DE102014014818A1 - Hot-cold forming of hollow bodies - Google Patents

Abstract

Process combination of hot and cold forming processes for the production of hollow bodies (preferably of pipe) with an extremely thin wall on the one hand and very high wall thickness or even solid self-contained areas, characterized by the following features: • the starting material (preferably pipe) is first in cold and / or mandrel cold thinning, and the wall locally thinned; the starting material (preferably tube) is preformed so that it is cylindrical inside and has the different wall thicknesses outwardly and / or vice versa is cylindrical outside; Has different wall thicknesses inside and / or has a combination of wall thicknesses inwards and outwards, • the areas to be formed hot remain in this upstream operation in their dimensions for the time being or possibly slightly thickened, • the warm areas to be reshaped mi t the remaining thicker wall heated in a subsequent process step and further thickened by hot upsetting and / or possibly even massively closed, • can be shown in the result extremely thin-walled and thus light hollow parts with almost any thickening.

Description

 short version

Technical problem of the invention = technical task and objective

Connecting shafts in the field of mechanical engineering, suspension and drive technology or rigidly used connecting or reinforcing struts are increasingly made of hollow material instead of solid rods for reasons of weight reduction and resource conservation. Since the shafts often require different diameters and in the areas with smaller diameters - often at the ends - require a thicker wall thickness than in the region of larger diameter in order to transmit the same forces or moments, the waves are processed in particular for higher numbers of forming technology. Here, for example, there is the rotary swaging method with which the wall thickness of a pipe can be reduced / stretched in a kind of hammering process via mandrel. In the areas with a smaller diameter, for example, reduced without a mandrel, so that the wall thickness is maintained or even increases. Another possibility is the drawing over mandrel, the deformation is usually done here to reduce the force here in several trains. Another technology is hot forming, in which the areas to be thickened are heated inductively, for example, and then populated in mechanical or hydraulic presses, thus thickening the wall, in extreme cases to a solid state. The material to be encountered during hot forming must first be provided and heated as an appropriate excess length. After a certain thinness, several upsetting steps are required one behind the other to avoid waves / wrinkles. If the outlet wall of the hollow body is too small, the process becomes unstable or impossible. The aim of the method according to the invention is to produce hollow bodies with, on the one hand, an extremely thin wall (S ₁ ) and, on the other hand, a very high wall thickness (S ₄ ) or even massively closed areas (S ₅ ).

Solution of the problem or the technical task

The combination of hot and cold forming process according to the invention provides to initially reduce the starting material (preferably pipe) cold in certain areas by drawing in or swaging over mandrel (S ₁ <S ₀ ). The areas to be hot-formed should retain the initial wall thickness (S ₂ = S ₀ ) or even slightly thickened by the cold-forming process (without mandrel) (S ₃ > S ₀ ). In this case, the starting material can be preformed so that the tubes are cylindrical inside and have the different wall thicknesses to the outside (D ₁ <D ₂ = D ₀ ) or vice versa outside cylindrical (D ₃ ≠ D ₀ ) and the thickenings go in or out . a combination of both (Fig. 1). In a further process step, the thick-walled areas are further puffed up by local heating by means of furnace, heat jets or induction and subsequent hot dipping on shaping upsetting tools, thickened and possibly even massively closed, as described above. As a result, extremely thin-walled wave ranges can be displayed with almost arbitrarily strong thickening at the pipe ends and / or other locations (Fig. 3). In a further embodiment of the method, the thick-thin-vorzuformenden pipes can also be produced by a continuous drawing process with variably positioned internal mandrel and dimensionally accurate (based on the thick-thin areas) are separated (Figure 2). A particular advantage of this method is that when using the above-described thick-drawn tubes as the starting material in combination with a single or multiple dies, only one operation (per shaft end) is required to produce a weight-minimized lightweight shaft with maximum thickening. To produce strength at the pipe ends or other locations.

field of use

Lightweight connecting shafts in the field of mechanical engineering, chassis and drive technology or rigidly used connecting or reinforcement struts.

Claims (3)

Process combination of hot and cold forming processes for the production of hollow bodies (preferably of pipe) with an extremely thin wall on the one hand and very high wall thickness or even solid self-contained areas, characterized by the following features: • the starting material (preferably pipe) is first in cold and / or mandrel cold thinning, and the wall locally thinned; the starting material (preferably tube) is preformed so that it is cylindrical inside and has the different wall thicknesses outwardly and / or vice versa is cylindrical outside; Has different wall thicknesses inside and / or has a combination of wall thicknesses inwards and outwards, • the areas to be formed hot in this upstream operation remain in their dimensions for the time being or possibly slightly thickened, • the warm areas to be reshaped mi t the remaining thicker wall in one heated subsequent process step and further thickened by hot upsetting and / or possibly even massively closed, • can be shown in the result extremely thin-walled and thus light hollow parts with almost any thickening. Process combination according to claim 1, additionally characterized by the following features: The starting material to be used is already produced from a thick-thin tube drawn continuously over a variably positioned inner mandrel, which is then accurately separated in relation to the present wall thickness distribution and fed to the final hot forming; • Thus, only one operation is required in each case to produce a weight-optimized lightweight shaft with greater thickening and strength at the ends and / or other locations. Process combination according to claim 1 and 2 in a further embodiment, additionally characterized by the following features: The process step of local heating takes place in a process-integrated manner via a conductive heating device, continuously accompanying the process during the final heat-upsetting, • thus an additional separate intermediate process step for local component heating is eliminated.

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