JPH06210370A - Mold for press molding - Google Patents

Abstract

(57) [Summary] [Purpose] It is an object of the present invention to provide a press-molding die capable of preventing the occurrence of molding defects such as cracks and wrinkles of a press material. According to the press-molding die of the present invention, a plurality of recesses are formed on a part or the entire surface of the die which is in contact with the press material at the time of molding the press material, and the recesses have an average diameter of 3 mm.
It is characterized in that the average depth is set to 0 μm to 100 μm and the average depth is set to 1 μm to 10 μm, respectively, and the average interval of the plurality of concave portions is set to 1.3 times to 3 times the average diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press-molding die, and more particularly to a press-molding die used for press-molding thin plates for automobiles.

[0002]

2. Description of the Related Art In recent years, in automobiles, home electric appliances and the like, the importance of their design has been increasing more and more in response to the demand for higher quality and differentiation from other companies' products. The requirements for this diverse design spread as requirements for the molding technology of the component parts that form the shape, and in order to meet that requirement, advanced press molding technology capable of press molding parts with complicated shapes is required. Has been done.

Conventionally, when a molding defect such as a crack or a wrinkle occurs during press molding of a component having a complicated shape, the following measures have been taken. (1) Increase the grade of the press material used and use a material with excellent moldability. (2) The parts are divided and the shape is changed (for example, the radius of curvature R of the shape portion is increased).

(3) Improve lubricity by using a high-viscosity press oil.

[0005]

However, if the grade of the press material is increased, the cost is increased and there is a limit, which is not preferable. Further, the division of parts and the change of shape are measures against the sacrifice of design, which is naturally not preferable, and may further deteriorate workability during assembly. Furthermore, when a high-viscosity press oil is used, there is a concern that the handling property and the subsequent coating process may be adversely affected.

Therefore, in addition to the above-mentioned conventional technique, the inventors have studied a technique focusing on the surface of the mold and made it possible to prevent the occurrence of molding defects during press molding. That is, the present invention is intended to prevent the occurrence of molding defects such as cracks and wrinkles of the press material by containing lubricating oil between the die surface and the press material during press molding to improve the sliding characteristics. An object is to provide a molding die.

[0007]

Conventionally, it has been considered desirable that the surface roughness of the mold be smooth. However, the inventors have found that by appropriately adjusting the surface roughness of the mold, it is possible to control the sliding characteristics between the mold and the press material and achieve an improvement in moldability.

That is, in the press-molding die of the present invention, a plurality of recesses are formed on a part or the entire surface of the die which is in contact with the press material when the press material is molded, and the average diameter of the recesses is 30 μm to 100 μm. And the average depth is 1 μm to 1
It is characterized in that each of the recesses is formed to have a thickness of 0 μm, and the average interval between the plurality of recesses is set to 1.3 to 3 times the average diameter.

Further, preferably, the press material is a thin plate for automobile having a surface roughness SRa of 1 μm or less. In the press-molding die of the present invention configured as described above, a plurality of concave portions are formed on a part or the entire surface of the die which is in contact with the press material when molding the press material. As a result, the lubricating oil is contained in this recess, and the slidability between the press material and the die can be improved.

Further, the recesses formed on the surface of the mold have an average diameter, an average depth and an average interval set within a specific range. The reason will be described below. First, the diameter of the recess is an important parameter corresponding to each oil (lubricating oil) pool on the mold surface. That is, the lubricating oil accumulated in the recesses on the surface of the die is sealed between the die and the press material by the pressure when sliding with the press material. If the lubricating oil is sufficiently supplied to the sliding surface due to the increase in the containment pressure at this time, the lubricating effect is exhibited. This increase in the containment pressure is achieved by the press material being properly intruded into the concave portion of the die surface, and the amount of this intrusion depends on the size of the diameter of the concave portion of the die surface. In the present invention, the average diameter of the recesses on the surface of the mold is 30 μm to 100 μm.
Is formed in. The diameter of the recess on the die surface is 30 μm
When the value is less than the above value, the pressure increase of the lubricating oil is small because the penetration of the press material in the recess due to the bending is slight. On the contrary, when the diameter of the concave portion on the surface of the mold exceeds 100 μm, the indentation due to the bending of the pressing material in the concave portion becomes too large, and the frictional resistance between the surface of the mold and the pressing material becomes too large. On the other hand, when the average diameter of the recesses on the surface of the mold is 30 μm to 100 μm, the relative frictional resistance between the press material and the mold is higher than that of the conventional one due to the pressure of the lubricating oil contained in the recesses. It can be reduced and slidability can be improved.

Next, in the present invention, the average depth of the concave portions on the surface of the mold is formed to be 1 μm to 10 μm. It has been found that when the diameter of the recesses on the mold surface is the same, the amount of indentation due to the bending of the press material in the recesses is the same, but the smaller the depth of the recesses, the greater the pressure rise of the lubricating oil. . As a result, the average depth of the recesses on the mold surface is
It is preferably 10 μm or less. However, if the depth of the recesses on the surface of the mold is less than 1 μm, the amount of lubricating oil contained in each recess is too small, and a sufficient lubricating effect cannot be obtained, which is not preferable. Also, it will be very difficult to manufacture,
Not preferable.

Further, the ratio of the average diameter of the recesses to the average spacing (average spacing / average diameter) is important as a parameter for determining the amount of lubricating oil retained per unit surface of the mold. In the present invention, the average interval of the plurality of recesses is 1.3 to 3 times the average diameter. If this ratio is less than 1.3, the area between the mold surface and the recess that directly contacts the press material becomes small, so that the contact surface pressure between the mold surface and the press material becomes too high and the recess This is not preferable because the sliding resistance increases because the amount of press material that is pressed in is increased. Conversely, if this ratio exceeds 3,
Since the amount of lubricating oil retained per unit surface of the mold is reduced, a sufficient lubricating effect is not exhibited, which is not preferable.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, 1 is a press-molding die, and this press-molding die 1 is composed of a die 2 and a punch 3. Reference numeral 4 denotes a plate retainer that applies a wrinkle retainer force. Further, 5 is a press material which is press-molded by the press-molding die 1. The press material 5 is an automobile side sill having a relatively complicated shape. Furthermore, as this press material 5, 0.7
Two types of thin plates having a plate thickness of mm, that is, a shot dull material (surface roughness SRa 0.86) and a low roughness laser dull material (surface roughness SRa 0.64) were used.

In FIG. 1, A, B and C indicate the R portion where the punch 3 has a small radius of curvature, and D, E and F indicate the R portions where the die 2 has a small radius of curvature. Generally, it is considered that cracks are likely to occur in the parts of the press material 5 that come into contact with these parts during press molding, and therefore it is preferable to form recesses described below in these parts A to F. .
In this example, the occurrence of cracks was confirmed by experiments, and a plurality of recesses described below were formed only in the E and F parts of the die 2 where the cracks occurred.

2 and 3 show a plurality of recesses formed in the E and F portions of the die 2. In the present invention, the average value of the diameter (W) of the recesses is 30 μm to 100 μm, the average value of the depth (H) is 1 μm to 10 μm, and the average value of the intervals (B) of the plurality of recesses is formed. Is formed to be 1.3 to 3 times its average diameter. Furthermore, in the most preferred embodiment, the average diameter of the recesses is 60.
and an average depth of 4 μm,
It was possible to obtain the one in which the average interval of the plurality of concave portions was formed to be 2.5 times the average diameter.

In order to process the E and F parts of the die 2 to form the recesses, well-known photo etching or machining can be used. For example, in the case of forming a recess by photoetching, place a film that specifies a black pond-shaped groove (light passes through only this part) on the die, and then irradiate this film with light (ultraviolet rays). To do. At this time, the light passing through the pond-shaped groove portion of the film reacts with the etching liquid to erode the surface of the die to form a pond-shaped concave portion. Further, the depth of the recess is determined by adjusting the light irradiation time.

Next, referring to FIGS. 4, 5 and 6, the average diameter, the average depth, and the ratio of the average diameter to the average interval (average interval / average diameter) of the recesses formed on the surface of the die, The relationship between the surface of the die 2 and the relative frictional resistance between the press material 5 will be described. FIG. 4 is a diagram showing the relationship between the average diameter of the recess and the relative frictional resistance. The relative frictional resistance is 10 when the average diameter of the recesses is zero, that is, when the conventional type mold having no recesses is used.
The numerical value when 0 is shown. Also, the average depth of the recesses (= 4 μm) and the average spacing / average diameter (= 0.5)
Is a constant value and the value of the average diameter of the recesses was changed.
As is clear from the experimental data shown in FIG. 4, it can be understood that when the average diameter of the recesses is formed in the range of 30 μm to 100 μm, the relative friction resistance is reduced and excellent sliding characteristics are obtained.

The diameter of the recess is an important parameter corresponding to each oil (lubricating oil) pool on the mold surface.
That is, the lubricating oil accumulated in the recesses on the surface of the die is sealed between the die and the press material by the pressure when sliding with the press material. If the lubricating oil is sufficiently supplied to the sliding surface due to the increase in the containment pressure at this time, the lubricating effect is exhibited. This increase in the containment pressure is achieved by the press material being properly inserted into the concave portion of the mold surface, and the degree of this insertion is changed by the size of the diameter of the concave portion of the mold surface. When the diameter of the concave portion of the die is less than 30 μm, the press material is slightly indented in the concave portion due to bending, so that the pressure increase of the lubricating oil is small, which is not preferable. On the contrary, if the diameter of the recess of the die exceeds 100 μm, the indentation due to the bending of the press material in the recess becomes too large, and the frictional resistance between the die surface and the press material becomes too large, which is not preferable. On the other hand, when the average diameter of the recesses of the die is 30 μm to 100 μm, the relative frictional resistance between the press material and the mold is reduced by the pressure of the lubricating oil contained in the recesses as compared with the conventional one. The slidability can be improved.

Incidentally, the relationship between the average diameter of the recesses and the relative frictional resistance shown in FIG. 4 has the same tendency in other experimental examples in which the average depth of the recesses and the value of the average interval / average diameter are different. I was able to confirm. FIG. 5 is a diagram showing the relationship between the average depth of the recess and the relative frictional resistance. Also,
The average diameter (= 60 μm) and average interval / average diameter (= 2.5) of the recesses were set to constant values, and the average depth value was changed. As is clear from the experimental data shown in FIG. 5, it can be understood that when the average depth of the recesses is formed in the range of 1 μm to 10 μm, the relative friction resistance is reduced and excellent sliding characteristics are obtained. .

When the dies have the same diameter, the amount of indentation due to the bending of the press material in the recesses is the same,
The smaller the depth of the recess, the larger the increase in the pressure of the lubricating oil. As a result, the average depth of the concave portions of the die is preferably 10 μm or less. However, the depth of the concave part of the die is
If it is less than 1 μm, the amount of the lubricating oil contained in each recess is too small, and a sufficient lubricating effect cannot be obtained, which is not preferable. In addition, it is difficult to manufacture, which is not preferable.

The relationship between the average depth of the recesses and the relative frictional resistance shown in FIG. 5 has a similar tendency in other experimental examples in which the values of the average diameter of the recesses and the average spacing / average diameter are different. I was able to confirm. FIG. 6 is a diagram showing the relationship between the ratio of the average diameter of the recesses to the average spacing (average spacing / average diameter) and the relative frictional resistance. The average diameter of the recesses (= 60 μm) and the average depth of the recesses (= 4 μm) are
The value of average interval / average diameter was changed with a constant value. As is clear from the experimental data shown in FIG. 6, the ratio of the average diameter of the recesses to the average interval (average interval / average diameter) is
It can be understood that in the case of being formed in the range of 1.3 to 3, the relative friction resistance is lowered and excellent sliding characteristics are obtained.

The ratio of the average diameter of the recesses to the average spacing (average spacing / average diameter) is important as a parameter for determining the amount of lubricating oil retained per unit surface of the die. This ratio is
If it is less than 1.3, the area between the recesses where the die surface and the press material come into direct contact becomes small, so the contact surface pressure between the die surface and the press material becomes too high, and the amount of the press material embedded in the recesses becomes too large. Is large, the sliding resistance becomes large, which is not preferable. Conversely, this ratio is 3
If it exceeds the range, the amount of lubricating oil retained per unit surface of the die becomes small, so that a sufficient lubricating effect is not exhibited, which is not preferable.

Incidentally, the relationship between the ratio of the average diameter of the recesses to the average spacing (average spacing / average diameter) and the relative frictional resistance shown in FIG. In the example as well, it was confirmed that there is a similar tendency.

[0024]

As described above, according to the mold for press molding of the present invention, a plurality of recesses are formed on a part or the entire surface of the mold, and the average diameter of the recesses is 30 μm to 1 μm.
At 00 μm, the average depth is formed to 1 μm to 10 μm, and the average interval of the plurality of recesses is set to 1.3 times to 3 times the average diameter, so that the lubricating oil is enclosed in the recesses, The slidability between the press material and the mold can be improved. As a result, it becomes possible to prevent the occurrence of molding defects such as cracks and wrinkles of the press material.

[Brief description of drawings]

FIG. 1 is an overall schematic view showing an embodiment of a press molding die of the present invention.

FIG. 2 is a partial cross-sectional view of a recess formed on the die surface of the press-molding die of the present invention.

FIG. 3 is a partial plan view of a recess formed in the die surface of the press-molding die of the present invention.

FIG. 4 is a diagram showing the relationship between the average diameter of recesses and relative frictional resistance.

FIG. 5 is a diagram showing the relationship between the average depth of recesses and relative frictional resistance.

FIG. 6 is a ratio of the average diameter of the recesses to the average interval (average interval /
Diagram showing the relationship between average diameter) and relative frictional resistance

[Explanation of symbols]

 1 die for press molding 2 die 3 punch 4 plate retainer 5 press material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Imanaka 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Technical Research Division (72) Inventor Toshiyuki Kato 1 Kawasaki-cho, Chuo-ku, Chiba Address: Kawasaki Steel Corporation Technical Research Division

Claims (2)

[Claims] 1. A plurality of recesses are formed on a part or the entire surface of a mold contacting the press material at the time of molding the press material, and the recesses have an average diameter of 30 μm to 100 μm and an average depth of 1 μm to 10 μm. With each forming,
A mold for press molding, characterized in that the average interval of the plurality of recesses is formed to be 1.3 to 3 times the average diameter. 2. The press material has a surface roughness SRa of 1.
The metal mold for press molding according to claim 1, which is a thin plate for automobile having a thickness of not more than μm.