JPH08164438A - Forcing method of thin disk - Google Patents

Abstract

PURPOSE: To secure the stability of stock while reducing load, to reduce outer peripheral burrs and to improve the yield of material. CONSTITUTION: In producing a thin disk by rotary forging, an inclined angle αand the number of revolution N of a forming die (upper die) are set to the range of (1.0 deg.<=α<=10.0 deg.) and (N>=60rpm). Further, a rolling reduction δ (mm/rev) per revolution of rotary forging is respectively adjusted to satisfy (δ<0.0003.α.df) at the initial stage of reduction (contacting time between forming die and material) or (δ>=0.0004.α.df) up to the neighborhood of the final stage of reduction (up to the range of t/tf>=1.2), provided, t: thickness (mm) of disk stock during forming, tf: rotary forging finished thickness (mm) of disk stock, df: rotary forging finished outer diameter (mm) of disk stock.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary forging method for producing a thin disk.

[0002]

2. Description of the Related Art The rotary forging method is a technology for processing the entire material to a desired shape by repeating partial processing, unlike processing the entire material at once by applying a large load. It is known as a plastic working means that can be formed with a relatively small working force. In particular, the rotary forging method is an extremely effective production means for the production of disc materials and the like that are produced in small quantities for a wide variety of products.
The "lower mold rotating type" in which the lower mold is rotationally driven and the upper mold is driven to perform molding, and the "oscillating die type" in which the lower mold is fixed and the upper mold is swung to perform molding are in practical use. In both types of rotary forging methods, the relative movements of the material to be molded and the lower mold and the upper mold are the same, and there is no particular difference in the molding principle itself. "For example, rotary forging will be explained.

Conventionally, the rotary forging is carried out by setting the "angle of inclination (tilt) α of the upper die (molding die)", the "rotational speed N of the lower die" and the "rolling speed v" to specific values. Has been done.
In this case, it is known that the following relationship exists between the setting items and the forming load, so that the processing force and processing time of rotary forging, especially the processing force, should be as small as possible. The upper mold tilt angle α ", the" lower mold rotation speed N ", and the" rolling speed v "have been carefully devised. a) The forming load decreases as the upper die inclination angle α increases, b) the forming load decreases as the lower mold rotation speed N increases, and c) the forming load increases as the reduction speed increases.

However, in this rotary forging method,
In particular, when forming a thin disk material, "stability of material during forming" and "outer peripheral burr" are major problems in addition to "processing force" and "processing time". This is because, in the case of a thin-walled disc, the material is warped during molding and the stability in the mold deteriorates, which tends to adversely affect the molding work. Is likely to be noticeable. However,
At present, a method for coping with the above problem has not been sufficiently established, and a means for efficiently and stably forming a thin disk by a rotary forging method has been urgently desired.

Therefore, the object of the present invention is to secure the stability of the material during molding while reducing the load, and to reduce the peripheral burr to improve the material yield. It is to establish a rotary forging forming method for thin-walled discs.

[0006]

Means for Solving the Problems In order to achieve the above object, the inventors of the present invention firstly conducted experiments to find out a factor for inhibiting the stability of a material which is a problem in the case of rotary forging a thin disk. It was found that the phenomena leading to instability of the material during molding are roughly classified into the following two types.

(A) When the material comes into contact with the upper mold in the initial stage of pressing, the upper mold acts to repel the material, so that the center of the material comes off. This is because the material does not move from the mold due to the friction between the lower mold and the material in the normal rolling state, but the material is not sufficiently pressed to the lower mold in the initial stage of rolling and therefore the friction with the lower mold is caused. It is considered that this is because the material does not move sufficiently due to the contact of the upper mold because the force does not sufficiently act. (b) Near the end of rolling, the material floats up from the lower die on the side opposite to the surface being pressed by the upper die, and in extreme cases, it bulges out of the lower die. This is because as the material becomes thinner, warping and bending are likely to occur, but in rotary forging, the contact surface between the upper die and the material is not the entire upper surface of the material but only a part as shown in FIG. 2, and therefore the metal flow on the pressing side is reduced. It is considered that this is because the material floats up from the lower mold on the side opposite to the part that is pressed by.

[0008] Therefore, as a result of research to eliminate the above-mentioned phenomenon leading to instability of the material during forming, the reduction rate is determined by "the initial stage of rotary forging" and "after that until the end stage". It has been found that it is effective to control (the amount of reduction per one rotation of the rotary forging) for each, and the occurrence of peripheral burrs is also suppressed by this.

That is, the phenomenon (displacement of the material) described in the item (a) can be prevented by slowly pressing down the upper die so as not to abruptly cut into the material at the initial stage of the pressing.
It was also found that the occurrence of peripheral burrs can be suppressed by eliminating this material deviation.

Regarding the phenomenon (partial lifting of the material) described in the item (b) near the end of rolling, if the rolling speed is as fast as possible, the contact surface between the upper die and the material increases and the material Although it was possible to prevent the floating of, the load was significantly increased if the rolling speed was unnecessarily increased. However, there is a specific relationship between "the degree of progress of molding of material" and "reduction rate" and "promotion of rising from the mold". From these relationships, the prevention of material lifting that minimizes the increase in load It became clear that it is possible to grasp the rolling speed.

Further, as described above, the setting of the rotary forging machine at the time of rotary forging is generally made for the three conditions of the upper mold tilt angle, the lower mold rotation speed, and the reduction speed, so that the reduction speed is defined as "remaining two conditions". "Rotating forged outer diameter of disc material"
If it is arranged as a function of and, the optimum rolling pattern can be determined given the final finishing shape.
It was also confirmed that the instability phenomenon of the material and the generation of burrs are suppressed by following the instructions.

The present invention is based on the above findings and the like. "When manufacturing a thin disk by rotary forging, the inclination angle α (°) of the upper die and the rotation speed N (rpm) are 1.0 °. ≦ α ≦ 10.0 °, N ≧ 60 rpm, and the reduction amount δ (mm / rev) per rotation of the rotary forging is δ <0.0003 in the initial stage of the reduction (when the die and the material are in contact).・ Α ・ df and δ ≧ 0.0004 ・ α ・ df until near end of rolling (range of t / tf ≧ 1.2) By performing the forming while adjusting each to satisfy the above conditions, while ensuring the stability of the material during forming with the smallest possible processing force, while suppressing the occurrence of peripheral burrs, efficient rotary forging of thin discs It has a great feature in that it is "moldable".

Here, the above-mentioned "rotary forging" may be either a "lower die rotating type" or an "oscillating die type", the rolling speed is v (mm / sec), and the rotating speed of the forming die is Needless to say, if N (rpm) is given, the amount of reduction δ (mm / rev) per rotation of the rotary forging is represented by δ = 60 × v / N.

[Action]

Hereinafter, the reason why the rotary forging conditions for the thin disk are limited as described above in the present invention will be explained together with its action. A) Tilt angle α of forming die (upper die) In rotary forging, the upper die is given an inclination angle α (see Fig. 1) to perform partial processing. However, if this angle α is less than 1.0 °, the load reduction effect is small. On the other hand, when the angle exceeds 10.0 °, not only the load reducing effect begins to be saturated, but conversely, the tendency of the material to rise increases, which is a disadvantage. Therefore, it was determined that the upper mold tilt angle α (°) satisfies the condition of 1.0 ° ≤ α ≤ 10.0 °.

B) Number of revolutions N of forming die (lower die) It is necessary to increase the number of revolutions of the upper and lower dies in order to shorten the processing time of the material, and the temperature drop when hot working is assumed. Therefore, it is necessary to set the speed to 60 rpm at least. Therefore, it has been determined that the rotation speed N (rpm) of the lower die satisfies the condition of N ≧ 60 rpm.

C) Reduction amount per rotation of rotary forging δ It was made clear by a study carried out while repeating the experiment, that is, the initial stage of reduction during rotary forging (at the time of contact between the upper die and the material). The reduction amount δ per rotation at
By setting the range to "0.0003 / α / df", it becomes possible to prevent the movement (deviation) of the material that tends to occur when the material and the upper mold are in contact with each other. On the other hand, if the amount of reduction δ per rotation in the initial stage of reduction is made larger than this, the material will be displaced from the molding die and stability will not be maintained, and peripheral burrs will occur. Therefore, it was decided to adjust the amount of reduction δ (mm / rev) per rotation in the range of δ <0.0003 · α · df in the initial stage of rolling (when the upper die and the material are in contact).

On the other hand, from the contact between the upper die and the material, at least until the end of the reduction (t / tf ≧ 1.2) at which the thickness t of the disk portion becomes 1.2 times the final finish thickness tf, the reduction speed is Even if the load is increased, the load does not suddenly increase. Therefore, it is possible to prevent the material from rising by increasing the rolling reduction amount δ per rotation of the rotary forging. In this case, if the reduction amount δ per rotation is in the range of “δ <0.0004 · α · df”, it is not possible to sufficiently prevent the material from floating,
For the first time, by setting the range of “δ ≧ 0.0004 ・ α ・ df”, the minimum contact area between the upper die and the material to prevent the material from rising can be secured and the material can be prevented from rising. The amount of reduction per revolution δ (mm / re) after the contact between the die and the material until near the end of the reduction (range of t / tf ≧ 1.2)
It was decided that v) should be adjusted within the range of δ ≧ 0.0004 · α · df. Since there is not so much metal flow after this, no material is lifted up regardless of the amount of rolling reduction δ per revolution, and therefore the rolling load per revolution is not so high. It suffices to set the reduction amount δ.

Next, the present invention will be described with reference to examples.

[Example] Using a "lower mold rotary type" rotary forging machine as shown in FIG. 1, a disk material having the shape and dimensions shown in FIG. 3 from a high carbon steel billet having an outer diameter of 450 mmφ and a thickness of 300 mm. The test which shape | molds was implemented.

In this rotary forging process, a plurality of the above high carbon steel billets are heated to 1250 ° C. and then the scale is removed to make the lower mold rotation speed N (rpm) constant at 90 rpm. The upper die tilt angle α (°) and the rolling speed v (mm / sec) were changed to form the disk material. Table 1 summarizes these test conditions and test results. Here, as described above, the reduction amount δ per one revolution of the forming die shown in Table 1 is represented by δ (mm / rev) = 60 × v / N.

[0020]

[Table 1]

From the results shown in Table 1, the following can be confirmed. That is, if the rotary forging molding conditions satisfy the requirements of the present invention, both the movement (deviation) and the lifting of the material in the initial stage of rotary forging are suppressed, and good moldability is shown.
When the rolling reduction δ per one rotation of the molding die does not satisfy the conditions specified in the present invention, an outer peripheral burr is generated, or the material is extruded from the mold at the initial stage of rotary forging to deteriorate the formability and form a burr on the outer peripheral portion. It is clear that also occurs.

[0022]

[Summary of Effects] As described above, according to the present invention, a thin-walled disk having a healthy shape can be produced with a good material yield while suppressing the inconvenience such as the material being lifted from the lower die during forming by rotary forging and the occurrence of peripheral burrs. Industrially useful effects such as stable molding become possible.

[Brief description of drawings]

FIG. 1 is an explanatory diagram related to rotary forging of a lower die rotary type.

FIG. 2 is an explanatory diagram of a contact surface between an upper die and a material during rotary forging.

FIG. 3 is an explanatory diagram regarding the shape and dimensions of a thin-walled disc material that was attempted to be manufactured in Examples.

Claims (1)

[Claims] 1. When manufacturing a thin disk by rotary forging, the inclination angle α (°) of the upper die and the rotation speed N (rpm) are set in the range of 1.0 ° ≦ α ≦ 10.0 °, N ≧ 60 rpm, and The amount of reduction δ (mm / rev) per rotation of rotary forging is δ <0.0003 · α · df at the initial stage of rolling (when the die and the material are in contact), and until the end of rolling (t / tf). ≧ 1.2 range) is δ ≧ 0.0004 ・ α ・ df A rotary forging method for thin-walled disks, which is characterized in that the molding is performed while adjusting so as to satisfy the above conditions.