Technical field
[0001]
　The present invention relates to burring of the plate-like member.
Background technique
[0002]
　Underbody components of an automobile is manufactured by performing press working or other process to a metal plate such as high-tensile steel plate. Sometimes performing burring to form a burring hole in the metal plate in the production process. Conventional burring, as shown in FIG. 1, first, a punched hole 52 formed in the metal plate 51, then, it is carried out by forming a vertical wall 53 by expanding press perforations 52 as shown in FIG. 2 . Molding process of the vertical wall 53 (hereinafter, "burring step"), the large tensile stress acts on the perforations 52 in spread press punched hole 52. Therefore, in the conventional burring method, cracking the vertical wall 53 in the burring step (hereinafter, "burring cracking") was sometimes occurs.
[0003]
　To solve this problem, Patent Document 1, after the metal plate is subjected to drawing so as to be U-shaped cross-sectional shape in a first pressing step, the punched hole is formed in the bottom portion in the second pressing step a method of forming a vertical wall in the third pressing process is disclosed.
[0004]
　In Patent Document 2, the hole after the first set larger aperture shoulder radius of the pressing step drawing, as well as the restriking the aperture shoulder portion in a second pressing step, the entire bottom surface machining end how to punching is disclosed.
CITATION
Patent Literature
[0005]
Patent Document 1: JP 2004-223583 Patent Publication
Patent Document 2: JP-A 6-87039 Patent Publication
Summary of the Invention
Problems that the Invention is to Solve
[0006]
　However, the method of processing patent document 1 is being carried out first pressing step in order to ensure the height of the vertical wall of the product, for example a flame-shaped material such as a high-tensile steel plate in the first pressing step during certain drawing, there is a problem that a crack on the bottom shoulder occurs.
[0007]
　Further, when the method of working Patent Document 2 has implemented a first pressing step for the purpose of avoiding the cracking that occurs on the bottom shoulder, using, for example, high-tensile steel plate as material, JP cracks in the bottom shoulder there is a problem generated 1 during drawing a first pressing step as well.
[0008]
　Thus, in the conventional burring method limited material to be processed is, there may not be suppressed the occurrence of burring cracking. Therefore, new burring method for inhibiting the burring cracking has been desired.
[0009]
　The present invention has been made in view of the above problem and an object thereof is to provide a suppressing burring method burring cracking.
Means for Solving the Problems
[0010]
　The present inventors have intensively studied to suppress the press molding method burring cracking. As a result, distortion occurs when spread press punching holes Noting that cause burring cracking to obtain a knowledge that can solve the above problem by removing the strain before the burring process.
[0011]
　That is, the gist of the present invention to solve the above problems, when subjected to burring to the plate-like member, a punching step for punching of the plate-like member, the holes of the punched hole formed by the punching step re punching which is expanding and the hole expansion step of performing processing, the re-stamping step of performing again punched to perimeter of the spreading was punched holes in the hole expansion step, punching a hole in which the formed re-stamping It is to implement the burring step for forming a vertical wall peripheral portion of the hole in the I pushed.
[0012]
　Incidentally, the "plate member" in the present invention is a press-formable plate-like member, for example steel plate, aluminum alloy plate, titanium alloy plate, a stainless alloy plate, a composite material made of a metal and a resin, a heterologous metal plate or the like composite material consisting of a metal, refers to a member such as carbon fiber.
Effect of the invention
[0013]
　According to the present invention, it is possible to suppress the burring cracks generated during burring of the plate-like member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014]
[Figure 1] is a view for explaining the steps conventional burring method, a diagram of the shape of the plate-like member shown schematically at the first pressing step.
[Figure 2] is a view for explaining the steps conventional burring method, a diagram of the shape of the plate-like member shown schematically in the second pressing step.
[Figure 3] is a view for explaining the steps of burring method according to an embodiment of the present invention, is a cross-sectional view of the shape of the plate-like member shown schematically at the first pressing step.
[Figure 4] is a view for explaining the steps of burring method according to an embodiment of the present invention, is a cross-sectional view of the shape of the plate-like member shown schematically in the second pressing step. Hatched only in the plate-like member in the figure, hatching of the components of the press die is omitted.
[Figure 5] is a view for explaining the steps of burring method according to an embodiment of the present invention, is a cross-sectional view of the shape of the plate-like member shown schematically in the third pressing step.
[Figure 6] is a view for explaining the steps of burring method according to an embodiment of the present invention, is a cross-sectional view of the shape of the plate-like member shown schematically in the fourth press step. Hatched only in the plate-like member in the figure, hatching of the components of the press die is omitted.
DESCRIPTION OF THE INVENTION
[0015]
　Hereinafter, burring method according to an embodiment of the present invention will be described with reference to the drawings. In the specification and drawings, in the elements having substantially the same function and structure are a repeated explanation thereof by referring to the figures.
[0016]
　Burring method in the present embodiment is performed four times pressing step against the plate-like member. For more information on each of the steps are as follows.
[0017]

　In the burring method of this embodiment, a punching process with respect to the plate-like member as a first first pressing step. Thus, hole diameter Φ as shown in FIG. 3 1 intermediate product 1 is obtained having a punched hole 2. Incidentally, diameter Φ of the time 1 is smaller than the diameter of the perforations 52 in the conventional burring as shown in FIG. 1.
[0018]

　Next, a second pressing step of the present embodiment, as shown in FIG. 4, the peripheral portion of the punched hole 2 was pressed using a punch 5 the cylindrical hole of the perforations 2 expanding processing I do. Thus, hole diameter [Phi 2 intermediate product 1 is obtained with a punched hole 3. The intermediate product 1, the strain of the peripheral portion of the punched hole 3 by the peripheral portion of the punched hole 2 before hole expansion is pushed open is large. In the following description, the portion distortion of the periphery of the punched hole 3 is larger as "strain concentrated portion".
[0019]
　The hole expansion step, the peripheral portion of the punched hole 2 before expanding hole by being pressed, a surface S that is punched hole 3 formed becomes high with respect to the reference plane P of the blank. Accordingly, the vertical wall corresponding portion 4 is a portion corresponding to the vertical wall 9 after burring described later (FIG. 6) is formed. Note that the "reference plane" refers to a horizontal plane in a fixed position of the fixed plate member in the die 6 and the holder 7. In the following description, from the reference plane P to form surface S of the perforations 3 the height of "vertical wall corresponding part of the height".
[0020]
　The burring process of the present embodiment, burring portion of vertical wall 9 formed in the burring step described below (FIG. 6) of the height H 3 (hereinafter, "vertical wall height") of the vertical wall portion corresponding 4 The height H 1 is lower than. That is, the height H of the vertical wall corresponding portion 4 in the hole expansion step 1 is too low, vertical wall height H 3 can not be sufficiently ensured. On the other hand, the height H of the vertical wall corresponding portion 4 1 is too high, a risk that becomes too large distortion occurs in the periphery of the punched hole 3, cracks at the periphery of the punched hole 3 during hole expansion processing occur there is. Therefore, the height H of the hole expandability vertical wall corresponding part 4 of step 1 , the vertical wall height H 3 is preferably set as appropriate in consideration of the hole expandability of the material. In this embodiment the height H of the vertical wall corresponding portion 4 1 is the height H of the vertical wall 9 3 is lower than.
[0021]
　Further, the angle θ between the inclined surface and the reference plane P of the vertical wall corresponding portion 4 in the hole expansion step 0 (hereinafter, "vertical wall angle equivalent unit") When too large, resulting in a peripheral portion of the punched hole 3 the strain becomes too large. On the other hand, the angle θ of the vertical wall corresponding part in the hole expansion step 0 is too small, it is necessary to increase the angle causing the vertical wall corresponding portion 4 when forming the vertical walls 9 by burring step described below. In this case, distortion of the vertical wall tip is increased, there is a possibility that the burring cracking occurs. Therefore, in the hole expansion step, the angle theta of the vertical wall portion corresponding 4 0 the angle between the vertical wall 9 and the reference plane P of the final product is shown in FIG. 6 theta (hereinafter, "vertical wall angle") with respect to it is preferable to perform the press-molded into a 20 to 70% angle.
[0022]
　In order to suppress the cracking of the periphery of the perforations 3 in the hole expansion step, shoulder radius size of the punch 5 and the die 6 is smaller desirable. However, the shoulder radius of the punch 5 and the die 6 is too small, depending on the material there is a possibility that cracks are generated during hole expansion processing. Therefore, the shoulder radius R of the punch 5 in the hole expansion step P shoulder radius R of, and the die 6 D is preferably set as appropriate in consideration of the bending of the material.
[0023]

　After the end of the hole expansion step, as the third pressing step of this embodiment, the stamping punching the periphery of the punched hole 3 by pressing performed. Thus, hole diameter Φ as shown in FIG. 5 3 intermediate product 1 is obtained with the perforations 8. In this specification, the present step for punching after the hole expansion step again called "re-stamping". Also, In the following description, the punched hole formed by the re-punching process called "re-punched hole".
[0024]
　Periphery of the perforations 3 are formed in the above-described hole expansion process by the process (Fig. 4) is punched. Thus, the strain concentrated portion near perforations caused by the hole expansion step is removed. That is, the peripheral portion of the re-punched holes 8 of the intermediate article 1 obtained in this step (Fig. 5) is the strain than the peripheral portion of the punched hole 3 after the hole expanding step is small. Therefore, even when a large distortion of the vertical wall tip by burring process to be described later, it is possible to reduce than the conventional accumulation strain, burring cracking is unlikely to occur.
[0025]
　Further, in the present embodiment has implemented punched so as to leave the forming surface S of the perforations 3 after hole expansion step is completed in the re-punching step. On the other hand the re-stamping process, it is also possible to perform the processing so leaving no perforations forming surface S by punching for example the inclined portion of the vertical wall corresponding part 4. Even in this case, it is possible to remove the strain concentration portions of the vertical wall portion corresponding 4, it is possible to suppress the burring cracking. However, in the re-punching step performs punching such leaving no punched hole forming surface S, may punching blade is damaged, there is a risk that scratches on the end face of the punched hole 8. This flaw is due cause cracks in the burring step described below, in order to improve the effect of suppressing burring cracking, the peripheral portion of the punched hole 3 as perforations forming surface S in the re-stamping remain punched it is preferable.
[0026]
　The height H of the vertical wall portion corresponding 4 after re punching step is completed 2 , by punching the inclined portion of the punched hole forming surface S or the vertical wall corresponding part 4 by punching in the process, hole expansion described above vertical wall corresponding portion height H of 4 in step 1 and substantially the same height or the height H 1 is lower than. The diameter of the punch to be used in the re-punching step is preferably sufficiently large relative to the diameter of the punch to be used in the above-described punching so that it can remove the strain concentration of the punched hole 3. When the difference in punch diameter of the punch diameter and re-punching step of punching step is too small, it is impossible to remove the strain concentration of the perforations 3 sufficiently. In this case, in the burring process to be described later, since that would cause a vertical wall corresponding portion 4 remains strain concentration portions remained around the re perforations 8, the strain is further increased is accumulated in the strain concentration portions, burring cracking is likely to occur.
[0027]

　After the completion of the re-punching step, as the fourth press step of the present embodiment, pushing the periphery of re perforations 8 as shown in FIG. 6, causing vertical wall corresponding portion 4 (FIG. 5) performing burring processing to form a vertical wall 9 and manner. Thus, hole diameter Φ as shown in FIG. 6 4 stampings final shape of the burring holes 10 are formed is obtained.
[0028]
　As described above, according to the burring method of this embodiment, the strain concentrated portion near perforations caused by the hole expansion step is once removed by the re-punching process. As a result, the strain accumulated in the vertical wall tip in burring process becomes smaller than conventional, it is possible to suppress the occurrence of burring cracking.
[0029]
　With the burring method of this embodiment the occurrence of burring cracking can be suppressed, product shape when compared with the case of using a conventional processing method, the material of high strength with excellent hole expandability, the use of low-strength material and it tends to be processed in the same shape. For example, when the tensile strength is subjected to burring to 590MPa grade steel sheet having a steel sheet equivalent to hole expansion ratio of 440MPa class, the processing method such as directly burring after punched out as in the prior art blanks, 440MPa grade sometimes burring cracking occurs when trying to process the product the same shape in the case of using a steel plate. On the other hand, in the burring method of this embodiment, it also becomes possible to process the product the same shape in the case of using the 440MPa class steel sheet without generating burring cracking even when using such a steel sheet . That is, to form a burring shape equivalent burring when using 440MPa grade steel which could not be obtained by the conventional processing method, it is possible to produce parts that only the intensity is improved. Therefore, it is possible to increase the degree of freedom of the product design.
[0030]
　Also, punching step described in the present embodiment, hole expansion step, the re punching step, each step itself burring process is a process that is usually implemented in a conventional part production process. In other words, burring method of this embodiment can be employed without increasing the special process with respect to conventional component manufacturing process. For example, if the process required to produce a certain component was 6 process, the above punching process, hole expansion step, the re punching step, burring step is a step which is usually included in the six steps . Therefore, when carrying out the punching step, for example according to the present embodiment, in addition to the punched hole is originally formed in a conventional stamping process, it may be performed press molding so as to increase the punched holes for the burring one place . Other hole expansion step, the re punching process is the same for burring process. That is, because of the burring of the present embodiment, it is not necessary to increase the separate step in addition to the conventional 6 step, burring method according to the present embodiment, without reducing the productivity, the burring cracking it can be suppressed.
[0031]
　Furthermore, burring method of this embodiment is particularly useful when the target material burring is high-tensile steel plate (e.g., tensile strength not less than 440 MPa). Since the target material burring processing in the case of a high-tensile steel elongation properties of the material are deteriorated, or unable burring is formed in the conventional machining method cracked in the course of processing, it is able to form a burring burring cracking is likely to occur. On the other hand, according to the burring method of this embodiment, since the re-stamping of removing distortions before burring, it is possible to form a burring even high-tensile steel plate, and a burring cracking it can be suppressed. That is, when the target material burring is high-tensile steel sheet, the effect of burring cracking inhibition of the present invention over the prior art appears remarkably.
[0032]
　Furthermore, burring method of this embodiment is particularly useful when the target material burring is hot-rolled steel sheet. For example, when the cold-rolled steel sheet that is subjected to burring processing, bulging processing, punching, it is possible to form a burring by machining such burring. However, the vertical wall height H of the burring portion 3 in the manufacture of components such as high, when applying such a processing method to hot-rolled steel sheet, it may be impossible to form a burring. On the other hand, hot-rolled steel sheet has excellent hole expandability properties (lambda values), burring method of this embodiment is a processing method utilizing a hole expansion of the material. Therefore, by applying the burring method of this embodiment the hot-rolled steel sheet, the vertical wall height H of the burring portion 3 becomes possible also to easily form a burring when to produce a high such parts, the effect of burring cracking inhibition of the present invention over the prior art appears remarkably.
[0033]
　In order to further suppress the cracking during the time hole expansion processing or burring, it is important to improve the punched end surface properties. The end surface properties as a method to improve, in at least one of the steps of stamping and re-punching step, as finishing for removing burrs of the perforations, at least one of machining or laser processing reaming etc. it is desirable to perform one. Thus, it is possible to further suppress the occurrence of burring cracking.
[0034]
　Having described the preferred embodiments of the present invention, the present invention is not limited to such an example. Those skilled in the art within the scope of the technical idea described in the claims, it is clear that could conceive various modifications, the technical scope of the present invention as for their It is understood to belong ones.
[0035]
　For example, in the above embodiment, punching, hole expansion step, the re punching step, it was decided to perform the burring process in four press, but is not limited to the press number. Desired hole diameter in two press a hole expansion process may be performed so as to obtain, for example in hole expansion process.
[0036]
　In the above embodiment, the vertical wall portion corresponding 4 height H in the hole expandability step 1 a vertical wall height H 3 was carried out hole expansion processing so as to be lower than the height of the vertical wall portion corresponding 4 H 1 is the vertical wall height H 3 may be carried out hole expansion processing so that the above. Even in this case, it is possible to remove the strain concentration portions near perforations caused by the hole expansion processing time, it is possible to suppress the burring cracking in burring process.
[0037]
　Further, in the above embodiment, the vertical wall angle of burring portion θ is performed burring so as to be perpendicular, vertical wall angle θ may not be perpendicular. Burring cracking, for generating a distortion caused in forming a vertical wall with a peripheral portion of the punched hole to press the vertical walls with respect to a plane perpendicular to the reference plane P is inclined toward the center of the burring hole It is shaped as, the tip portion of the vertical wall strain concentration portions are formed. On the other hand, according to the burring process according to the present invention, even in the final product shape is such a shape, for performing burring after removing the strain concentration unit time, it is possible to suppress the burring cracking .
[0038]
　However, the larger the angle to cause vertical wall 9 in the burring step shown in FIG. 6, the strain of the distal end portion of the vertical wall 9 increases. In other words, burring cracking tends to occur is when the vertical wall angle θ to practice the press-molding such that the vertical in burring process. Since the conventional machining methods are still concentrated part distortion in burring process, it is impossible to sufficiently suppress the burring cracking. On the other hand, burring method according to the present invention, since even when carrying out the burring as the vertical wall angle θ is perpendicular, and removing the concentrated part distortion in the re-punching process, to suppress the burring cracking It can become. That is, when the vertical wall angle θ to form a vertical burring in the burring process, the effect of the crack suppressing burring according to the present invention over the prior art appears remarkably. In this specification, rather than vertical in the strict sense the term "vertical" relates to the vertical wall angle theta, a wording also includes the concept of substantially vertical.
Example
[0039]
(Example 1)
　As an example according to the present invention, plate thickness 3.0 mm, tensile strength using 780MPa grade steel were performed burring test against a blank of diameter 180 mm.
[0040]
　Molding process of Example 1 is as follows. First, in the first pressing step, to form a punched hole with a diameter of 35 mm. Then, in the second pressing step, using a die press die composed of a punch and a shoulder radius 3mm cylindrical diameter 60 mm, it was subjected to hole expansion by 12mm stroke processing. Thereafter, the third pressing step, performed punching to perimeter of the punched hole was expanded to a diameter of 42mm in hole expansion processing, to form a punched hole with a diameter of 57 mm. The fourth press step of the final step, press molding was carried out by using a burring punch diameter 70 mm. The height of the final burring portion was 15 mm.
[0041]
　It was then evaluated for the presence of burring cracking the obtained member by press molding. It was also measured strain of the vertical wall tip at that time. Strain of the vertical wall tip transfers the scribed circle on the surface of the blank burring is performed, is calculated from the shape change.
[0042]
　In Example 1, the member after press forming burring cracks was confirmed that not occur. Also, the strain of the vertical wall tip was 28%.
[0043]
(Comparative Example 1)
　Next, as a comparative example 1, the same material as in Example 1 were carried out burring tested using the blank of the same size. First, in the first pressing step, to form a punched hole with a diameter of 47mm so as in Example 1 and the same shape. Then, as the second pressing step, press molding was carried out by using a burring punch diameter 70 mm. The resulting member was evaluated in the same manner as in Example 1, Comparative Example 1, burring cracking has occurred. Also, distortion of the portion cracking has not occurred was found to be 40% and higher.
[0044]
(Comparative Example 2)
　As Comparative Example 2, the same material as in Example 1, using the blank of the same size, were performed molded test in the processing method described in Patent Document 1. First, in the first pressing step, by using a press die composed of a die punch and a shoulder radius 3mm cylindrical diameter 60 mm, it was overhanging processing by 12mm stroke. However, in Comparative Example 2, the first pressing step crack to the bottom shoulder portion of the material occurs, it is impossible to continue the processing more, it was not possible to form a burring.
[0045]
　As shown in the results of Example 1, according to the burring process according to the present invention, it is possible to reduce the amount of strain occurring in burring edges of the press part, it can be seen that the burring cracking can be suppressed.
[0046]
(Example 2)
　Next, the same material as in Example 1, using the blank of the same size were carried out press-molded test by machining as finishing punched hole formed in the material. Conditions except that mechanical processing with respect perforations are the same conditions as in Example 1. As a result, as compared with the workpiece that was not subjected to machining, it was confirmed that small micro cracks generated in the product end face after burring. According to the results of Example 2, in at least one of stamping and re-punching step, it can be seen that it is preferable to perform machining or laser processing as finishing to remove burrs or the like.
Industrial Applicability
[0047]
　The present invention can be applied to burring of the plate-like member such as a high-tensile steel plate. Furthermore, burring is applied a plate-like member according to the present invention can be used as various vehicle, general machinery, home appliances, members such as a ship, including automobiles.
DESCRIPTION OF SYMBOLS
[0048]
1 intermediate product　
2 perforations
3 after hole expansion of perforations
4 vertical wall corresponding part
5 punch
6 die
7 holder
8 again perforations
9 vertical wall
10 burring holes
51 metal plate
52 punched holes
53 vertical wall
H 1　vertical wall corresponding part of the the height
H 2　vertical wall portion corresponding height after re punching
H 3　vertical wall height
S perforations forming surface
P reference plane
R D　die shoulder radius
R P　punch shoulder radius
[Phi 1　diameter of perforations
[Phi 2　holes diameter of punched holes after expanding
[Phi 3　diameters of re perforations
[Phi 4　diameter of the burring holes
theta vertical wall angle
theta 0　angle of the vertical wall portion corresponding

The scope of the claims
[Claim 1]
　A burring method of the plate-like member,
　a punching step for punching the plate-like member,
　a step hole expansion performing hole expansion processing of punching holes formed in the punching step,
　press in the hole expansion step and re-punching step, performed again punched to perimeter of the spread was punched hole
　burring step for forming a vertical wall peripheral part at do push the re-punched holes are punched hole formed in the re-stamping with the door.
[Claim 2]
　In burring method of claim 1,
　wherein the re-punching step, punching out a peripheral portion of the ball striking drain hole to leave the forming surface of the hole expansion perforations after the process is completed.
[Claim 3]
　In burring method according to claim 1 or 2,
　wherein the plate-like member is a high-tensile steel plate.
[Claim 4]
　In burring method according to any one of claims 1 to 3,
　the plate-like member is a hot rolled steel sheet.
[Claim 5]
　In burring method according to any one of claims 1 to 4,
　a vertical wall angle to form the vertical wall so as to be perpendicular in the burring step.
[Claim 6]
　In burring method according to any one of claims 1 to 5,
　in the punching step, at least one of machining and laser machining as finishing the punched hole.
[Claim 7]
　In burring method according to any one of claims 1 to 6,
　in the re-punching step, at least one of machining and laser machining as finishing the re-punched holes.