 3 or the branch passage 4 having an inner diameter of φ40 to 80 mm, similarly to the equation (1). Further, it is established when the casting flow rate per runner 3 is 0.3 t / min to 2 t / min and the weight range of the ingot is 0.5 ton to 50 ton.
Further, in principle, the radius of curvature R of the round chamfered portion 13 does not exceed the dimension X of the square box portion 12. That is, a relationship of X ≧ R is established between the dimension X of the square box portion 12 and the radius of curvature R of the round chamfered portion 13.

Further, the square box portion 12 of the present embodiment shows an example in which the dimension X in the left-right direction and the dimension in the up-down direction are equal to each other, but the dimension in the up-down direction is Z (with respect to the dimension X in the left-right direction). It can also be formed into a shape such that ≠ X).

Next, in Examples and Comparative Examples, scrap was melted in an AC arc type electric furnace having a capacity of 40 tons, and the melted molten steel was ejected by the EBT method (eccentric furnace bottom ejection method), and the molten steel was ejected. Was adjusted by the LF method and inclusions were removed. Further, the molten steel for which the component adjustment and the removal of inclusions were completed was charged into the ladle 6 and degassed. The ladle 6 is covered with a lid, and the inside is in a vacuum state of about 70 Pa. Further, Ar gas is blown into the molten steel inside the ladle 6 from an Ar gas plug (bottom blowing plug), and vacuum dehydrogenation treatment is performed for 20 minutes. The molten steel of the ladle 6 that has been subjected to the vacuum dehydrogenation treatment in this way is cast into a plurality of molds 5 by a bottom pouring ingot method through the runner 3 and the branch path 4.

Further, the above-mentioned bottom pouring incubator 1 has four runners 3 radially from the injection pipe 2, and each runner 3 is provided with five molds 5, for a total of 20 runners. It is configured to perform casting with the mold 5 of. In each mold 5, a bag containing a mold inner material (molten steel coating agent) is provided in a suspended state. That is, when the molten steel is injected into the mold 5 and the depth of the molten steel becomes deeper, the molten metal level rises and the distance from the bag becomes closer.

Eventually, when the distance between the two reaches a predetermined distance, the bag containing the mold inner material suspended in the mold 5 burns due to radiant heat, causing the mold inner material to fall to the surface of the molten steel and the surface of the molten steel. The material inside the mold is sprayed on. The method of adding the inner material of the mold is the same for both the conventional bottom pouring and ingot making equipment 1 and the under pouring ingot making equipment 1 of the present invention. The inner material added and sprayed in this way invades between the mold 5 and the ingot during casting and is consumed as slag skin. Therefore, if bare water is visible on the surface of the molten steel, , The inner material of the mold may be additionally charged.

When the molten steel reaches the hot water press portion in this way, a board-shaped heat insulating material is provided on the surface of the molten steel (upper part of the inner material of the mold). Then, after the casting is completed to a predetermined position (hot water surface height), the ingot is allowed to stand until it is completely solidified, and after the ingot is completely solidified, it is demolded and the forging process is started.
In the forging step described above, the ingot is heated, and forging and heating are repeated until the size of the round bar reaches a predetermined value. Then, after forging, the surface layer was turned to a depth of 2 mm with a lathe to remove black skin (oxidation scale). Finally, an ultrasonic flaw detection test was performed to inspect the product shape for inclusions (subcutaneous inclusion inspection).

As described above, when the subcutaneous inclusions were investigated by an ultrasonic flaw detection test on the ingot cast by the bottom pouring ingot incubator 1 equipped with five molds 5 in one runner 3, the ladle 6 was used. Many peaks indicating the presence of subcutaneous inclusions were detected in the ingot on the side where the distance between the two was short (injection tube 2 side). In this way, the ingots for which peak detection was detected in the ultrasonic flaw detection test are the molds 5 from the injection pipe 2 side to the third mold 5, and the mold 5 on the farther side (fourth and subsequent molds from the injection pipe 2 side). No peaks were detected in the cast ingots. At this time, in the third mold 5 from the injection pipe 2 side, molten steel was discharged from the injection port at a maximum discharge flow velocity of 0.60 m / s. From this, it was judged that the maximum discharge flow velocity of molten steel at the injection port should be controlled to 0.60 m / s or less, which suppresses the generation of inclusions in the ingot, that is, the entrainment of the inner material in the mold. Judged as possible.

Next, for the branch portion 10 in which the runway 3 and the branch passage 4 intersect in a T shape, the molten steel flow state generated in the branch portion 10 was analyzed by simulation. The branch portion 10 for which the fluid analysis was performed distributes molten steel to a mold 5 provided at a position closest to the ladle 6 among the branch portions 10 provided in the runner 3. The conditions for fluid analysis are as shown in Table 1 below.

The calculation conditions and physical property values for fluid analysis are as shown in Tables 2 and 3.

"Examples corresponding to the bottom pouring ingot-forming equipment of the first embodiment (Examples 1 to 28)"
Based on the above-mentioned fluid analysis conditions, the maximum discharge flow velocity of molten steel generated at the injection port of the branch portion 10 not provided with the recess 11 is obtained as a comparative example, and the radius of curvature X is 0 of the inner diameter d of the branch path 4. The maximum discharge flow velocity of the molten steel generated in the branch portion 10 having the recess 11 changed from 1 time to 0.7 times was obtained as an example of the first embodiment. Further, since the maximum discharge flow velocity of molten steel also changes depending on the casting flow velocity (runner casting flow velocity) flowing through the runner 3, the above-mentioned runner casting flow velocity is based on the normal casting flow rate (hereinafter referred to as the base flow rate). The maximum discharge flow velocity of molten steel was determined by changing the flow velocity so as to be 0.5 to 3.0 times the base flow rate.

The maximum discharge flow velocity of the molten steel was measured upward from the upper surface of the runner 3 at a position 2.54 times the runner diameter D, or 127 mm at the bottom injection port position of the actual size. .. The measurement position of the maximum discharge flow velocity is preferably selected at the position of the injection port at the bottom of the mold in the range of 100 mm to 200 mm from the upper surface of the runner 3.
The results are shown in Table 4.

In Table 4, it occurs in the branch portion 10 of Examples 1 to 28 having the recess 11 as compared with the maximum discharge flow velocity generated in the branch portion 10 of Comparative Examples 1 to 4 not provided with the recess 11. The ratio of the maximum discharge flow velocity to be performed is shown by "round hole maximum discharge flow velocity / R-applied maximum discharge flow velocity".
Looking at the results in Table 4, in Examples 1 to 28 in which the radius of curvature X of the recess 11 was 0.1 to 0.7 times the inner diameter d, "maximum round hole discharge flow velocity / maximum R imparted discharge". The "flow velocity" is 30 to 75, and it can be seen that the maximum discharge flow velocity is significantly lower than that of the comparative example.

Further, the rate at which the maximum discharge flow velocity discharged at the injection port of the mold 5 increases with respect to the flow velocity of the molten steel flowing through the runner also becomes small. For example, as shown in FIG. 6, the flow velocity of molten steel flowing through the runner is taken as the "average flow velocity of the runner" on the horizontal axis, and the maximum discharge flow velocity discharged at the injection port is taken as the "maximum flow velocity at the discharge port". When adopted for the shaft, in Comparative Examples 1 to 4 in which the recess 11 is not provided, the rate of increase of the maximum discharge flow velocity with respect to the average flow velocity of the runner is large, and if the flow velocity flowing through the runner becomes even a little, it is discharged at the injection port. It can be seen that the flow velocity of the molten steel also increases. However, in Examples 1 to 28 in which the recess 11 is provided, the rate of increase in the maximum discharge flow velocity is small, and the flow velocity of the molten steel discharged at the injection port does not increase so much even if the flow velocity flowing through the runner increases. I understand.

The "average flow velocity of the runner" and the "maximum flow velocity of the discharge port" used in FIG. 6 are the flow velocities of the molten steel at the positions shown in FIG. 7, and follow the definitions shown in Table 5.

From the above, when the recess 11 having a shape such that the radius of curvature X of the recess 11 is 0.1 to 0.7 times the inner diameter d is provided in the branch portion 10, the injection port of the mold 5 is used. It is judged that the occurrence of drift and the entrainment of the inner material of the mold can be effectively suppressed, and a healthy and highly clean steel ingot can be manufactured at low cost by using a simple equipment configuration.
Even if the maximum discharge flow velocity is in the range of 0.60 m / s or more, the cut-off weight of the molten steel coating agent entrainment range at the bottom of the ingot, which was conventionally cut off, is reduced by reducing the maximum discharge flow rate compared to the conventional method. There is an effect that can be done. That is, the reduction of the maximum discharge flow velocity is very important by the ingot pouring, and even if the maximum discharge flow velocity is not 0.6 m / s or less, the reduction as much as possible has the effect of improving the yield of the steel material. Therefore, regarding the table, the range of 0.60 m / s or more is also treated as included in the present invention.
"Examples corresponding to the bottom pouring ingot-forming equipment of the second embodiment (Examples 29 to 52)"
Based on the above-mentioned fluid analysis conditions, the maximum discharge flow velocity of molten steel generated at the injection port of the branch portion 10 not provided with the square box portion 12 and the round chamfer portion 13 is obtained as a comparative example, and the square box portion 12 is used. Dimension X is 0.2 to 0.7 times the inner diameter d of the branch path 4, and the radius of curvature R of the round chamfered portion 13 is changed to 0.1 to 0.5 times the inner diameter d. The maximum discharge flow velocity of the molten steel generated in the above was determined as an example of the second embodiment.

The analysis conditions, calculation conditions, physical property values, etc. of the molten steel flow state are according to Tables 1 to 3 as in the first embodiment. Similar to Examples 1 to 28 of the first embodiment, the maximum discharge flow velocity of the molten steel is 0. The runner casting flow velocity described above is the base flow rate based on the normal casting flow rate (hereinafter referred to as the base flow rate). The maximum discharge flow velocity of the molten steel was determined by changing the flow velocity so as to be 5 to 3.0 times.

Further, the maximum discharge flow velocity of the molten steel was measured from the upper surface of the runner 3 upward at a position 2.54 times the runner diameter D, or 127 mm at the actual size of the mold bottom injection port. .. The measurement position of the maximum discharge flow velocity is preferably selected at the position of the injection port at the bottom of the mold in the range of 100 mm to 200 mm from the upper surface of the runner 3.
The results are shown in Table 6.

In Table 6, a comparison in which the branch portions 10 of Comparative Examples 5 to 8 and the square box portion 12 and the round chamfer portion 13 are provided but the round chamfer portion 13 is not provided. The branching portions of Examples 29 to 52 including both the square box portion 12 and the round chamfered portion 13 as compared with the maximum discharge flow velocity of the molten steel generated at the branching portions 10 of Examples 9 to 20 respectively. The ratio of the maximum discharge flow velocity generated in No. 10 is indicated by "round hole maximum discharge flow velocity / R-applied maximum discharge flow velocity".

Looking at the results in Table 6, the dimension X of the square box portion 12 is 0.2 to 0.7 times the inner diameter d, and the radius of curvature X of the round chamfer portion 13 is 0.1 times the inner diameter d. In Examples 29 to 52, which are ~ 0.5 times, the "round hole maximum discharge flow velocity / R-applied maximum discharge flow velocity" is 30 to 75, and the maximum discharge flow velocity is larger than that of the comparative example. You can see that it is down.
Further, the rate at which the maximum discharge flow velocity discharged from the injection port of the mold 5 increases with respect to the flow velocity of the molten steel flowing through the runner 3 also becomes small.

For example, as shown in FIG. 12, the flow velocity of the molten steel flowing through the runner 3 is taken as the "runner average flow velocity" on the horizontal axis, and the maximum discharge flow velocity discharged at the injection port is taken as the "discharge port maximum flow velocity". When adopted on the vertical axis, Comparative Examples 5 to 8 (“round hole” in the legend in the figure) having neither the square box portion 12 nor the round chamfer portion 13 and the square box portion 12 having a round surface. In Comparative Examples 9 to 20 (“15 squares”, “25 squares”, and “35 squares” in the legend of the figure), which are not provided with the taking portion 13, the rate of increase of the maximum discharge flow velocity with respect to the average flow velocity of the runner is large, and it is a little. However, it can be seen that as the flow velocity flowing through the runner 3 increases, the flow velocity of the molten steel discharged at the injection port also increases. However, in Examples 29 to 52 (“15 square R10”, “25 square R10”, “35 square R10” in the legend of the figure) including both the square box portion 12 and the round chamfer portion 13, hot water is used. It can be seen that the rate of increase of the maximum discharge flow velocity with respect to the road average flow velocity is small, and the flow velocity of the molten steel discharged at the injection port does not increase so much even if the flow velocity flowing through the runner 3 increases.

Further, as shown in FIG. 13, in the square box portion 12 having a constant dimension X of 25, the radius of curvature R of the round chamfered portion 13 is set to “R5 (corresponding to“ 25 square R5 ”in the figure)” to Consider the case of "R20 (corresponding to" 25-sided R20 "in the figure)". In this case, the maximum discharge flow velocity is compared with Comparative Examples 5 to 20 in which the round chamfer portion 13 is not provided, in other words, the radius of curvature is "R0 (corresponding to" 25 angles "in the figure)". It can be seen that the flow velocity of the molten steel discharged at the injection port does not increase so much even if the rate of increase is small and the flow velocity flowing through the runner 3 increases.

The "average flow velocity of the runner" and the "maximum flow velocity of the discharge port" used in Table 6 also follow the same definitions as those of the first embodiment shown in Table 5.
From the above, as shown in Examples 29 to 52 described above, the square box portion 12 having a dimension X of 0.2 to 0.7 times the inner diameter d and the radius of curvature X having an inner diameter d. When the round chamfer portion 13 is provided in the branch portion 10 so as to be 0.1 to 0.5 times that of the mold 5, the occurrence of drift at the injection port of the mold 5 and the entrainment of the inner material in the mold are effectively suppressed. It is judged that a healthy and highly clean steel ingot can be manufactured at low cost by using a simple equipment configuration.

Even if the maximum discharge flow velocity is in the range of 0.60 m / s or more, the cut-off weight of the molten steel coating agent entrainment range at the bottom of the ingot, which was conventionally cut off, is reduced by reducing the maximum discharge flow rate compared to the conventional method. The effect that can be achieved is exhibited in the same manner as in the first embodiment. That is, the reduction of the maximum discharge flow velocity is very important by the ingot pouring, and even if the maximum discharge flow velocity is not 0.6 m / s or less, the reduction as much as possible has the effect of improving the yield of the steel material. Therefore, as in Table 5, the range of 0.60 m / s or more is also included in the present invention in Table 6.

It should be noted that the embodiments disclosed this time are exemplary in all respects and are not restrictive. In particular, in the embodiments disclosed this time, matters not explicitly disclosed, such as operating conditions, operating conditions, various parameters, dimensions, weights, volumes of components, etc., deviate from the scope normally implemented by those skilled in the art. A value that can be easily assumed by a person skilled in the art is adopted.

1 Bottom pouring ingot mass equipment 2 Injection pipe 3 Runway 4 Branch path 5 Mold 6 Ladle 7 Base 8 Through hole 9 Injection nozzle 10 Branch 11 Recess 12 Square box 13 Round chamfer

Claims (3)

It is an ingot making facility that introduces molten steel into a T-shaped branch from a runner and injects molten steel into a mold at the end of the branch to ingot.
In the branch portion where the branch path branches upward from the runner in a T shape, a square box portion in which the upper corner of the branch portion is recessed upward in a square box shape and a square box portion A round chamfered portion with rounded corners from the branch road is formed.
When the dimension of the square box along the runner is X, the radius of curvature of the round chamfer is R, and the inner diameter of the runner and the branch path on the discharge port side is d, the dimension of the square box is A bottom pouring ingot making facility characterized in that the relationship of the following equation (2) is established between X, the radius of curvature R of the round chamfered portion, and the inner diameter d.
[Number 2]
d × 0.2 ≦ X ≦ d × 0.7
d × 0.1 ≦ R ≦ d × 0.5 ... (2) At least two or more molds are arranged side by side in the runner along the flow direction of the molten steel in the runner.
The lower pouring according to claim 1 , wherein the square box portion and the round chamfered portion are formed at a branch portion for branching the molten steel into a mold arranged on the upstream side in the flow direction of the molten steel. Ingot making equipment. The first or second aspect of the present invention, wherein the square box portion and the round chamfered portion are formed on the downstream side of the flow direction of the branch portion with respect to the flow direction of the molten steel in the runner. Chamfering ingot equipment.