KR20130015633A - Hot press forming die using local softening of press formed part method of for reducing shearing load - Google Patents

Abstract

PURPOSE: A hot press mold capable of locally softening a molded product by the same in order to reduce shear load is provided to prevent heat transfer by forming a slit on a mold, and properly control cooling temperature for the shear portion of the product with the insertion of a heater, thereby locally softening the shear portion of the product in order to reduce the shear load. CONSTITUTION: A hot press mold comprises an upper die(10), a lower die(20), cooling channels(30) formed at the upper die and the lower die. Air cooling portions(40), which are internally cut and opened, are formed at both sides of the upper die and the lower die. Shear portions(S) for the post-process of a molded product(P) are separated from the surfaces of the air cooling portions, and are contact with ambient air to be air-cooled through the air cooling portions. The temperatures of the air cooling portions are externally controlled so that the cooling temperatures of the shear portions are controlled. Curved offset portions(42) are formed at the internal end portions of the air cooling portions so that the internal end portions are separated from the shear portions at regular distances.

Description

Hot press forming die using loCal softening of press formed part method of for reduCing shearing load}

The present invention relates to a hot press die, and more particularly, to a hot press die having a structure capable of locally softening the front end portion of a molded article in order to reduce shear load and improve mold life during shearing of a hot press molded article. It is about.

Conventionally, the method of manufacturing a molded article by cold-pressing a metal plate material in order to obtain auto parts or mechanical parts has been performed. However, in the cold press molding method, the molded article has a characteristic of ductility deteriorating with its high strength, so that breakage (so-called cracking) occurs, which makes it difficult to obtain a press product having a complicated shape.

In addition, even in a press product having a simple shape, elastic recovery (so-called spring back) caused by the release of residual stress after molding may be a problem, and good dimensional accuracy may not be obtained.

As a technique of obtaining a high-strength molded article or molded part that replaces the cold press molding method, a hot press molding method of press molding a heated metal sheet is known. Since the metal sheet is heated, the ductility is improved and the deformation resistance is lowered. Thus, in hot press molding, it is often possible to alleviate the problem of fracture or spring back.

In hot press molding, however, in order to secure a predetermined quenching hardness, it is necessary to maintain the bottom dead center of the molded article (metal plate) for a predetermined time, but there is a problem such that the tact time becomes longer and productivity is lowered by this holding.

Therefore, when press-molding a heated metal plate or press-molding a heated metal plate, a quenching is performed by making a molded article contact with a refrigerant | coolant from a metal mold, and cooling a molded article. Thereby, the time of bottom dead center holding | maintenance can be shortened and productivity of a molded article can be improved.

Here, as a mechanism for cooling a molded article, a cylindrical supply passage (channel) for allowing a refrigerant to pass through a mold in contact with the molded article is formed, and the refrigerant is blown toward the molded article from the surface of the die, which is an end of the supply passage.

1 is a cross-sectional view showing the structure of a conventional hot press die.

In general, a hot press die is composed of a die holder 1, an upper die 2 and a lower punch 3, and springs 4 and pads 5 inserted into the die 2, as shown. . In addition, a plurality of cooling channels 6 are formed in the die 2, the punch 3, and the pad 5.

Shear molds (punches and dies) due to the high strength (having tensile strength of 1500 MPa or more) when molding (molding, trimming, piercing, blanking, etc.) processing of molded articles molded in conventional hot press dies having such a structure. ) Premature wear or plastic deformation and breakage (chipping, fatigue failure) occurs.

That is, in the mold structure of the conventional hot press molding, the entire surface of the product is cooled at a critical cooling rate because the part of the product and the part made of the product are cooled in a state of being in contact with the mold as a whole. Therefore, the entire surface is transformed into martensite of 1500 MPa or more, and the life of the shear die is greatly reduced in the post process shear (including outer circumference trimming, hole punching, blanking, etc.) process.

Therefore, it is impossible to mass-produce and inevitably take time and costly laser cutting because of the damage of the shear mold. Laser cutting includes trimming to cut the outside of the product and piercing (or punching) to cut the inner holes.

On the other hand, in order to solve this problem, there is a method of shearing in a hot state, which requires a separate heat source (for example, high frequency induction heating) around the front end, so that the material must be sheared in a heated state in terms of cost Or there was a problem with the environment.

Embodiments of the present invention are to provide a hot press mold structure in which the front end portion of the molded article is spaced apart from the mold but has a structure that can be air cooled in contact with the air to reduce the shear load by locally softening the front end portion of the molded article. .

In addition, by inserting an insulating insert to block the heat transfer to the front end of the molded article to provide a hot press mold structure that can soften the front end of the molded part locally to reduce the shear load.

In addition, by forming a slit in the mold to block heat transfer and insert a heater to properly control the cooling temperature of the front end of the molded part to provide a hot press mold structure that can soften the front end of the molded part locally to reduce the shear load.

According to an aspect of the present invention, in the hot press die consisting of a cooling channel formed in the upper die and the lower die and the upper die and the lower die, on both sides of the upper die and the lower die, the front end surface for the post-processing of the molded article and An air-cooled part is formed to be inwardly opened so as to be contacted with air to be spaced apart to be spaced apart, thereby controlling the cooling temperature of the front end part by controlling the temperature of the air cooled part from the outside. A hot press mold capable of local softening can be provided.

According to another aspect of the present invention, in the hot press mold consisting of the upper die and the lower die and the cooling channel formed in the upper die and the lower die, both sides of the upper die or the lower die, the front end surface for post-processing the molded article and An air-cooled part is formed to be inwardly opened so as to be contacted with air to be spaced apart to be spaced apart, thereby controlling the cooling temperature of the front end part by controlling the temperature of the air cooled part from the outside. A hot press mold capable of local softening can be provided.

In this case, the inner end of the air cooling portion may be formed in the curved offset portion so as to be spaced apart from the front end by a predetermined distance.

And one side of the air cooling unit may be further provided with a cooling control means for controlling the cooling temperature of the front end portion.

In addition, the air-cooling portion may be inserted into an insulating insert to block heat transfer to the front end portion, the insulating insert may be made of a ceramic material.

According to another aspect of the present invention, in the hot press die consisting of a cooling channel formed in the upper die and the lower die and the upper die and the lower die, on both sides of the upper die and the lower die, the blocking slits are formed to face the inside Heat transfer to the outside, and the heater is inserted into the outer side of the blocking slit to control the cooling temperature of the front end portion for the post-processing of the molded product, it is possible to locally soften the hot press molded product for shear load reduction Press molds can be provided.

Here, the inlet of the blocking slit may be formed with a rounded portion of a constant curvature.

Embodiments of the present invention have a structure in which the front end portion of the molded part is spaced apart from the mold to block heat transfer and air cooled in contact with the air, thereby softening the front end portion of the molded part locally to reduce the shear load in the shear processing In addition to improving the life of the tool or the mold used, the optimum shear load can be determined by appropriately controlling the cooling temperature according to conditions such as the material and thickness of the molded product from the outside, such as cooling control means.

In addition, by inserting an insulation insert or forming a slit in the mold to block heat transfer and inserting a heater to properly control the cooling temperature of the front end of the molded part, the front end softens locally to reduce the shear load, thereby improving the life of the tool or the mold. There is a big advantage.

1 is a cross-sectional view showing the structure of a conventional hot press die.
Figure 2 is a cross-sectional view showing a first embodiment of the hot press die capable of local softening of the hot press molded article for reducing the shear load according to the present invention.
Figure 3 is a cross-sectional view showing a second embodiment of the hot press die capable of local softening of the hot press molded article for reducing the shear load according to the present invention.
Figure 4 is a cross-sectional view showing a third embodiment of the hot press die capable of local softening of the hot press molded article for reducing the shear load according to the present invention.
Figure 5 is a cross-sectional view showing a fourth embodiment of the hot press die capable of local softening of the hot press molded article for reducing the shear load according to the present invention.
6 is a graph of shear load comparison between a conventional hot press die and the hot press die of the present invention.
7 is a temperature distribution diagram of a mold in the first and second embodiments of the present invention.
8 is a temperature distribution diagram of a mold in the third embodiment of the present invention.
9 is a temperature distribution diagram of a mold in the fourth embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention. The following description and the accompanying drawings are presented for the overall understanding of the present invention, and thus the technical scope of the present invention is not limited thereto. And a detailed description of known configurations and functions that may unnecessarily obscure the subject matter of the present invention will be omitted.

The present invention relates to a structure of a hot press die, which basically consists of an upper die 10 and a lower die 20, and the upper die 10 and the lower die 20 have a plurality of cooling channels 30. It has a formed structure.

In addition, the upper die 10 may have a structure in which a spring 12 and a pad 14 are further provided.

In addition, between the upper die 10 and the lower die 20, a molded article P such as a metal plate is installed to be hot pressed, and both ends of the molded article P are finished after molding, that is, shearing ( Punching, trimming, piercing, blanking, etc.).

Here, the position where the shear processing is performed at both ends of the molded product (P) is called the shear portion (S), the present invention is described in the structure of the hot press mold that can be locally softened by slow cooling the shear portion (S) There is a characteristic.

Hereinafter, various embodiments of the present invention will be described.

<First Embodiment>

2 is a cross-sectional view showing a first embodiment of a hot press die capable of local softening of a hot press molded article for reducing shear load according to the present invention.

Referring to FIG. 5, an air cooled part 40 capable of air cooling is formed on both sides of the upper die 10 and the lower die 20 of the present invention.

The air cooling unit 40 is in such a manner that the upper die 10 and the lower die are separated from each other without being in close contact with each other, and at the same time, the surfaces of the upper die 10 and the lower die 20 are not contacted with the molded product P. It has a shape dug into.

That is, since both ends of the molded article P may be exposed by having an open shape to the outside, the structure may be air cooled by contacting the outside air.

To this end, the upper die 10 and the lower die 20 may be a groove having a fine shape so as to open outwardly, it may be an upper and lower open air-cooling portion 40a.

Due to the structure of the air-cooled portion 40, the front end portion S of the molded product P may be locally softened because it is slowly cooled by air without cooling heat transmitted from the cooling channel 30. Thus, the shear load can be reduced.

In addition, since the air cooling part 40 and the front end part S are exposed to the outside structure, the air cooling part 40 and the front end part S are provided with a separate cool cooling control means, thereby forcibly cooling the air according to the material or thickness of the molded product P. Etc. can be controlled. At this time, the cooling control means 80 may be a blower that can blow hot or cold air or an injection device, and may be a heater that can contact the front end (S).

And it is preferable that the inner end of the air-cooled portion 40 may be located to be spaced in the predetermined distance from the front end portion (S) as shown. In particular, it is preferable that the offset portion 42 having a curved shape is formed so that the cooling heat due to the cooling channel 30 is not directly transmitted to the front end portion S.

The offset part 42 may be determined at an appropriate distance from the front end part S, which may be selected according to physical properties such as material and thickness of the molded product P.

For example, the offset portion 42 may be about 2-6 mm in the front end portion (S).

&Lt; Embodiment 2 >

Figure 3 is a cross-sectional view showing a second embodiment of the hot press die capable of local softening of the hot press molded article for reducing the shear load according to the present invention, where (a) is the upper open air-cooled portion (b) is the lower open type The air cooled part is shown.

Referring to FIG. 5, an air cooling unit 40 is formed on both sides of either the upper die 10 or the lower die 20 of the present invention.

Referring to (a), the air cooled part 40 may be an upper open air cooled part 40b having a shape that is recessed inwardly so that the surface of the upper die 10 is spaced apart from the contacted part P without being contacted.

That is, since both sides of the upper die 10 has an open shape to the outside, both front end portions S of the molded article P may be exposed, and thus the air may be cooled by contacting with the outside air.

Due to the structure of the upper open air-cooling part 40b, the front end part S may be locally softened because the heat of cooling is not slowly transmitted from the cooling channel 30 formed in the upper die 10 but is slowly cooled by air. Can be. Thus, the shear load can be reduced.

Alternatively, as shown in (b), the air cooled portion 40 may be a lower open air cooled portion 40c having an inwardly recessed shape such that the surface of the lower die 20 is spaced apart from contact with the molded product P. .

That is, since both sides of the lower die 20 have an open shape to the outside, both front end portions S of the molded product P may be exposed, and thus the air may be cooled by contacting the outside air.

Due to the structure of the lower open air-cooling part 40c, the front end part S may be locally softened because cooling heat is not slowly transmitted from the cooling channel 30 formed in the lower die 20, but is slowly cooled by air. Can be.

In this structure, as in the first embodiment, a separate cool cooling control means () may be forced to air-cool to control the cooling temperature, the cooling speed, and the like. Similarly, the cooling control means 80 may be a blower that can blow hot or cold air or an injector, or a heater that can contact the front end portion (S).

And it is preferable that the inner end of the upper open air-cooled portion 40b or lower open air-cooled portion 40c may be positioned to be spaced inward from the front end portion (S) as shown. In addition, it is preferable that the offset portion 42 having a curved shape is formed so that the heat of cooling due to the cooling channel 30 is not directly transmitted to the front end portion S.

Third Embodiment

Figure 4 is a cross-sectional view showing a third embodiment of the hot press die capable of local softening of the hot press molded article for reducing the shear load according to the present invention.

As shown, another embodiment of the present invention may insert the insulation insert 50 having a low heat transfer rate to the air cooled portion 40.

That is, the insulating insert 50 contacts the upper and lower portions of the front end portion S of the molded product P to minimize heat transfer from the upper die 10 or the lower die 20 to the front end portion S. have.

To this end, the insulating insert 50 may be installed to be embedded in the upper die 10 or the lower die 20, preferably a ceramic material.

Fourth Embodiment

Figure 5 is a cross-sectional view showing a fourth embodiment of the hot press die capable of local softening of the hot press molded article for reducing the shear load according to the present invention.

Alternatively, the present invention can be implemented as shown in FIG. 5.

That is, the blocking slits 60 are formed on both sides of the upper die 10 and the lower die 20, and the heater 70 is inserted and installed outside the blocking slits 60.

The blocking slit 60 is formed inside each of the upper die 10 and the lower die 20, and has a shape such as a thin gap to block heat of one side from passing through the blocking slit 60. Do it.

At this time, the blocking slits 60 formed in the upper die 10 and the lower die 20 are preferably formed to face each other, and are formed vertically, and are formed at a point where the front end portion S is located. Can be.

In addition, the heater 70 is installed on the outer side of the blocking slit 60, that is, the opposite direction to where the cooling channel 30 is located with respect to the blocking slit 60.

Here, the heater 70 may be in the form of a cartridge to be inserted into or detached from any one of the cooling channels 30 formed in the upper die 10 and the lower die 20.

Therefore, the heater 70 can be slow cooled by heating the front end S, and the cooling temperature or the cooling rate can be controlled by the control of the heater 70.

On the other hand, the inlet side of the blocking slit 60, it is preferable that the rounded portion 62 is formed rounded with a constant curvature.

Due to the rounding 62, the surfaces of the upper die 10 and the lower die 20 do not come into close contact with the front end S. FIG. That is, since the rounding part 62 provides an effect that the blocking slit 60 opens toward the entrance, the upper die 10 or the lower die 20 has a non-contact area with the surface of the molded product P. Expand Therefore, the cooling heat is delayed to be immediately transmitted to the front end portion (S).

In addition, it serves to minimize back transfer of heat from the heater 70 to the blocking slit 60.

Hereinafter, the experimental results and the analysis results during the molding operation with the hot press mold according to the present invention will be described.

6 is a comparison graph of shear load between a conventional hot press die and the hot press die of the present invention, FIG. 7 is a temperature distribution diagram of the mold in the first and second embodiments of the present invention, and FIG. 8 is a third embodiment of the present invention. In the case of the example, the temperature distribution diagram of the mold, Figure 9 is a temperature distribution diagram of the mold in the fourth embodiment of the present invention.

Figure 6 is a graph showing the shear load during shearing (particularly trimming) of the conventional mold and the molded product P molded by the mold according to the present invention, it can be seen that the shear load reduction of about 30%. Here, Conventional hot stamping (CHS) denotes a conventional hot press process, and LSHS (Local softening hot stamping) denotes a local softening hot press process according to the present invention.

And (a) in Figure 7 is the case of having the upper and lower open air cooling portion, (b) is the temperature distribution in the case of having a lower open air cooling portion.

It can be seen that due to the air cooling portion 40, the front end portion S of the molded article P is relatively high in temperature and is cooled slowly without being quenched.

In addition, as shown in FIG. 8, when the insulation insert 50 is inserted, the cooling heat is not transmitted, and thus the temperature of the front end portion S is relatively high.

9 is a case where the blocking slit 60 and the heater 70 are provided, (a) is a case where there is no rounding part in the blocking slit, and (b) is a case where there is a rounding part.

As described above, it can be seen that the cooling heat is blocked due to the blocking slit 60, and the cooling of the front end portion S is delayed by the heater 70, and the cooling temperature or the cooling rate can be controlled. You can expect that.

In addition, it can be seen that the inside of the front end portion S of the molded article P is preferably cooled due to the rounding portion 62.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as defined by the appended claims. And changes may be made without departing from the spirit and scope of the invention.

10: upper die 12: spring
14: Pad
20: lower die
30: cooling channel
40: air cooled part 40a: upper and lower open air cooled part
40b: upper open air cooled part 40C: lower open air cooled part
42: offset part
50: insulated insert
60: blocking slit 62: rounding part
70: heater
80: cooling control means
P: Molded Product S: Shear

Claims (8)

In the hot press mold consisting of the upper die 10 and the lower die 20 and the cooling channel 30 formed in the upper die 10 and the lower die 20,
On both sides of the upper die 10 and the lower die 20,
The air-cooling part 40 of the open shape is formed by digging inward so that the front end portion S for the post-processing of the molded product P is spaced apart from the surface and cooled in contact with the outside air.
A hot press die capable of local softening of a hot press molded product for reducing shear load, characterized in that the cooling temperature of the front end portion can be controlled by controlling the temperature of the air cooling portion from the outside. In the hot press mold consisting of the upper die 10 and the lower die 20 and the cooling channel 30 formed in the upper die 10 and the lower die 20,
On both sides of either the upper die 10 or the lower die 20,
The air-cooling part 40 of the open shape is formed by digging inward so that the front end portion S for the post-processing of the molded product P is spaced apart from the surface and cooled in contact with the outside air.
A hot press die capable of local softening of a hot press molded product for reducing shear load, characterized in that the cooling temperature of the front end portion can be controlled by controlling the temperature of the air cooling portion from the outside. 3. The method according to claim 1 or 2,
The inner end of the air-cooled portion 40 is a curved offset portion 42 is formed so as to be spaced apart from the front end portion (S), characterized in that the hot pressing capable of local softening of the hot press molded article for reducing the shear load Press mold. 3. The method according to claim 1 or 2,
One side of the air cooling unit 40 is further provided with a cooling control means 80 for controlling the cooling temperature of the front end portion (S) it is possible to locally soften the hot press molded product for reducing the shear load Hot press mold. 3. The method according to claim 1 or 2,
Insulating insert (50) is inserted into the air cooling part (40) to block the heat transfer to the front end portion (S) hot pressing die capable of local softening of the hot press molded product for reducing the shear load. The method of claim 5, wherein
The insulating insert 50 is made of a ceramic, the hot press die capable of local softening of the hot press molded product for reducing the shear load, characterized in that the ceramic. In the hot press mold consisting of the upper die 10 and the lower die 20 and the cooling channel 30 formed in the upper die 10 and the lower die 20,
On both sides of the upper die 10 and the lower die 20,
Blocking slits 60 are formed to face the inside to block heat transfer to the outside,
The heater 70 is inserted into the outer side of the blocking slit 60 to control the cooling temperature of the front end portion S for the post-processing of the molded product P. Hot press mold for local softening. The method of claim 7, wherein
The inlet of the blocking slit (60) is a hot press mold capable of local softening of the hot press molded product for shear load reduction, characterized in that the rounded portion 62 of a predetermined curvature is formed.

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