JP2017094372A - Core pin and metal mold for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core pin in which a failure such that a bottom of a taper part thereof is broken is suppressed.SOLUTION: A core pin comprising a body part formed along an axis X1, and a projection 20 which is connected to a tip side of the body part and is projected into a cavity part 300 from an insertion hole. The projection 20 has a taper part 21 of which an outer diameter is gradually reduced from a first position P1 on a base end side toward a second position P2 on a tip side, and on which a draft angle, in which an inclination angle with respect to the axis X1 is changed from an angle θ1 to an angle θ2 at a gradient change position Pc, is formed, thereby providing a core pin 100 which satisfies D1<L1. Herein, D1 represents an outer diameter of the taper part 21 at the first position P1, and L1 represents a distance along the axis X1 from the first position P1 to the gradient change position Pc.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a core pin and a casting mold.

2. Description of the Related Art Conventionally, a core pin used to form a pilot hole or the like of a bolt hole to which a fastening bolt is fastened is formed in a cast product (for example, see Patent Document 1).
For cast pins, shrinkage force when the molten metal solidifies, rapid cooling due to spray and air blow, stress difference caused by partial expansion and contraction, and bending load when the cast product is released from the mold And tensile load (release resistance) acts repeatedly.
The core pin described in Patent Document 1 is an inner pin and a sleeve for suppressing breakage due to repeated stress acting on a boundary portion between a middle diameter portion and a taper taper portion of an integrally formed core pin. Are combined. The cast pin disclosed in Patent Document 1 can suppress breakage from the base of the tapered portion by removing the stress concentration portion between the medium diameter portion and the tapered portion.

Japanese Patent No. 5616404

  However, when a draft angle of a certain angle is formed in the tapered taper portion of the cast pin protruding into the cavity portion, a substantially uniform mold release resistance acts in the entire region of the tapered taper portion. Therefore, the mold release resistance that has acted on the entire region of the taper taper portion repeatedly acts on the base of the taper taper portion, and metal fatigue due to the mold release resistance is accumulated at the base of the taper taper portion. And the accumulated metal fatigue will eventually break the root of the tapered portion.

  The present invention has been made in view of the above points, and has reduced the mold release resistance that acts on the tapered portion of the protruding portion that protrudes into the cavity portion, thereby suppressing the problem that the root of the tapered portion is broken. An object of the present invention is to provide a punch pin and a casting mold into which the punch pin is inserted.

The present invention employs the following means in order to solve the above problems.
A cast pin according to an aspect of the present invention is inserted into an insertion hole formed along the axis in a casting mold, and a main body formed along the axis so as to correspond to the shape of the insertion hole And a protrusion that is coupled to the distal end side of the main body portion and protrudes from the insertion hole to the cavity portion, the protrusion being directed from the first position on the proximal end side toward the second position on the distal end side. A cast pin that has a taper portion in which a draft angle in which an inclination angle with respect to the axis changes from a first angle to a second angle at a gradient change position with a gradually decreasing outer diameter and satisfying D1 <L1. Here, D1: an outer diameter of the tapered portion at the first position, L1: a distance along the axis from the first position to the gradient change position.

According to the core pin according to the aspect of the present invention, the first position on the proximal end side of the taper portion on which a bending load, a tensile load, and the like (mold release resistance) act when the cast product is released from the mold. A draft angle is formed in the taper portion so that an inclination angle with respect to an axis along which the core pin extends changes at a gradient change position between the second position on the distal end side.
In a cast pin in which a draft angle with a constant inclination angle is formed from the first position to the second position, a substantially uniform release resistance acts in the entire area of the taper portion, and metal is formed on the proximal end side of the taper portion. Excessive fatigue accumulates. On the other hand, according to the cast pin according to one aspect of the present invention, since a region having a large inclination angle is formed on the base end side or the tip end side of the gradient change position, the mold release resistance is reduced in a partial region of the tapered portion. Therefore, metal fatigue accumulated on the proximal end side of the tapered portion is reduced.

According to the inventors, it has been found that in the region from the first position to a position separated by a distance corresponding to the outer diameter D1 of the tapered portion at this position, the frequency of occurrence of breakage of the core pin is high. Further, the metal fatigue accumulated on the proximal end side of the taper portion by disposing the gradient change position further on the distal end side than the position separated from the first position by a distance corresponding to the outer diameter D1 of the taper portion at the position. The knowledge that it reduces is obtained.
Therefore, the core pin according to one aspect of the present invention satisfies D1 <L1. Here, L1 is the distance along the axis from the first position to the gradient change position.

In the cast pin according to one aspect of the present invention, the first angle may be larger than the second angle.
By doing so, the mold release resistance in the region closer to the base end side than the gradient change position of the taper portion is reduced, and the core pin is broken due to metal fatigue accumulated on the base end side of the taper portion. Can be suppressed.

In the cast pin according to one aspect of the present invention, the second angle may be larger than the first angle.
By doing so, the mold release resistance in the region closer to the tip side than the gradient change position of the taper portion is reduced, and the problem that the core pin is broken due to metal fatigue accumulated on the base end side of the taper portion is suppressed. can do.

In the cast pin according to one aspect of the present invention, the main body portion and the protruding portion may have a bottomed hole extending along the axis.
In this way, a cooling pipe that guides cooling water to the bottomed hole formed inside the core pin is arranged to cool the cast product around the core pin and promote solidification of the cast product. Can do.

A casting mold according to an aspect of the present invention is obtained by inserting the core pin according to any one of the above-described portions into the insertion hole.
According to the casting mold according to one aspect of the present invention, the die-casting in which the mold release resistance acting on the tapered portion of the projecting portion projecting to the cavity portion is reduced and the problem that the root of the tapered portion is broken is suppressed. A casting mold in which pins are inserted can be provided.

  According to the present invention, a cast pin in which a mold release resistance acting on a taper portion of a projecting portion projecting into a cavity portion is reduced and a problem that the root of the taper portion breaks down is suppressed, and for casting in which the pin is inserted Mold can be provided.

It is a longitudinal cross-sectional view which shows the metal mold | die for die-casting of 1st Embodiment. It is a longitudinal cross-sectional view which shows the protrusion part vicinity of the core pin shown in FIG. It is a longitudinal cross-sectional view which shows the gradient change position vicinity of the taper part shown in FIG. It is a longitudinal cross-sectional view which shows the protrusion part vicinity of the cast pin of 2nd Embodiment. It is a longitudinal cross-sectional view which shows the gradient change position vicinity of the taper part shown in FIG.

[First Embodiment]
A die casting mold 200 according to a first embodiment of the present invention will be described with reference to the drawings.
A die casting mold 200 according to the present embodiment shown in FIG. 1 is a mold used in a die casting apparatus for casting a product by injecting a molten metal such as aluminum, zinc, or magnesium into a mold.

  The die casting mold 200 includes a movable mold and a fixed mold. In FIG. 1, only a fixed die of the die casting die 200 is shown. The movable type is a member that moves in a direction close to or away from the fixed type in the direction of the axis X1 by a drive mechanism (not shown) such as a hydraulic cylinder. In the movable mold, a cavity portion 300 is formed between the movable mold and the fixed mold in a state in which the movable mold is close to the fixed mold.

The die casting apparatus casts a product that matches the shape of the cavity 300 by injecting molten metal into the cavity 300 of the die casting mold 200 and cooling it. In the die casting apparatus, after the molten metal is cooled to become a product, the movable mold is separated from the fixed mold by the drive mechanism, and the cast product is released from the fixed mold. When the cast product is taken out, in order to release the cast product from the movable mold, an extrusion pin (not shown) is pushed against the cast product and pushed out.
As described above, the die casting apparatus releases the cast product from the fixed mold and the movable mold.

As shown in FIG. 1, the die-casting mold 200 is formed with an insertion hole 210 formed in a fixed mold along an axis X1 that is the moving direction of the movable mold. The insertion hole 210 is a cylindrical through hole having a circular cross-sectional view in a plane orthogonal to the axis X1.
As shown in FIG. 1, a die casting die 200 is provided with a core pin 100 that is fixed to a fixed die while being inserted into an insertion hole 210. The cast pin 100 is used for forming a pilot hole or the like of a bolt hole to which a fastening bolt is fastened in a cast product.

In the above description, the insertion hole 210 is formed in the fixed mold and the cast pin 100 is fixed to the insertion hole 210. However, other modes may be used.
For example, the insertion hole 210 may be formed in the movable mold and the cast pin 100 may be fixed to the insertion hole 210.
For example, you may fix to the sliding core (slide core) which can move relatively with respect to a movable type | mold.

  As shown in FIG. 1, the core pin 100 includes an inner pin 110 formed in a columnar shape extending along the axis X <b> 1 and a sleeve 120 formed in a cylindrical shape extending along the axis X <b> 1. The cast pin 100 is formed by combining a sleeve 120 having an outer diameter substantially the same as the outer diameter of the inner pin 110 on the outer side of the inner pin 110 and combining these components.

  In the cast pin 100 of the present embodiment, the root portion 20 a of the protruding portion 20 that protrudes into the cavity portion 300 is formed by a separate member of the sleeve 120 and the inner pin 110. When the sleeve 120 and the inner pin 110 shown in FIG. 1 are formed as an integral member, a boundary portion (a portion where the outer diameter with respect to the axis X1 rapidly increases) is formed in the root portion 20a. This boundary portion is likely to break when metal fatigue is accumulated due to a bending load and a tensile load (release resistance) when the cast product is released from the mold.

  On the other hand, since the core pin 100 of this embodiment uses the sleeve 120 and the inner pin 110 as separate members, it can have a structure that excludes the boundary portion. Therefore, as compared with the case where the sleeve 120 and the inner pin 110 are formed as an integral member, the stress concentration portion in the root portion 20a of the core pin 100 can be eliminated and breakage can be suppressed. As a material constituting the inner pin 110 and the sleeve 120, alloy tool steel (for example, SKD61) obtained by adding tungsten, molybdenum, chromium, vanadium, or the like to carbon tool steel can be used.

  As shown in FIG. 1, a bottomed cooling hole (bottomed hole) 110 a extending along the axis X <b> 1 is formed inside the inner pin 110. The cooling hole 110a is a hole into which a cylindrical cooling pipe 130 indicated by a broken line in FIG. 2 is inserted along the axis X1. The cooling water that has flowed out of the cooling pipe 130 to the bottom of the cooling hole 110a (the tip side of the casting pin 100) flows through the gap between the outer peripheral surface of the cooling pipe 130 and the inner peripheral surface of the cooling hole 110a. It is returned to the base end side of the pin 100 (arrow shown in FIG. 2). In addition, the core pin 100 shown in FIG. 1 omits illustration of the cooling pipe 130 arrange | positioned inside the inner pin 110. FIG.

Next, each part of the core pin 100 of this embodiment will be described.
As shown in FIG. 1, the core pin 100 of the present embodiment includes a main body 10 formed along the axis X1 so as to correspond to the shape of the insertion hole 210, and a front end side (cavity 300 of the main body 10). And a projecting part 20 projecting from the insertion hole 210 to the cavity part 300 and a diameter-enlarged part (positioning part) 30 for positioning the position of the main body part 10 and the projecting part 20 on the axis X.

  The main body 10 is a portion having an outer diameter that is substantially the same as the inner diameter of the insertion hole 210, and the insertion hole is in close contact with the inner peripheral surface of the insertion hole 210 so that the molten metal does not enter from the cavity part 300. 210 is inserted. The main body 10 has a constant outer diameter centered on the axis X1 from the proximal end side (the enlarged diameter portion 30 side) to the distal end side (the protruding portion 20 side).

The enlarged diameter portion 30 is a portion having an outer diameter larger than that of the main body portion 10 so as to abut on a stepped portion 220 formed on the proximal end side of the insertion hole 210. The enlarged diameter portion 30 is also formed in a cylindrical shape along the axis X <b> 1 so as to correspond to the shape of the insertion hole 210 similarly to the main body portion 10.
As shown in FIG. 1, the end surface 30 a on the distal end side of the enlarged diameter portion 30 is abutted against the stepped portion 220 of the insertion hole 210 while being inserted into the insertion hole 210. Thereby, the position on the axis line X1 of the main-body part 10 and the protrusion part 20 of the core pin 100 is fixed.

Next, the protrusion 20 of the core pin 100 will be described with reference to FIGS. 2 and 3.
As shown in FIG. 2, the protruding portion 20 is connected to a tapered portion 21 having a draft angle, a proximal end portion 22 connected to the proximal end side of the tapered portion 21, and a distal end side of the tapered portion 21. And a tip portion 23.

The taper portion 21 is a substantially truncated cone having a draft angle gradually decreasing from the proximal end position P1 (first position) to the distal end position P2 (second position) on the axis X1. It is a shaped part.
As shown in FIGS. 2 and 3 (a longitudinal sectional view showing the vicinity of the gradient change position Pc of the taper portion shown in FIG. 2), the inclination angle of the taper portion 21 with respect to the axis X1 is an angle on the base end side at the gradient change position Pc. The angle changes from θ1 (first angle) to an angle θ2 (second angle) on the front end side.

  An axis X2 shown in FIG. 3 is an axis parallel to the axis X1. As shown in FIG. 3, the inclination angle of the outer peripheral surface (draft gradient) of the tapered portion 21 in the region closer to the base end than the gradient change position Pc is an angle θ1. Similarly, the inclination angle of the outer peripheral surface (draft gradient) of the tapered portion 21 in the region on the tip side of the gradient change position Pc is an angle θ2. Since the axis X2 is parallel to the axis X1, the angle θ1 indicates the inclination angle of the outer peripheral surface (draft angle) of the tapered portion 21 with respect to the axis X1, and the angle θ2 is the outer surface (draft angle) of the tapered portion 21 with respect to the axis X1. Indicates the tilt angle.

In the present embodiment, the angle θ1 and the angle θ2 satisfy all of the following conditional expressions.
θ1> θ2 (1)
0.5 ° <θ1 ≦ 2.0 ° (2)
0.5 ° ≦ θ2 <2.0 ° (3)
For example, the angle θ1 and the angle θ2 satisfying all the conditional expressions (1) to (3) are, for example, the angle θ1 is 1.5 ° and the angle θ2 is 0.5 °.

The imaginary line IL shown in FIGS. 2 and 3 is a line indicating the position of the outer peripheral surface of the tapered portion when the draft angle of the draft from the position P1 to the position P2 is constant. In this case, the outer diameter of the tapered portion gradually decreases at a constant rate from the outer diameter D1 at the position P1 to the outer diameter D2 at the position P2.
On the other hand, the inclination angle of the outer peripheral surface of the tapered portion 21 of the present embodiment indicated by the solid line with respect to the axis line X1 is larger on the base end side than the inclination change position Pc compared to the inclination angle indicated by the imaginary line IL, and is greater than the inclination change position Pc. Is also smaller on the tip side.

As shown in FIG. 2, the outer diameter D1 of the tapered portion 21 at the position P1 and the distance L1 along the axis X1 from the position P1 to the gradient change position Pc satisfy the following conditional expression.
D1 <L1 <2 · D1 (4)
The reason why D1 <L1 in the above conditional expression is satisfied is because the inventors have obtained the following knowledge.
In the region from the position P1 to a position separated by a distance corresponding to the outer diameter D1, the frequency of breakage of the core pin 100 is high.
The metal fatigue accumulated on the proximal end side of the tapered portion 21 is reduced by disposing the gradient change position Pc further on the distal end side than the position separated from the position P1 by a distance corresponding to the outer diameter D1.

  Further, L1 <2 · D1 in the conditional expression (4) is satisfied because if the gradient change position Pc is too far away from the position P1, the taper is formed from the inner peripheral surface of the cooling hole 110a having the inner diameter D3 in the vicinity of the position P2. This is because the distance (wall thickness) to the outer peripheral surface of the portion 21 is shortened and becomes thin, and the core pin 100 is easily broken near the position P2.

The proximal end portion 22 is a portion from a position P0 that coincides with an end face on the proximal end portion side of the cavity portion 300 to a position P1 on the proximal end portion side of the tapered portion 21. The outer peripheral side of the base end portion 22 is a distal end portion of the sleeve 120, and the inner peripheral side of the base end portion 22 is an inner pin 110. As shown in FIG. 2, the base end portion 22 has a shape in which the outer diameter sharply decreases from the position P0 toward the position P1.
The distal end portion 23 is a portion from a position P2 on the distal end side of the tapered portion 21 to a position P3 that coincides with the distal end of the core pin 100. As shown in FIG. 2, the distance from the position P1 to the position P3 is L2.

<Example>
Next, an example and a comparative example when a product is cast using the cast pin 100 satisfying the above conditional expressions (1) to (4) will be described. The present embodiment is an experimental example in which the number of products cast from the start of use of the core pin 100 until breakage is measured.
In this embodiment, in FIGS. 2 and 3, D1 = 4.5 mm, D2 = 3.9 mm, L1 = 6.0 mm, D3 = 2.0 mm, L2 = 22.4 mm, θ1 = 1.5 °, θ2 This was carried out using a cast pin 100 at 0.5 °.

  In the present embodiment, the internal hardness of the material constituting the tapered portion 21 is adjusted to be HRC (Rockwell hardness) 47 or more and HRC 49 or less, and the surface hardness is HV (Vickers hardness) 1000 or more and This is performed using SKD61, which is an alloy tool steel adjusted to HV1200 or lower. As the surface treatment for improving the hardness of the surface of the tapered portion 21 used in the example, a salt nitriding treatment which is a nitriding treatment using a salt solvent was used. Specifically, salt nitriding treatment was performed using PS treatment (Prevents Scoring and scuffing treatment) by Daido DM Solution Co., Ltd.

The comparative example is an example using a cast pin similar to the present example except that θ1 and θ2 are each 1.0 °.
That is, in the present embodiment, the inclination angle of the tapered portion 21 changes from 1.5 ° to 0.5 ° at the gradient change position Pc, whereas in the comparative example, the inclination angle of the tapered portion 21 changes from the position P1 to the position P2. It is constant at 1.0 ° until reaching.
As a result of this example, the number of products cast from the start of use of the core pin 100 to the breakage was about 34,000 in this example (about 34,000 castings), In the comparative example, there were about 2000 pieces (about 2000 castings).
Thus, in the example using the core pin 100 of the present embodiment, the number of products cast from the start of use until breakage was about 17 times that of the comparative example.

The operation and effect of the cast pin 100 of the present embodiment described above will be described.
According to the core pin 100 of the present embodiment, the position P1 on the proximal end side and the distal end side of the taper portion 21 on which a bending load and a tensile load (release resistance) when the cast product is released from the mold are applied. The draft angle is formed in the taper portion 21 so that the inclination angle with respect to the axis X1 in which the core pin 100 extends changes from the angle θ1 to the angle θ2 at the gradient change position Pc between the first position P2 and the second position P2.

  In the cast pin of the comparative example in which a draft angle with a constant inclination angle is formed from the position P1 to the position P2, a substantially uniform release resistance acts in the entire area of the tapered portion, and the proximal end side of the tapered portion is Excessive accumulation of metal fatigue. On the other hand, according to the cast pin 100 of the present embodiment, a region having a large inclination angle is formed on the base end side of the gradient change position Pc, and the mold release resistance is reduced in the region on the base end side of the tapered portion 21. Further, metal fatigue accumulated on the proximal end side of the tapered portion 21 is reduced.

According to the inventors, it has been found that the frequency of breakage of the core pin 100 is high in a region from the position P1 to a position separated by a distance corresponding to the outer diameter D1 of the tapered portion 21 at the position P1. . Further, the gradient change position Pc is accumulated on the proximal end side of the tapered portion 21 by disposing the gradient change position Pc further on the distal end side than the position separated from the position P1 by a distance corresponding to the outer diameter D1 of the tapered portion 21 at the position P1. The knowledge that metal fatigue is reduced was obtained.
Therefore, the core pin 100 according to the present embodiment satisfies D1 <L1. Here, L1 is a distance along the axis X1 from the position P1 to the gradient change position PC.

[Second Embodiment]
Next, a die casting die according to a second embodiment of the present invention will be described with reference to the drawings.
The die-casting mold of this embodiment is a modification of the die-casting mold 200 of the first embodiment, and is the same as the die-casting mold 200 of the first embodiment except as specifically described below. Suppose that

In the die casting die 200 of the first embodiment, the inclination angle of the projecting portion 20 of the core pin 100 with respect to the axis of the tapered portion 21 changes from the angle θ1 to the angle θ2 smaller than the angle θ1 at the gradient change position Pc. Met.
On the other hand, in the die casting mold according to the present embodiment, the inclination angle with respect to the axis X1 of the taper portion 21 ′ of the protruding portion 20 ′ of the cast pin 100 ′ is greater than the angle θ1 ′ from the angle θ1 ′ at the gradient change position Pc. The angle changes to a large angle θ2 ′.

As shown in FIG. 4, the tapered portion 21 ′ is formed on the axis X <b> 1 so that the outer diameter gradually decreases from the proximal position P <b> 1 (first position) to the distal position P <b> 2 (second position). It is a substantially frustoconical portion in which a gradient is formed.
As shown in FIG. 4 and FIG. 5 (longitudinal sectional view showing the vicinity of the gradient change position Pc of the taper portion shown in FIG. 4), the inclination angle of the taper portion 21 ′ with respect to the axis X1 is the base end side at the gradient change position Pc. The angle θ1 ′ (first angle) changes to the angle θ2 ′ (second angle) on the distal end side.

  An axis X3 shown in FIG. 5 is an axis parallel to the axis X1. As shown in FIG. 5, the inclination angle of the outer peripheral surface (draft gradient) of the tapered portion 21 ′ in the region closer to the base end than the gradient change position Pc is an angle θ <b> 1 ′. Similarly, the inclination angle of the outer peripheral surface (draft gradient) of the tapered portion 21 'in the region on the tip side of the gradient change position Pc is an angle θ2'. Since the axis X3 is parallel to the axis X1, the angle θ1 ′ indicates the inclination angle of the outer peripheral surface (draft angle) of the tapered portion 21 ′ with respect to the axis X1, and the angle θ2 ′ indicates the outer peripheral surface of the tapered portion 21 ′ with respect to the axis X1 ( The draft angle is shown.

In the present embodiment, the angle θ1 ′ and the angle θ2 ′ satisfy all of the following conditional expressions.
θ1 ′ <θ2 ′ (5)
0.5 ° ≦ θ1 <2.0 ° (6)
0.5 ° <θ2 ≦ 2.0 ° (7)
For example, the angle θ1 ′ and the angle θ2 ′ that satisfy all of the above conditional expressions (5) to (7) are, for example, an angle θ1 ′ of 0.5 ° and an angle θ2 ′ of 1.5 °.

The imaginary line IL shown in FIGS. 4 and 5 is a line indicating the position of the outer peripheral surface of the tapered portion when the draft angle of the draft from the position P1 to the position P2 is constant. In this case, the outer diameter of the tapered portion gradually decreases at a constant rate from the outer diameter D1 at the position P1 to the outer diameter D2 at the position P2.
On the other hand, the inclination angle of the outer peripheral surface of the tapered portion 21 of the present embodiment indicated by the solid line with respect to the axis X1 is smaller than the inclination change position indicated by the imaginary line IL on the base end side, and is smaller than the gradient change position Pc. Is also larger on the tip side.

As shown in FIG. 4, the outer diameter D1 of the tapered portion 21 ′ at the position P1 and the distance L1 along the axis X1 from the position P1 to the gradient change position Pc satisfy the following conditional expression.
D1 <L1 <2 · D1 (8)
The reason why D1 <L1 in the above conditional expression is satisfied is because the inventors have obtained the following knowledge.
In the region from the position P1 to a position separated by a distance corresponding to the outer diameter D1, the frequency of breakage of the cast pin 100 ′ is high.
The metal fatigue accumulated on the proximal end side of the tapered portion 21 ′ is reduced by disposing the gradient change position Pc further on the distal end side than the position separated from the position P1 by a distance corresponding to the outer diameter D1.

  Further, L1 <2 · D1 of the conditional expression (8) is satisfied because if the gradient change position Pc is too far away from the position P1, the region where the release resistance is reduced becomes narrow, and the base end of the taper portion 21 is satisfied. This is because the metal fatigue accumulated on the side increases.

<Example>
Next, an example and a comparative example when a product is cast using a cast pin 100 ′ that satisfies the above conditional expressions (5) to (8) will be described. The present embodiment is an experimental example in which the number of products cast from the start of use of the cast pin 100 ′ to breakage is measured.
4 and 5, D1 = 4.5 mm, D2 = 3.9 mm, L1 = 6.0 mm, D3 = 2.0 mm, L2 = 22.4 mm, θ1 ′ = 0.5 °, This is performed using a cast pin 100 ′ with θ 2 ′ = 1.5 °.
In the present embodiment, the internal hardness of the material constituting the taper portion 21 'is adjusted to HRC (Rockwell hardness) 47 or more and HRC 49 or less, and the surface hardness is HV (Vickers hardness) 1000 or more. And it was performed using SKD61 which is alloy tool steel adjusted to HV1200 or less. As the surface treatment for improving the hardness of the surface of the tapered portion 21 ′ used in the experimental example, a salt nitriding treatment that is a nitriding treatment using a salt solvent was used. Specifically, salt nitriding treatment was performed using PS treatment (Prevents Scoring and scuffing treatment) by Daido DM Solution Co., Ltd.

The comparative example is an example using a cast pin similar to that of this example except that θ1 ′ and θ2 ′ are 1.0 °.
That is, in the present embodiment, the inclination angle of the taper portion 21 ′ changes from 0.5 ° to 1.5 ° at the gradient change position Pc, whereas in the comparative example, the inclination angle of the taper portion 21 ′ changes from the position P1. It is constant at 1.0 ° until reaching the position P2.
As a result of the present example, the number of products cast from the start of use of the core pin 100 ′ to breakage was about 13,000 (about 13,000 castings) in this example. In the comparative example, there were about 2000 pieces (the number of castings was about 2000 times).
Thus, in the example using the cast pin 100 ′ of the present embodiment, the number of products cast from the start of use until breakage is about 6.5 times that of the comparative example. .

The operations and effects of the cast pin 100 ′ of the present embodiment described above will be described.
According to the cast pin 100 ′ of the present embodiment, the position P1 on the proximal end side of the tapered portion 21 ′ on which a bending load, a tensile load, etc. (release resistance) when the cast product is released from the mold acts. A draft angle is formed in the tapered portion 21 ′ so that the inclination angle with respect to the axis X1 in which the casting pin 100 extends changes from the angle θ1 ′ to the angle θ2 ′ at the gradient change position Pc between the front end position P2. Yes.

  In the cast pin of the comparative example in which a draft angle with a constant inclination angle is formed from the position P1 to the position P2, a substantially uniform release resistance acts in the entire area of the tapered portion, and the proximal end side of the tapered portion is Excessive accumulation of metal fatigue. On the other hand, according to the cast pin 100 of the present embodiment, a region having a large inclination angle is formed on the tip side of the gradient change position Pc, and the mold release resistance is reduced in the region on the tip side of the taper portion 21. Metal fatigue accumulated on the base end side of the portion 21 is reduced.

According to the inventors, in the region from the position P1 to a position separated by a distance corresponding to the outer diameter D1 of the tapered portion 21 at the position P1, the knowledge that the frequency of occurrence of breakage of the cast pin 100 ′ is high. It was. Further, the gradient change position Pc is accumulated on the proximal end side of the tapered portion 21 by disposing the gradient changing position Pc further on the distal end side than the position separated from the position P1 by a distance corresponding to the outer diameter D1 of the tapered portion 21 ′ at the position P1. The knowledge that the metal fatigue is reduced.
Therefore, the cast pin 100 ′ of the present embodiment satisfies D1 <L1. Here, L1 is a distance along the axis X1 from the position P1 to the gradient change position PC.

[Other Embodiments]
In the above description, the cast pin is a combination of the two members of the inner pin 110 and the sleeve 120, but other modes may be used.
For example, the cast pins 100 and 100 ′ formed by the inner pin 110 and the sleeve 120 may be formed as a single member.

  Further, in the above description, the draft angle of the tapered portions 21 and 21 ′ is changed only at the gradient change position Pc, but other modes may be used. For example, one or more other gradient change positions may be provided on the tip side of the gradient change position Pc, and the draft angle may be changed in multiple stages. In this case, the draft angle is changed in multiple steps so that the outer diameter gradually decreases from the position P1 toward the position P2.

DESCRIPTION OF SYMBOLS 10 Main body part 20 Protruding part 20a Root part 21,21 'Taper part 22 Base end part 23 Tip part 30 Wide diameter part (positioning part)
30a End face 100, 100 'Casting pin 110 Inner pin 110a Cooling hole (bottomed hole)
120 Sleeve 130 Cooling Pipe 200 Die Casting Mold 210 Insertion Hole 220 Step 300 Cavity IL Imaginary Line P1 Position (First Position)
P2 position (second position)
Pc Gradient change position X1, X2, X3 Axis θ1, θ1 ′ Angle (first angle)
θ2, θ2 'angle (second angle)

Claims (5)

A casting pin inserted into an insertion hole formed along the axis of the casting mold,
A main body formed along the axis to correspond to the shape of the insertion hole;
A protrusion that is connected to the distal end side of the main body and protrudes from the insertion hole to the cavity;
The protrusion is
A draft angle is formed in which the outer diameter gradually decreases from the first position on the proximal end toward the second position on the distal end side, and the inclination angle with respect to the axis changes from the first angle to the second angle at the gradient change position. A cast pin having a tapered portion and satisfying D1 <L1.
here,
D1: an outer diameter of the tapered portion at the first position;
L1: A distance along the axis from the first position to the gradient change position.   The core pin according to claim 1, wherein the first angle is larger than the second angle.   The core pin according to claim 1, wherein the second angle is larger than the first angle.   The core pin according to any one of claims 1 to 3, wherein a bottomed hole extending along the axis is formed in the main body portion and the protruding portion.   A casting mold in which the core pin according to any one of claims 1 to 4 is inserted into the insertion hole.

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