DE102009010490A1 - Process for producing a hollow body by subjecting such a hollow body blank inserted in a cavity with internal pressure at elevated temperature - Google Patents

Abstract

The invention relates to a method for producing a hollow body (1, 10) by applying such in a cavity hollow body blank with internal pressure at elevated temperature, wherein the hollow body blank is produced by at least one previous forming or forming process, wherein the hollow body blank on its circumference at least has a deviation in the circumferential length of at least 10%.

Description

The The present invention relates to a process for producing a Hollow body by applying such in one Cavity of a cavity inserted hollow body blank with internal pressure at elevated temperature.

Methods of the type mentioned are well known. Known in this connection are the so-called hydroforming processes, ie processes for hydrostatic forming of hollow bodies, the transformation taking place substantially at room temperature. Such a method is for example from the DE 41 03 082 C2 known.

However, it is also known z. B. from the DE 196 42 824 A1 to set a hollow profile body made of metal with heated oil under internal pressure, which should be avoided by subsequent rapid cooling of the workpiece undesirable structural changes.

A method for expanding a hollow body by pressurizing the hollow body with pressurized gas at elevated temperature also describes the DE 10 2004 013 872 B4 ,

It is also known from the DE 102 20 429.2 B4 a method of manufacturing a hollow metal body having a longitudinally varying cross-sectional shape in a tool shape formed to the desired final contour. The forming takes place here at elevated temperatures, wherein in the areas of the highest degrees of deformation a higher temperature is provided than in the areas of lower degrees of deformation. It is also known here to compress the hollow body for the purpose of material tracking.

From the DE 199 44 679 C a method is known in which a tubular blank is pushed at its two ends during hot forming with internal pressure, that is compressed. Here is in the range of the highest degrees of deformation of the blank at the warmest.

all These blanks or tooling forms is common to that such tubular hollow body at both ends of the tube or in the Umformachse is open and an over the body or the lateral surface of the body distributed having a substantially equal circumferential length.

At the Deformation of hollow bodies by means of internal pressure under elevated Temperature is the concern about the reshaped Area a substantially equal material thickness or to obtain a desired wall thickness profile, even if these bodies after forming large differences have in their cross sections. Partially this premise complied with when the hollow body blanks over their lateral surface a different material cross-section exhibit. In addition, there is the possibility to compress or lengthen such a hollow body, to a substantially equal material thickness or a desired wall thickness over the lateral surface of the To ensure hollow body. It turned out that the measures described above, however, certainly are not always sufficient to get close to the goal, one Hollow body to form over the lateral surface or surface a substantially same or desired Has material cross-section.

to Achieving the goal of a hollow body with an over the lateral surface same or any material cross section According to the invention, it is proposed that the hollow body blank on its circumference at least one deviation in the circumferential length of at least 10%. That is, the gist of the invention consists in the hollow body blank, for example by a forming process - for example, deep drawing - or produced by a molding process such as casting, already give a shape of the final shape of the hollow body to a certain extent. That means that at least in the places of the hollow body, which in the deformation experience a high change in cross section due to internal pressure at elevated temperature, this change in cross section through the shaping of the hollow body blank in anticipated to a certain extent.

There are known areas of use of hollow bodies, in which only one end is open, the other end, however, must be closed. This is known, for example, in certain taps or door handles in particular. When using such a hollow body as a blank is so far always required that this tubular hollow body is closed after hot forming at one end. This is done, for example, by welding or soldering and thus always has a structural change result. In an example subsequent anodization the structural change remains visually always visible, which is often not desirable for aesthetic reasons. In addition, the method by z. B. the additional welding process more expensive. In this respect, it is also known to produce such hollow bodies as a cast construction, welded construction or structural construction or the like. However, these methods are complex and expensive, since often, especially when the corresponding items are to be subsequently anodized, an expensive post-processing is required. In this respect, it is provided to form the hollow body blank at one end closed or to provide a hollow body blank, the le has only an open end. In this case, the bottom can also have an opening, which can ultimately serve for example for screwing in a thread for a water outlet.

By a closed at one end hollow body blank, the also preferably has only one open end, are Thus, designs of hollow bodies possible, the essentially require no post-processing, for example by Welding of one end, and thus free of structural changes are visible, for example, when anodizing or chrome plating stay. Such hollow body blanks with only one open end, the extent to another end preferably one Soil are, for example, by means of extrusion, for example, the forward and / or backward Napffließpressens or deep drawing in principle in any Shape inexpensive to produce. These blanks become the next Forming by internal pressure, by z. As a gas, by forming (elastically compressible), bulk material or a liquid acted upon in a cavity of a die. Especially there is a possibility, when deep-drawn, forward and back pressed, forged or Rolled blanks to realize different wall thicknesses. Ie. for example, that in the range of high degrees of deformation large Wall thicknesses are provided to after hot working a profiled hollow body with over the length to obtain substantially the same wall thickness; Target can but also from z. B. strength or stiffness reasons be a different wall thickness. A material supply in the sense upsetting or pulling the blank is then in these areas not necessarily required. The hollow body shows after the invention already a special form, as z. In the Claim 1 is set forth. Due to the special shape design is the final shape after forming by internal pressure and at elevated Temperature taken into account; d. H. the shape of the hollow body blank anticipates the final shape to some extent. Still, it may be necessary be, the hollow body blank during forming to compress or pull.

It It has been found that by the previous mechanical Forming, z. B. by deep drawing or extrusion, the Material for the subsequent forming process significantly better Has properties such as a simple, pressed Pipe. This is in particular due to the fact that by Pressure deformed and in particular thermoformed body have a fine grain, which causes at a subsequent under internal pressure, optionally also at elevated temperature deformed body no post-processing, z. B. before next Anodization or polishing, must be done. This is because the body is over the surface essentially little or no roughness which is due to the fine-grained microstructure and the material hardening of the blank is conditional. Especially have the hollow body blanks, with a closed Are hot formed at the end, no welds and press seams on which the further deformation by means of internal pressure due to the different Affect microstructure. Has also been shown that produced by prototypes, for example, casting Blanks also have material properties that in subsequent Forming by means of internal pressure and elevated temperature essentially no or only minor microstructural changes Experienced.

Of Furthermore, it can be provided that the hollow body at the closed End is upset. As explained elsewhere, serves the upsetting of the workpiece material tracking, in particular one over the forming axis or lateral surface the workpiece uniform wall thickness or to achieve the required wall thickness profile. Furthermore, can be provided that the hollow body in the region of the closed End is additionally deformed during the compression process.

Further advantageous features and embodiments will become apparent from the dependent claims.

To an embodiment is provided that the hollow body blank is formed spherical, in the way of the or Urformung, wherein the blank has at least one opening. Also Such a body can therefore be on its surface at least one deviation in the circumferential length of at least 10%.

So is provided in particular that the hollow body in the area higher degrees of deformation or greater wall thicknesses has a higher temperature than in the lower range Forming degrees or thinner walls. Furthermore is advantageous if the temperature for forming below the melting temperature of the workpiece material is. Around Scaling corrosion-prone materials such as copper, steel, titanium, etc., or the risk of burn-off with oxygen (Magnesium, titanium, steel) is provided for the Application of the internal pressure the use of an inert gas, z. Nitrogen or argon; otherwise air is used.

As already explained elsewhere, in particular warm to be formed hollow body large differences have in the degrees of deformation, which in the end by a corresponding the desired degrees of deformation provided temperature profile is possible.

Farther can be provided, the hollow body partially or completely to heat before inserting into the cavity, in particular with a temperature profile that matches the desired degrees of deformation or Forming process over the Umformachse of the hollow body correlated. In addition, in addition, too the cavity is fully or partially heated be, in particular according to the temperature profile of the hollow body or in addition to the hollow body. In detail, it is furthermore advantageously provided in this context that that the hollow body has a thermal profile with temperature differences for example, between 2 ° and 100 ° C to run the forming process in the desired Umformabfolge allow. Longer hollow bodies are larger Temperature differences better shape than short hollow body. That means that the temperature profile is reached, that the forming process is initiated at a specific location, and Although in most cases in the places of the highest degree of deformation or wall thicknesses, for example to ensure, in particular, thereby that the forming process reliable with the least possible friction runs off the wall of the cavity.

To Another feature of the invention is the hollow body after forming by internal pressure from the forming heat remunerated. That is, the hollow body will match the desired structural properties cooled from the forming heat.

Of Further, the hollow body before forming under internal pressure optionally bent at elevated temperature, which means that the bending process the forming process for the production preceded by the blank to be formed warm. But that also means that the blank has been pulled deep, for example, before bending is. Furthermore, the hollow body when closing the Forming dies are deformed by the die, z. B. can from a round cross section to be made of an oval cross section.

Also it is conceivable that the hollow body consists of several parts, the continuous with each other for the forming medium communicate or connect through internal pressure can, and the z. B. by bursting the partition. It is also conceivable that the compound kept closed can be. From this it becomes clear that, for example, a Hollow body is deformable, in the Umformachse only one opening owns, however, for example, has a branch, however connected to the hollow body so that a forming pressure can be built.

Also is conceivable that the hollow body blank on the Cavity survives. When upsetting or pulling the Hollow body blanks are sealed during loading with internal pressure in the region of the device for applying thrust or Pressure with which the blank is compressed or pulled. This means, the blank is sealed outside the cavity.

Based of the drawings, the invention will be exemplified in more detail below explained.

1a shows a deep-drawn blank with over the length of different inner diameter, wherein the one end of the blank is closed;

1b shows, for example, a mold after hot working under internal pressure of the body according to FIG 1a under internal pressure and elevated temperature;

2a shows a body as a blank according to 1a but not with circular exit sections;

2 B shows as a final product a hollow body with examples of different cross-sectional shapes over the Umformachse of the hollow body;

3a . 3b show blanks which have a different outer contour before forming by internal pressure with elevated temperature;

4 shows a formation of a blank for hot forming according to 2 B , wherein only the closed end-side end has a conical contour;

5 shows a representation of a blank according to 4 with hemispherical, frontal contour;

5a shows a blank according to 5 with different wall coverings on the circumference;

6 shows an embodiment in which the blank has a nosepiece prior to hot working;

7a . 7b show further examples of hollow body blanks;

8th - 8b show examples of spherical hollow body blanks;

9 shows an education according to 1 , wherein the bottom has only one opening.

The in 1a shown blank carries the reference numeral 1 , The blank 1 has over its length a different wall thickness (arrow 2 ). The one end (arrow 3 ) of the blank 1 is closed. The hollow body arises after the deformation of the blank according to 1a for example as in 1b The wall thickness is in this case quite different, which is also due to the fact that the hollow body was not substantially compressed in the thickened areas during hot forming for material tracking.

The representation according to the 2a and 2 B is different from the 1a and 1b essentially in that the hollow body blank according to 2 B three different cross-sectional shapes 5 . 6 and 7 may possess, namely oval, round and rectangular. The shape of the blank thus corresponds to that of the cavity into which the blank has been formed when exposed to internal pressure.

3a shows an initial shape of a blank 1 with constricted end before the Innendruckumformvorgang. 3b shows an initial shape of a blank 1 with constricted and flared end before Innendruckumformvorgang.

The 4 and 5 show the hollow body blank 1 with differently shaped end face (arrows 8th and 9 ).

5a shows a hollow body as a blank with different wall thickness over the circumference. Due to the different wall thickness of the fact is taken into account that z. B. at different degrees of deformation yet an approximately equal wall thickness over the circumference of the hollow body to be achieved or the desired wall thickness distributions are achieved.

In the representation of the hollow body blank according to 6 has the hollow body 1 an approach 20 on, with the hollow body by welding, soldering or z. B. clinching is connected. Although the approach is to be deformed with, the transition to the hollow body 1 (Arrow 12 ) to be open. However, there is also the possibility that the connection to the approach 20 first through a wall 12 is closed, which, however, burst at appropriate internal pressure, and then to deform the approach accordingly by internal pressure at elevated temperature. The wall in the transition to the approach 20 However, it can also be designed so that it remains during the forming process with internal pressure.

7a and 7b show examples of hollow body blanks whose diameter and width are substantially the same, but which nevertheless have a different cross-section, respectively on their circumferential inner and outer circumferential surface different circumferential lengths.

Regarding the 8th to 8b show spherical hollow body blanks 10 with an approach 10a for introducing the gas for generating the internal pressure, a spherical hollow body blank with an additional opening 10b ( 8a ). 8b shows a spherical hollow body 10 with an approach 10a and an outlet 10b , which also serves as a flange-like approach as in 10a is trained.

9 shows a hollow body blank 1 according to 1 whose bottom 3 an opening 3a having.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4103082 C2 [0002]
• - DE 19642824 A1 [0003]
• DE 102004013872 B4 [0004]
• - DE 10220429 B4 [0005]
• - DE 19944679 C [0006]

Claims (19)

Method for producing a hollow body ( 1 . 10 ) by applying such an inserted in a cavity hollow body blank with internal pressure at elevated temperature, wherein the hollow body blank is produced by at least one previous forming or forming process, wherein the hollow body blank has on its circumference at least one deviation in the circumferential length of at least 10%. Method according to claim 1, characterized in that the hollow body blank ( 1 . 10 ) has only one open end. Method according to claim 1 and 2, characterized in that the hollow body blank ( 1 ) has a bottom. Method according to one of the preceding claims, characterized in that the bottom has an opening. Method according to one of the preceding claims, characterized in that during the hot forming by internal pressure of the hollow body blank ( 1 ) is axially compressed to prevent unwanted reduction in wall thickness or to increase the wall thickness. Method according to one of the preceding claims, characterized in that during hot working is pulled by internal pressure of the hollow body blank to to achieve the desired wall thickness distribution. Method according to one of the preceding claims, characterized in that the hollow body ( 1 ) is bent prior to forming or while closing the cavity. Method according to one of the preceding claims, characterized in that the hollow body blank ( 1 ) is compressed at the closed end. Method according to claim 8, characterized in that the hollow body blank ( 1 ) is additionally deformed in the region of the closed end during the upsetting process. Method according to claim 1, characterized in that the hollow body blank ( 10 ) is formed spherical and is produced by at least one previous forming or forming process, wherein the blank has at least one opening. Method according to one of the preceding claims, characterized in that the hollow body blank ( 1 . 10 ) has a higher temperature in regions of higher degrees of deformation and / or wall thicknesses than in regions of lower degrees of deformation and / or wall thicknesses. Method according to one of the preceding claims, characterized in that the temperature for the deformation is lower than the melting temperature of the workpiece material by internal pressure. Method according to one of the preceding claims, characterized in that for applying the internal pressure air or an inert gas, e.g. As nitrogen or argon is used. Method according to one of the preceding claims, characterized in that the hollow body blank ( 1 ) is heated partially or completely. Method according to one of the preceding claims, characterized in that the cavity partially or is completely heated. Method according to one of the preceding claims, characterized in that the hollow body blank ( 1 . 10 ) and / or the cavity (forming engraving) has a heat profile with temperature differences, preferably between 2 ° and 100 ° C, to run the forming process in the desired Umformabfolge. Method according to one of the preceding claims, characterized in that the hollow body blank ( 1 . 10 ) is tempered out of the forming heat after forming. Method according to one of the preceding claims, characterized in that the hollow body blank ( 1 ) of several parts ( 1 . 20 ), which communicate with each other for the forming medium throughout. Method according to one of the preceding claims, characterized in that the hollow body blank ( 1 ) is sealed when upsetting or pulling outside the cavity.