Metal deforming – By use of non-deforming work-gripping clamp and relatively... – With cutting
Reexamination Certificate
2001-02-22
2002-06-04
Crane, Daniel C. (Department: 3725)
Metal deforming
By use of non-deforming work-gripping clamp and relatively...
With cutting
C072S335000, C072S462000, C076S104100, C076S107100, C076S116000, C219S076160, C219S121470, C219S121590, C083S694000
Reexamination Certificate
active
06397651
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a die assembly such as a pressing die assembly for bending a blank to a desired shape or a trimming die assembly for drawing a blank and trimming a peripheral edge thereof, and a method of manufacturing such a die assembly.
2. Description of the Related Art
Automotive bodies are produced by pressing, drawing, and trimming blanks.
Die assemblies for pressing, drawing, and trimming blanks are generally made of cast iron or cast steel, and so rigid that they can withstand several hundred thousand pressing cycles. However, such die assemblies are expensive to manufacture.
Other die assemblies which do not machine blanks, but are relatively inexpensive to manufacture and suitable for manufacturing products of many different types in small quantities are made of base materials of zinc alloy, as disclosed in Japanese laid-open patent publications Nos. 5-84591, 5-195121, 5-208296, and 5-237656.
Specifically, Japanese laid-open patent publication No. 5-84591 discloses that a zinc alloy containing magnesium and aluminum and having a Vickers hardness of 150 or more is welded on a zinc alloy containing aluminum and copper by build-up welding.
Japanese laid-open patent publication No. 5-195121 proposes a zinc alloy for a pressing die assembly, which is made of 9.5-30 wt % of aluminum, 6.0-20 wt % of copper, 0.01-0.2 wt % of magnesium, and the remainder of zinc.
Japanese laid-open patent publication No. 5-237656 shows a method of repairing a die assembly of aluminum by plating only a peripheral region of the die assembly, except for a region to be repaired, with Ni—P, and padding the region to be repaired with a filler metal for thereby achieving desired hardness of the peripheral region.
According to Japanese laid-open patent publication No. 5-208296, it has been proposed to use a zinc alloy as a base material of a die assembly for molding plastics and to use an aluminum alloy containing Si or the like as a filler metal for repairing the die assembly.
Die assemblies made of base materials of zinc alloy are lightweight, easy to cast, and of excellent maintainability. Though zinc alloys have excellent machinability, they are soft. Therefore, a different metal needs to be added to a certain region of zinc alloy if a cutting edge or the like is mounted on the zinc alloy.
Specifically, even if a zinc alloy containing magnesium and aluminum or an aluminum alloy containing Si or the like is welded on a zinc alloy containing aluminum and copper by build-up welding, as disclosed in Japanese laid-open patent publications Nos. 5-84591 and 5-208296, the welded region is not sufficiently hard for use as a trimming blade. The method disclosed in Japanese laid-open patent publication No. 5-237656 fails to achieve a sufficient level of hardness.
Therefore, die assemblies of zinc alloy are actually limited to use as die assemblies for molding plastics.
Japanese laid-open patent publication No. 5-195121 proposes a pressing die assembly, which has a cutting edge that needs to be hard and a bending member that needs to be resistant to wear. However, the problems of the cutting edge and the bending member remain to be solved.
According to other proposals, a cutting edge that needs to be hard is not formed by build-up welding, but a region to serve as a cutting edge is plated with a hard chromium layer or a cutting edge is formed by evaporation, sputtering, or the like. With these proposals, however, it is difficult to form a cutting edge of a thickness required to keep it durable. In addition, these proposed processes are not cost-effective enough.
Furthermore, as disclosed in Japanese patent No. 2838657, a cutting edge is formed by defining a bevel on an edge of a die assembly, welding a filler metal of high hardness on the bevel by build-up welding, and then grinding the filler metal with a grinder. However, it is known in the art that only a Cu-based or Zn-based material can be directly welded to a zinc alloy, but there is no Cu-based or Zn-based material that is hard enough for use as a cutting edge material.
SUMMARY OF THE INVENTION
The weldability of a zinc alloy and a nickel alloy with respect to each other is so poor that the nickel alloy cannot be welded on the zinc alloy to form a highly hard build-up welded region. As a result of studies made by the inventors of the present invention, it has been found that a copper alloy can be welded to both a zinc alloy and a nickel alloy. The present invention resides in that an underlying layer of copper alloy is welded on a base material and an overlying layer of nickel alloy is welded on the underlying layer.
A die assembly according to the present invention comprises an upper die and a lower die for trimming or bending a workpiece, at least one of the upper die and the lower die having a cutting edge or a bending member. The upper die and the lower die being made of a base material of an aluminum/copper-based zinc alloy, the cutting edge or the bending member having a machined build-up welded region comprising an underlying layer made of a filler metal of a copper-based material that can be welded to a zinc alloy and an overlying layer made of a filler metal of a nickel-based material that has a sufficient hardness and can be welded to the underlying layer of the copper-based material.
If the overlying layer is brought into contact with the base material when it is welded on the underlying layer, sputtering occurs, causing a welding defect. It is therefore necessary to weld the overlying layer on the underlying layer out of contact with the base material.
The at least one of the upper die and the lower die may have a bevel on which the cutting edge or the bending member is disposed. The bevel has a vertical dimension which substantially corresponds to the width of one weld pass of weld beads and a horizontal dimension which substantially corresponds to the width of two weld passes of weld beads, and including a flat area in a transversely outer region thereof, the flat area having a width which substantially corresponds to the width of one weld pass of weld beads. With this structure, the underlying layer is prevented from falling, and sputtering and blow holes are prevented from occurring due to contact between the base material and the overlying layer.
For effectively preventing blow holes from occurring, the bevel may have a chamfered surface and an extension extending therefrom. The underlying layer is disposed in covering relation to the bevel in its entirety and made of a copper-based material, and the overlying layer is disposed on the underlying layer out of contact with the base material and made of a nickel-based material. The overlying layer can be welded while a produced gas is being discharged through the underlying layer formed on the extension.
The copper-based material may be pure copper, aluminum bronze, silicon bronze, or the like. For better weldability, silicon bronze is most preferable.
The silicon bronze is preferably composed of 1.0-8.0 wt % of Si, 0.3-4.0 wt % of Mn, 0.03-4.5 wt % of Pb, 0.03-11.0 wt % of Al, 0.03-7.0 wt % of Ni, 0.03-6.0 wt % of Fe, and the remainder of Cu.
Si (silicon) is an element required for deoxidization, and is also an element for increasing hardness. If the amount of Si were less than 1.0 wt %, then deoxidization would be insufficient and blow holes would be liable to occur. If the amount of Si exceeded 8 wt %, then the silicon bronze would not be of a one-phase structure, but many phases would be precipitated, and the structure would become fragile.
Mn (manganese) is an element required for deoxidization and desulfurization. If the amount of Mn were less than 0.3 wt %, then the effect of its addition would not appear. If Mn were added in excess of 4.0 wt %, then no further effect would be achieved.
Pb (lead) is an element for increasing machinability. If the amount of Pb were less than 0.03 wt %, then almost no effect would be obtained from its addition. If the amount of Pb exceeded 4.5 wt %, then it would easily bring ab
Uchida Tohru
Usui Toshiyuki
Birch & Stewart Kolasch & Birch, LLP
Crane Daniel C.
Honda Giken Kogyo Kabushiki Kaisha
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