EP1110637A2 - Method for producing a component and component - Google Patents

Abstract

A component is formed from two or more metal tubes of different cross sections and/or materials. The cross section of at least one tube end section is altered, so that section end faces fit with each other, and the profiles of the end sections conform mainly to a final shape. The end faces of both tubes are welded together to create a tubular semi-finished component (8). This is subsequently formed at least partially in an internal pressure forming process.

Description

The invention relates to a method for producing a tubular molded component and on such a molded component.

EP 0 620 056 B1 already describes such a method and such a molded component. Here pipes are different Cross-section, different wall thickness and different Material properties in a first step welded to a semi-finished product on the face. This tubular Semi-finished products can then be produced using a hydroforming process be expanded to a tubular molded component. By using the composed of different pipes Semi-finished products can be molded components with greater variations the wall thickness and greater variations in the cross-sectional area be made than it is when using a simple Pipe is possible as a semi-finished product, with larger areas radial expansion causes a greater thinning of the wall thickness becomes. By welding the tubular semi-finished product conventional, inexpensive pipes is produced, it can be relative can be produced inexpensively and yet for the production different molded components with larger variations can be used along its axial length.

In this manufacturing process, however, in the connection area of the two metal pipes, especially if metal pipes are different Wall thicknesses and different expansion behavior problems are encountered. So can with the hydroforming process the pipe with the smaller wall thickness be expanded first so that it is in its end region, i.e. in the Connection area of the semi-finished product at the weld, stronger is stretched and thinned. In this case, with greater thinning if necessary, cracks in the weld seam, in one Heat affected zone next to the weld seam and / or in a base material occur outside the heat affected zone of the metal pipe. It can also be used for the subsequent expansion of the tube greater wall thickness in the previously stretched end area of the tube with less wall thickness to an undesirable wrinkling come.

Furthermore, the diameters of conventionally manufactured inexpensive pipes, especially continuously in roll forming manufactured pipes, tolerances, for example a wall thickness of one or more millimeters a few tenths Can be millimeters. So with simple face welding of the pipes, in particular pipes with thin walls, possibly bad or incomplete Connection of the pipe ends or an undesirable step formation achieved become. For this purpose, the end areas of the Pipes are checked and measured; however, this requires again an additional step.

Due to the relatively tight weld between the pipe ends in the case of the internal high-pressure forming process, the inner surface in the long term the outer shape, especially if the The weld seam in the connection area protrudes outwards in a wedge shape.

The invention has for its object improvements over to create the prior art and in particular a method for producing a molded component and a corresponding molded component to create a safe with relatively little effort and preferably inexpensive manufacture of molded components various pipes, especially molded parts with stronger ones Allow variation along the axial length.

This task is solved on the one hand by a method for manufacturing a molded component in which at least one metal tube of at least two metal pipes of different cross-sections and / or different wall thickness and / or different Material properties of the cross section of at least one End area is changed so that end faces the end regions of the two metal tubes matched to one another and the cross sections of the end regions of the metal pipes are the corresponding ones Cross sections of the molded component or one of the hydroforming process used outer shape at least essentially correspond. The metal pipes are on the front End faces subsequently together to form a tubular semi-finished product welded, the following in a hydroforming process is deformed.

Furthermore, this task is carried out in the molded component mentioned at the beginning solved by connecting the two tubular sections The weld seam is at least largely stress-free. This Molded component is in particular by the method according to the invention producible. By a tubular end region or tubular End areas of both metal tubes in their cross section of an end shape of the molded component must at least largely correspond to the area the weld seam in the subsequent hydroforming process just widened a little so that the metal in the area of the weld, advantageously only in one Dimensions are expanded so that it remains in its flowable area and thus no or only low tensions in the Area of the weld.

According to the invention, the cross section of the end region of a metal pipe or the cross sections of the end regions of both metal pipes thus changed so that the end faces of the End areas are adapted to each other, so that a good connection the pipe ends can be guaranteed during the welding process. Thus, not only precise, drawn tubes or drawn and annealed tubes, but for example inexpensive, continuous roll-formed or discontinuously roll-rolled or die-bent Pipes are used. The end faces of metal pipes different wall thicknesses can e.g. flush with the scope be adjusted so that there is a smooth outer surface of the tubular Semi-finished product and later the molded component, so that the different wall thicknesses of the pipe materials from the outside are recognizable. There is also a central connection of the end faces or a connection of the End faces of the metal pipes of different wall thickness possible. This adjustment of the end faces of the metal pipes can be dependent the subsequent process steps such. B. Bending with Thorn.

According to the invention, the cross sections of the end regions of the Metal pipes of the corresponding cross section of the final shape, that is the cross section of the molded component or the area of the outer shape, the the end areas of the pipes or the connecting area of the Surrounds semi-finished product when inserted into the outer shape, at least largely adjusted or adjusted. In particular, a uniform gap between the connection area of the semi-finished product and the inner surface of the outer mold remain; however, it is also the formation of an uneven gap possible, so that subsequent IHU deformations a greater deformation of a part of the connection area is reached. The gap between that Connection area and the inner surface of the outer shape can for example a few millimeters or a few tenths of a millimeter. The gap is advantageously chosen such that the metal during the subsequent hydroforming only experiences a relative stretch at which it is still in its is flowable area, so in the area of the weld no or only low voltages are generated. The end regions of the metal tubes can in particular be mechanical be deformed. To widen the pipe ends, for example an expanding mandrel can be used, for example a taper by means of a narrowing ring and / or an end pulling device can be achieved. The changed cross section of the metal pipe is independent of the tolerances of the original workpieces and is only determined by these tools. Thus experienced the end area of the metal tube or experience the end areas Both metal tubes have a bonded deformation that is independent on the wall thickness or the material properties of the pipes can. After the pipe ends have been welded, a force-related forming by loading the interior of the semi-finished product with fluid. Because the connection area of the semi-finished product only slightly widened in the area of the weld the problems existing in the prior art arise the uneven expansion of the different pipe ends only still to a small or negligible extent. Farther become little or no hydraulic expansion Tension is generated in the metal of the weld seam, making it problematic Area is largely spared and at most in is hardened to a small extent.

According to the invention, this can advantageously be used to change the cross section of the end area used tool in the following Welding process remain on the metal pipe so that through the tool a good fixation of the end area of the tube is achieved, without resilience of the metal after the change in cross-section again a change in shape of the end area occurs. As a result, an accurate and fast production and thus a high productivity guaranteed because between the two steps not the one used to change the cross-section Tool must be removed before the welding device is attached becomes. The welding device can in particular already during or before the step of changing the cross-section, i.e. in particular the expansion process or the narrowing process to which Pipe ends are created.

If the end portions of both pipes are widened or narrowed, this can be done using a common tool, e.g. one common narrowing ring in which the pipe ends from both sides be inserted or by a common expanding mandrel the two pipe ends are pushed on from two sides. If the common expanding mandrel as a retractable expanding mandrel is formed, it can be retracted after welding or folded and axially from the tubular semi-finished product be removed. The common tool can be used in the subsequent Welding process basically also in the welding process be included, e.g. serve as an electrode for welding; if the tool is not used in the welding process it can advantageously be grounded.

According to the invention, only the end region of one of the two can also be used Pipes in cross section can be changed if the cross section a tube already essentially the final shape of the molded component corresponds. In particular, the cross section of the end region can of the pipe can be changed with a smaller wall thickness. The Tolerances in the pipe with a larger wall thickness are particularly then not significant if the pipe has a thinner wall inside of the tolerance range with its entire face End face on the front end face of the tube with a larger Wall thickness is present.

In the outer shape or the inner surface of the outer shape, an in Circumferential groove may be formed for receiving the weld between the pipe ends serves. This will, on the one hand post-processing of the semi-finished product in the area of Switzerland seam and on the other hand a strain on the outer shape the solidified, generally wedge-shaped weld in the hydraulic Expansion process avoided or at least kept low, so that the life of the outer shape is increased. Farther the stress on the weld seam and the problematic deformation the weld seam avoided during hydraulic expansion or at least kept low. The groove can also be axial Fixing the semi-finished product during the hydroforming process be used.

An outer mold or a die or a device for hydroforming, in the inside surface of the outer shape such a circumferential groove for receiving a weld seam is already in itself Unique position viewed as an essential concept of the invention.

The groove can be so deep in relation to the weld seam be designed so that the weld seam even during expansion does not rest on the groove base and only the pipe end areas lie next to the weld seam on the outer shape; in this Fall is only by the axial forces at the weld Expanding burdened. Alternatively, the groove can be made smaller Depth are formed so that the weld seam during of widening rests on the base of the groove and, if necessary, is slightly deformed becomes.

According to the invention, after welding the pipe ends to a Post-treatment of the weld seam can be dispensed with if the outer shape is formed with the groove running in the circumferential direction, because in this case damage to the tool and the load the weld seam and the load on the surrounding weld seam Metal is avoided during expansion or at least is low.

Electrodes can be used to weld the end faces or a friction welding process can be used. Advantageously but the end faces are controlled by means of a magnet Arc welding process welded together.

During the hydroforming process, the semi-finished product in in the axial direction to avoid excessive thinning to prevent the pipe material in areas of greater expansion. As a result, tubular molded components with any Cross-sectional areas and any wall thickness distribution achieved become. The axial tracking of the pipe material can advantageously one in the connection area of the end areas of Metal pipes of different wall thickness, beveled step or be equalized, whereby the strength of the Connection is increased and a smoother connection surface is created becomes. The pipe material can only be axial Direction (for example from the side of the pipe with less Wall thickness and / or smaller diameter or the tube with larger wall thickness and / or larger diameter) or both axial directions are tracked. The tracking from the both axial directions can be the same or advantageous different ways, for example at different speeds and / or staggered and / or over a shorter one or longer distance. Both when tracking out an axial direction as well as from both axial directions when using an outer shape with a groove on its inner surface Fixation of the weld seam of the semi-finished product reached in the axial direction become; however, it is also a corresponding axial tracking possible without such a fixation.

According to the invention, steel pipes in particular can be used; however, it is also the use of other metals, in particular Light metals, such as magnesium, aluminum or a magnesium or aluminum alloy possible. According to the invention also metal pipes with different material properties be connected, e.g. different types of steel, e.g. Steel grades with different composition or different Structure.

Fig. 1 -

die Endbereiche von zwei Metallrohren vor dem erfindungsgemäßen Aufweiten der Rohre;

Fig. 2 -

die aufgeweiteten Rohrenden nach dem erfindungsgemäßen Aufweiten;

Fig. 3 -

ein in eine IHU-Form eingelegtes erfindungsgemäßes Halbzeug vor dem hydraulischen Aufweiten gemäß dem erfindungsgemäßen Verfahren.

The invention is explained in more detail below with the aid of the accompanying drawing in some embodiments. Show it:

Fig. 1 -

the end regions of two metal pipes before the pipes are expanded according to the invention;

Fig. 2 -

the widened pipe ends after the widening according to the invention;

Fig. 3 -

a semifinished product according to the invention inserted into an IHU mold before hydraulic expansion according to the method according to the invention.

1, a first metal tube 1 and a second metal tube 2 used, e.g. a circular cross section, a have a rectangular cross section or another cross section. The metal tubes 1, 2 have different, as shown in FIG. 1 Wall thicknesses and / or different diameters.

2, end regions 3, 4 of the metal tubes are expanded in such a way that that end faces 5, 6 of the end regions 3, 4 are matched to one another and subsequently the metal tubes 1, 2 can be placed against each other at their end faces 5, 6, so that advantageously at least one end face, e.g. as in Fig. 2 shown the smaller end face 5, completely on the other Face 6 rests.

The end regions 3, 4 have already been expanded in such a way that their cross sections the cross section of the final shape, that is, the later Molded component at this point, at least largely correspond, or their outer diameter the inner diameter of the in used later IHU expansion process, shown in Fig. 3 9 correspond at least largely. Here, in particular only a small gap 11 between the end regions 3, 4 and the outer shape 9 remain. The pipe ends 3, 4 can be on Fig. 2 following welding process e.g. through a pressure welding process, especially a magnetically controlled arc welding process are welded together. For metal pipes 1, 2 with a round cross-section can e.g. also a friction welding process be used; an electrode welding process can also be used be used, where appropriate, to expand the Pipe ends 3, 4 used expanding mandrel, not shown in Fig. 2 can be used as one of the electrodes.

By welding the end faces 5, 6 according to FIG tubular semifinished product 8 is formed, which has a widened connection area 13, which has the end regions 3, 4 as the starting material used metal pipes 1, 2 corresponds. In the connection area 13 is a weld 7 which is formed as in Fig. 3 shown can protrude in particular to the outside. For internal high pressure forming is the semifinished product 8 in a manner known per se inserted into an outer shape 9, which is the final shape of the later tubular Determined component. To expand this is known in Way fluid, as shown by arrow F, inside the Semi-finished product 8 pressed, generally the other end of the Semi-finished product 8 is closed.

Since the connection area 13 already during the previous expansion area of the outer shape 9 surrounding it is at least largely adapted is and advantageously only a small, ring-shaped Gap 11 between the connection area 13 and the outer shape 9 remains, this connection area in the hydroforming process only slightly stretched, so that in particular also the load on the end region 3 of the metal pipe with less Wall thickness near the weld 7 kept low is so that there is no or only a small amount in the weld seam Voltages are generated. Here are the diameter of the metal pipe and the gap is coordinated so that the Elongation of the metal in the radial direction within the flow area of the metal takes place.

An annular groove 10 can be formed in the outer shape 9, which is suitable for receiving the weld seam 7. In the hydroforming process the weld seam 7 thus enters the groove, so that a flat pressing of the weld 7 on a smooth inner surface the outer shape 9 can be avoided. The groove 10 can are so deep that the weld 7 is not at all or only partially comes to rest on the groove base, so that the Load on the weld 7 is low. Alternatively, you can a deliberate deformation of the weld when using a groove can be achieved with a smaller depth, so that the Weld 7 is somewhat flattened.

During the hydroforming process can be known in itself The semi-finished product 8 in an axial direction P or in the to P opposite axial direction to track the Wall thickness of the molded component in the desired areas, in particular in areas with greater cross-sectional enlargement. As a result, the step between the end regions 3, 4 of the pipes are somewhat flattened and thus the connection of the Metal pipes 1, 2 can be improved.

The axial length of the end regions changed in their cross section 3, 4 can in the mechanical expansion according to the invention before Welding of the two metal tubes is different his. For example, in Fig. 2 the axial length of the end region 3 of the metal tube 1 with smaller wall thickness larger or smaller chosen as the axial length of the end region 4 of the metal tube 2 are, depending on the desired load on the pipe material at mechanical expansion as well as in the subsequent hydroforming.

As an alternative to the widening of the end regions 3 shown in FIG. 2, 4, one or both end areas can also be narrowed. At Use of a first tube with a smaller diameter and one second pipe with a larger diameter can, for example End region of the first tube expanded and the end region of the second tube are narrowed, so that the end regions against each other are adjusted. A narrowing of both end areas can, for example be made when the connection area in the later Molded component has a smaller diameter than the surrounding areas of the molded component and for example below the molded component in the relatively flexible connection area should be bent.

According to the invention, in particular, sheet metal can be produced continuously roll-formed or discontinuously roll-rolled or die-bent, relatively inexpensive pipes are used. This can then pulling and annealing the pipes if necessary to be dispensed with because the subsequent widening of the pipe ends according to the invention also larger tolerances of the output pipes can be accepted. This can also weaken the material by pulling and Glow pipes are avoided.

According to the invention, tubes 1, 2 can be of constant or non-uniform Wall thickness can be used. An uneven wall thickness can be done, for example, by pretreatment for pipe manufacturing used sheets can be achieved.

Claims (18)

Method for producing a molded component, in which In the case of at least one metal tube of at least two metal tubes (1, 2) of different cross-section and / or different wall thickness and / or different material properties, the cross-section of at least one end region (3, 4) is changed in such a way that end faces (5, 6) of the end regions ( 3, 4) of the two metal tubes (1, 2) are adapted to one another, and the cross sections of the end regions (3, 4) of the metal tubes (1, 2) correspond at least substantially to cross sections of an end shape, the metal tubes are welded together at the end faces (5, 6) to form a tubular semi-finished product (8), and the tubular semifinished product (8) is subsequently deformed, at least in regions, using an internal high-pressure forming process. A method according to claim 1, characterized in that in both metal tubes (1, 2) at least the cross section of an end region is changed. Method according to claim 1 or 2, characterized in that the end region (3, 4) of at least one metal tube, preferably the end regions (3, 4) of both metal tubes (1, 2) are mechanically expanded and / or tapered. A method according to claim 3, characterized in that at least the end region (3, 4) of one of the metal tubes (1, 2) is expanded by means of an axially inserted expanding mandrel which during the welding of the end faces (5, 6) in the end region (3 , 4) of the metal tube remains. A method according to claim 4, characterized in that the end regions (3, 4) of both metal tubes (1, 2) are expanded by a common expanding mandrel, in particular a common expanding mandrel. Method according to one of claims 1 to 5, characterized in that when the cross section of the at least one end region (3, 4) is changed, the geometric shape of the cross section is changed. Method according to one of claims 1 to 6, characterized in that the cross section of the tubular semifinished product (8) in a connecting region (13) of the metal pipes (1, 2) corresponds at least substantially to the cross section of an outer mold (9) used in the internal high pressure forming process . A method according to claim 7, characterized in that when the tubular semi-finished product (8) is inserted into the outer mold (9), an essentially uniform gap (11) is formed between the connecting region (13) of the metal tubes and the outer mold (9). Method according to one of Claims 1 to 8, characterized in that in an end face of an outer shape (9) used in the internal high-pressure forming process, a groove (10) running in the circumferential direction for receiving a weld seam (7) of a connecting region (13) of the metal tubes (1 , 2) is formed. Method according to one of claims 1 to 9, characterized in that after the welding of the end faces (5, 6) of the end regions (3, 4), the semifinished product (8) without prior post-processing of a weld seam (7) by the internal high-pressure forming process is deformed. Method according to one of claims 1 to 10, characterized in that the semifinished product (8) is bent before the hydroforming process. Method according to one of claims 1 to 11, characterized in that the end faces (5, 6) are welded to one another by a pressure welding process, in particular a magnetically controlled arc welding process or a friction welding process. Method according to one of claims 1 to 12, characterized in that during the hydroforming process, the semi-finished product is tracked in at least one axial direction (P), preferably in two opposite axial directions in the same or different way. Method according to one of claims 1 to 13, characterized in that in a first process step, the metal tubes made of sheet metal by a batch process, such as. B. roll or die bending, or a continuous process such. B. a roll forming process, and the cross sections of their end regions (3, 4) are changed and adapted to one another without a subsequent drawing process or annealing process. Method according to one of claims 1 to 14, characterized in that a metal tube or both metal tubes (1, 2) is / are bent before welding. Tubular molded component made of metal, can be produced with a Method according to one of claims 1 to 15, with at least two tubular sections of metal that over one Weld seam (7) are connected to each other, wherein the weld seam is at least largely free of tension. A tubular molded component according to claim 16, characterized in that the weld seam (7) protrudes on an outer circumference of the molded component. Molded component according to claim 16 or 17, characterized in that the sections have different material properties, preferably consist of different metals.

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