JP2002239644A - Square drawing method and its mold - Google Patents

Abstract

(57) [Summary] [PROBLEMS] When performing corner drawing on a magnesium alloy sheet having low elongation, cracks do not occur at corners and ridges, and cracks do not occur at shoulders of corners and ridges, and the number of steps is small. An object of the present invention is to provide a corner drawing method capable of finishing a corner or a ridge line to a minimum R equal to or less than the plate thickness of the plate material, and a mold therefor. SOLUTION: A first drawing process for thickening is performed by a partially tapered die plate, a drawing punch, and a pad to locally increase the thickness of the corners and ridges of the plate material 7, and then, The portion where the thickness of the ridge is increased is subjected to re-drawing to a minimum R smaller than the thickness t of the plate material 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for corner drawing of a magnesium alloy sheet having poor drawability and a mold therefor.

[0002]

2. Description of the Related Art Conventionally, when a magnesium alloy sheet having a low elongation rate and poor drawability of a material itself is squeezed by square drawing as shown in FIG. The corner 4 where the two side surfaces 2 and 2 intersect the top surface 3 and the ridge line 5 where the two side surfaces 2 and 2 intersect are formed by simply bending the plate material 1 without drawing. Unlike the ridge line 6 where the top surface 3 intersects with the ridge line 6, the material necessary for molding is squeezed out of the plate material 1, so that the plate thickness is thin, and cracks and cracks may occur in the corners 4 and the ridge line 5. there were.

Therefore, conventionally, in order to finish the corner portion 4 and the ridge line 5 to a minimum R smaller than the plate thickness t of the plate material 1 by square drawing by press working of a magnesium alloy plate material having poor drawability, first, FIG. As shown in the drawing drawing of a), in the first drawing step, the corners 4 and the ridge lines 5 of the plate material 1 having a thickness t are drawn at R> R, and several steps are taken while R is close to t. After the aperture is squeezed by R of R> t, as shown in the drawing process diagram of FIG. 11B, the corner 4 and the ridgeline 5 squeezed in the first squeezing process are re-squeezed by R ≦ R. It required a process.

[0004]

However, when performing the angular drawing on a magnesium alloy sheet having low elongation by the above-described conventional angular drawing by press working, it is necessary to perform redrawing in several steps as described above. There is a problem that the number of steps becomes very large, and even if the re-drawing process is performed for several steps, the number of steps is gradually reduced from R> t to R ≦ R. Since the elongation of the magnesium alloy sheet is low, at the corners and ridges, the tensile strength exceeds the limit value of the elongation of the sheet, the material required for forming is insufficient, and the thickness of the corners and ridges is locally reduced. It was inevitable that the film became thin, cracks occurred at the corners and ridges, and the shoulders were completely broken.

The present invention solves the above-mentioned problems. Even when a magnesium alloy sheet having low elongation is subjected to angular drawing by press working, cracks occur at corners and ridges, and shoulders of corners and ridges are formed. It is an object of the present invention to provide a corner drawing method and a mold thereof capable of finishing corners and ridges to a minimum R less than the plate thickness t of the plate material in a small number of steps without completely cracking. It is.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a method of forming a magnesium alloy sheet by square pressing of the sheet by warm pressing using a heating means. Is a square drawing method in which the sheet is heated and drawn by a punch and die plate.
By performing square drawing by warm pressing, the elongation of the sheet material increases, the deformation resistance decreases, cracks occur at the corners and ridges of the corner drawn product, and the corners and ridge shoulders are completely It does not break, and the number of drawing steps can be reduced.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is characterized in that, in the angular drawing of a magnesium alloy sheet, the sheet is heated to a temperature at which the elongation of the sheet increases by warm pressing by a heating means. This is a square drawing method in which a square drawing is performed with a drawing punch and a die plate.
It has the effect of reducing the deformation resistance.

According to the invention of claim 2 of the present invention, the heating of the magnesium alloy sheet is limited to the ridgeline where the two side surfaces intersect with the corner where the two side surfaces and the top surface intersect with each other. The corner drawing method described above has an effect that, by limiting the heating of the plate material to the corners and ridges, the annealing effect does not extend beyond the corners and ridges of the plate.

In the invention according to claim 3 of the present invention, immediately before drawing, a heating means is provided in a die plate and a wrinkle holding plate for holding a magnesium alloy plate, a drawing punch for drawing the plate, and a die plate. A die for carrying out the square drawing method according to claim 1, which has an effect that drawing can be performed while the plate material is heated by a heating means provided in a die plate, a wrinkle holding plate, and a drawing punch.

According to a fourth aspect of the present invention, when a magnesium alloy sheet is subjected to angular drawing, a corner portion where the two side surfaces and the top surface of the angular drawn product intersect with each other and a ridge line where the two side surfaces intersect with each other are firstly drawn. In a square drawing die for performing a thickening process by drawing and then performing a drawing process to an R having a thickness less than or equal to a thickness t by a redrawing process, a die plate for a first drawing process for thickening the corners and ridges This is a square drawing die with a tapered part of the side surface and top surface of the drawing punch and pad, and a tapered part of the side and top surface of the die plate, drawing punch and pad. This has the effect that the corners and ridges of the plate material to be subjected to the corner drawing are locally thickened.

An embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a side sectional view of a die for performing a square drawing method according to Embodiment 1 of the present invention in a state of a top dead center of a press, and FIG. FIG. 3 is a side cross-sectional view of the same die in a press bottom dead center state, and FIG. 4 is a side view of a thickening punch and a die plate used for the first drawing in the same die. Sectional view of the part,
FIG. 5 is a cross-sectional view of the top surface of the thickening drawing punch and pad used in the first drawing process in the same die, and FIG. 6 is the first drawing process of the square drawing method according to the first embodiment of the present invention. FIGS. 7 (a) and 7 (b) are drawing process drawings of the angular drawing method according to Embodiment 1 of the present invention, and FIGS.
In FIG. 3, reference numeral 7 denotes a plate material placed on a die plate 8, 9 denotes a plate material placed on the die plate 8 between the die plate 8 by entering a central hole of the die plate 8. The drawing punch 10 for drawing is a wrinkle holding plate for pressing the plate material 7 placed on the die plate 8 on the die plate 8 through the center hole of the drawing punch 9, and 11 is a center hole of the die plate 8. A pad for holding the plate 7 together with the drawing punch 9 entering the central hole, 12 a punch plate for fixing the base of the drawing punch 9 and moving the drawing punch 9 up and down, 13 a die plate 8, a drawing punch 9, wrinkles Temperature control heaters 14 provided on the holding plate 10 are temperature control devices for controlling the temperature control heater 13.

In FIG. 4, reference numeral 15 denotes a taper formed on a side surface of a die plate 88 which plays the same role as that of the die plate 8 in FIGS.
3 is a taper formed at a position facing the taper 15 of the die plate 88 in a side surface portion of the draw punch 99 which plays the same role as the draw punch 9 in FIG.

In FIG. 5, reference numeral 17 denotes an aperture punch 99 having the same function as the aperture punch 9 in FIGS.
Taper formed on the top surface portion of FIG.
And a taper formed at a position facing the taper 17 of the aperture punch 99 on the top surface of the pad 111 which plays the same role as the pad 11 in FIG.

A square drawing die having a thickness of t = 0.5 mm made of a magnesium alloy having a low elongation of Al: 3% and Zn: 1% is pressed by a square drawing die having the above-described configuration. In order to obtain a corner drawing product in which the corner where the two side surfaces and the top surface intersect and the ridge line where the two side surfaces intersect with each other and the ridge line where the two side surfaces intersect are the plate thickness t or less, that is, the inner R: 0.5 mm and the outer R: 1 mm. First, the die plate 8, the drawing punch 9, and the pad 11 in FIGS. 1 and 2 are replaced with a die plate 88 having a taper 15 and a taper 1 shown in FIGS.
The temperature control heater 13 and the temperature control device 1 were replaced with a draw punch 99 having 6, 17 and a pad 111 having a taper 18.
4, the plate 7 is previously held between the die plate 88 and the wrinkle holding plate 10 and heated to 270 ° C., and then the plate 7 is tapered 15 of the die plate 88, tapers 16 and 17 of the drawing punch 99, and taper of the pad 111. 18, the first drawing for thickening is performed by warm press working, and the first drawn product for which drawing for thickening has been performed is a processing explanatory diagram of the first drawing of FIG. 6 and FIG. As shown in the drawing process drawing of (1), portions A, A of the side surfaces a, a are tapered so as to expand at a constant angle toward a ridge line D1 where the side surfaces a, a intersect, and a portion of the top surface b is provided. B1 and B2 have side faces a,
Toward the ridge lines D2 and D3 where a and the top surface b intersect, a portion near the corner C is tapered so as to expand at a certain angle.

Next, the die plate 88 having the taper 15, the drawing punch 99 having the tapers 16 and 17, and the pad 111 having the taper 18 are returned to the original die plate 8, the drawing punch 9 and the pad 11, and FIG. As shown in the drawing drawing, the thickened portions of the corners C and the ridge lines D1, D2, and D3 are subjected to re-drawing by a warm press working to a minimum R having a thickness t or less of the plate material 7. .

As described above, according to the die for performing the square drawing method according to the first embodiment, in both the first drawing and the redrawing, the warm pressing is performed.
Since the sheet material 7 is instantaneously heated to a temperature at which the elongation increases, and the drawing is performed in a state where the deformation resistance is reduced, cracks or cracks are generated at the corners C, ridge lines D1, D2, and D3 of the square drawn product. In addition, the corner portions C and the ridge lines D1, D2, and D3 where the plate thickness is reduced because the plate material 7 is formed by drawing out the plate material 7 are locally formed by the first drawing process for thickening. Since the thickness of the plate 7 is increased, the corners C and ridge lines D1, D2, and D3 can be redrawn to a minimum R less than the thickness t of the plate material 7 without shortage of the material required for molding. Even if it is performed, no cracks or cracks are generated. Therefore, several round drawing steps are repeated from R having the thickness t of the plate material 7 or more, and the final process of reducing the thickness of the plate material 7 to the thickness t or less is successively performed. There is no need to advance the angular drawing to the minimum R. There are those that can be reduced.

(Embodiment 2) The difference between the angular drawing method in Embodiment 2 and the angular drawing method in Embodiment 1 is that in Embodiment 1, the drawing for thickening in FIG. In the cross section of the side part of the punch and die plate,
Taper 1 on the side of die plate 88 and draw punch 99
In contrast to the second and fifth embodiments, which are formed over the entire length of the ridgeline D1, in the second embodiment, only the ridgeline D1 near the corner C is formed. In the cross-sectional view of the top surface of the thickening aperture punch and pad shown in FIG. 5, the side surfaces of the die plate 88 and the aperture punch 99 are linear, whereas in the second embodiment, the corner C
6 is tapered at a ridge line D1 close to FIG.
In the second embodiment, the shape of the first drawn product shown in the working drawing of the first drawing is changed to the shape of the first drawn product shown in the working drawing of the first drawing in FIG. .

The other FIGS. 1 to 3 and the drawings in FIG. 7 in the first embodiment also apply to the second embodiment as they are, so they will not be particularly described, and the second embodiment will be described with reference to FIGS. 7 and the drawing of FIG.

The shape of the processed product subjected to the first drawing by the square drawing method according to the second embodiment is, as shown in the processing drawing of the first drawing in FIG. A is provided with a taper bulging at a constant angle toward a corner C, and a portion B of a top surface b is provided with a taper bulging at a constant angle toward a corner C, thereby forming a first drawn product. The corner C has a shape which is locally expanded and thickened as compared with other portions of the side surfaces a and a and the top surface b.

In the same manner as in the first embodiment, the first drawn product having the above-mentioned structure is finally subjected to re-drawing by a warm press working to a minimum R having a thickness t or less of the plate material 7, The effect obtained is that the corner portions C and the ridge lines D1, D2, and D3 where the plate thickness is reduced because the plate material 7 is formed by squeezing the plate material 7 are originally formed by the first drawing for thickening as in the case of the first embodiment. Since the thickness is locally increased by the processing, there is no shortage of the material necessary for molding, and cracks and cracks are generated at the corners C and the ridges D1, D2, and D3 of the square drawn product. Therefore, the number of drawing steps can be reduced.

As a material for supporting that drawing work can be performed in a state where deformation resistance is reduced by heating the plate material 7 to a temperature at which elongation is increased by warm pressing.
9 is a graph showing the relationship between temperature and elongation of the magnesium alloy of FIG. 9 by a tensile test. That is, FIG.
%, Zn: 1% using a magnesium alloy. It can be seen that the elongation of the alloy increases as the temperature increases, and that the sheet material 7 clearly extends in the warm forming. In this case, it goes without saying that an appropriate heating temperature is determined by the ratio of the magnesium alloy.

Further, the taper for increasing the wall thickness of the first drawn product is not limited to the shapes shown in FIGS. 6 and 8 of the above-described embodiments, but can be originally formed by combining tapers of various shapes. , To squeeze and form the plate material,
It is needless to say that the same effect can be obtained by increasing the thickness of the thinned portion.

When the entire plate 7 is heated, the strength of the entire plate 7 decreases due to the annealing effect.
When the entire strength is required, only the corner C and the ridge lines D1, D2, and D3 of the corner drawing product may be locally heated, so that the strength of the other parts does not decrease and the entire plate material 7 is not heated. Is maintained. At this time, the surface of the wrinkle holding plate 10 and the die plate 8 or the die plate 88 other than the portions corresponding to the corners C and the ridge lines D1, D2, and D3 of the square drawn product is made of a heat insulating material or the like. Alternatively, the wrinkle holding plate 10 and the die plate 8 or the die plate 88 are provided at the corners C, ridge lines D1, D2, and D3 of the angular drawing product.
Contact only

In both embodiments, a heater is used as a heating element. However, a heating element other than a heater may be used.
It goes without saying that it may be placed below.

[0026]

As described above, according to the angular drawing method and the mold of the present invention, when performing angular drawing by pressing on a magnesium alloy sheet having low elongation, cracks occur at corners and ridges. In addition, the corners and the shoulders of the ridges are not completely broken, and the corners and the ridges can be finished to a minimum R equal to or less than the plate thickness of the plate material with a small number of steps.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a die for performing a square drawing method according to a first embodiment of the present invention in a state of a top dead center of a press.

FIG. 2 is a side cross-sectional view showing a state immediately before drawing of a mold for performing the square drawing method according to Embodiment 1 of the present invention.

FIG. 3 is a side sectional view of a die for performing the angular drawing method according to the first embodiment of the present invention in a state of a bottom dead center of a press.

FIG. 4 is a cross-sectional view of a side wall of a drawing punch for increasing wall thickness and a die plate used in a first drawing in a mold for performing the square drawing in Embodiment 1 of the present invention.

FIG. 5 is a cross-sectional view of a top punch of a thickening punch and a pad used in the first drawing in a mold for performing the square drawing in Embodiment 1 of the present invention.

FIG. 6 is an explanatory diagram of a first drawing process in the square drawing method according to the first embodiment of the present invention.

FIG. 7 is a drawing process diagram of the angular drawing method according to the first embodiment of the present invention.

FIG. 8 is an explanatory diagram of a first drawing process in a square drawing method according to a second embodiment of the present invention.

FIG. 9 is a graph showing the relationship between temperature and elongation in a tensile test of a magnesium alloy.

FIG. 10 is a partial perspective view of a square drawing product.

FIG. 11 is a drawing process drawing of a conventional square drawing method.

[Explanation of symbols]

 1,7 plate material 2, a side surface 3, b top surface 4, C corner 5,6, D1, D2, D3 ridge line 8,88 die plate 9,99 drawing punch 10 wrinkle holding plate 11,111 pad 12 punch plate 13 Temperature control heater 14 Temperature control device 15, 16, 17, 18 Taper A, B, B1, B2 part

Claims (4)

[Claims] In the angular drawing of a magnesium alloy sheet, the sheet is subjected to warm pressing by heating means.
A square drawing method in which the sheet is heated to a temperature at which the elongation of the sheet material rises, and a square drawing is performed using a drawing punch and a die plate. 2. The corner drawing method according to claim 1, wherein heating of the magnesium alloy sheet material is limited to a corner where the two side surfaces and the top surface of the corner drawing product intersect and a ridge line where the two side surfaces intersect. 3. The square drawing method according to claim 1, wherein a heating means is provided in the die plate, the wrinkle holding plate, the drawing punch for drawing the plate material, and the die plate immediately before the drawing process. To carry out the mold. 4. When corner drawing of a magnesium alloy sheet material, a corner portion where two side surfaces and a top surface intersect with each other and a ridge line where the two side surfaces intersect with each other are subjected to a first drawing process to increase the thickness. In a square drawing die for drawing to an R having a plate thickness of t or less by redrawing, a die plate for first drawing, a drawing punch, a side portion of a pad, Square drawing die with tapered surface.