EP1068916A1 - Method of manufacturing composite metal sandwich sheet by rolling - Google Patents

Abstract

Production of composite sheets made up of covering layers of sturdy material and a core layer between them comprises molding a flat closed hollow profile in the passage made of a strip material; filling the hollow mold with a metal powder mixture; and compacting the hollow profile and the powder mixture by rolling so that the powder mixture goes into the surface of the hollow profile on all sides.

Description

The invention relates to a method for producing composite sheets by rolling and after composite sheets produced by this method. The composite sheet consists of both sides Cover layers made of solid material and a powder metallurgy located between them manufactured core layer. Between the cover sheets and the core layer is a by rolling produced metallic composite, after which, if necessary, a shaping of the composite sheets produced in this way can be done in the usual way.

A process relating to a core layer made of a foamable material is in DE 44 26 627 C2. Here, the core layer is first compressed by the action of pressure and temperature a mixture of at least one metal powder and at least one produced gas-releasing propellant powder. The foamable, to be called semi-finished product Core layer is placed between cut cover sheets, after which a cold or Hot rolling or diffusion welding the package so formed is carried out around a to produce a metallic bond between the cover plates and the core layer. The subsequent one Shaping can be done by pressing, bending or deep drawing. If after that the so manufactured If the composite sheet is sufficiently heated by a thermal process, foaming takes place the core location.

The process described is cumbersome and for an economical production of Composite sheets in a continuous process are not suitable.

DE 41 01 630 C2 also describes a process for producing foamable metal bodies described by rolling, which consists in that a powder mixture of at least one gas-releasing blowing agent powder and at least one metal powder by suitable Devices, e.g. B. funnel, passed directly into the nip and there by the roller pressure is compacted. In this process, there are differences in sealing after the rolling process in the strip transverse to the rolling direction. Flow disturbances or stagnation of the powder in the funnel, which at any time can also lead to density fluctuations along the rolling direction. Based on these and still further disadvantages a method is described in DE 41 24 591 C1, in which the Powder mixture is filled into a predetermined hollow profile before being fed into the roll gap, whereby it is achieved that a uniform powder feed to the roll gap without Density fluctuations along the rolling direction takes place and further by a special shape of the A special density distribution in the rolled strip can be achieved. Hereby and due to a special design of the hollow profile, the otherwise frequently occurring tearing open Metal edges can be avoided.

The disadvantage of this method is that a prefabricated hollow profile must be present in that the powder mixture is filled. There is no description of how this filling is done, however, this can only be done in hollow sections that are closed on one side and are essentially vertical respectively. It is obvious that such hollow profiles only have a finite, limited length can and may have, otherwise a complete filling of hollow profiles, in particular those with narrow cross sections is not possible. An indication of difficulties with filling of the hollow profile results from the fact that the bulk density is increased by vibration or tapping should.

It thus follows that the method described in DE 41 24 591 C1 economic production of large quantities of composite sheets can not be achieved.

The invention is therefore based on the problem of a method for producing composite sheets to create the type mentioned above, which can be carried out in a run and in a simple manner Wise to produce composite sheets that are practically endless, not even in width are limited and have a uniform density distribution in the longitudinal and transverse directions.

Based on this problem, a method for producing composite sheets is developed cover layers on both sides made of solid material and a powder metallurgy located between them Manufacture proposed core position by rolling, in which a flat, closed Hollow profile is formed in the pass from strip material, the cavity of which is simultaneous with the Shaping the hollow profile is filled with a powder mixture containing metal, after which the hollow profile and the powder mixture are compacted by rolling so that the Powder mixture in itself and with the inner surface of the hollow profile on all sides a metallic composite comes in.

The invention is based on the consideration that the shaping of the hollow profile in the pass must be done simultaneously with the filling of the powder mixture if the production of Composite sheets with any width and length should be inexpensive to carry out. At the subsequent compacting of the powder mixture in the hollow profile by rolling prevents the powder mixture escapes at the side edges or is compacted unevenly.

The edges of a horizontally running belt can preferably be bent up by roll forming and the powder mixture is introduced into the groove thus formed. After that, the Powder mixture in the channel pre-compressed by rolling, the channel into a hollow profile closed and the metallic composite is produced by rolling out the closed hollow profile become.

The channel can be closed to form a hollow profile by bending the bent edges, if they are so wide that the entire powder layer is covered by the bending.

A second strip can be rolled onto these bent edges. In this case it can second tape also serve to cover the powder layer so that the bent edges do not need to cover the entire area of the powder layer.

Another way of closing the gutter to the hollow profile is to insert a second band insert the area between the bent edges and then the closed Roll out the hollow profile, preferably the bent edges on the second band are bent.

The same or different materials can be used for the belts and the powder material use. For example, aluminum strips or steel strips can be used for the cover layers are used while the core layer is made of aluminum or a powder metallurgy Aluminum alloy is manufactured.

When rolling out a composite sheet from outer steel sheets and a core layer from aluminum or an aluminum alloy, the thickness reduction essentially takes place in the core layer, while the cover layers change only insignificantly in their thickness.

If straps made of aluminum or an aluminum alloy are used and there is also Core layer made of aluminum or an aluminum alloy, can be a decrease in the thickness of the strips of at least 50%. The layer thickness of the powder mixture and the thickness of the strip or strips is preferably chosen so that the layer thicknesses of the rolled Bands and the powder mixture are approximately the same.

To ensure a perfect metallic bond between the cover tapes and the core layer can reach the surfaces of the strip or strips facing the powder layer activated, preferably roughened by brushing, the rolling preferably cold done, but can also be carried out warm.

The thickness of the strips can be between at least 0.5 mm and at most 8 mm, one Band thickness of 0.5 mm is suitable for steel bands, while a band thickness of 8 mm is suitable Hot strips made of aluminum or aluminum alloys can be used.

Starting from an aluminum hot band with a thickness of 8 mm, rolling out with a Thickness reduction of at least 50% carried out, a final thickness of the composite material can be of up to 12 mm.

By means of the powder layer between the cover layers of the composite sheets produced according to the invention special properties can be set. The mechanical properties of the Composite sheet is determined by the top layers, while the powder layer has additional properties brings about.

Because aluminum and aluminum alloys have a relatively low modulus of elasticity have, can increase the elastic modulus of the powder mixture Composite sheet cause, for example, that a particle or fiber reinforced Powder mixture of aluminum or an aluminum alloy between strips of aluminum or an aluminum alloy is arranged.

Furthermore, a suitable adjustment of the powder mixture can reduce the Cause coefficients of thermal expansion of the composite sheet and / or its thermal conductivity, if, for example, a high-silicon powder mixture of aluminum is used.

A powder mixture of at least one powder containing blowing agent and is particularly preferred a metal powder. This can be used to produce composite sheets which, after being rolled out, form a low overall thickness and approximately the same thickness of the cover layers and the powder layer have, but in which a foaming of the powder mixture takes place by heating, so that the Layer thickness increases many times over.

In this way, composite sheets made of solid cover sheets and a foamed one Make the core with a much greater thickness.

In order to get clean edges on the composite sheets, the hollow profiles after the Rolling are trimmed in one pass, d. H. the closed edges are cut off. Likewise, the rolled strips can be split to a desired width, this Splitting then preferably takes place in the area where the ends of the bent edges are are located.

Fig. 1

Eine Anlage zum Herstellen von Verbundblechen durch Walzen, wobei unterhalb bestimmter Bereiche das Band bzw. das Verbundblech im Querschnitt dargestellt ist und

Fig. 2

eine Querschnittsdarstellung bestimmter Bereiche gemäß einer anderen Ausführungsform.

The invention is described below with reference to an embodiment shown in the drawing. The drawing shows:

Fig. 1

A plant for the production of composite sheets by rolling, the strip or the composite sheet being shown in cross section below certain areas and

Fig. 2

a cross-sectional view of certain areas according to another embodiment.

A first strip 9 is drawn off a reel 1 and passed through a first roll-forming installation 2.

Here the edges 10 are bent up on both sides, whereby a groove 11 is formed. This A powder mixture 12 is fed in a metered manner by means of a feed device 3, so that a certain layer thickness is reached. The rollers are precompressed by means of a pair of rollers 4 Powder mixture 12. Then a second band 13 is drawn off a reel 5 and into the area between the bent edges 10 led to the powder mixture 12. The above regions of the bent edges 10 protruding from the second band 13 are in a second Roll forming system 6 bent onto the second belt 13, and form bent edge regions 14. The hollow profile thus formed in the pass and filled with the powder mixture 12 passes through now a cold rolling plant 7, where the powder mixture is compacted by rolling so that it a metallic bond forms in itself and with the strip material.

If the strip material and the powder material are of the same material, e.g. B. Aluminum or an aluminum alloy can not only be in the cold rolling mill 7 Compacting the powder mixture to achieve a practically non-porous state, but also the strip material can be reduced in thickness to at least 50%. That way starting from an aluminum hot band with a thickness of 8 mm, rolling out with a Carry out a reduction in thickness of at least 50%, which leads to a final thickness of the composite sheet including the powder metallurgy intermediate layer of 10 to 12 mm leads. This Composite sheet can in turn be wound onto a reel 8 and then processed further.

The edges of the composite sheet can before winding on the reel 8 in not shown Trimmed way, but this trimming can also be carried out in another system.

The processing of the composite sheet can in the usual way by stamping, pressing and the like. The intermediate layer consists of a powder mixture of at least one powder containing a blowing agent and a metal powder can be formed after shaping the composite sheet or foaming of the intermediate layer beforehand by appropriate heating.

From Fig. 2 it can be seen that the first belt 9 in the first roll forming system 2 in the Forms way that the side edges 10 set up vertically and the end regions 15th are bent again by 90 °. The powder mixture 12 is introduced into this channel 11, after which the second band 13 is applied and the rolling out in the manner already described he follows.

If the bent edge areas are so wide that they are in the longitudinal median plane touch, it may be necessary to dispense with the application of a second tape.

The system for carrying out the method according to the invention is shown in the Embodiment shown as a horizontal system. However, it is also possible sloping or vertical system. In all cases it is possible to use the composite sheet with great threadiness in the throughput, without the length and width of the belt to be limited.

Claims (17)

A process for the production of composite sheets from double-sided cover layers made of solid material and a core layer between them, produced by powder metallurgy by rolling, in which a flat, closed hollow profile is formed in the pass from band material, the cavity of which is simultaneously filled with a metal-containing powder mixture when the hollow profile is formed, after which the hollow profile and the powder mixture are compacted by rolling so that the powder mixture forms a metallic bond on all sides in itself and with the inner surface of the hollow profile. The method of claim 1, wherein the edges of a horizontally running belt Roll forms are bent and the powder mixture is introduced into the groove formed in this way becomes. A method according to claim 2, wherein the powder mixture in the trough is by rolling pre-compressed, the channel closed to form a hollow profile and the metallic bond through Rolling out the closed hollow profile can be produced. A method according to claim 3, wherein the closing of the channel to the hollow profile by bending the bent edges are done. The method of claim 3, wherein the closing of the channel to the hollow profile by insertion a second band in the area between the bent edges. The method of claims 4 and 5, wherein the bent edges on the second band be bent. The method of claim 2 or 3, wherein the bent edges after the introduction of the Powder mixture bent into the channel and the channel to the hollow profile by rolling one second volume can be closed. Method according to one of claims 1 to 7, wherein the layer thickness of the powder mixture and the thickness of the tape or tapes are chosen so that the layer thicknesses of rolled strips and the powder mixture are approximately the same. Method according to one of claims 1 to 8, wherein the strips made of aluminum or one Aluminum alloy are used and the rolling out with a decrease in thickness Band or tapes of at least 50% is carried out. Method according to one of claims 1 to 9, in which those facing the powder layer Surfaces of the tape or tapes activated, preferably roughened by brushing are. Method according to one of claims 1 to 10, wherein the thickness of the strips between is at least 0.5 mm and at most 8 mm. The method of claim 11, wherein starting from an aluminum hot strip with a Thickness of up to 8 mm rolling to a final thickness of the composite sheet of up to 12 mm is carried out. Composite sheet produced by the method according to one of claims 1 to 12, in which the Powder mixture causes an increase in the modulus of elasticity. Composite sheet according to claim 13 with strips made of aluminum or an aluminum alloy and a particle or fiber reinforced powder mixture made of aluminum or Aluminum alloy. Composite sheet produced by the method according to one of claims 1 to 12, in which the Powder mixture a reduction in the coefficient of thermal expansion and / or Thermal conductivity causes. Composite sheet according to claim 15, with strips made of aluminum or an aluminum alloy and a high-silicon powder mixture. Composite sheet produced by the method according to one of claims 1 to 10, in which the Powder mixture of at least one powder containing blowing agent and a metal powder consists.

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