JP5206042B2 - Metal plate press forming equipment - Google Patents

Description

The present invention relates flop press forming apparatus of the metal plates due to local heating.

In recent years, environmentally friendly manufacturing has been promoted globally. In the automobile industry, in order to improve fuel efficiency, a steel sheet for automobiles having a high strength and a thin wall is used, and a car body is formed by a press-molded product to reduce the weight of the car body.
However, if a high-strength or thin-walled metal plate is used as the material, cracks will occur in the punch shoulder and the molding part with a small curvature, or even if it can be press-molded, the molded product taken out from the mold It is known that a springback or the like occurs and the dimensional accuracy deteriorates.

As a press forming method of a metal plate that can solve such a problem, a warm and hot press forming method in which a metal plate material is softened in a mold and then press formed by the mold is proposed (non- Patent Document 1, Patent Document 1).
In addition, a sheet metal working method is disclosed in which the entire deformation region is heated and softened to bend or deform the sheet metal into a predetermined shape (Patent Document 2).
Press Technology, Volume 43, Issue 9 (August 2005) p23-26 Patent No. 3882474 Patent No. 2915646

  However, in the press forming method described in Patent Document 1 and Non-Patent Document 1, it is necessary to apply current to the plate material of the metal plate and directly heat the plate material, and thus locally heat the forming site where cracks are likely to occur. There is a problem that mass production products such as automobile fenders cannot be efficiently obtained due to the occurrence of cracks. In particular, in the press molding method described in Patent Document 1, even when the size of the plate material is 300 mm x 80 mm, a holding time of energization heating is required for 30 seconds, which is inferior in productivity and can be applied to mass-produced molded products. There was a problem that was difficult.

In addition, the sheet metal processing method described in Patent Document 2 is not a press molding method in which a metal plate material is molded into a predetermined shape with a mold, but has a problem that dimensional accuracy is difficult and application to a mass-produced molded product is difficult. was there.
In addition, the sheet metal processing method described in Patent Document 2 includes a first step of heating and softening the entire deformation region almost simultaneously by scanning the laser beam into an arbitrary shape at high speed, and the subsequent deformation region. Although it has the 2nd process of making it change into a desired shape, since the forming part which is easy to generate a crack was not heated locally, there was a problem that it was difficult to prevent generation of a crack.

The present invention is described above to solve the prior art problems, cracking in the molded article can be prevented from occurring, the dimensional accuracy was good and mass moldings flop press forming apparatus of the metal plate applied it is possible to The purpose is to provide.

  As a result of intensive studies on the press forming method and press forming apparatus of the metal plate, the present inventor has found that the metal plate is attached to the die before the main forming of the metal plate by press forming. Molding that is easy to crack by this gas blowing (blowing) through a heating process to locally heat and soften the molding part that tends to occur and a blowing process to blow a gas of a predetermined pressure to the softened heating part It was found that the above problems can be solved by pre-molding the part and adding too much material (referred to as molding allowance) to the molding part where cracking is likely to occur, and the present invention has been made based on this knowledge. .

That is, the present invention is as follows.
1. A press molding apparatus that press-molds a metal plate into a predetermined shape with a mold, and a heating unit that locally heats and softens a molding site where cracks are likely to occur while the metal plate is mounted on the mold. , the softened heated portion provided with blowing means for blowing gas of a predetermined pressure, Ri na are likely to occur shaped portion of the crack by the blowing means arranged to pre-formed, the mold is at least punch The blowing means is a flow path through which a gas of a predetermined pressure formed in the punch passes, and a gas heating heater disposed around the flow path is provided in the punch. A metal plate press forming apparatus .

2 . 2. The metal plate press-forming apparatus according to 1 above, wherein the blow means includes, in addition to the gas heating heater, a gas cooling pipe disposed around the flow path in the punch. .
3 . The molding auxiliary mechanism for limiting the region to be preformed and controlling the preformed shape comprises a rod for pressing the vicinity of the heated portion heated by the heating means, and a cylinder connected to the rod. 1. Or 2. 2. A press forming apparatus for a metal plate according to 1.

According to the present invention, before performing the main forming of press forming a metal plate with a mold, local heating for locally heating and softening a molding portion where cracking is likely to occur, and subsequent heating to a softened heating portion is predetermined. By using a blow that blows a gas having a pressure of 5 mm, it is possible to pre-mold a molding site where cracks are likely to occur.
As a result, an appropriate amount of material (formation allowance) is added to the molding site where cracking is likely to occur, so it is possible to prevent cracks and wrinkles from occurring in the molded product obtained by press molding, and productivity It is also possible to apply to mass-produced molded products such as automobile fenders with strict dimensional accuracy without lowering.

  Here, in the heating step described above, since heating is locally performed and softened, it is possible to shorten the temperature raising time until the temperature reaches a predetermined temperature. Further, in the blowing process, since a gas having a predetermined pressure is blown to a softened heated portion where the material strength is significantly lower than that of a normal temperature material, it can be easily pre-deformed. That is, the decrease in the molding speed is extremely small, and the productivity is higher than that of the above-described conventional technology.

The press molding apparatus of the present invention will be described with reference to FIG. In the following description, a mold having a punch, a die, and a plate press will be described as an example. However, the present invention is not limited to this, and is also applicable to a mold configuration including a combination of a punch and a die, a punch and a pad, and the like. Is possible.
Fig.1 (a)-(d) showed the molding process by a press molding apparatus in order.

As shown in FIG. 1, the molding process by the press molding apparatus of the present invention includes a heating process for locally heating and softening a molding site where a crack is likely to occur in a state where the metal plate S is mounted on a mold. Then, after a blowing process in which a gas having a predetermined pressure is blown onto the softened heated portion, a molding portion where cracking is likely to occur due to this blowing is preformed. The molding site where cracking is likely to occur is a punch shoulder or a site with a small curvature.

  FIG. 1A shows a state in which the metal plate S is sandwiched between the die 2 of the mold and the plate holder 3. At this stage, plastic strain is not applied to the portion other than the plate presser of the metal plate S. FIG. 1 (b) shows a state in which a molding part where cracking is likely to occur is locally heated and softened by the heating means 4, and FIG. 1 (c) shows a gas blow state. It was. In the blowing process, a gas having a predetermined pressure is blown out from the flow path 5 which is a blowing means to the heated part that has been softened.

In the molding process by the press molding apparatus of the present invention, an appropriate amount of material (referred to as a molding margin) can be imparted to a molding site where cracks are likely to occur through a heating process and a blowing process. When performing the main molding in which S is press-molded into a predetermined shape with a mold, it is possible to prevent the molded product from being cracked or wrinkled. The main molding is a step of lowering the die 2 and relatively inserting the punch 1 into the die 2 so that the metal plate S and the punch 1 come into contact with each other and the metal plate S is formed into a predetermined shape. (FIG. 1 (d)).

Next, a press forming apparatus for a metal plate according to the present invention will be described.
In FIG. 1, 4 is a heating means by plasma heating or laser heating arranged in the die 2, and 4a is plasma or laser light. Reference numeral 5 denotes a blow means, which is a flow path formed in the punch 1 so that the gas 5a can be blown onto a heated portion softened by heating. The flow path 5 which is a blow means is connected to a pressurizing pump (not shown) for pressurizing gas. The heating means 4 and the blowing means 5 that blows the gas 5a to the softened heating part are arranged opposite to each other with the metal plate S interposed therebetween.

As described above, the metal plate press forming apparatus of the present invention is softened with the heating means 4 for locally heating and softening the forming portion where the crack is likely to occur in a state where the metal plate S is mounted on the mold. Blowing means 5 for blowing a gas of a predetermined pressure to the heating part is provided, and a molding part where cracking is likely to occur is configured to be preformable.
Press forming apparatus suitable metal plate of the present invention is as follows.

As the heating means 4, plasma heating or laser heating is preferable because it can shorten the temperature rising time until it reaches a predetermined temperature from room temperature. May be used.
Blowing means, it includes a gas heater 6 arranged around the flow path 5 into the punch 1. It is preferable to heat the gas with the gas heating heater 6 because the higher the temperature of the gas to be blown, the lower the temperature drop of the softened heated part. Furthermore, when performing the main forming after pre-forming by gas heating, it is possible to prevent cracking of the overhang forming portion (see FIG. 1). The reason for this is that, since the elongation of the material is dominant in the cracking of the overhang forming part in the molded product, it is advantageous to maintain the temperature of the forming part where cracking is likely to occur at a high temperature during the main forming. is there.

  On the other hand, in order to prevent cracking of the deep drawing portion when performing the main forming after the pre-forming, in addition to the gas heating heater 6 shown in FIG. It is preferable to provide a cooling pipe in the punch 1. After the predetermined pre-forming by the blowing means is completed, the gas cooled by the gas cooling pipe and having a reduced pressure is blown by the blowing means to a portion where cracks are likely to occur during deep drawing, and the temperature of the portion is lowered. Like that. As a result, the effect of preventing the occurrence of cracks in the deep-drawing part during the main molding by the mold is further improved.

The reason for this is that, since the strength of the material dominates the cracks in the deep-drawn molding part of the molded product, it is advantageous to lower the temperature of the molding part where cracking is likely to occur when performing the main molding. .
Further, as shown in FIG. 2, it is preferable to include a rod 7 that holds the vicinity of the heated portion heated by the heating unit 4 and a cylinder (not shown) connected to the rod 7 as a forming auxiliary mechanism. .

The reason for this is that the cylinder connected to the rod 7 is operated in a state where the metal plate S is mounted on the mold, and is brought into contact with the surface of the metal plate S as shown in FIGS. 2 (a) to 2 (c). This is because the rod 7 makes it easy to limit the region for preforming and control the preforming shape.
Subsequently, the cylinder connected to the rod 7 is operated so as to be separated from the surface of the metal plate S, and the rod 7 is raised as the die 2 is lowered as shown in FIG. S can be brought into a non-contact state.

In the above description, the case where the heating means 4 and the blowing means 5 for blowing the gas 5a to the softened heating part is illustrated as one set, but a plurality of metal plates S may be arranged.
According to such a metal plate press forming apparatus, it is possible to press-mold a mass-produced molded product typified by an automobile fender with high accuracy while preventing cracking and wrinkling of the molded product.
As described above, the press molding apparatus of the present invention pre-molds a molding site where cracks are likely to occur before performing the main molding in a state where the metal plate S is mounted on a mold, so that cracks are likely to occur. A material is added to the molding site (referred to as a molding allowance).

This forming margin has two control parameters: a temperature at which it is locally heated and softened, and a pressure of gas blown to the heated part that has been heated to a predetermined temperature and softened. For this reason, the amount of forming margin can be controlled by the material characteristics of the metal plate S (see FIG. 3), and the risk of cracks and wrinkles occurring in the molded product can be significantly reduced, which is effective.
For example, when the temperature at which the heating means 4 locally heats and softens cannot be so high due to the material properties of the metal plate S, the pressure of the gas blown from the blowing means 5 is increased as shown in FIG. Here, when the gas pressure is too low, the molding margin is small and cracks are likely to occur. Conversely, when the pressure is excessively increased, the molding margin becomes excessively large and wrinkles are likely to occur. On the other hand, when the pressure of the gas blown from the blowing means 5 cannot be increased too much, the heating temperature of the heating means 4 may be increased locally to soften the gas. Therefore, the degree of freedom in designing the mold and the press device is increased.

  In that case, for materials that easily oxidize, such as steel sheets, as raw materials for molded products, in consideration of productivity and surface properties of molded products, hot-rolled and cold-rolled steel plates are locally heated and softened. The temperature is preferably up to 700 ° C, and up to 500 ° C for galvanized steel sheets. As the gas to be blown, air whose temperature and pressure are adjusted, nitrogen or an inert gas such as argon or helium can be used, but nitrogen is preferably used from the viewpoint of preventing oxidation of the metal plate.

According to the press molding apparatus of the present invention described above, the molding margin can be controlled before performing the main molding of press molding a metal plate with a mold, and the molded product is not restricted by the mold or the press apparatus. Since the risk of occurrence of cracks and wrinkles can be significantly reduced, it can be applied to mass-produced molded products.

A die with punch, die, and plate holder, and three types of steel plates (A: 270 MPa class, B: 340 MPa class, C: 440 MPa class) with different strength levels shown in Table 1 are made into the fender shape of an automobile. It was press-molded and compared between the inventive example (local heating + blow pre-molding), the comparative example (with local heating and no pre-molding), and the conventional example (no heating and no pre-molding). After press-molding into a fender shape with a mold, the molded product is taken out from the mold, and whether or not cracks have occurred in the molded product (no crack: ○, with crack: x) The evaluation results are shown in Table 2. The dimensional accuracy is OK (○) if the amount of peeling from the design shape of the molded product is within the shipping standard value (0.5 mm in this example), and NG (×) if it exceeds. evaluated.

The relationship between the heating time and temperature in the example of the present invention is shown in FIG. FIG. 3 shows the relationship between the pressure of the gas when the gas is blown onto the material C heated to a temperature of 400 ° C. and the molding allowance generated in the material C. Based on the same characteristic diagram, the pressure of the gas blown to the molding site where the materials A and B were heated to 400 ° C. and softened was determined. In the present invention example , nitrogen heated to 80 ° C. by a gas heating heater was blown by a blow means and preformed, and then nitrogen cooled to room temperature by a gas cooling pipe was blown before starting the main molding in a mold. It was. In the example of the present invention, as apparent from the relationship between the heating time and temperature shown in FIG. 4, the time required to form one fender shape by pre-molding and main molding was about 8.5 seconds. . Pre-forming is completed at about 7 seconds when the temperature starts to decrease from 400 ° C.
(Determined gas pressure) Material A: 0.7 MPa, Material B: 0.8 MPa, Material C: 1.0 MPa.

From the results shown in Table 2, in the example of the present invention (local heating + blow pre-molding), the molded product obtained even when using the high-strength and thin-walled material C does not crack, and the dimensional accuracy is also good. Met.
On the other hand, in the comparative example (with local heating and without preforming) and the conventional example (without heating and without preforming), when the material C is used, cracks are generated in the obtained molded product. The part where the crack occurred is a punch shoulder part or a molding part having a small curvature. Moreover, when there was no crack generation using the materials A and B, the dimensional accuracy was inferior.

FIG. 6 shows an example of the dimensional accuracy measurement result of a molded product molded using the present invention example and the conventional example . From the results shown in FIG. 6, it can be seen that in the example of the present invention, the deviation from the design shape is smaller than in the conventional example , and the dimensional accuracy is greatly improved.
The amount of deviation from the design shape is the difference in position between the shape of the molded product and the design shape at the position of the mark ● shown in the product design drawing shown in FIG.

According to the example of the present invention, it can be seen that a molded product for an automobile having high accuracy and no cracking can be mass-produced with high productivity.

A die with punch, die, and plate holder, and three types of steel plates (D: 590MPa class, E: 780MPa class, F: 980MPa class) with different strength levels shown in Table 3 are pressed into a rocker shape for automobiles. The present invention example (local heating + blow pre-molding) was compared with a comparative example (with local heating and no pre-molding) and a conventional example (no heating and no pre-molding). After press-molding into a rocker shape with a mold, the molded product is taken out from the mold, and the result of visual judgment and dimensional accuracy of whether or not the molded product is cracked (no crack: ○, with crack: x) The evaluation results are shown in Table 4.

The evaluation method of dimensional accuracy is the same as in the case of Example 1, but the shipping standard value in this example is 0.7 mm. The relationship between the heating time and temperature in the example of the present invention is shown in FIG. Moreover, the pressure of the gas sprayed onto the materials D, E, and F heated to 600 ° C. was determined as follows based on the characteristic diagram showing the relationship between the gas pressure and the molding allowance. In the examples of the present invention, nitrogen heated to 80 ° C. was blown by a blowing means in the same manner as in Example 1, and preformed. However, cooling nitrogen blowing after the pre-molding was not performed. In the example of the present invention, the time required to form one piece into the rocker shape was 10 seconds or less. Pre-forming is finished at about 7.5 seconds.
(Determined gas pressure) Material D: 0.8 MPa, Material E: 1.0 MPa, Material F: 1.2 MPa.

From the results shown in Table 4, in the example of the present invention (local heating + blow pre-molding), even when the materials E and F having high strength and thinness are used, the molded product does not crack and the dimensional accuracy is also good. Met. On the other hand, in the comparative example (with local heating and without preforming) and the conventional example (without heating and without preforming), when the material F is used, the molded product is cracked. In the conventional example , cracks also occur when the material E is used. In the case where no crack was generated in the comparative example and the conventional example , the dimensional accuracy was inferior.

FIG. 9 shows an example of the dimensional accuracy measurement result of a molded product molded using the example of the present invention and the conventional example . From the results shown in FIG. 9, it was also found that in the example of the present invention, a rocker-shaped molded product having a smaller deviation from the design shape than that of the conventional example and having greatly improved dimensional accuracy can be obtained. The amount of deviation from the design shape is the difference in position between the shape of the molded product and the design shape at the position of the mark ● shown in the perspective view of the molded product shown in FIG.

According to the example of the present invention, it can be seen that a molded product for an automobile having high accuracy and no cracking can be mass-produced with high productivity.

It is principal part sectional drawing explaining the press molding apparatus of the metal plate of this invention. It is principal part sectional drawing explaining the suitable example of the press molding apparatus of the metal plate of this invention. It is a characteristic diagram showing the relationship between pressure and molding allowance of gas definitive to the onset bright. It is a characteristic view which shows the relationship between the heating time and temperature in the example of this invention. It is a design drawing of the product showing the dimensional accuracy measurement position of the molded product. It is a characteristic view which shows the dimensional accuracy of the molded product which press-molded the metal plate shown in FIG. 5 with the metal mold | die. It is another characteristic view which shows the relationship between the heating time and temperature in the example of this invention. It is a perspective view of a molded product showing the dimensional accuracy measurement position of the molded product. It is another characteristic view which shows the dimensional accuracy of the molded article which press-molded the metal plate with the metal mold | die.

Explanation of symbols

S metal plate 1 punch 2 die 3 plate retainer 4 heating means (plasma heating or laser heating)
4a Plasma or laser light 5 Blowing means (flow path)
5a Gas blown from blowing means 5 6 Heater for gas heating 7 Rod

Claims (3)

A press molding apparatus that press-molds a metal plate into a predetermined shape with a mold, and a heating unit that locally heats and softens a molding site where cracks are likely to occur while the metal plate is mounted on the mold. , the softened heated portion provided with blowing means for blowing gas of a predetermined pressure, Ri na are likely to occur shaped portion of the crack by the blowing means arranged to pre-formed, the mold is at least punch The blowing means is a flow path through which a gas of a predetermined pressure formed in the punch passes, and a gas heating heater disposed around the flow path is provided in the punch. A metal plate press forming apparatus. 2. The metal plate press forming apparatus according to claim 1 , wherein the blow means includes, in addition to the gas heating heater, a gas cooling pipe disposed around the flow path in the punch. . The molding auxiliary mechanism for restricting a region to be preformed and controlling a preforming shape includes a rod that holds the vicinity of a heated portion heated by the heating means, and a cylinder connected to the rod. Item 3. A metal plate press forming apparatus according to Item 1 or 2 .

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