JPH07265993A - Die forging method - Google Patents

Abstract

PURPOSE:To improve the yield without developing any under fill by positioning the center of gravity of a rough shaped material for die forging and the position of the center of gravity in an impression cross section onto almost perpendicular. CONSTITUTION:In a preforming process for forming the rough-shaped material 4 to a prescribed shape of the preform with a rough die impression 2, the rough- shaped material 4 is formed so that the position of the center of gravity G in the optional cross section vertically cut in the reference direction at the time of laying on the impression 2 positions almost on the perpendicular line of the position of the center of gravity (g) in the cross section of the corresponding impression 2. At the time of laying on the finishing die impression instead of the rough die impression, too, the rough-shaped material is formed by the same way. By this method, as the position of the center of gravity of the rough- shaped material in each optional cross section almost corresponds to the position of the center of gravity of the impression in the forging direction, at the time of forging, the material of the rough-shaped material in each cross section is filled to the impression in one average and the under fill is not developed and the burr is uniformized in the whole periphery.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die forging method for forming a forged product from a rough material by using an impression.

[0002]

2. Description of the Related Art It is usually difficult to form a metal material into a desired shape by die forging in a single molding.
Multiple moldings are required, the process being related to the cross-sectional area of the forged product. Then, in the final forging, the waste land fills the finishing mold impression and the surplus is extruded as burr. In this case, it is desirable that the length of the portion extruded as burrs be uniform. Therefore, it is said that it is desirable that the rough land shape is a theoretical rough land shape that is distributed to a shape that is closest to the total cross-sectional area of the forged product and the burr.

The theoretical cross-sectional area of rough land is expressed by the sum of the cross-sectional area of the forged product and the cross-sectional area of the burr, and is used for setting the forging process together with the cross-sectional diagram, determining each impression, and determining the material size. Used ("Forging die design" issued by Forgiken Co., Ltd.).

[0004]

If the shape of the wasteland is determined based on the theoretical idea of wasteland, the theoretical yield is 80%.
That is all. However, in reality, the yield is 80% or more, which is extremely small, and the yield is usually 50 to 70%. Moreover, the concept of theoretical wasteland is applied to a single-cavity cross-section with a symmetrical shape or something similar, and when two-cavity or an asymmetric cross-section is used, the idea is difficult to apply and yield is extremely high. It is currently low.

That is, when forming an asymmetrical waste from a rough material by a rough molding type impression, it is difficult to completely eliminate the lack of wall in the theoretical rough, and a rough material having a larger cross-sectional area than the theoretical rough is used. There is no choice but to use it, and as a result, the yield is greatly reduced. For example, in the case of taking two pieces, it is usually formed by inverting one of them and facing each other, but the impression is asymmetric with respect to the center, and as a result, forging is performed on the side where the cross-sectional area of the impression is small. Sometimes there are many burrs. On the side where the cross-sectional area of the impression is large, there may be a case where the thickness is lacking.

The present invention has been made in view of such circumstances, and it is an object of the present invention to secure a high yield even when the impression shape is asymmetrical such as two-cavity production.

[0007]

A die forging method according to the present invention which solves the above-mentioned problems includes a rough land forming step in which a rough shape material is made into a rough land of a predetermined shape by a rough forming die impression, and a finish forming die imprinting process for the rough land. In the die forging method consisting of the forging process of forging in the rough section, the rough shape material is the center of gravity of the cross section of the rough shape material cut perpendicular to the reference direction when placed on the rough forming die impression in the rough forming step. It is characterized in that it is formed so as to be positioned substantially on the vertical line of the center of gravity of the cross section of the corresponding rough forming die impression.

Further, in the die forging method in which the rough material is forged by the finish molding impression when the rough molding step is not carried out, the rough material is perpendicular to the reference direction when placed on the finish molding impression. It is characterized in that the position of the center of gravity of the cross section of the rough-shaped material cut into is located substantially on the vertical line of the position of the center of gravity of the cross section of the corresponding finishing molding die impression.

[0009]

In the die forging method of the present invention, a metal material is first prepared. As this metal material, a generally cylindrical roll material processed by rollers is used. The shape of the roll material is determined according to the shape of the impression, and in the case of the present invention, since there is no lack of wall and less burr is generated, a shape having a cross-sectional area of 100 to 125% with respect to the cross-sectional area of the impression. Can be

This roll material is a rough shaped material having a shape corresponding to the shape of the rough molding die impression or the finish molding die impression. Generally, it is crushed into a substantially plate shape between a crushing mold composed of an upper mold and a lower mold. Here, in the present invention, when the shape of the rough material is placed on a rough molding die impression or a finishing molding die impression, the position of the center of gravity of the cross section of the rough material cut perpendicular to the reference direction corresponds to the impression. The shape is located on the substantially vertical line of the center of gravity of the cross section.

The reference direction means, for example, the longitudinal direction. In this case, the center of gravity of the cross section at any position cut perpendicular to the longitudinal direction of the rough material is on the substantially vertical line of the center of gravity of the cross section of the corresponding impression. It is located in. The term “on a substantially vertical line” means that it is in the vicinity of the vertical line, and it is most preferable that the lines coincide with the vertical line, but a deviation of about ± 5% is acceptable.

Therefore, the barycentric position of the rough shaped material and the barycentric position of the impression substantially coincide with each other in each forging section in the forging direction, so that the material of the rough shaped material is averaged and filled in each cross section during forging. To do. In other words, since the small volume portion of the rough material is located in the small volume impression and the large volume portion of the rough material is located in the large volume impression, there is no thin wall Is even over the entire circumference.

[0013]

EXAMPLES Hereinafter, examples and conventional examples will be specifically described. In this embodiment, the present invention is applied to the case where an automobile arm is formed. As shown in FIG. 2, one of them is turned upside down and the other is opposed to the arm.
The impression is formed so that it can be taken individually.

First, a roll material 1 shown by a chain line in FIG. 2 is prepared. The roll material 1 has a substantially cylindrical shape processed by rollers, and the cross-sectional area perpendicular to the longitudinal direction is changed according to the cross-sectional area of the impression 2 in FIG. Here, the description will be made by paying attention to the AA cross section of FIG. In the AA cross section of the impression 2, as shown in FIG.
0 and the large volume portion 21 are connected by a narrow passage 22.

In the conventional die forging method, as shown in FIG. 4, the center of gravity G of the roll material 1 is located near the small volume portion 20 of the narrow passage 22 and the space of the impression 2 at the AA cross section position. Is away from the center of gravity g of. Therefore, when die forging is performed in this state, the meat of the roll material 1 is substantially evenly divided into left and right parts, so that the small volume portion 20 becomes excessive and the large volume portion 21 becomes insufficient, and the burr becomes uneven.

Even if the roll material 1 is crushed into a crushed material, the position of the center of gravity G does not change because the upper and lower surfaces of the crushed material 10 are parallel in the conventional crushing processing. Therefore,
As shown in FIG. 5, although the difference may be smaller than that of the roll material 1, there still remains a problem that the small volume portion 20 has an excessive amount and the large volume portion 21 has an insufficient amount. Therefore, in this embodiment, as shown in FIG. 3, the roll material 1 is crushed by an upper die 30 having a die surface 32 inclined downward to the right in the AA cross section and a lower die 31 having a flat die surface. To do. The shape of the inclined mold surface 32 of the upper mold 30 is formed according to the shape of the impression 2. That is, when the roll material 1 is crushed, it is analyzed by the finite element method (FEM), and the crushed product of the crushed product of the roll material 1 is crushed so that the center of gravity G of an arbitrary cross section matches the center of gravity g of the cross section of the corresponding impression. There is.

Explaining this with reference to the drawings, the roll material 1 having a circular cross section is pressed by an upper die 30 having a die surface 32 inclined downward to the right in a section corresponding to AA as shown in FIG. And roughly left wedge-shaped coarse material 4
Becomes At this time, the center of gravity G of the cross section of the roll material 1 moves to the left side of the drawing as the crushing process progresses, and in the rough material 4, the position of the center of gravity G of the cross section of the roll material 1 deviates to the left side of the drawing. When it is arranged in the impression 2 as shown in FIG. 1, it coincides with the center of gravity g of the cross section of the impression 2. This is the same for any cross section perpendicular to the longitudinal direction.

In FIG. 3, the roll material 1 has an inclined mold surface 32.
It seems that it is pressed with and moves to the left and right,
The inclination direction of the inclined mold surface 32 in an arbitrary cross section is determined according to the shape of the impression 2 as described above, and there is a downward slope to the right or a downward slope, so the roll material 1 does not move. Further, the crushed width of the rough material 4 needs to be inside the impression 2, and the crushed thickness needs to be a predetermined dimension or more depending on the size of the impression 2. If this condition is not satisfied, it can be solved by changing the cross-sectional area of the roll material 1.

The rough-shaped material 4 obtained above is forged by the finishing mold impression 2 so that the burr is small and the yield is good, so that two arms shown in FIG. 2 can be formed. In the above-mentioned embodiment, the rough shape material 4 is forged as it is into the product by the finishing mold, but it is also possible to form the rough land by using the roughing mold and then forge it with the finishing mold.
In this case, the mold surface shape of the upper mold 2 is formed in the same manner as described above in accordance with the rough molding die impression, thereby forming a rough shaped material having a center of gravity that matches the center of gravity of the rough molding die impression in an arbitrary cross section. It is possible to form a wasteland with good yield.

[0020]

That is, according to the die forging method of the present invention,
Since defectiveness of wall thickness can be prevented and burrs can be made uniform, the shape of the material can be reduced as compared with the conventional one, and the yield is remarkably improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the relationship between a rough material and an impression in one embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an impression and a shape of a material according to an embodiment of the present invention.

FIG. 3 is an explanatory view showing a method for forming a rough shape material in one embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a relationship between an impression and a material in a conventional method.

FIG. 5 is an explanatory diagram showing a relationship between an impression and a rough material in a conventional method.

[Explanation of symbols]

1: Roll material 2: Impression
4: Coarse shaped material 30: Upper mold 31: Lower mold G,
g: center of gravity

Claims (2)

[Claims] 1. A die forging method comprising: a rough land forming step of forming a rough shape into a rough land with a rough forming die impression; and a forging step of forging the rough land with a finish forming die impression. The rough shape material has a cross section of the rough molding die impression which corresponds to the position of the center of gravity of the cross section of the rough shape material cut perpendicularly to the reference direction when placed on the rough molding die impression in the rough molding step. The die forging method is characterized in that it is formed so as to be positioned on a substantially vertical line of the center of gravity of the. 2. A die forging method for forging a rough shaped material with a finish molding die impression, wherein the rough shaped material is cut into a rough shape perpendicular to a reference direction when the rough shaped material is placed on the finish molding die impression. A die forging method, characterized in that it is formed so that the position of the center of gravity of the cross section of the shape member is located substantially on the vertical line of the position of the center of gravity of the cross section of the corresponding finish forming die impression.