JPH0871652A - V-bending method excellent in bending limit and shapeability - Google Patents

Abstract

PURPOSE: To provide a bending method excellent in the bending limit and the shapeability in a method where an aluminum sheet is bent In the V--shape by a V-shaped die and a V-shaped punch. CONSTITUTION: When an aluminum sheet is bent in the V-shape after it is heated to the temperature of >=150 deg.C to <=350 deg.C in the condition held by a punch l and a die 2 heated by an incorporated heating device, the value to be obtained by the formula P/(A×Ys)} is regulated so as to be in the range of 0.35-1.75 where P(Kg) is the punch pressing force, A(mm<2> ) is the area of a work to be held by the punch 1 and the die 2, and Ys(Kg/mm<2> ) is the proof load of the aluminum sheet when heated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to automobile parts, building materials,
For improving the bending limit of V-bending products for household appliances and other general applications, and for suppressing the problems of springback and saddle warpage that occur during bending processing, and the effects of suppressing springback and saddle warpage. Excellent aluminum plate V
The present invention relates to a bending method.

[0002]

2. Description of the Related Art Conventionally, V bending of an aluminum plate material is performed at room temperature (0 ° C. to 35 ° C.) at a room temperature (0 ° C. to 35 ° C.), a bending die having a V punch and V die attached to a press, or a V punch and V die to a shear bender. Using the attached bending die, insert an aluminum plate between the V punch and V die,
The aluminum plate was bent by pushing the V punch into the die.

However, the bending limit is generally better for materials having a large elongation of the work material, and all alloy-based materials other than pure Al are greatly inferior in bending limit and it is difficult to obtain a sharp shape such as 0r. was there.

In the bending process, a tensile stress is applied to the outside and a compressive stress is generated in the width direction, and the stress difference between the inside and the outside appears as spring back. Further, simultaneously with the pulling of the bending outside portion, the material shrinks and deforms in the width direction, and the inside compressed portion is laterally (widthwise) expanded and deformed due to the restraint due to the contact of the punch, resulting in saddle warpage.

The obtained bent product is used alone or in combination with another part by welding, adhesion, fitting, bolting, etc., but the shape property such as spring back after bending, saddle warping, etc. is poor. Therefore, there is a problem in that the desired shape cannot be obtained by twisting or the desired shape is not obtained. Further, if the shape is not so good, the assembly cannot be assembled, and thus the accuracy of the shape of the bend-formed product is required.

Therefore, in general, as a measure against springback that occurs during bending, a spring is designed in advance so that the desired bending angle can be obtained by designing the die by designing the die in consideration of the amount of springback. However, compared to steel plates, aluminum plate materials have a spring back amount of 2-3 times,
If the alloy type is changed or it is applied to materials with different strengths (proof strength), it is difficult to obtain the desired bending angle, and there is a problem that it is difficult to design the mold. It was

[0007]

The springback that occurs during V-bending depends on the strength of the plate material, especially the proof stress.
Since it changes depending on the type and plate thickness of the aluminum alloy, it is difficult to control the springback amount when the type and plate thickness of the alloy changes. In addition, the higher the strength of the material, the more easily the bending r is increased, so that cracks are more likely to occur, and the material of higher strength has a drawback that it is difficult to obtain a sharp bent shape. Further, there is a problem that it is difficult to suppress saddle warp at the same time as V-bending.

The present invention has been made in view of the above circumstances, and provides a processing method capable of obtaining a bend-formed product which is excellent in V-bending limit, and which is excellent in springback and saddle warp and in shape. The purpose is to do.

[0009]

Means for Solving the Problems The inventors of the present invention have repeatedly conducted original experiments and studies to solve the above-mentioned problems, and as a result, in a V-bending method, a heating device was incorporated in a punch and a die of a V-bending die. By holding an aluminum plate in a certain temperature range while sandwiching it with a heated punch and die, and bending it while controlling the punching force when pushing the work material with the punch to a certain range It was found that the V-bending limit, the springback after bending, and the amount of saddle warp can be significantly reduced as compared with the conventional processing method, and the present invention has been accomplished.

Specifically, an aluminum plate is sandwiched between a V-shaped die and a V-shaped punch facing the V-shaped die,
In a method of pushing a punch into a die and bending it into a V shape, after heating the aluminum plate to a temperature of 150 ° C. or higher and 350 ° C. or lower while sandwiched by a heated punch and a die incorporating a heating device, V When bending into a letter shape, the punch pressing force is P (Kg), and the area of the work piece between the punch and the die is A (mm
² ), the proof stress of the aluminum plate during heating is Ys (Kg / m
m ² ), the bending limit and formability are characterized in that the value obtained by the relational expression of {P / (A × Ys)} is regulated to be in the range of 0.35 to 1.75. It is an excellent V-bending method.

[0011]

First, the reasons for limiting the V-bending conditions for the aluminum plate material of the present invention will be described.

Generally, the bending limit is better for a material having a large elongation of the work material, and all the alloy-based materials other than pure Al are greatly inferior in the bending limit, and it is difficult to obtain a sharp shape such as 0r. Therefore, this problem can be solved by V-bending after the aluminum plate material is heated and held at a specified temperature by a die heated during bending.

The aluminum plate material is heated by placing it on a die incorporating a heating device and sandwiching it with a punch. The aluminum plate material is sufficiently heated just by placing it on the die. The aluminum plate may be heated outside the mold, but it is important to heat the mold because the temperature of the mold decreases at room temperature during bending.
Further, since lubricating oil is usually applied and bending is performed, if the aluminum plate material coated with lubricating oil is heated outside the mold, the lubricating oil will be burnt. Therefore, also from this point, it is desirable to apply the lubricating oil to the aluminum plate material at a room temperature outside the mold and heat the aluminum plate material with a punch and a die.

The reason for limiting the heating temperature range is as follows. Aluminum materials, regardless of whether they are pure Al or alloy type, have the characteristics that the characteristic value changes depending on the heating temperature and the higher the temperature, the lower the tensile strength and proof stress and the increase in elongation and the softening of the material, which makes bending easier. is there. However, when the temperature is 150 ° C. or lower, the elongation does not change much from room temperature, the V-bending limit does not improve, cracks occur during bending, and springback and changes in saddle warp amount are also effective. Absent. Also, the temperature of the aluminum plate is set to 3
Even if the temperature is raised to 50 ° C or higher, the bending characteristics such as bending limit, springback, and saddle warp do not improve further, and conversely, a large capacity heating device is required to raise the mold temperature, resulting in high mold costs. At the same time, it is difficult to handle due to the high temperature, and the work material and the mold are likely to be galled. If a lubricant is used to prevent this galling, degreasing after bending becomes difficult. Problems such as occur. Therefore, the temperature for bending the aluminum plate material is set within 150 ° C to 350 ° C, preferably 200 ° C to 300 ° C.

The punch pressing force is P (Kg), and the area of the material to be processed between the punch and the die is A (mm).
² ), when the yield strength during heating is Ys (Kg / mm ² ), the value obtained by the relational expression of {P / (A × Ys)} is within the range of 0.35 to 1.75. This value is 0.3
If it is less than 5 times, the temperature of the aluminum plate is 150 ° C to 35 ° C.
If it is heated in the range of 0 ° C., the bending limit is improved, but the effect of suppressing springback and saddle warpage is not the same as that at room temperature.

If it is 1.75 or more, the bending limit can be improved, spring back and saddle warp can be suppressed sufficiently. However, the punching force is too large to reduce the plate thickness, and the bending direction and the width direction can be reduced. There is a risk that the desired shape will not be obtained due to problems such as material jumping out. Therefore, {P /
(A × Ys)} is 0.35.
The range is from 1.75 to 1.75.

As a method of heating the die of the present invention, a rod-shaped electric heater is incorporated in a die such as a punch or a die.
The heated liquid may be passed through the mold for heating, or the mold may be directly heated by a burner or the like, but a device incorporating a device for controlling the mold temperature is preferable.

The V-bending method of the present invention can be applied to any alloy and bend r as long as it is an aluminum material, but it is particularly effective for a soft material of 5000 series Al--Mg alloy. Also, the smaller the bending r, the greater the effect. It is also applicable to H18 temper material and the like.

Since the aluminum plate material to be worked becomes softer by further heating, the pressing force required for bending work is small, and it becomes possible to bend thick plate materials with existing equipment compared to room temperature. There is also an effect that the applicable plate thickness range is expanded.

Further, when the aluminum plate material is bent by the bending method of the present invention, it is preferable to use a lubricant to prevent galling, and as the lubricant, graphite, boron nitride, Teflon, metallic soap is used. What is suitable for warm forming containing the above may be applied to the aluminum plate and the mold before processing.

As for the holding time of the work material, the temperature of the work material may not reach the set temperature of the mold if the holding time is not sufficient. Therefore, the work material should be held for 30 seconds or more. It is desirable to perform bending after stabilizing the heating temperature of.

The bending of the H18 temper material is preferably performed at a temperature of 250 ° C. or higher at which the material is sufficiently recovered and at a forming speed of 100 mm / min or less. If it is low or the processing speed is too fast, the effect may be reduced and the bending limit may not be improved.

[0023]

EXAMPLE One example of the present invention will be described below.

[Tensile Test] Table 1 shows the composition of the test materials and the tensile property values at room temperature. Table 2 shows the warm tensile property values of the experimental materials. As the conditions for the warm tensile test at this time, a test piece as shown in FIG. 5 was used, and the test piece of each material was heated in a heating furnace, and the temperature of each test piece was 15
After reaching 0 ° C, 250 ° C, 350 ° C, hold for 5 minutes and then start pulling, and set the pulling speed to 10 mm / min.
The distance between the scores was 10 mm.

[0025]

[Table 1]

[0026]

[Table 2]

[V-bending test] The aluminum alloy plate material shown in Table 1 was V-bent. As a method of V-bending test, width 30 mm, length 150 mm, plate thickness 5 mm
After the test piece of t (the area A of the material to be sandwiched between the punch and the die is 30 × 150 = 4500 mm ² ) mixed with MoS ₂ as a lubricant aqueous solution was applied and dried, FIG. As shown in Fig.4, the work piece is placed on a heated V-shaped die with an angle of 90 °, and the heated punch is brought into contact with the work piece. After reaching 150 ° C. to 350 ° C., a punch was pushed in to perform a bending test as shown in FIG. The bending speed at this time was 100 mm / min, and the pressing pressure of the punch was variously changed within the range of 2.5 to 50 Ton.

The bendability was evaluated by the presence or absence of cracks caused by a punch having a tip of 0r. No cracks; ○ Fine cracks; △ Large cracks; × Springback evaluated the opening angle of the bent product with respect to the punch and die angle of 90 °. 90 ° ± 0.5 ° or less; ○ ± 0.6 or more; × Saddle warpage was evaluated by the size of the step (concave amount) between the center portion in the width direction and the shoulder portions at both ends. 0 to 7% of plate thickness: ◯ More than that; × Mold separation and deformability were evaluated by the degree of difficulty in taking out a molded product from a mold after bending. It does not stick to the mold and does not bend easily; ○ It adheres to the mold and the molded product deforms when taken out; × The results are shown in Table 3.

[0029]

[Table 3]

As is clear from the examples of Table 3, under the bending conditions of Nos. 1 to 20 according to the method of the present invention, the heating temperature of the work piece is in the range of 150 ° C. to 350 ° C., and {P The value of / (A × Ys)} is also within the range of 0.35 to 1.75, which shows that it is excellent in bending limit, spring back, saddle warp, mold separation deformation and the like. On the other hand, under the conditions of Nos. 21, 24, and 28 shown in the comparative example, since the room temperature is used, the bending limit is inferior, and the springback and saddle warp are inferior. Also, the comparative examples 22, 24, 25, 2
In all of the conditions of 9, the heating temperature of the workpiece is in the range of 150 ° C. to 350 ° C. of the present invention, but {P /
Since the value of (A × Ys)} is 0.35 or less, springback, saddle warp, etc. are inferior. Furthermore, in Comparative Example 2
Under the conditions of 3, 27 and 30, the heating temperature of the work material is 3
It is as high as 50 ° C-400 ° C and has excellent bending limit, but {P /
Since the value of (A × Ys)} is 1.75 or more, after bending,
There is a problem that the molded product adheres to the mold and is easily deformed when taken out. Further, under the condition of 26 of the comparative example, since the temperature of the work material is as high as 400 ° C., the bending limit is excellent, and {P / (A
XYs)} is 0.35 or less, so that it is excellent in mold separation deformation, but inferior in springback and saddle warp.

[0031]

As described above, the V-bending method according to the embodiment of the present invention is excellent as a V-bending method for an aluminum material, which is excellent in bending limit, springback, saddle warp, and has no problems such as mold separation deformation. It turns out to be excellent.

That is, by heating the plate material to a high temperature in the mold, the strength of the material is lowered and the elongation is improved,
By performing V-bending in the softened state, the bending limit is improved, and even an alloy plate material having high strength can be bent without causing defects such as cracks, and a sharper bent shape can be obtained. In addition, by controlling the punching force to be pressed within the range of the present invention, a V-bending molded product having a good shape with suppressed springback amount and saddle warp can be obtained.
Since the aluminum plate material to be processed becomes softer due to further heating, the pressing force required for bending work is small, and it is possible to bend thick plate materials with existing equipment compared to room temperature. It also has the effect of expanding the thickness range.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a workpiece is placed on a die before bending.

FIG. 2 is a cross-sectional view of a state in which the punch after the bending process is pressed and bent.

FIG. 3 is a cross-sectional view showing the amount of springback of a molded product after bending.

FIG. 4 is a perspective view showing a state of saddle warpage occurring in a molded product after bending.

FIG. 5 is a plan view showing the shape of a warm tensile test piece.

[Explanation of symbols] 1 V punch 2 V die 3 V aluminum 3 Aluminum plate 5 Tensile test piece θ Spring amount h Back saddle amount

Claims (1)

[Claims] 1. A method of heating an aluminum plate in a method of sandwiching an aluminum plate between a V-shaped die and a V-shaped punch opposite thereto, pushing the punch into the die, and bending it into a V-shaped shape. 350 ° C or more in a state of being sandwiched by a heated punch and die incorporating
After heating to a temperature within ℃, when punching into a V shape, the punch pressing force is P (Kg), the area of the workpiece between the punch and the die is A (mm ² ), heating When the proof stress of the aluminum plate at that time was Ys (Kg / mm ² ), the value obtained by the relational expression of {P / (A × Ys)} was regulated to fall within the range of 0.35 to 1.75. A V-bending method which is excellent in bending limit and shape.