Abstract:
The invention relates to a molded part which is configured by initially forming a tubular body with a welded flange. Subsequently, the body is shaped in a mold placing the body under internal pressure to form a part or preform. Thus, preforms with a welded flange can be obtained and connectedn with other parts.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a method for the production of a formed sheet-metal component which is formed by internal high-pressure forming. The invention also relates to a formed component produced according to the method. 
     It is known to shape components by internal high-pressure forming of butt-welded tubular preforms which are cut from corresponding bar stock to the length required. From EP-A-0620056 it is also known to weld together a number of such butt-welded tubular preforms of different diameter and thickness into a single tube which is then formed into a tubular component by internal high-pressure forming. 
     Extended formed components made from tubular preforms may especially be used as components in motor vehicle construction. Here, these components usually have to be joined to other components, eg. by further welding or by bonding. For certain purposes, it is then necessary for one component to be provided with at least one attachment flange. At least one operation is required to add such a flange to the said components, which is a disadvantage in terms of cost, so that, in this case, several components formed by deep-drawing or pressing are usually welded together in a conventional manner into one formed component. 
     From EP-A-0589370 it is known to provide two essentially flat metal sheets with a conduit for introducing the fluid for the internal high-pressure forming, and to weld the sheets together at their edges; the result is a formed body with a surrounding flange, which is not desired in edges; the result is a formed body with a surrounding flange, which is not desired in many applications in motor vehicle construction. DE-C-900085 likewise discloses the internal high-pressure forming of two essentially flat metal sheets which have been both welded together and which have a chamber in the middle formed from two domes for the introduction of the pressure fluid. This also produces a formed body with a surrounding flange. Similarly, DE-A 3418691 shows the forming of two or four flat metal sheets which are joined together at their edges. U.S. Pat. No. 5,070,717 shows a flangeless butt-welded tube being formed in such a way that a flange is produced in the forming process. In this way it is possible to produce an extended formed body with a flange on one side only, but additional cutting and welding operations are necessary to obtain a flange form with a straight end face. 
     SUMMARY OF THE INVENTION 
     Therefore, the problem which the invention by internal high-pressure forming, provides a component which can easily be produced and be joined to other components, in particular an elongate component with a flange on one side only, or with two flanges on opposite sides of the component. 
     This object is achieved by forming a body from sheet metal with at least one flange extending outwardly from an edge region of the sheet metal, the flange being welded, and then transforming the body into a preform by means of internal high-pressure forming. 
     By firstly forming, by rounding, a tubular body with an outwardly directed flange, production is facilitated, since the flange serves as a welding flange which can be welded by conventional low-cost methods at a high rate of production. In the completed formed component, this already existing flange serves as an attachment point for other components, which makes the use of such a formed component advantageous in many applications in comparison with conventional bodies formed by internal high-pressure forming. 
     In an alternative solution, two half-rounded metal sheets each provided with two projecting flat tongues are first of all joined to form one essentially tubular body with two flanges. 
     Another object of the invention is to provide a component formed by internal high-pressure forming which can be easily joined to other components. This object is achieved with a formed component made from a sheet metal body provided with an outwardly projecting flange and molded into a shape by the application of internal high-pressure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will now be described in detail by way of example, with reference to the drawings, in which: 
     FIGS. 1 a - 1   e  show schematically the steps in the production of a formed component produced in accordance with the invention; 
     FIG. 2 shows in profile a formed component according to the invention, and its use as a roof edge section for a motor vehicle; 
     FIG. 3 shows in profile a formed component according to the invention, and its use as a door sill section for a motor vehicle; 
     FIG. 4 shows in profile a formed component according to the invention, and its use as a door post for a motor vehicle; 
     FIG. 5 shows in profile a formed component according to the invention, and its use as a hinge bracket or lock bracket for a motor vehicle; and 
     FIG. 6 shows a further embodiment of formed component according to the invention prior to internal high-pressure forming. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 a - 1   e  show schematically a sequence of process steps in the production of a formed component or body according to the invention. In FIG. 1 a ,  1  denotes a sheet-metal blank from which the body will be formed. This blank  1  may be homogeneous, eg. a wholly steel or aluminium blank consisting of a single piece of the requisite size and with uniform thickness, as illustrated in FIG. 1 a . The blank may, however, consist of two or more sheet-metal portions joined together by welding, so that the blank  1  has portions of different thickness and/or with other dissimilarities of material characteristics or properties, which impart to the subsequent formed component local differences in characteristics or properties. Such blanks consisting of portions joined together (so-called tailored blanks) are known, and are used eg. in motor vehicle construction, where they are formed into components in a known manner. The “tailored blank” can be assembled in any desired direction and using any desired welding processes. 
     As shown in FIG. 1 b  the blank is formed into an essentially cylindrical tube  2 , two margins  3  and  4  of the blank being formed into tongues projecting from the tubular part  2 , these tongues together constituting a flange  7  projecting from the tube. The forming of the blank  1  into the tubular part  2  may be performed on a rounding machine in a conventional manner, with unrounded margins  3 , 4  forming the tongues. 
     Fabrication of the tubular body  2  continues with the welding together of the tongues  3 , 4  to constitute the flange  1  (FIG. 1 c ). This may be performed eg. by lap seam welding with welding rollers  5  and  6 , a wire electrode being provided in a known manner at each of the welding rollers  5 , 6 . This has the advantage that coated metal blanks, eg. tinned or galvanized blanks, can be welded without any problem, as the wire electrode is continuously replenished from a spool. Alternatively the flange  7  may be welded eg. by edgewise laser welding, as illustrated in FIG. 1 c  by the additional arrow A symbolically representing the laser beam impinging on the tongues  3 , 4 . Both roller seam welding and laser beam welding allow lengthy flanges  7  to be continuously welded at a high rate of feed and with high weld quality. It is also possible to employ laser welding in which the flange is through-welded from above or below. Alteratively the margins may be joined together edgewise by other known welding processes such as MIG, MAG, plasma or oxyacetylene welding. Electron-beam welding is also possible. By employing these processes, practically all kinds of sheet metal including, in particular, coated sheet-metal blanks, can be welded with high quality. The welded body  2  has an essentially tubular form with open ends and with a sealingly welded flange  7 . 
     In a next step (FIG. 1 d ) the body  2  thus formed is placed in a mould  8  for internal high-pressure forming. The inner surface of this mould has a configuration which corresponds to the shape of the formed body to be produced. The mould also has means for closing off the open ends of the tubular body  2  and means for introducing—usually via the end—a fluid at high pressure. The fluid for forming may also be introduced through an orifice or nozzle within the cylindrical portion of the preform. The process of internal high-pressure forming is known in itself and the corresponding devices for carrying out this process are likewise known and available on the marker, and will therefore not be described in further detail here. In the present case, however the mould  8  is configured so that the flange  7  can be clamped in the mould by the mould itself or by additional means, so that the flange  7  is impinged on both faces, over as nearly as possible its entire length, and preferably its full width, during the internal high-pressure forming process, so that the weld seam of the flange is not subjected to opening or pealing forces due to the pressure exerted in the interior of the body  2 . 
     FIG. 1 e  shows the resulting formed body  10 , which has the desired shape imparted by internal high-pressure forming, and is provided with a flange  7  which can be used for attaching be body  10  to another component. 
     FIG. 2 shows as an example a formed body  11  which has been produced by the steps  1   a  to  1   e  described above, used as a roof edge section for a car roof  15 . FIG. 2 shows this application in schematic and highly simplified form. It will be seen that the formed body  11  is attached to the roof  15  by its flange  7 , eg. by a laser-welded joint (seam  16 ). Of course, other known attachment techniques (such as spot welding or bonding) might be employed. 
     FIG. 3 shows a further formed body  12  produced in accordance with the invention. This body—likewise shown only in simplified form—is used as a door sill section for a motor vehicle.  17  denotes a part of the vehicle floor to which the formed body  12  is attached by the flange  7 , eg. by spot welding or laser welding. 
     FIG. 4 shows schematically an end view of a formed body  13  according to the invention, which can be used as a door post (B-pillar) of a motor vehicle. 
     FIG. 5 shows a further formed body  14  fitted as a formed section in the hinge or lock region of a car engine bonnet or boot lid. The formed body  14  is attached by the flange  7  to the bent-over end  21  of the outer skin  19  of the bonnet or lid. The inner skin is fitted to the outer skin on interposed rubber mountings, and stiffeners  22  are provided. 
     FIG. 6 shows a tubular body  25  made up of two half-round formed blanks  26  and  27 . Each blank has two projecting margins or tongues which are paired to provide flanges  28  and  29 . These are welded as described above with reference to the flange  7  of FIG.  1 . The body  25  is also formed by internal high-pressure forming, the two flanges  28  and  29  being gripped over as nearly as possible their entire area. After forming, a formed body  30  with two flanges  28  and  29  results. 
     Of course, the method according to the invention can be used for producing a large number of formed components for other applications besides motor vehicle construction, such as eg. railcar building or aircraft construction.