JP5397582B2 - Ingot casting mold and ingot casting method - Google Patents

Description

  The present invention relates to, for example, an ingot casting mold for casting a molten metal made of a Ti alloy or the like into an ingot having a cylindrical shape or a substantially quadrangular prism, and an ingot casting method using the mold.

For example, in order to obtain a large-diameter cylindrical ingot having a high melting point and an active Ti alloy and having a weight of several tons, a Ti raw material is melted by a cold crucible induction melting method, and the obtained Ti alloy melt After casting a plurality of small ingots of about several hundred kg on the mold, the plurality of small ingots are joined along the radial direction or the axial direction to have a large diameter and a weight of several tons. An ingot manufacturing method for manufacturing an ingot has been proposed (see, for example, Patent Document 1). The ingot is used for vacuum arc remelting as a consumable electrode, for example.
JP 2006-341280 A (pages 1 to 11, FIGS. 1 to 3)

By the way, it is also possible to manufacture a large-diameter cylindrical ingot having the same weight as described above by pouring a molten metal such as Ti alloy into the mold cavity a plurality of times (charging) sequentially. is there. Such a stacking casting method is performed by using a mold having a cylindrical shape and a cavity having a large inner diameter, and sequentially pouring a molten metal into the cavity several times.
However, in the case of the above-described stacking casting method, since the previously cast molten metal is solidified into an ingot, a cylindrical gap due to solidification shrinkage occurs between the inner wall surface of the cylindrical cavity, A part of the newly cast molten metal enters (so-called plugging) into the gap. As a result, the gap between the cast ingots and the inner wall surface of the cavity becomes extremely small, and when the ingot including a plurality of such ingots is extracted from the mold, the peripheral surface of the ingot and the cavity Since the frictional force works widely with the inner wall surface, the ingot extraction work becomes difficult.

Moreover, since molten metal is poured into the cavity from the upper end side of the mold, a part of the molten metal adheres to the upper end surface of the mold and the inner wall surface of the cavity. The molten metal adhering to the upper end surface of the mold, the molten metal adhering to the inner wall surface of the cavity, and the ingot cast into the cavity are connected together, and when the molten metal solidifies and shrinks, the ingot is lifted up. Try to let them. As a result, when the inner wall surface of the cavity has a taper whose diameter is reduced on the bottom side, the gap between the ingot in the cavity and the inner wall surface of the cavity expands, and the molten metal to be poured next is Since the amount to be inserted into the enlarged gap due to the floating increases, it may be more difficult to remove the obtained ingot.
Further, when the adhesion of the molten metal to the inner wall surface of the cavity becomes uneven, the ingot cast in the cavity floats upward obliquely, and when the ingot obtained by the ingot is extracted, the peripheral surface of the ingot And the inner wall surface of the cavity are in a state of being twisted with each other, and there is a possibility that the extraction becomes more difficult.

  The present invention solves the problems described in the background art, and an ingot casting mold capable of easily and reliably extracting an ingot obtained by pouring a molten metal into a cavity from an opening. It is an object to provide an ingot casting method to be used.

Means for Solving the Problems and Effects of the Invention

In order to solve the above-mentioned problems, the present invention provides the following in the gap formed between the ingot and the inner wall surface of the cavity due to solidification shrinkage when the molten metal poured into the cavity becomes an ingot. It is conceived to form a step portion on the inner wall surface of the cavity for preventing the molten metal poured into the wall from being inserted.
That is, an ingot casting mold according to the present invention (Claim 1) is a mold for casting an ingot by casting a molten metal a plurality of times, and has a cavity having an opening at an upper end and an inner wall surface of the cavity. in the multiple form and plan view including a stepped portion facing the opening exhibiting a cyclic or frame-like, it is characterized.

According to this, when the molten metal was poured into the mold cavity, the molten metal was obtained by solidifying and shrinking by sequentially casting so that the molten metal surface was higher than each of the plurality of steps . The ingot is formed with a plurality of step portions substantially equal to the shape of each step portion of the inner wall surface of the cavity. At this time, the step formed on the ingot side and the step on the inner wall surface of the cavity overlap in plan view, so that the molten metal to be poured next has a gap between the cavity and the ingot. However, it is not inserted into the gap below the stepped portion. Therefore, the ingot obtained after a plurality of castings can be easily and reliably extracted from the cavity of the mold with a relatively small force, and the ingot can be prevented from being damaged to have a required shape.

The molten metal includes, for example, a Ti alloy melt obtained by melting a Ti raw material by semi-levitation (semi-magnetic levitation) or vacuum induction melting, a low alloy steel, a high alloy steel melted in an arc furnace or an induction furnace, Or a molten metal such as special steel is included.
The mold cavity may have a taper that decreases in diameter from the opening toward the bottom with the stepped portion interposed therebetween.
Furthermore, since a plurality of stepped portions on the inner wall surface of the cavity is formed, the number of the step portion of the one or the more smaller than the number of the molten metal is cast. In addition, the step part to be omitted is the bottom side of the cavity where the molten metal has a long drop distance and the temperature is lowered, so that the molten metal does not easily enter the gap between the inner wall surface of the cavity and the ingot.
In addition, the shape of the ingot and the cavity includes not only a columnar shape including the stepped portion but also a long columnar shape including the stepped portion, an elliptical columnar shape, or a square columnar shape with rounded corners. .
Furthermore, the present invention includes an ingot casting mold (Claim 2), wherein the stepped portion is an inclined surface inclined toward the bottom side of the cavity .

In the present invention, a mold cover having a through hole located inside the opening at the upper end of the cavity in a plan view is attached to the upper end surface side of the mold. Item 3 ) is also included.
According to this, the molten metal adhering on the surface of the mold cover and the molten metal adhering to the inner wall surface of the cavity due to the splash when the molten metal is poured can be separated. As a result, when the molten metal adhering to the upper end surface of the mold and the inner wall surface of the cavity is solidified and contracted, it is possible to prevent the ingot in the cavity from floating up. For this reason, the cast ingot can be inclined and lifted up and the inner wall surface of the cavity can be prevented from being twisted, so that the ingot can be easily pulled out. Furthermore, in the case where a mold having a cavity with a taper (inclination) that reduces the diameter of the bottom side is used, it is possible to avoid a situation in which the ingot rises and a gap between the cavity and the inner wall surface becomes large.

Furthermore, in the present invention, the distance between the inner surface of the through hole of the mold cover and the inner surface of the opening of the cavity is 15 mm or more in all directions from the axial center of the cavity to the outside in a plan view. An ingot casting mold (Claim 4 ) is also included.
According to this, the molten metal adhering on the surface of the mold cover and the molten metal adhering to the inner wall surface of the cavity can be reliably separated. The inner surface of the through hole of the mold cover includes a form in which the length along the axial direction of the through hole is extremely short.

In addition, the present invention also provides an ingot casting mold (Claim 5 ) in which the mold cover is attached to the upper end surface of the mold surrounding the periphery of the opening at the upper end of the cavity via an elastic material. included.
According to this, a lot of droplets are generated from the poured molten metal, the molten metal adhering to the surface of the mold cover, the molten metal adhering to the inner wall surface of the cavity due to the above-mentioned droplets, and the ingot in the cavity are continuously connected to each other. Even if the molten metal adhering to the inner wall surface of the metal is solidified and contracted, the elastic material absorbs the contraction allowance. As a result, the ingot is lifted up, and the molten metal to be poured is inserted into the enlarged gap between the ingot and the inner wall surface of the cavity due to the uplift, or the ingot obtained by multiple castings is axially It is possible to prevent the mold cavity from rubbing and twisting in a direction that intersects with.
In addition to the plurality of coil springs, the elastic material includes a plurality of leaf springs, an arc-shaped or ring-shaped heat resistant rubber material, or a heat resistant resin material.

On the other hand, the ingot casting method of the present invention (Claim 6 ) uses an ingot casting mold so that the molten metal is placed in the cavity from the opening of the casting mold so that the molten metal surface is positioned above the stepped portion. And a casting step.
According to this, when pouring the molten metal into the mold cavity, the ingot and the cavity obtained by casting so that the molten metal surface is higher than the uppermost step among the plurality of steps. A plurality of gaps sandwiching the stepped portion are formed between the inner wall surface and the inner wall surface. For this reason, the said ingot can be smoothly and reliably extracted from a casting_mold | template with comparatively little force. Therefore, efficient ingot casting can be performed.
The mold once extracted from the ingot is cooled to near a predetermined temperature, and after the cavity returns to the original dimensions, a plurality of casting steps are performed to obtain the next ingot.

In the following, the best mode for carrying out the present invention will be described.
FIG. 1 is a vertical cross-sectional view schematically showing an ingot casting mold 1 of the present invention and a melting furnace 20 for casting a molten metal M therein. The taper attached to the cavity C in the mold 1 is exaggerated in FIG. 1 and the subsequent drawings.
As shown in FIG. 1, an ingot casting mold (hereinafter simply referred to as a mold) 1 is opened to a substantially cylindrical main body 2 made of a metal such as cast steel or cast iron, and an upper end surface 3 of the main body 2. In addition, it is formed on a substantially cylindrical cavity C having a slight taper (inclination) so as to reduce the diameter toward the through hole 5 opened in the bottom surface 4 and the inner wall surface of the cavity C, and the plan view is And a plurality of step portions 6 to 8 having a ring shape.
The mold 1 is placed on the surface of the surface plate 9, and the surface of the surface plate 9 exposed at the bottom surface of the through hole 5 of the mold 1 constitutes the bottom surface of the cavity C.

The cavity C is inclined so that the diameter is reduced by about 1 to 2 mm per 100 mm in the axial direction from the opening at the upper end toward the bottom surface 4. The step portions 6 to 8 are each an annular horizontal plane that is orthogonal to the axial (vertical) direction of the cavity C and faces the opening of the cavity C.
In addition, as will be described later, the positions of the step portions 6 to 8 are lower than the level of the molten metal surface L (n) of the molten metal M that is poured every plurality of casting steps. Further, the step portions 6 to 8 are inclined surfaces that are orthogonal to the vertical axial direction of the cavity C and are inclined toward the horizontal surface facing the opening or the bottom side described later. It is desirable that the shrinkage allowance when M is solidified to become an ingot m is greater than or equal to half. That is, when the width of the step portions 6 to 8 in plan view is smaller than half of the shrinkage allowance when the molten metal M is solidified, the convex portion formed at the upper end portion of the ingot m solidified and contracted is the step portion 6. The next molten metal is inserted into the gap formed on the lower side of the stepped portions 6 to 8 without being supported by the horizontal surface or the inclined surface. For this reason, it is recommended that the range of the width of the stepped portion be the above range.

As shown in FIG. 1, a mold cover 10 is attached to the upper end surface 3 of the mold 1 so as to surround the opening of the cavity C. The mold cover 10 includes an annular main body 12 made of the same metal as described above, an annular surface 14 that forms an upper side thereof and is inclined downward toward the opening side of the cavity C, and is located on the inner side thereof. A through-hole 16 located right above the opening of the cavity C and a plurality of concave portions 18 provided downward on the bottom surface of the main body 12 are provided. A coil spring (elastic material) b is interposed between the concave portion 18 and a plurality of concave portions 3 a provided to face the upper end surface 3 of the mold 1, so that the mold cover 10 is placed on the mold 1. Above the end face 3, it is supported so that it can be raised and lowered.
The inner diameter d of the through hole 16 of the mold cover 10 is set to be smaller than the inner diameter D of the opening of the cavity C by 30 mm or more. That is, the distance between the inner surface of the through hole 16 of the mold cover 10 and the inner surface of the opening of the cavity C is 15 mm or more.

As shown in FIG. 1, above the mold 1 and the mold cover 10, for example, a Ti alloy such as Ti-6 mass% Al-4 mass% V is melted and the molten metal M is poured down. A melting (semi-magnetic levitation) melting furnace (hereinafter simply referred to as a melting furnace) 20 is installed.
The melting furnace 20 includes a water-cooled copper crucible 22 made of copper and having a cylindrical shape as a whole by a plurality of segments in which cooling water is circulated and connected via an insulating material along the circumferential direction. Inductive coil c1 wound along the outer periphery of the crucible 22 and hung along the outer surface of the pouring cylinder 26 that hangs down from the center of the bottom 25 of the crucible 22 and has a pouring hole 28 for the molten metal M. An induction coil c2 is provided.

Here, the ingot casting method of the present invention using the mold 1 will be described.
When a necessary high frequency current is supplied to the induction coil c1 after charging Ti raw material such as sponge Ti or Ti scrap in the inner side 24 of the copper crucible 22 in advance, the current flows along the inner and outer surfaces of the induction coil c1. The magnetic field excited in this way penetrates into the Ti raw material charged in the inner side 24 of the copper crucible 22. With this magnetic field, the Ti raw material is induction-heated, and simultaneously, the Lorentz repulsion force causes the molten Ti alloy M to rise in a substantially hemispherical shape, and the inner wall surface of the inner side 24 of the copper crucible 22 is shown in FIG. Get away from.
A solidified layer S made of a Ti alloy is formed in a substantially disk shape on the bottom 25 of the copper crucible 22. Further, in the pouring hole 28 of the pouring tube 26, a solidified piece g which is the remaining portion of the molten metal M previously melted is positioned in advance, and the pouring hole 28 is closed. In other words, the pouring cylinder 26 and the induction coil c2 constitute an electromagnetic nozzle.

Next, when a predetermined high-frequency current is applied to the induction coil c2 surrounding the pouring cylinder 26, the solidified piece g is melted, and together with the newly melted molten Ti alloy M, as shown in FIG. Almost the entire amount of the molten metal M melted in the furnace 20 is successively poured into the bottom side in the cavity C of the mold 1 successively.
As shown in the partial vertical sectional views on the left side of FIGS. 2 and 3, the molten metal M is above the surface of the surface plate 9 on the bottom surface 4 side in the cavity C and above the lowermost step 6 located above it. Is poured to the level of the hot water surface L1 (first casting step).
As shown in the partial enlarged view on the right side of FIG. 3 in which the one-dot chain line portion X in the partial sectional view on the left side of FIG. It is set to be half z (shown in the right side of FIG. 4 to be described later) or more than half of the shrinkage allowance (reduction in the diameter direction of the ingot).

As a result, as shown in the partial vertical sectional view on the left side in FIG. 4 and the partial enlarged view on the right side in FIG. 4 in which the one-dot chain line portion Y is enlarged, the molten metal M poured down by the first casting step is In the process of cooling, it solidifies and shrinks along the radial and axial directions. Therefore, a substantially cylindrical gap s1 is formed between the outer peripheral surface of the obtained ingot m and the inner wall surface of the cavity C.
On the other hand, the upper end portion of the ingot m at a position higher than the step portion 6 is also smaller in diameter than the outer diameter of the step portion 6 because the diameter that is equal to or larger than the outer diameter of the step portion 6 is solidified and contracted. It becomes an annular convex portion v. A ring-shaped gap s2 (coagulation allowance) having a low height is formed between the convex portion v and the inner wall surface of the cavity C above the step portion 6.

At this time, as shown in FIG. 4, the bottom surface of the annular convex portion v formed at the upper end portion of the ingot m is in surface contact with the step portion 6 or is in a similar state. For this reason, the lower gap s1 is separated from the upper gap s2, and is sealed between the inner wall surface of the cavity C and the ingot m. As a result, the molten metal M to be poured next time is not inserted into the gap s1.
In addition, a part of the new molten metal M poured down above the stepped portion 6 is inserted into the upper gap s2, but as will be described later, a convex portion r having a larger diameter than the convex portion v is obtained. The convex portion r is in contact with the inner wall surface of the cavity C or a very small gap is formed.
Further, new molten metal M melted in the melting furnace 20 is sequentially poured into the cavity C above the ingot m and cast to the level of the molten metal surface (not shown) above the stepped portion 7. (Second casting process).

Next, as shown in FIG. 5, in the cavity C located below the uppermost step 8, above the ingot m where the molten metal M melted in the third time solidifies in the second casting step. Is poured down to the level of the molten metal surface L3 (third casting step).
At this time, as shown on the left side of FIG. 5, a part M1 of the molten metal M dropped from the melting furnace 20 and adhered to the surface 14 of the mold cover 10 and a molten metal M2 adhered to the inner wall surface of the cavity C are: It is separated by the mold cover 10. As a result, even if the molten metal M2 contracts during solidification, the ingot m in the cavity C does not rise. Therefore, the pouring of the molten metal M in the fourth casting process can be performed without any trouble.
Even if a part M1 of the molten metal M poured from the melting furnace 20 falls carelessly to a position deviating from the vicinity of the axis of the cavity C, it falls onto the annular surface 14 of the mold cover 10. Then, it falls into the cavity C from the through hole 16 and becomes a part of the ingot m. Further, as shown in FIG. 5, an annular convex portion r partially connected to the molten metal M2 is formed at the upper end portion of the ingot m.

Basically, when the mold cover 10 is attached to the upper end of the mold 1 as described above, the molten metal M1 attached to the surface 14 of the cover 10 and the molten metal M2 attached to the inner wall surface of the cavity C Integration can be prevented and lifting of the ingot m can be prevented.
By the way, as shown on the right side of FIG. 5, the molten metal M from the melting furnace 20 is shaken, and a large amount of molten metal M3 adheres to the surface 14 of the mold cover 10 and adheres to the inner surface of the molten metal M3 and the cavity C. The molten metal M2 may be connected in series through the belt-shaped molten metal j. In such a case, if the coil spring b is not provided, an upward force acts on the ingot m due to solidification shrinkage of the molten metal M2 and the molten metal j, and the ingot m tends to float. In contrast, in the present embodiment, since the mold cover 10 is supported by the coil spring b, the coil spring b contracts by an amount corresponding to the compression allowance as indicated by the solid line arrow in the right side of FIG. As a result, the ingot m in the cavity C can be prevented from floating to the upper end surface 3 side of the mold 1.

Finally, in the cavity C located above the uppermost step 8, the melt M melted at the fourth time is poured in the same manner as described above, and solidifies to become an ingot m. Ingot G is obtained (fourth casting step).
And after removing the said surface plate 9, the knockout rod which is not shown in figure is raised toward the opening part side from the bottom side of the cavity C, The ingot G in which the several ingots m continued in the axial direction is made into the casting_mold | template 1 The step of extracting from the cavity C is performed. At this time, since the gap s1 is located around each ingot m and the frictional force generated in the vicinity of each of the step portions 6 to 8 is small, the ingot G can be easily and reliably extracted with a small force. .

By the above manufacturing method, as shown in FIG. 6, a substantially cylindrical ingot G having portions 1p to 4p in which four ingots are continuous along the axial direction is obtained.
The ingot G is used as, for example, a vertically supported consumable electrode in a vacuum arc remelting furnace, and is melted again by an arc generated between the lower end of the ingot G and the electrode on the furnace bottom side facing the lower end. It is made into an ingot with a dense alloy structure.
In the mold 1, at least the lowermost step 6 has a long drop distance of the molten metal M in the second casting step, and the temperature of the molten metal M is lowered and is easily solidified. It is difficult to enter the gap between the ingot m cast into the inner wall and the inner wall surface of the cavity C, and may be omitted.
Furthermore, when the runout of the molten metal M poured from the melting furnace 20 is small, the coil spring b may be omitted and the mold cover 10 may be directly attached to the upper end surface 3 of the mold 1.

7 to 9 are partial vertical sectional views showing a mold 1a of a modified form of the mold 1, and partial schematic views showing steps of an ingot casting method using the mold 1a.
As shown in FIG. 7, a mold 1a having the same main body 2 and cavity C as described above has step portions 6a to 8a formed on the inner wall surface of the cavity C in the same position along the axial direction. As illustrated by the step portion 7a in FIG. 7, the step portions 6a to 8a are inclined in a ring shape in a plan view inclined so as to face the opening side of the cavity C and the central axis side of the cavity C is lowered. Surface. In addition, the width w of the step portions 6a to 8a in plan view is set to be not less than half of the shrinkage allowance when the cast molten metal M is solidified.
As shown in FIGS. 7 and 8, a casting process is performed in which a new molten metal M is poured from the melting furnace 20 to a level of the molten metal surface L2 higher than the stepped portion 7a.
The cast molten metal M is solidified and shrunk along the radial direction and the axial direction as it cools, and becomes an ingot m as shown in FIG. A cylindrical gap s1 is formed between the inner wall surface.

At the same time, as shown in FIG. 9, above the stepped portion 7a, the upper end portion of the ingot m is solidified and contracted to form a ring-shaped convex portion v having a smaller diameter than the outer diameter of the stepped portion 7a. A ring-shaped gap s2 having a low height is formed between the convex portion v and the inner wall surface of the cavity C above the stepped portion 7a.
At this time, the convex portion v of the ingot m is in surface contact with the inclined surface of the stepped portion 7a or is in an equivalent state. As a result, the gap s1 positioned on the lower side of the stepped portion 7a is separated from the upper gap s2, so that the next insertion of the molten metal M does not occur.
By performing each step of the manufacturing method using the mold 1a as described above, the same operation as described above can be performed, the same ingot G can be cast, and the ingot G can be easily extracted. It becomes.
In the mold 1a, at least the lowest step 6a may be omitted.

In the present invention, the cavity of the mold is not limited to a circular cross section, but may be a cross section having a substantially square cross section with rounded corners, or an oval or elliptical cross section .
Further, in the cavity of the same mold, or in the hotel form the stepped portion is different from the position of the step portion of the horizontal inclined surface.
Further, the mold cover is not limited to an annular surface, and may have an angular shape in plan view as long as a through hole is disposed near the center.
In addition, the molten metal to be cast is not particularly limited, but may be made of carbon steel, low alloy steel, high alloy steel, special steel, copper, copper alloy, or the like in addition to Ti or Ti alloy.

1 is a vertical sectional view showing an embodiment of an ingot casting mold according to the present invention. The vertical sectional view showing the outline of one process of the ingot casting method of the present invention. FIG. 3 is a partial vertical sectional view and a partially enlarged view showing a step following FIG. 2. FIG. 4 is a partial vertical sectional view and a partial enlarged view showing a step following FIG. 3. FIG. 5 is a partial vertical sectional view and a partially enlarged view showing a step following FIG. 4. The typical sectional view showing the ingot obtained by the above-mentioned casting method. The partial vertical sectional view which shows the deformation | transformation form of the said casting_mold | template. The schematic sectional drawing which shows 1 process of the ingot casting method using the casting_mold | template of FIG. FIG. 9 is a schematic cross-sectional view showing a step following FIG. 8.

Explanation of symbols

1, 1a ……………… Ingot casting mold 3 ………………………… Upper end face 6-8, 6a-8a… Step 10 …………………… Mold cover 14 ………… …………… Round ring 16 …………………… Through hole M ……………………… Molten metal C ……………………… Cavity w ………………… ...... Step width D, d ............ Inner diameter b ............ ……………… Coil spring (elastic material)
L1 ~ L3 ……………… Bath surface G ……………………… Ingot

Claims (6)

A mold for casting an ingot by casting a molten metal multiple times,
A cavity having an opening at the upper end;
Are multiple formed on the inner wall surface of the cavity, and a plan view including a step portion that faces and the opening an annular shape or frame-like,
An ingot casting mold characterized by that. The step is an inclined surface inclined toward the bottom side of the cavity .
The ingot casting mold according to claim 1. On the upper end surface side of the mold, a mold cover having a through hole located inside the opening at the upper end of the cavity is attached in plan view.
The ingot casting mold according to claim 1, wherein the casting mold is an ingot casting mold. The distance between the inner surface of the through hole of the mold cover and the inner surface of the opening of the cavity is 15 mm or more in all directions from the axial center of the cavity to the outside in plan view.
The ingot casting mold according to claim 3 . The mold cover is attached to the upper end surface of the mold surrounding the opening at the upper end of the cavity via an elastic material,
Ingot casting mold according to claim 3 or 4, characterized in that. Using the ingot casting mold according to any one of claims 1 to 5 ,
Casting the molten metal into the cavity from the opening of the mold so that the molten metal surface is positioned above the stepped portion,
An ingot casting method characterized by the above.

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