JP2005095925A - Method for forming panel parts and laser beam welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming panel parts and a laser beam welding method with which the strength at the joined portion of the panel parts composed of a galvanized steel sheet can be held to high. <P>SOLUTION: In the method for forming the panel part, with which a blank material 3 of the galvanized steel sheet is arranged in a metallic die and the surrounding part of the blank material 3 is interposed with a blank holder 9 and a die 5, and under such a state, the blank material 3 is drawn into the inner part of the die 5 by pushing a punch to the die 5 side, the forming method for panel part is performed, with which a projecting bead 11 is formed on the blank holder 9 and a recessing part 13 engaged with the projecting bead 11 is formed on the die 5, and further, to the portion of the blank material 3 interposed with the projecting bead 11 and the recessing part 13, the bending and unbending are applied and also, the portion applied with the bending and unbending is set as the joining portion of the laser beam welding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for forming a panel part formed by press working from a galvanized steel sheet, and a laser welding method using the panel part.

  Conventionally, when panel parts are formed by press working, deep drawing is performed using a die composed of a convex punch, a concave die that engages with the punch, and a blank holder that is arranged opposite to the die. It is formed by molding or bulging.

  Specifically, the peripheral part of the flat blank material is sandwiched between the blank holder and the die, and in this state, the punch is moved toward the die and abutted against the bottom of the die, thereby forming the panel component. Is going.

Moreover, the conventional laser welding of a panel component makes the welding flange parts of the panel parts used as a junction part contact | abut, and in this state, irradiates a laser beam toward a welding flange part, WHEREIN: It joins (for example, refer nonpatent literature 1).
Journal of the Japan Welding Society Vol.15, No.3 "Laser lap welding of galvanized steel sheet" pp. 438-444

  However, in the conventional example, when a galvanized steel sheet is used as the blank material, there is a concern that the joint portion such as a welding flange may decrease the strength.

  In other words, the galvanized steel sheet is obtained by galvanizing at least one of the front surface and the back surface. When laser light is irradiated on the plated surface of the galvanized steel sheet, zinc vapor is generated from the irradiated portion. . Therefore, when the welding flanges of the panel parts made of galvanized steel plates are brought into contact with each other and irradiated with laser light, the zinc plating is evaporated and the vapor cannot be sufficiently removed, and the strength of the joint may be reduced. was there.

  Therefore, an object of the present invention is to provide a method for forming a panel component and a laser welding method capable of maintaining a high strength of the joint portion of the panel component made of a galvanized steel sheet.

  In order to achieve the above object, a method for forming a panel component according to the present invention includes a blank holder made of a galvanized steel sheet having a galvanized surface sandwiched between a blank holder and a die, and the punch is placed on the die side. In the panel part molding method, the blank material is squeezed into the inside of the die, and a convex bead is formed on one side of the blank holder and the die, and the convex bead is engaged on the other side. A concave portion is formed, and the peripheral portion of the blank material is sandwiched between these convex beads and concave portions, and in this state, the punch is pushed into the die side to bend into the blank material portion sandwiched between the convex beads and concave portions. And bending back, and a portion where the bending and bending back are added is set to a joint portion of laser welding.

  According to the method for forming a panel part according to the present invention, since a portion subjected to bending and bending back is set in a laser welding joint (joint part), the residual stress in the vicinity of the joint is set by heat input during laser welding. Is released, and a minute gap, for example, 50 μm or more is generated between the joint surfaces. Thus, even when the joint is irradiated with laser light, the vapor of zinc escapes from the gap, so that porosity due to galvanization does not occur and the strength of the joint can be kept high.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First embodiment]
FIG. 1 is a cross-sectional view showing a state in which a blank material 3 is arranged in a mold 1 according to the first embodiment of the present invention. The mold 1 includes a die 5 disposed on the lower side, and a punch 7 and a blank holder 9 disposed on the upper side opposite to the die 5, and the punch 7 and the blank holder 9 are independent of each other. It can be moved up and down. Further, the lower surface of the punch 7 is formed in a shape corresponding to the upper surface of the die 5, and a product shape is formed by these lower surface and upper surface. A blank holder 9 is arranged on the side of the punch 7.

  On the lower surface of the blank holder 9, a convex bead 11 formed in a convex shape downward is provided. On the other hand, the die 5 positioned below the blank holder 9 is formed with a recess 13 that engages with the convex bead 11 of the blank holder 9. The concave portion 13 is formed so as to engage with the convex bead 11 when the blank holder 9 is lowered to the bottom dead center. By pressing the peripheral edge portion of the blank material 3 with the convex beads 11 and the concave portions 13, the blank material 3 can be securely pressed when the punch 7 is pushed into the die 5 side. In this embodiment, the convex bead 11 is formed on the blank holder 9 side and the concave portion 13 is formed on the die 5 side. Conversely, the convex bead 11 is formed on the die 5 side and the blank holder 9 side is formed. The recess 13 may be formed.

  Moreover, the blank material 3 used for forming the panel parts uses a galvanized steel sheet in which at least one of the front surface and the back surface is galvanized. This galvanized steel sheet uses the most widely used hot dip plating method, and galvanization is also called galvanizing. The steel sheet is dipped in a plating bath having a bath temperature of about 450 ° C., and the zinc deposited on the surface is solidified by pulling up to form a plating layer on the steel sheet surface. Since galvanized steel sheets have excellent corrosion resistance in the atmosphere, they are widely used in automobile parts, building materials, household electric appliances, and the like.

  A procedure for press-molding a panel component using the mold 1 having the above-described configuration will be briefly described.

  First, as shown in FIG. 1, a blank 3 made of a flat galvanized steel plate is placed in a mold 1. At this time, the punch 7 and the blank holder 9 are located at the top dead center.

  Next, as shown in FIG. 2, the blank holder 9 is lowered to the bottom dead center, and the blank material 3 is sandwiched between the blank holder 9 and the die 5. As described above, the convex holder 11 is formed in the blank holder 9, and the concave portion 13 is formed in the die 5. Therefore, as shown in FIG. 3 which is an enlarged view of FIG. 2, the blank member 3 is sandwiched in a shape along the convex bead 11, that is, in a state of being convex downward.

  After that, as shown in FIG. 4, when the punch 7 is lowered, the punch 3 is bent so that the blank material 3 is wound around the lower surface that is the processed surface of the punch 7. Here, as shown in FIG. 5, the edge 15 of the blank 3 moves in the direction of the arrow in FIG. 5. That is, when the punch 7 is lowered and the blank material 3 is pushed downward, the edge 15 of the blank material 3 is gradually dragged inward of the die 5, and the blank material is interposed between the convex bead 11 and the concave portion 13. 3 is bent at the outer vicinity 17 of the convex bead 11, bent back at the apex 19 of the convex bead 11, and further bent again at the inner vicinity 21 of the convex bead 11. In this way, the peripheral edge of the blank 3 is subjected to bending and unbending alternately while moving between the convex bead 11 of the blank holder 9 and the concave 13 of the die 5. Dragged inward.

  As shown in FIGS. 6 and 7, the edge 15 of the blank 3 moves to the inside of the convex bead 11 in a state where the punch 7 is lowered to the bottom dead center. Here, the point P in FIG. 2 described above is a portion of the blank material 3 that is initially sandwiched between the convex beads 11 and the concave portions 13. Accordingly, the outer peripheral edge W1 outside the point P of the blank 3 shown in FIG. 6 is a portion where bending and bending back are repeatedly performed by the convex bead 11 and the concave portion 13, and residual stress is generated by this bending and bending back. And is formed flat by the surface of the die 5.

  A method of performing laser welding using the panel component 23 (see FIGS. 6 and 7) formed as described above will be briefly described.

  The outer peripheral edge portion W1 described with reference to FIG. 6 is a flat portion where residual stress is generated. In this embodiment, the outer peripheral edge portion W1 is used as a joint portion (for example, a welding flange) of the panel component 23 in laser welding. ).

  Therefore, when joining the some panel component 23 mutually by laser welding, the junction parts of the panel component 23 are piled up, and a laser beam is irradiated to this junction part.

  Then, the joint irradiated with the laser beam becomes high temperature by the heat input of the laser beam, and the residual stress is released. Thereby, a slight distortion is generated in the joint portion, and an extremely small gap (for example, 50 μm or more) is generated between the joint portions. Therefore, the zinc plating layer formed on the surface of the blank 3 evaporates when irradiated with laser light, but since zinc vapor escapes from this small gap, porosity due to galvanization may occur at the joint. In addition, the bonding strength of the bonded portion can be kept high.

  Moreover, since the said junction part is formed flat, a clearance gap adjustment can be easily performed with a pressure roller.

[Second Embodiment]
Next, a second embodiment will be described. Components having the same contents as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  FIG. 8 is a cross-sectional view of a mold 31 used in the second embodiment. The die 31 is composed of a die 33 disposed on the upper side and a punch 35 having a shape corresponding to the die 33, and the die 33 can be moved up and down. A plurality of corners are formed on the lower surface of the die 33 and the upper surface of the punch 35.

  Also in the second embodiment, similarly to the first embodiment, the blank 35 of galvanized steel sheet is disposed between the punch 35 and the die 33, and the upper die 33 is lowered to Bending and unbending are applied to the blank 3 at the corners of the die 33.

  For example, as shown in FIGS. 8 and 9, the side portion of the blank member 3 is squeezed up and down at the upper corner portion 37 of the die 33, whereby the blank member 3 is bent and bent back. Further, the point Q shown in FIG. 8 is a portion where the lower corner portion 39 of the die 33 first contacts the blank 3, but when the die 33 is lowered, the point Q gradually becomes the die 33. And is moved to the position shown in FIG. In the state of FIG. 10, the panel component 41 is molded. Therefore, the outer peripheral edge W2 located outside the point Q in FIG. 10 is a part that has been bent and bent back by the corner 39 of the die 33, and residual stress is generated by bending and bending back. Further, it is formed flat by the surfaces of the die 33 and the punch 35.

  A method for performing laser welding using the panel component 41 formed as described above will be briefly described.

  The outer peripheral edge W2 is a flat portion where residual stress is generated. In the present embodiment, the outer peripheral edge W2 is set as a joint portion of the panel component 41 when laser welding is performed.

  Therefore, when joining the some panel component 41 mutually by laser welding, the junction parts of the panel component 41 are piled up, and a laser beam is irradiated to this junction part.

  Then, the joint irradiated with the laser beam becomes high temperature by the heat input of the laser beam, and the residual stress is released. Thereby, a slight distortion is generated in the joint portion, and an extremely small gap (for example, 50 μm or more) is generated between the joint portions. Therefore, the zinc plating layer formed on the surface of the blank 3 evaporates when irradiated with laser light, but since zinc vapor escapes from this small gap, porosity due to galvanization may occur at the joint. In addition, the bonding strength of the bonded portion can be kept high.

  Below, the Example for confirming this embodiment mentioned above is demonstrated easily.

  FIG. 11 is a graph showing the relationship between the gap between the joint portions of the lap joint and the tensile shear strength when laser welding a galvanized steel sheet, and the weld bead length is 20 mm. When the thickness of the blank material is 2.3 mm, there is not much variation in tensile shear strength due to the size of the gap.

  On the other hand, when the plate thickness is 0.8 mm, the tensile shear strength can be ensured by setting the gap to 0.4 mm or less, but when the gap is 0 mm, there is a variation in the tensile shear strength. Very big. For this reason, it turns out that it is important to manage the clearance gap of a junction part in an appropriate range.

  FIG. 12 is a graph showing the relationship between the dimension of the gap and the decrease rate of the tensile shear strength when the gap between the joints is extremely small, and the vertical axis indicates the tensile shear strength when the base material strength is 100%. The gap is taken in units of 5 μm. As shown in FIG. 12, in the galvanized steel sheet, the tensile shear strength decreases as the basis weight of zinc increases, and when the gap is 50 μm or less, the galvanized steel sheet greatly decreases in strength.

Moreover, FIGS. 13-16 is a photograph which shows the external appearance of the surface of the weld bead which gave the laser welding in the state without a space | interval of joining parts, and the galvanized steel plate of 0-60 g / m < ² > of zinc areal weights. The case of welding is shown.

  As shown in these photographs, it can be seen that large bubbles are generated on the surface of the weld bead and the longitudinal section when the gap is 0 mm, and the vapor of zinc blows away the molten metal.

  Accordingly, it has been found that it is desirable to manage the gap between the joint portions to be 50 μm or more also in these examples.

It is sectional drawing which shows the state which has arrange | positioned the blank material in the metal mold | die by 1st Embodiment of this invention. It is sectional drawing which shows the state which clamped the blank material with the blank holder. It is sectional drawing to which the A section of FIG. 2 was expanded. It is sectional drawing which shows the state which pushed the punch into the die | dye side. It is sectional drawing to which the B section of FIG. 4 was expanded. It is sectional drawing which shows the state which pushed the punch to the bottom dead center. It is sectional drawing to which the C section of FIG. 6 was expanded. It is sectional drawing which shows the state which has arrange | positioned the blank material in the metal mold | die by 2nd Embodiment of this invention. It is sectional drawing to which the D section of FIG. 8 was expanded. It is sectional drawing which shows the state which pushed the die | dye to the bottom dead center with respect to the punch. It is a graph which shows the relationship between the clearance gap between joining parts and tensile shear strength, when laser-welding a galvanized steel plate. It is a graph which shows the relationship between the dimension of a clearance gap, and the fall rate of tensile shear strength in case the clearance gap between junction parts is very small. It is the photograph which shows the external appearance of the surface of the weld bead which gave laser welding in the state where there is no gap between joined parts, and shows the case where the zinc galvanized steel plate whose amount of zinc is 0g / m ² is welded. It is the photograph which shows the external appearance of the surface of the weld bead which gave the laser welding in the state where there is no gap between joined parts, and shows the case where the galvanized steel plate whose amount of zinc is 20g / m ² is welded. It is the photograph which shows the external appearance of the surface of the weld bead which gave laser welding in the state where there is no gap between joined parts, and shows the case where the zinc galvanized steel plate whose amount of zinc is 40g / m ² is welded. It is a photograph which shows the external appearance of the surface of the welding bead which gave laser welding in the state where there is no gap between joined parts, and shows the case where the galvanized steel plate whose amount of zinc is 60g / m ² is welded. It is a photograph which shows the longitudinal cross-section of the weld bead of FIG.

Explanation of symbols

W1, W2 ... Outer peripheral edge (peripheral edge)
DESCRIPTION OF SYMBOLS 1,31 ... Die 3 ... Blank material 5,33 ... Die 7,35 ... Punch 9 ... Blank holder 11 ... Convex bead 13 ... Concave part 23, 41 ... Panel component

Claims (5)

Place the blank material of the galvanized steel sheet in the mold, sandwich the peripheral edge of this blank material with the blank holder and the die, and in this state, push the punch to the die side, the blank material is placed inside the die In the method of forming panel parts to be squeezed into
A convex bead is formed on one side of the blank holder and the die, and a concave portion that engages with the convex bead is formed on the other side, and a peripheral portion of the blank material is sandwiched between the convex bead and the concave portion, In this state, by pushing the punch to the die side, the blank material sandwiched between the convex bead and the concave portion is bent and bent back, and the bent and bent portion is joined by laser welding. A method for forming a panel part, characterized by being set in a part.   Placing a blank material of a galvanized steel sheet in a mold consisting of a convex punch having a plurality of corners and a concave die formed to match the punch, and pushing the punch into the die side to By narrowing the blank material to the inside of the die, bending and bending back the blank material at the corners of the punch and die, and setting the part where the bending and bending back are applied to the laser welding joint A method of forming a panel part characterized by the above. Laser welding in which the joint parts of a plurality of panel parts obtained by press forming a blank material of a galvanized steel sheet are brought into contact with each other, and in this state, the joint parts are irradiated with laser light to join the panel parts together. In the method
A laser welding method characterized in that a portion subjected to bending and unbending of these panel parts is set as a joint.   The joint portion forms a convex bead on one side of the blank holder and die constituting the mold, and forms a concave portion that engages with the convex bead on the other side. In this state, the punch is pushed into the die side, and the portion of the blank material sandwiched between the convex bead and the concave portion is bent and bent back. The laser welding method according to claim 3.   The joint portion includes a blank material of a galvanized steel sheet disposed in a mold including a convex punch having a plurality of corners and a concave die formed to match the punch, and the punch is attached to the die. 4. The laser according to claim 3, wherein the blank material is a portion where the blank material is bent and unbent at the corners of the punch and the die by being pushed inward and narrowing the blank material toward the inside of the die. Welding method.