JP2020163396A - Core for mold - Google Patents

Abstract

To provide a core for a mold in which the fatigue breakdown of a projection part can be hard to occur.SOLUTION: A core for a mold comprises: an installation part installed to a mold having an edge face facing the cavity of a mold; and a projection part projected from a part of the edge face. The installation part and the projection part include: an elastic part formed at a region including a corner in which the outer surface of the projection part and the edge face are crossed; and a body as a part other than the elastic part, and the elastic limit of the elastic part is higher than the elastic limit of the body. In this way, the plastic deformation in the vicinity of the corner in which stress is easy to be concentrated can be made hard to occur, the fatigue breakdown of the projection part caused by the repeat of the plastic deformation in the vicinity of the corner can be suppressed.SELECTED DRAWING: Figure 1

Description

The present invention relates to a mold core capable of making it difficult for the protruding portion to be fatigued and broken.

At the corners connected to the outer surface of the protruding part of the core protruding into the cavity of the mold, there are solidification shrinkage of liquid raw materials such as molten metal, bending stress during mold release, and stress due to expansion and contraction of the core due to temperature changes. It may be concentrated and the protrusions may easily break due to fatigue. In order to suppress the concentration of stress in the corner where the end face of the mounting part mounted on the mold and the outer surface of the protruding part intersect, the inner pin is fitted into the bush so that the inner pin protrudes from the end face of the bush. There is a core in which a corner is formed by the end face of the bush and the outer surface of the inner pin (Patent Document 1).

Japanese Unexamined Patent Publication No. 2005-334961

However, in the above-mentioned conventional technique, when bending stress is applied to the inner pin, the bending stress is concentrated on the portion of the inner pin that hits the corner of the bush, so that fatigue fracture of the protruding portion cannot be sufficiently suppressed.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a core for a mold capable of preventing fatigue fracture of a protruding portion.

In order to achieve this object, the mold core of the present invention includes a mounting portion to be mounted on the mold with its end face facing the cavity of the mold, and a protruding portion protruding from a part of the end face. The mounting portion and the protruding portion include an elastic portion formed in a region including a corner where the outer surface of the protruding portion and the end face intersect, and a main body which is a portion other than the elastic portion. The elastic limit of is higher than the elastic limit of the main body.

Further, the mold core of the present invention includes a fixing portion arranged on the side opposite to the cavity of the mold, and a protruding portion protruding from the inner wall surface of the mold toward the cavity side and connected to the fixing portion. The mounting portion and the protruding portion include an elastic portion formed in a region including a corner where the outer surface of the protruding portion and the inner wall surface intersect, and a main body which is a portion other than the elastic portion, and the elastic portion. The elastic limit of is higher than the elastic limit of the main body.

According to the mold core according to claim 1, an elastic portion having an elastic limit higher than the elastic limit of the main body is formed in a region including a corner where the outer surface of the protruding portion and the end surface of the mounting portion intersect. , It is possible to prevent plastic deformation near the corner where stress is likely to be concentrated. As a result, fatigue fracture of the protruding portion due to repeated plastic deformation near the corner can be suppressed.

According to the mold core according to claim 2, the outer surface of the elastic portion constitutes at least a part of the end face or a part of the outer surface. As a result, since the elastic portion is provided in a wide region near the corner, in addition to the effect of claim 1, the protruding portion can be made more difficult to fracture due to fatigue.

According to the mold core according to claim 3, the outer surface of the elastic portion constitutes at least a part of the end face and a part of the outer surface, respectively. Since the elastic portion is provided in a wider region near the corner, in addition to the effect of claim 1, the protruding portion can be made less likely to be fatigue-fractured.

According to the die core according to claim 4, the interface between the elastic portion and the main body is an arc shape convex toward the main body in the cross section of the protruding portion in the protruding direction. Since the maximum value of the curvature of the interface is smaller than the maximum value of the curvature of the corner that determines the shape of the cavity, it is possible to make it difficult to concentrate stress near the interface of the main body. Therefore, in addition to the effect of any one of claims 1 to 3, the protruding portion can be made more difficult to be fatigue-fractured.

According to the mold core according to claim 5, an elastic portion having an elastic limit higher than the elastic limit of the main body is formed in a region including a corner where the outer surface of the protruding portion and the inner wall surface of the mold intersect. Therefore, it is possible to prevent plastic deformation in the vicinity of the corner where stress is likely to be concentrated. As a result, fatigue fracture of the protruding portion due to repeated plastic deformation near the corner can be suppressed.

According to the core for molds according to claim 6, since the elastic portion is a weld metal welded to the main body, an alloy layer is formed in which the proportion of the material mainly constituting the elastic portion decreases toward the main body. Has been done. As a result, stress concentration at the interface between the main body and the elastic portion can be suppressed. As a result, in addition to the effect of any one of claims 1 to 5, the protruding portion can be made less likely to be fatigue-fractured.

It is sectional drawing of the mold which attached the core for the mold in 1st Embodiment. (A) and (b) are explanatory views which show the manufacturing process of the core for a mold. It is sectional drawing of the mold which attached the core for the mold in 2nd Embodiment. It is sectional drawing of the mold which attached the core for the mold in 3rd Embodiment. It is a perspective view of the core for a mold in 4th Embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The mold core 10 (hereinafter referred to as “core 10”) in the first embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view of a mold 1 equipped with a core 10 according to the first embodiment.

As shown in FIG. 1, the core 10 is a so-called casting pin mounted on a casting die 1. The core 10 includes a mounting portion 11 mounted on the mold 1 and a protruding portion 13 projecting into the cavity 2 formed by the inner wall surface 4 of the mold 1. The mounting portion 11 is a shaft-shaped portion that fits into the mounting hole 3 of the mold 1. The mounting portion 11 is fixed to the mold 1 with the axial end surface 12 facing the cavity 2. The end surface 12 is located on substantially the same surface as the inner wall surface 4 of the mold 1.

The protruding portion 13 is a substantially truncated cone-shaped portion that protrudes from the center of the end surface 12. The outer surface (outer peripheral surface) 14 of the protrusion 13 is a tapered surface whose diameter decreases toward the tip. A corner 15 where the end surface 12 of the mounting portion 11 and the outer surface 14 of the protruding portion 13 intersect is formed over the entire circumference of the core 10.

The corner 15 is a curved surface that smoothly connects the end surface 12 and the outer surface 14. When a liquid raw material such as molten metal injected into the cavity 2 of the mold 1 is cured to form a molded product (not shown), a hole with an R-chamfered opening end is formed by a core 10 having a corner 15. Formed into a product. That is, the shape (curvature) of the corner 15 is determined based on the chamfered shape (shape of the cavity 2) of the molded product.

The mounting portion 11 and the protruding portion 13 include an elastic portion 16 formed in a region including the corner 15 and a main body 17 which is a portion other than the elastic portion 16. The elastic portion 16 is provided on the entire circumference of the substantially truncated cone-shaped protrusion 13. The entire outer surface of the elastic portion 16 is a corner 15.

The main body 17 is made of a metal material for a mold such as SKD61 in which each part is integrally molded. The elastic portion 16 is mainly composed of a metal material having an elastic limit higher than that of the main body 17. Titanium alloy is exemplified as a metal material having a high elastic limit. In particular, the elastic portion 16 is composed of a rubber metal (registered trademark) which is a β-type titanium alloy having a composition of Ti ₃ (Nb, Ta, V) + (Zr, Hf) + O, which has a high elastic limit and a large tensile strength. Is preferable.

The elastic limit of the elastic portion 16 and the main body 17 conforms to the tensile test method of JIS Z2241: 2011, and when the molded product is removed from the mold 1 and the core 10 according to the type of the molded product (detachment). This is the stress when a permanent elongation of 0.02% occurs in the test piece of the same metal material as the elastic portion 16 and the main body 17, which is measured at the temperature of the core 10.

In the cross section of the protruding portion 13 in the protruding direction, the interface 18 between the elastic portion 16 and the main body 17 has an arc shape that is convex toward the main body 17. The maximum value of the curvature of the interface 18 is smaller than the maximum value of the curvature of the corner 15. The curvature of each of the interface 18 and the corner 15 is substantially constant over the entire surface. Further, in the cross section of the protruding portion 13 in the protruding direction, the starting point of the corner 15 (the boundary point between the substantially linear end surface 12 and the outer surface 14 and the arc-shaped corner 15) and the starting point of the interface 18 are substantially the same. ..

Next, a method for manufacturing the core 10 will be described with reference to FIGS. 2 (a) and 2 (b). 2 (a) and 2 (b) are explanatory views showing a manufacturing process of the core 10. First, as shown in FIG. 2A, the mounting portion 11 and the protruding portion 13 in which the corner 15 set based on the shape of the cavity 2 is recessed and the recess 19 is provided are composed of only the metal material of the main body 17. To do. The recess 19 may be provided at the same time when the mounting portion 11 and the protruding portion 13 are formed, or the corner 15 may be provided by cutting or grinding after the mounting portion 11 and the protruding portion 13 are formed.

Next, as shown in FIG. 2B, a metal material having an elastic limit higher than the elastic limit of the main body 17 (a metal material mainly constituting the elastic portion 16) is supplied from the nozzle 5 to the recess 19 from the nozzle 5. A laser is irradiated to perform overlay welding on the recess 19. As a result, the elastic portion 16 is formed by the weld metal including the alloy layer of the metal material of the main body 17 and the metal material having a higher elastic limit than the main body 17. After overlay welding, the core 10 is manufactured by cutting the elastic portion 16 by cutting or grinding to form the corner 15.

In the elastic portion 16 which is a weld metal, the proportion of the metal material (metal material having a high elastic limit) mainly constituting the elastic portion 16 decreases toward the main body 17 (interface 18), and the metal material of the main body 17 An alloy layer is formed in which the proportion of That is, the elastic limit of the alloy layer of the elastic portion 16 increases from the interface 18 toward the corner 15 (outer surface).

In particular, by overlay-welding the recess 19 in which the corner 15 is recessed in advance to provide the elastic portion 16, the portion (recess 19) shown by the alternate long and short dash line in FIG. 2B and the corner 15 indicated by the alternate long and short dash line are provided. Most of the elastic portions 16 between the two can be made of a metal material having a high elastic limit. That is, the elastic limit of the portion of the elastic portion 16 near the corner 15 (outer surface) can be made higher.

According to the core 10 as described above, the elastic portion 16 having an elastic limit higher than the elastic limit of the main body 17 is formed in the region including the corner 15. As a result, even if bending stress is applied to the protruding portion 13 when the molded product is pulled out from the mold 1 and the core 10 (at the time of mold release), it is possible to prevent plastic deformation in the vicinity of the corner 15 where the stress tends to concentrate. Further, by repeating heating and cooling of the core 10 in each molding cycle, even if the stress caused by the expansion and contraction of the core 10 is concentrated in the corner 15, it is possible to prevent plastic deformation in the vicinity of the corner 15. As a result, even if stress is repeatedly applied to the protruding portion 13, fatigue fracture of the protruding portion 13 due to repeated plastic deformation near the corner 15 can be suppressed.

In particular, since the bending stress at the time of mold release is larger than the stress due to the temperature change, it is preferable that the elastic limit of the elastic portion 16 is higher than the elastic limit of the main body 17 at the temperature of the core 10 at the time of mold release. As a result, the protruding portion 13 can be made less likely to be fatigued and fractured.

In the cross section of the protruding portion 13 in the protruding direction, the maximum value of the curvature of the interface 18 is smaller than the maximum value of the curvature of the corner 15 that determines the shape of the cavity 2. Therefore, as compared with the case where the main body 17 is provided with the corner 15. It is possible to make it difficult to concentrate stress near the interface 18 of the main body 17. As a result, the main body 17 can be made less likely to be fatigued, and the protruding portion 13 can be made more difficult to be fatigued.

Here, when the curvature of the corner 15 is not constant, stress tends to concentrate on the portion of the corner 15 where the curvature is maximum. On the other hand, in the present embodiment, since the corner 15 is formed from an arc shape having a substantially constant curvature, the stress can be dispersed over the entire corner 15. Therefore, the protruding portion 13 can be made less likely to be fatigued and fractured. Similarly, since the interface 18 is formed from an arc shape having a substantially constant curvature, stress can be dispersed over the entire interface 18. Therefore, the protruding portion 13 can be made less likely to be fatigued and fractured.

Since the elastic portion 16 is a weld metal and an alloy layer is formed in which the elastic limit increases from the interface 18 (main body 17) toward the corner 15, the elastic limit is sharply increased at the interface 18 between the main body 17 and the elastic portion 16. Can be prevented from changing to. As a result, stress concentration on the interface 18 can be suppressed, so that the protrusion 13 can be made less likely to be fatigue-fractured.

By overlay welding the elastic portion 16 into the concave portion 19 in which the corner 15 is recessed in advance, an alloy layer in which the metal material of the main body 17 is melted into the elastic portion 16 is provided on the corner 15 (outer surface) side of the elastic portion 16. It can be difficult. As a result, the elastic limit on the corner 15 side of the elastic portion 16 can be made higher, so that the outer surface side of the elastic portion 16 where the stress tends to increase can be made less likely to be plastically deformed. As a result, the protruding portion 13 can be made less likely to be fatigued and fractured.

Since the starting point of the corner 15 and the starting point of the interface 18 are substantially the same in the cross section of the protruding portion 13 in the protruding direction, a substantially uniform stress can be applied to the elastic portion 16 along the corner 15. As a result, the elastic portion 16 can be less likely to be fatigue-fractured.

Next, the second embodiment will be described with reference to FIG. In the first embodiment, the case where the elastic portion 16 is a weld metal has been described. On the other hand, in the second embodiment, the case where the elastic portion 26 of another member is attached to the main body 27 will be described. The same parts as those in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 3 is a cross-sectional view of the mold 1 to which the mold core 20 (hereinafter referred to as “core 20”) according to the second embodiment is attached.

As shown in FIG. 3, the core 20 is a cast pin including a mounting portion 21 mounted on the mold 1 and a protruding portion 23 protruding into the cavity 2 of the mold 1. The mounting portion 21 is a shaft-shaped portion that fits into the mounting hole 3 of the mold 1. The mounting portion 21 is fixed to the mold 1 with the axial end surface 22 facing the cavity 2. The end surface 22 projects toward the cavity 2 with respect to the inner wall surface 4 of the mold 1.

The protruding portion 23 is a substantially truncated cone-shaped portion that protrudes from the center of the end face 22. The outer surface (outer peripheral surface) 24 of the protrusion 23 is a tapered surface whose diameter decreases toward the tip. A corner 25 where the end surface 22 of the mounting portion 21 and the outer surface 24 of the protruding portion 23 intersect is formed over the entire circumference of the core 20.

The mounting portion 21 and the protruding portion 23 include an elastic portion 26 formed in a region including the corner 25, and a main body which is a portion other than the elastic portion 26. The elastic portion 26 is provided on the entire circumference of the substantially truncated cone-shaped protruding portion 23. In the present embodiment, the elastic portion 26 is provided only on the mounting portion 21. Specifically, the annular elastic portion 26 constitutes the outer peripheral side of the mounting portion 21 of the portion protruding from the inner wall surface 4 of the mold 1 toward the cavity 2. Therefore, the entire surface of the end face 22 forming the cavity 2 is composed of the elastic portion 26.

The main body is composed of the entire protruding portion 23 and the main body 27 which is a part of the mounting portion 21. The protruding portion 23 and the main body 27 are made of a metal material for a mold such as SKD61 in which each portion is integrally molded. The elastic portion 26 is made of a metal material having an elastic limit higher than that of the protruding portion 23 and the main body 27.

In the cross section of the protruding portion 23 in the protruding direction, the interface 28 between the elastic portion 26 and the main body 27 has an arc shape that is convex toward the main body 27. The elastic portion 26 is integrated with the protruding portion 23 and the main body 27 by fitting the annular elastic portion 26, which is a member different from the protruding portion 23 and the main body 27, into the arcuate interface 28 provided on the protruding portion 23 and the main body 27. The core 20 is manufactured. By making the elastic portion 26 removable in this way, even if a crack or the like occurs in the elastic portion 26, only the elastic portion 26 can be replaced.

In the cross section of the protruding portion 23 in the protruding direction, the interface 28 is recessed inward in an undercut shape from the extension line (not shown) extending the outer surface 24 toward the mounting portion 21, so that the elasticity is fitted to the interface 28. The part 26 can be hard to come off. Further, after fitting the elastic portion 26 divided into a plurality of parts in the circumferential direction into the interface 28, the divided surface may be welded or welded.

According to the core 20 as described above, as in the first embodiment, the elastic portion 26 having an elastic limit higher than the elastic limit of the protruding portion 23 and the main body 27 is formed in the region including the corner 25. It is possible to prevent plastic deformation in the vicinity of the corner 25 where stress is likely to be concentrated. As a result, fatigue fracture of the protruding portion 23 due to repeated plastic deformation near the corner 25 can be suppressed.

In the cross section of the protruding portion 23 in the protruding direction, the corner 25 where the end surface 22 of the elastic portion 26 and the outer surface 24 of the protruding portion 23 intersect is sharp, but since the elastic portion 26 and the protruding portion 23 are separate members, they are sharp. It is possible to make it difficult to concentrate stress on the corner 25. Further, even if the corner of the elastic portion 26 hits the protruding portion 23 and the main body 27, since the elastic limit of the elastic portion 26 is high, it is possible to make it difficult to plastically deform the portion of the protruding portion 23 and the main body 27 where the corner of the elastic portion 26 hits. ..

Since the outer surface of the elastic portion 26 constitutes the end surface 22, the elastic portion 26 is provided in a wide region near the corner 25. As a result, it is possible to make it difficult for the wide region near the corner 25 to be plastically deformed, so that the protruding portion 23 can be made less likely to be fatigue-fractured. Further, since the outer surface of the elastic portion 26 constitutes the entire surface of the end surface 22 and also constitutes the outer peripheral surface of the mounting portion 21, the elastic portion 26 is provided in a wider region near the corner 25. As a result, the protruding portion 23 can be made less likely to be fatigued and fractured.

Further, since the interface 28 between the elastic portion 26 and the main body 27 provided in a wide region is formed of an arc shape having a substantially constant curvature, stress can be more easily dispersed over the entire large interface 28. As a result, the protruding portion 23 can be made less likely to be fatigued and fractured.

Next, a third embodiment will be described with reference to FIG. In the first embodiment, the case where the elastic portion 16 is provided in the region including the corner 15 where the end surface 12 of the mounting portion 11 and the outer surface 14 of the protruding portion 13 intersect is described. On the other hand, in the third embodiment, the case where the elastic portion 36 is provided in the region including the corner 35 where the outer surface 34 of the protruding portion 33 and the inner wall surface 4 of the mold 1 intersect is described. The same parts as those in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 4 is a cross-sectional view of the mold 1 to which the mold core 30 (hereinafter referred to as “core 30”) according to the third embodiment is attached.

As shown in FIG. 4, the core 30 has a fixing portion 31 arranged on the opposite side of the cavity 2 of the mold 1 and a protrusion extending from the inner wall surface 4 of the mold 1 toward the cavity 2 and continuing to the fixing portion 31. A cast-out pin including a portion 33. The fixing portion 31 is a shaft-shaped portion that fits into the mounting hole 3 of the mold 1.

The protruding portion 33 is a substantially truncated cone-shaped portion. The outer surface (outer peripheral surface) 34 of the protrusion 33 is a tapered surface whose diameter decreases toward the tip. Of the protruding portions 33, the outer diameter on the fixed portion 31 side and the outer diameter of the fixed portion 31 are substantially the same. That is, the outer peripheral surface of the fixed portion 31 and the outer surface 34 of the protruding portion 33 are continuous.

A corner 35 where the outer surface 34 of the protrusion 33 and the inner wall surface 4 of the mold 1 intersect is formed over the entire circumference of the core 30. The fixed portion 31 and the protruding portion 33 include an elastic portion 36 formed in a region including the corner 35, and a main body 37 which is a portion other than the elastic portion 36. The elastic portion 36 is provided on the entire circumference of the substantially truncated cone-shaped protruding portion 33.

The main body 37 is made of a metal material for a mold such as SKD61 in which each part is integrally molded. The elastic portion 36 is made of a weld metal formed by welding a metal material having an elastic limit higher than that of the main body 37 to the main body 37.

The outer surface 34 of the protruding portion 33 is composed of a first portion 34a formed by the main body 37 and a second portion 34b formed by the outer surface of the elastic portion 36. A corner 35 is formed by the second portion 34b of the elastic portion 36 and the inner wall surface 4. Further, in the cross section of the protruding portion 33 in the protruding direction, the interface 38 between the elastic portion 36 and the main body 37 has an arc shape that is convex toward the main body 37.

According to the core 30 as described above, as in the first and second embodiments, the elastic portion 36 having an elastic limit higher than the elastic limit of the main body 37 is formed in the region including the corner 35, so that the stress is increased. It is possible to prevent plastic deformation in the vicinity of the corner 35 where concentration is easy. As a result, fatigue fracture of the protruding portion 33 due to repeated plastic deformation near the corner 35 can be suppressed.

Since no corners are formed in the fixed portion 31 and the protruding portion 33, it is possible to easily suppress the stress concentration caused by the volume change of the fixed portion 31 and the protruding portion 33. Further, in the cross section of the protruding portion 33 in the protruding direction, the corner 35 where the outer surface 34 and the inner wall surface 4 of the protruding portion 33 intersect is sharp, but the elastic portion 36 near the corner 35 and the mold 1 are separate members. , It is possible to make it difficult to concentrate stress on the sharp corner 35.

Since the outer surface of the elastic portion 36 constitutes the second portion 34b of the outer surface 34, the elastic portion 36 is provided in a wide region near the corner 35. As a result, it is possible to make it difficult for the wide region near the corner 35 to be plastically deformed, so that the protruding portion 33 can be made less likely to be fatigue-fractured. Further, since the interface 38 between the elastic portion 36 and the main body 37 provided in a wide region is formed of an arc shape having a substantially constant curvature, stress can be easily dispersed over the entire large interface 38. As a result, the protruding portion 33 can be made less likely to be fatigued and fractured.

Next, a fourth embodiment will be described with reference to FIG. In the first embodiment, the case where the protruding portion 13 has a substantially truncated cone shape has been described. On the other hand, in the fourth embodiment, the case where the plate-shaped protrusion 43 protrudes from the mounting portion 41 will be described. The same parts as those in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 5 is a perspective view of the mold core 40 (hereinafter referred to as “core 40”) according to the fourth embodiment.

As shown in FIG. 5, the core 40 includes a mounting portion 41 mounted on the mold 1 (see FIG. 1) and a protruding portion 43 projecting into the cavity 2 (see FIG. 1) of the mold 1. It is a cast pin. The mounting portion 41 is a curved plate-shaped portion that fits into the mounting hole 3 (see FIG. 1) of the mold 1. The mounting portion 41 is fixed to the mold 1 with the end surface 42 perpendicular to the plate thickness direction facing the cavity 2.

The projecting portion 43 is a curved plate-like portion projecting from the center of the end surface 42 in the plate thickness direction, and is provided so as to extend in the projecting direction and the extending direction intersecting the plate thickness direction. The outer surface 44 of the protrusion 43 in the plate thickness direction is a tapered surface whose plate thickness decreases toward the tip. The plate thickness of the protruding portion 43 is thinner than the plate thickness of the mounting portion 41. Therefore, a corner 45 where the end surface 42 of the mounting portion 41 and the outer surface 44 of the protruding portion 43 intersect is formed over the extending direction of the protruding portion 43. The corner 45 is a curved surface that smoothly connects the end surface 42 and the outer surface 44.

The mounting portion 41 and the protruding portion 43 include an elastic portion 46 formed in a region including the corner 45, and a main body 47 which is a portion other than the elastic portion 46. The elastic portion 46 is provided in the entire corner 45 provided over the extending direction of the protruding portion 43.

In the cross section of the protruding portion 43 in the protruding direction, the interface 48 between the elastic portion 46 and the main body 47 has an arc shape that is convex toward the main body 47. In the cross section of the protruding portion 43 in the protruding direction, the curvature of the interface 48 is substantially constant, and the curvature of the corner 45 is also substantially constant.

The end surface 42 of the mounting portion 41 is composed of a first portion 42a formed by the main body 47 and a second portion 42b formed by the outer surface of the elastic portion 46. Further, the outer surface 44 of the protruding portion 43 is composed of a first portion 44a formed by the main body 47 and a second portion 44b formed by the outer surface of the elastic portion 46. The outer surface of the elastic portion 46 constitutes a corner 45, an end surface 42 adjacent to the corner 45, and a part of the outer surface 44.

The main body 47 is made of a metal material for a mold such as SKD61 in which each part is integrally molded. The elastic portion 46 is made of a metal material having an elastic limit higher than that of the main body 47. In the present embodiment, the main body 47 and the elastic portion 46 are integrally molded from the same steel, and then only the portion corresponding to the elastic portion 46 is annealed (completely annealed) with a laser or an electron beam to set the elastic limit. A high elastic portion 46 is obtained.

An elastic portion 46, which is a metal material different from the main body 47 and has a high elastic limit, may be welded to the main body 47. However, the elastic portion 46 can be easily formed by annealing as compared with the case where the elastic portion 46 having a high elastic limit is welded to the main body 47. The cross section of the annealed elastic portion 46 has a homogenized crystal grain size as compared with the cross section of the main body 47. Further, since the annealed elastic portion 46 has fewer defects, it is possible to suppress the occurrence of cracks or the like starting from the defects.

According to the core 40 as described above, since the elastic portion 46 having an elastic limit higher than the elastic limit of the main body 47 is formed in the region including the corner 45, the stress is concentrated on the elastic portion 46 near the corner 45. However, it is possible to prevent plastic deformation in the vicinity of the corner 45. As a result, fatigue fracture of the protruding portion 43 due to repeated plastic deformation near the corner 45 can be suppressed.

Since the outer surface of the elastic portion 46 constitutes the second portion 42b of the end surface 42 and the second portion 44b of the outer surface 44, the outer surface of the elastic portion 46 covers only a part of either the end surface 42 or the outer surface 44. The elastic portion 46 can be provided in a wider area near the corner 45 as compared with the case of the configuration. As a result, it is possible to make it difficult for the wide region near the corner 45 to be plastically deformed, so that the protrusion 43 can be made less likely to be fatigue-fractured.

Since the plate-shaped projecting portion 43 extending in the extending direction intersecting the projecting direction and the plate thickness direction is resistant to bending stress in the extending direction, the elastic portion 46 is not provided on the end surface of the projecting portion 43 in the extending direction. You may. Therefore, the elastic portion 46 can be easily formed.

Here, by regarding only the first portion 42a of the end surface 42 as the end surface of the mounting portion 41 and the second portion 42b as a part of the outer surface of the protruding portion 43, the first portion 42a and the second portion 42b can be combined. The corner 49 is a corner between the mounting portion 41 and the protruding portion 43. Since the elastic portion 46 is also formed in such a region including the corner 49, it is possible to prevent plastic deformation in the vicinity of the corner 49 even if stress is concentrated on the elastic portion 46 in the vicinity of the corner 49. As a result, the protruding portion 43 can be less likely to be fatigue-fractured.

Although the present invention has been described above based on the above-described embodiment, the present invention is not limited to the above-described embodiment, and it is easy to make various modifications and improvements within a range that does not deviate from the gist of the present invention. It can be inferred. For example, the shapes and dimensions of the mounting portions 11, 21, 41, the protruding portions 13, 23, 33, 43, the fixing portions 31, the corners 15, 25, 35, 45, 49 and the like may be appropriately changed. Various coatings and heat treatments may be applied to the outer surfaces 14, 24, 34, 44 and the end faces 12, 22, 42 of the main bodies 17, 27, 37, 47.

The present invention may be applied not only to the case where the cores 10, 20, 30 and 40 are cast pins, but also to the drawn cores and placing cores other than the cast pins. Further, the cores 10, 20, 30, and 40 may be attached to the mold 1 used for molding resin products and rubber products, not limited to the mold 1 for casting.

As in the first and third embodiments, the elastic portions 26 and 46 of the second and fourth embodiments may be formed by overlay welding. The overlay welding is not limited to the case where a laser is used, and plasma or the like generated by an electron beam may be used. When the elastic portions 16, 26, 36, 46 are formed by overlay welding, it is not necessary to provide the recess 19 in advance. By forming the elastic portion 46 having a high elastic limit from the weld metal, an alloy layer having a lower elastic limit is formed toward the main body 47. In this case as well, stress concentration at the interface 48 between the elastic portion 46 and the main body 47 can be suppressed. Further, as in the second embodiment, the elastic portions 16, 36, 46 of the first, third and fourth may be integrated into the main body 17, 37, 47 by fitting. The elastic portions 16, 26, 36, 46 of another member may be integrated with the main body 17, 27, 37, 47 by welding or welding.

In each of the above embodiments, the case where the curvatures of the corners 15, 45 and the interfaces 18, 28, 38, 48 are substantially constant has been described, but the present invention is not necessarily limited to this. The curvatures of the corners 15, 45 and the interfaces 18, 28, 38, 48 may be changed. Even in this case, if the maximum value of the curvature of the interfaces 18, 28, 38, 48 is smaller than the maximum value of the curvature of the corners 15, 45, the protrusions 13, 23, 33, 43 can be less likely to be fatigue-fractured. Further, in the cross section in the protruding direction, the interfaces 18, 28, 38, 48 may be formed from a plurality of straight lines or a combination of straight lines and curves.

In the second embodiment, the case where the elastic portion 26 is provided only on the mounting portion 21 has been described, but the present invention is not necessarily limited to this. Elastic portions may be provided only on the protruding portions 13, 23, 43 near the corners 15, 25, 45. In this case, the interface between the elastic portion and the main body can be smoothly connected to the end faces 12, 22, 42 of the mounting portions 11, 21, 41. As a result, it is possible to suppress the concentration of stress at the boundary portion between the end faces 12, 22, 42 and the interface, so that the protrusions 13, 23, 43 can be made more difficult to fracture due to fatigue.

1 Mold 2 Cavity 4 Inner wall surface 10, 20, 30, 40 Mold core 11, 21, 41 Mounting part 12, 22, 42 End face 13, 33, 43 Protruding part 14, 24, 34, 44 Outer surface 15 , 25, 35, 45 Corner 16, 26, 36, 46 Elastic part 17, 27, 37, 47 Main body 18, 28, 38, 48 Interface 23 Protruding part (main body)
31 Fixed part

Claims (6)

A mounting portion that is mounted on the mold with its end face facing the cavity of the mold,
With a protrusion protruding from a part of the end face,
The mounting portion and the protruding portion include an elastic portion formed in a region including a corner where the outer surface of the protruding portion and the end surface intersect.
It is provided with a main body that is a part other than the elastic part.
A mold core characterized in that the elastic limit of the elastic portion is higher than the elastic limit of the main body. The core for a mold according to claim 1, wherein the outer surface of the elastic portion constitutes at least a part of the end face or a part of the outer surface. The core for a mold according to claim 1, wherein the outer surface of the elastic portion constitutes at least a part of the end face and a part of the outer surface. In the cross section of the protruding portion in the protruding direction, the interface between the elastic portion and the main body has an arc shape convex toward the main body.
The mold core according to any one of claims 1 to 3, wherein the maximum value of the curvature of the interface is smaller than the maximum value of the curvature of the corner. A fixed part located on the opposite side of the mold cavity,
A protrusion that protrudes from the inner wall surface of the mold toward the cavity and is connected to the fixing portion is provided.
The mounting portion and the protruding portion include an elastic portion formed in a region including a corner where the outer surface of the protruding portion and the inner wall surface intersect.
It is provided with a main body that is a part other than the elastic part.
A mold core characterized in that the elastic limit of the elastic portion is higher than the elastic limit of the main body. The core for a mold according to any one of claims 1 to 5, wherein the elastic portion is a weld metal welded to the main body.

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