Abstract:
The present invention relates to an apparatus for attachment to a conventional sheet metal forming press. The apparatus allows the sheet metal forming process to be preformed fully submerged in an oil. Methods for sheet metal forming in oil are also provided.

Description:
BACKGROUND 
       [0001]    Isothermal forging is a metal-forming process developed since the 1960s. Isothermal forging requires dies, usually heated, to be kept at the same temperature at the work piece when forging. It has been used as an effective way of achieving highly desired thin walled and quality drawn products. The implementation of isothermal forging requires a custom-made production line or equipment to maintain a uniform elevated forming temperatures and prevent oxidation of the part being formed. Equipment incapable of satisfying these requirements will significantly lower the process formability and cause formation of oxide/scale on the product surface. 
         [0002]    Several developments have attempted to address a non-uniform raised temperature. U.S. Pat. No. 4,616,449 teaches a method of fabricating products wherein an alloy is thermochemically treated before forging occurs. U.S. Pat. No. 6,908,519 teaches heating an alloy to a high temperature and then forging at that temperature. Another method, U.S. Pat. No. 6,059,904, teaches combining isothermal forging, selecting a suitable blank or preform, subsolvus forging, and annealing. However, the prior art fails to address a consistent temperature through the blank or preform, nor the difference in temperature between the die  101  and the blank or preform. 
         [0003]    It is an object of the present invention to overcome the disadvantages and problems in the prior art. 
       DESCRIPTION 
       [0004]    The present invention relates to an apparatus for implanting the sheet metal forming process in a bath of heat transfer oil. In one embodiment, the punch, die, and blank or preform are submerged in an exothermic bath at a steady raised temperature during the forming process. In this embodiment, the process is auto-lubricated. Through the invention, the tool life is prolonged, and formability enhanced. Further, the apparatus is a self-contained system, allowing minimization of production cost. 
     
    
     
         [0005]    These and other features, aspects, and advantages of the apparatus and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings where: 
           [0006]      FIG. 1  shows formed products from the present system; 
           [0007]      FIG. 2  shows an embodiment of the present invention, wherein pressing occurs in a completely oil submerged environment; 
           [0008]      FIG. 3  is a schematic of the fully submerged press apparatus of the present invention. 
       
    
    
       [0009]    The following description of certain embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Throughout this specification, the term “blank” shall refer to a metal piece that has not yet been treated. The term “preform” shall refer to a metal that has undergone preliminary treatment, but is not yet in final form. 
         [0010]    Now, to  FIGS. 1-3 , 
         [0011]      FIG. 1  exhibits several alloy cups  100  manufactured by the present system. Whereas all cups were manufactured fully submerged in isothermally heated transfer oil, the temperature of the oil is important for the constituency of the final product. 
         [0012]      FIG. 2  is an embodiment of a system of the present invention. The system is made from two primary units, a top unit  200  (upside down) and a bottom unit  204 . The top unit  200  includes a die  201  for forming a variety of products and components. 
         [0013]    With regard to the present system, the press may be mechanically or hydraulically operated. Via the bottom unit  204 , a stable, raised temperature can be maintained between the die and blank or preform, and throughout the blank or preform. The bottom unit  204  includes sliding bushings  205 , an oil tank  207 , and heaters  202 . 
         [0014]    In use, the tank is filled with a heat transfer oil, submerging all components including the punch  206 , die  201 , and the blank or preform (not shown). The oil is heated via the heaters  202 , to between 210° C. to 270° C., preferably 250° C. to about 260° C. Because the components involved in formation are fully submerged in the heat transfer oil, an isothermal environment is created with small temperature variations. Additionally, by fully submerging components, the benefits of anti-oxidation and lubrication are obtainable. The present invention is useful with blanks and preforms made from alloys of magnesium, aluminum, zinc, copper, tin, and lead. 
         [0015]      FIG. 3  is a schematic of an apparatus embodiment of the present invention, used in conjunction with a conventional press. From the bolster plate  300  up, the apparatus comprises several layers of insulation  333 / 331 / 327  sandwiched underneath a lower die shoe  325 ; a joint plate  353  is positioned adjacent to the base of the oil tank  351 . As stated, the oil tank  351  is positioned around the punch  319 , allowing the punch  319 , die, and blank or preform to be fully submerged in oil  302 . The oil  302  can be heat transfer oil well-known in the art, for example #281 Heat Transfer Oil (Schaeffr Manufacturing, Missouri) or D-A Heat Transfer Oil No. 300 (D-A Lubricant, IN). The oil  302  can be a 100% paraffinic heat transfer fluid or a blend, such as paraffin with polyalphaolefin. Blends can include synthetics, hot oil, and silicones. Synthetics can include diphenyl oxide/biphenyl fluids, diphenylethanes, dibenzyltoluenes, and terphenyls. Hot oils can include parafinnic and napthoic hydrocarbon. The heat transfer oil  302  should maintain it&#39;s stability up to 400° C. 
         [0016]    The sides of the tank  345 / 349  extend to slightly below the bushings  337 . The inner workings of the apparatus includes, but is not limited to, punch holder  317 , strippers  315 / 313 , springs  339 , pressure pins  321 , depth indicators  323 , columns  347 , and the like. The tank shall further include a heating coil  341  for increasing the temperature of the heating oil  302 . 
         [0017]    The top side of the apparatus can include die components such as inserts  311 , backing plates  304 , as well as upper die shoe  307 , insulation  303 / 305 , and backing plate  301 . 
         [0018]    Having described embodiments of the present system with reference to the accompanying drawings, it is to be understood that the present system is not limited to the precise embodiments, and that various changes and modifications may be effected therein by one having ordinary skill in the art without departing from the scope or spirit as defined in the appended claims. 
         [0019]    In interpreting the appended claims, it should be understood that: 
         [0020]    a) the word “comprising” does not exclude the presence of other elements or acts than those listed in the given claim; 
         [0021]    b) the word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements; 
         [0022]    c) any reference signs in the claims do not limit their scope; 
         [0023]    d) any of the disclosed devices or portions thereof may be combined together or separated into further portions unless specifically stated otherwise; and 
         [0024]    e) no specific sequence of acts or steps is intended to be required unless specifically indicated.