JPH04105721A - Press forming method for metallic sheet - Google Patents

Abstract

PURPOSE:To control the material flow with a simple means by radiating the high energy-beam preliminarily to the part where the blank material is pressed with the blank holder and the dies. CONSTITUTION:The melting bead 2 is formed by radiating the high energy beam 6 in the direction orthogonal to the flowing direction of the material followed with the shrink flange deforming or the flange deforming. The reason for the irradiation is that the welding bead 2 formed in this manner can exhibit the most effective resisting force against the shrink flange deforming or the stretch flange deforming. Accordingly, it is not required to use the drawing bead, to increase the pressure at the time of blank holding or to use the complicate blank shape, etc., and as the material control can be executed, so it is extremly effective for the ununiform flowing state of the material or the generation of wrinkles, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of press-molding a metal plate into a predetermined shape using a mold.

(Prior Art) It is known that when a metal plate is used as a raw material and press-molded to obtain products of various shapes, the shape of the flange after forming is different from the shape of the blank before forming. This is due to the in-plane anisotropy of the material, but from the perspective of the molding conditions, in areas with large die radii and corner radii, or areas where the molding height is partially high, the material may not enter the die. This is because the amount of inflow increases and the remaining amount of the flange becomes small, while the remaining amount of the flange becomes large especially in other parts.

Further, due to the above-mentioned local differences in the amount of material inflow, "wrinkles" may occur, especially in molded products whose molding heights differ locally.

Furthermore, it is well known that when the molded product is removed from the mold after molding, the molded product deforms into a shape that differs from the shape and dimensions of the mold, resulting in deformation due to so-called reduced elastic recovery, resulting in shape defects in the molded product. It is being

One possible reason for this is that sufficient tensile elongation strain cannot be applied to the molded product because the material flows easily.

In order to prevent these defective phenomena, conventionally, the flow of material is controlled by installing a throttling repeat in the part of the mold where the flange tends to flow, and the flow of material is balanced with the part where the material easily flows, or The base plate is made thicker in areas where material easily flows in, so that after molding, the remaining amount of the flange is the same as that in areas where material does not easily flow.

In addition, from the perspective of dimensional accuracy, methods for applying tensile elongation strain to molded products include replacing the aforementioned drawing repeat shape with a fixed bead to prevent the material from flowing in, or increasing the pressure when pressing the wrinkles to strengthen the material. Measures are being taken to prevent or restrict the influx.

(Problems to be Solved by the Invention) However, the following problems have been pointed out in the conventional method for controlling material inflow during press forming described above.

■The aforementioned method of controlling the inflow of material through repeated squeezing requires repeated mold modifications in order to obtain a bead shape that generates the optimal bead passage resistance force, which requires a large amount of cost and time. shall be. In addition, since the metal plate undergoes extremely severe bending deformation at the drawing repeat section,
Cracks occur due to material deterioration after passing through the bead, mold wear, mold galling problems, and plating peeling when plating materials are used.

■The method of changing the shape of the blank plate according to the amount of material inflow in order to make the remaining amount of flange of the molded product the same at the end of press forming often requires a complicated blank shape. Problems arise such as a decrease in material yield and an increase in the cost of the die for blank punching.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is possible to control material inflow by simple means when press-forming a metal plate into a molded product of a predetermined shape using a mold. The purpose is to provide a method that makes it possible.

(Means for Solving the Problems) In order to solve the above problems, the present inventors have conducted intensive research and found that the flange portion (the portion pressed by the wrinkle presser plate and the die) of the raw plate before forming, By pre-irradiating with a high-energy beam.

We have discovered a method to control the inflow of material during forming by forming a weld bead and taking advantage of the increased deformation resistance due to increased hardness in that area.

The present invention will be explained in more detail below.

(Function) A metal plate formed by a type of press forming in which the flange part of a blank plate is pressed by a presser plate and a die is subject to shrinkage flange deformation in which the material flows in while shrinking in a direction perpendicular to the material inflow direction during forming, or a right angle In many cases, the fluid flows in while being accompanied by stretch flange deformation in which the fluid flows in while stretching in the direction.

The present invention aims at reducing the flange portion of the flange that flows into the die hole with such shrinkage flange deformation or expansion flange deformation, by suppressing the inflow using conventional drawing repeats or by changing the shape of the blank plate. A high-energy beam is irradiated to the area where the residual amount was being adjusted, and by utilizing the increase in deformation resistance due to the increase in hardness caused by the rapid heating and cooling of that area,
It controls the inflow of materials.

Specifically, a molten bead is provided in a direction perpendicular to the material inflow direction with contraction flange deformation or stretch flange deformation.

Here, it is preferable that the molten bead is formed in a direction perpendicular to the material inflow direction. This is because such a weld bead can exhibit the greatest resistance to shrinkage flange deformation or stretch flange deformation.

Furthermore, as a mode of forming a molten bead in a right angle direction,
For example, if the blank is circular, it is formed on all or part of the circumference, and when the blank is rectangular, it is formed with a predetermined dimension on the right side near a part of the corner.

Furthermore, as shown in Fig. 1, the molten bead (■) produced by irradiation with these high-energy beams (■) can be formed into any width or shape as needed.
The number is fine.

The depth of the molten bead can be roughly divided into cases where only the surface is melted and cases where it is melted to a depth substantially equivalent to the plate thickness, but considering that the deformation resistance by the molten bead is used. , melting to a depth corresponding to the plate thickness is most effective and preferred. In the case of the latter (welded bead), it is desirable that the increase in plate thickness at the molten bead portion be ε = 5% or less in order to prevent the occurrence of flange wrinkles. In addition, ε
, is defined by the following formula.

t'-t ε□= -X 10 Q (%) In the present invention, the reason for using a high-energy beam is that by concentrating high energy locally,
This is because it is possible to suppress an increase in thermal strain due to thermal influence on the metal plate base material. Here, the high-energy beam refers to an energy beam that imparts heat to an irradiated object, such as a laser beam, electron beam, or plasma beam.

Of course, other press molding conditions are not particularly limited.

In addition, the metal plates to which the present invention can be applied include not only steel plates such as cold- and hot-rolled steel plates and plated surface-treated steel plates, but also plate-shaped plates of non-ferrous metals such as titanium, aluminum, and copper. It is.

(Example) Examples of the present invention are shown below.

This example is applied to cylindrical deep drawing as shown in Fig. 2, and Fig. 3 shows the laser irradiation pattern of the raw plate before forming.

In Figures 2 and 3, ■ indicates a steel plate (sample material), ■ indicates a molten bead formed by irradiating this steel plate with a laser beam, ■ indicates a punch, ■ indicates a die, and ■ indicates a wrinkle presser. .

First, as a test material, the thickness is 0.7μm and the diameter is 10Qmm.
A cold-rolled steel plate with a tensile strength of 30 kg was prepared.

In the case of such cold-rolled steel sheets, the r value is 0° with respect to the rolling direction.
, is often high in the 900 direction and low in the 45' direction, and when this is cylindrical deep drawing, the material flows in faster in the direction with a low r value, resulting in a high r value of O', 90
It is well known that the 'direction' remains as an 'ear' and reduces yield.

Therefore, as shown in FIG. 3, a laser beam was irradiated circumferentially on the flange portion in the θ=45'' direction to form a molten bead in the manner shown in FIG.

The length of the molten bead is expressed as the angle θ from the center.

Here, the reason why the beads are formed in the circumferential direction is to most effectively provide resistance against shrinkage flange deformation at the flange portion during molding.

In this way, press molding was performed using a blank plate whose flange portion had a molten bead formed by laser beam irradiation and a conventional blank plate that was not irradiated with a laser beam.

Figure 4 shows the molding height when θ = 60' and the difference between the maximum and minimum outer diameters of the flange during molding (ΔD
). Here, ΔD is an index representing the size of the ear, and the plot marked with 0 in the figure is θ
= 60° (example of the present invention), plots marked with * represent the case where no laser is irradiated (example of the prior art).

From FIG. 4, it can be seen that in the material of the comparative example that was not irradiated with the laser beam, ΔD increased as molding progressed and ears were generated, whereas in the material that was irradiated with the laser beam of the inventive example, the ΔD increased. It can be seen that there is no occurrence of "ears", which are slight. This is due to the deformation resistance caused by the molten bead.
This is because the inflow of material in the 5° direction is suppressed, and even as the molding progresses, the material flows in uniformly.

FIG. 5 shows the relationship between θ, which represents the length of the molten bead, and ΔD in the case of a molding height of 25 mm in an example of the present invention.

From FIG. 5, it can be seen that ΔD shows a good value in the range of θ=50° to 70°.

This example is an example in which the present invention is applied to a large curved panel that is prone to wrinkles during press molding.

When a blank plate having such a shape is press-molded, wrinkles (2) called body wrinkles occur around a part of the corner because it is easier to flow into the right side part than the corner R part. 6th
The figure is a perspective view showing a molded large curved panel, and the base plate has a board thickness of Q, 7+am, 70 C) am
A cold-rolled steel plate with a tensile strength of 30 kg was used.

In order to suppress this, a laser beam was irradiated to the position (2) shown in FIG. 7 in the manner shown in FIG. 1 to form a molten bead (2), and press molding was performed in the same manner as in Example 1.

The height (H) of wrinkles generated at some corners of the obtained large curved panel was examined.

FIG. 8 is a diagram showing the relationship between the length (CQ/R) of the formed molten bead and the wrinkle height (H) based on the above investigation results, and plots 0 and . in the diagram.

The 0 mark indicates the results when one, two, and three molten beads were formed, respectively. Here, the reason why the Q/R was evaluated is that, in general, the smaller the corner R, the larger the wrinkles, so a long bead is required to suppress this.

As shown in Figure 8, it is clear that these fused beads are very effective against wrinkle formation. This is because the resistance of the molten bead suppressed the flow of material in a portion of the corner, and the state of material flow in this portion was improved.

(Effects of the Invention) As described in detail above, according to the present invention, in press forming of a metal plate, it is possible to use a drawing bead as in the past, increase the pressure when pressing wrinkles, or to form a blank sheet with a complicated shape. Since it is possible to control the material inflow without the need to use a holder, etc., it is extremely effective against uneven material inflow conditions and the occurrence of wrinkles. In addition, it is possible to implement the method without being restricted by material properties such as the type and shape of the metal plate used as the raw material, and the means are simple, so the practical effects are significant.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the irradiation method of the high-energy beam used in the present invention and the molten bead formed, Fig. 2 is a cross-sectional view explaining the concept of the cylindrical deep drawing method of Example 1, Fig. 3 Figure 4 is a diagram explaining the laser beam irradiation pattern of Example 1, and Figure 4 is a diagram showing the relationship between the difference (ΔD) between the maximum and minimum outer diameters of the flange part during press forming in Example 1 and the molding height. , Figure 5 shows the length (θ) and Δ of the molten bead in Example 1.
FIG. 6 is a perspective view showing a large curved panel to which the present invention is applied in Example 2. FIG. 7 is a diagram explaining the laser irradiation pattern in Example 2. FIG. 8 is an example 2 is a diagram showing the relationship between the length (Q/R) and the wrinkle height (H) of the molten bead of No. 2. FIG. ■... Test material, ■... Molten bead, ■... Punch, ■... Dice, ■... Wrinkle suppression, ■... High energy beam, ■... Wrinkle. Figure 1 Patent Applicant Kobe Steel Co., Ltd. Patent Attorney Takashi Nakamura Figure 2 Figure Figure 1] τ (Paper-) Figure Sise & Fox L.-Do & J θ (°)

Claims (1)

[Claims] In a press forming method in which a metal plate is molded into a predetermined shape using a mold, the press forming process is characterized in that a high-energy beam is irradiated in advance to the area where the blank plate is pressed by a wrinkle holding plate and a die. material inflow control method.