TECHNICAL AREA

The present invention concerns a method for ma- nufacturing of an object of fibre metal, at which metal fibres are separated by cutting from e.g. a material, which can be constituted by a wire, in a cutting-machine showing one or several cutting edges. The invention also includes metal objects of different shape, which are ma- nufactured by the method according to the invention. BACKGROUND TECHNICS

It is already known to use metal fibres as re¬ inforcing elements in gaskets, e.g. gaskets for pipes. The german patent publication no 695 579 (from 1910) de- scribes a method for manufacturing of a gasket material containing metal fibres, which are manufactured by cut¬ ting, and which are bounded together with an organic bin¬ der as e.g. rubber. A gasket manufactured this way shows a good heat conducting ability, but is not useable at higher temperatures, e.g. at such temperatures prevailing in an exhaust system to a combustion engine, in particu¬ lar in connection to the exhaust openings of the engine. The british patent publication no 2 136 512 A describes a sealing material which is manufactured from thin metal wires, preferably of stainless steel, which in an initial position are knitted to a mesh. The mesh is convoluted into a cylinder preform around a mandrel, after which it will be compressed in a die into a desired form and with a density of 40 - 70 % of the density of the metal wire. The compressed object after that is dipped into a liquid containing metal oxides, at which this is penetrating the porous structure of the object. This metal oxide can be constituted by titanum dioxide and be suspended in water containing acrylic-resin and polyester-resin. The british patent publication no 2 136 890 A describes a sealing material which is manufactured from a mesh of thin metal wires. The sealing material is formed

as a plane ring-shaped gasket, along which inner diameter rings of refractory material are arranged in that way that the metal wire material at the compressing of the gasket is imparted a structure with a higher density in the area closed to the refractory rings. This sealing ma¬ terial is not provided with any further additional mate¬ rial for filling up the pores between the integral metal wires, but its gas tightness is defined of the compres¬ sion closed to the refractory rings. The american patent publication no 4 549 741 de¬ scribes another embodiment of a ring-shaped gasket, con¬ taining a layer of metal wires formed as a mesh, which has been compressed to a density of 35 to 45 % of the density of the actual metal wire. The gasket has been provided with a collar of sheet metal, which is preven¬ ting e.g. hot gases in an exhaust system to come in con¬ tact with the compressed layer of wires, which is too porous to prevent the gases to penetrate out of the sy¬ stem. DESCRIPTION OF THE INVENTION

The purpose with the present invention is to achieve a method for manufacturing of an object of fibre metal, at which fibres are separated from e.g. a mate¬ rial, which can be constituted by a wire, in a cutting machine showing one or several cutting edges, which gives a finished fiber metal object, which qualities surpasses the qualities of up to now known objects manufactured of fibre metal or of a mesh of thin metal wires. The purpose has been achived with a method, which is characterised in that a liquid containing oxide forming additives in solu¬ tion, emulsion or suspension is added to the wire before the cutting, or to the metal fibres close to the cutting before the temperature of the metal fibres is lowered below a critical oxidation temperature of the additives, at which the liquid is vaporized and the additives are oxidized upon the surface of the fibres. The fibres coa¬ ted whith the additives after that are compressed into a

on fore hand given shape, e.g. a semi-finished product, which is proposed to be worked further in subsequent ope¬ rations.

Preferably the liquid with the additives is ad- ded to the parts of the wire by help of a absorbating pad before the cutting. Further the, into a semi-finished product compressed and with additives coated metal fib¬ res, can be heated at least up to a temperature, at which at least a part of the metal fibres are sintering. There- by it is to prefer that the semi-finished product is hea¬ ted in the presens of a protective gas, which prevents oxidation of the metal fibres in the semi-finished pro¬ duct. This protective gas can be constituted of e.g. ar¬ gon, nitrogene or gases from a combustion in a combustion engine or the similar.

In an alternative embodiment of the invention the metal fibres in the semi-finished product are welded together in a heated condition by further compression. In this embodiment of the invention the fibre metal object shows a density, which principally conformes whith the density of the joining fibres. Metal fibres of a carbon steel whith a corbon content of 0,08 % gives a density of the object of around 7,8 kg/dm , i.e. corresponding to the density of the steel in the metal fibres. The fibre metal object according to the inven¬ tion is characterised in that a part of the metal fibres is constituted of a steel with a fibre thickness of 8-80 _Λ_m and that additives, which are constituted of compounds of oxygen and sulphur and/or phosphorus and/or fluorene, are added so that they together with oxides from the ele¬ ments Cu, Al, Cr, Mo, Mn and Ni, which in different com¬ bination can join in the metal fibres, are filling up the porousities between the metal fibres. Preferably the un¬ alloyed steel in the metal fibres has a carbon content of 0,08-0, 12 %.

By the present invention a method has been achieved which permits manufacturing of fibre metal

objects, which can show very varied physical characteris¬ tics. In a first example of an embodiment of such a fibre metal object the metal fibres consist of an unalloyed carbon steel whith a carbon content of 0,08-0,12 %. This gives a relative soft metal object, which is specially suitable for use e.g. as a sealing to be brought into an exhaust system in a combustion engine, e.g. an engine for a car. Through the softness of the material the sealing can be elastically compressed at its mounting, which makes the gasket to follow the thermical movements of the surrounding material in the exhaust system. By the addi¬ tives the gasket becomes complete tight at least after operation for a while when the gasket is heated to a tem¬ perature, which contributes a further oxidation of the additives and an alloying whith the present steel fibres.

In a second example, where the fibre metal ob¬ ject also consists of a sealing to be used in an exhaust system, but where the temperature, at the point where the sealing is proposed to be used, is lower than the desired oxidation temperature, a gasket has to bee heated to oxi¬ dation temperature before' mounting in the exhaust system. Thereby the gasket becomes the same characteristics as in the first example.

In a third example the metal fibres also contain other alloys, as chrome and nickel, mixed together with the unalloyd fibres of carbon steel. By this the fibre metal object, particularly after heating up to sintring temperature and welding of the metal fibres, can show a uniform alloy of the parcipitating metals, which grants the metal fibre object new characteristics. Such charac¬ teristics can consist in a higher hardness and abraison resistance and corrosion resistance. Such steel can be formed into objects of a desired shape before heat treat¬ ment, e.g. hardening in finished shape the same way as it is known to manufacture steel objects in a powder metal¬ lurgical way. E.g. it is also possible to make austenitic steel this way containing 18 % chrome and 8 % nickel.

It is also within the scope of the invention to let the metal fibres be constituted of a mixture of an unalloyed carbon steel and alloyed steel, if it is possi¬ ble to separate fibres from thees by cutting. It is also within the scope of the invention to mix up the steel fibres with fibres from other metals as well as non-me¬ tallic material.

In a fourth example cellulose fibres are mixed up together with metal fibres of an unalloyed carbon steel with a carbon content of 0,08 %. The fibre mixture is compressed to a semi-finished product, which is heated in a protective gas to a temperature at which the cellu¬ lose fibres carbonize. The fibre metal object this way becomes a more porouse structure but was will be achived in Llic examples mentioned above and uhowo a dcnaity of "around 6 kg/dm . The everage carbon content of the me¬ tal fibre object also is higher than in accompanying steel fibre. DESCRIPTION TO FIGURES The invention is described below in an embodi¬ ment according to the accompanying figures.

Figure 1 shows schematically, from one side a cutting-machine for manufactoring of metal fibres from a wire. Figure 2 shows the machine according to figure 1 from obove, at which some details has been left.

Figure 3 shows a track of metal fibre which is going to be convoluted on to a hollow cylinder, which is to be compressed. Figure 4 shows the hollow cylinder according to figure 3 brought into a compression die.

Figure 5 shows a fibre metal object after com¬ pressing of the hollow cylinder according to figure 4.

In a known cutting-machine 1 according to figure 1 and 2 a wire 2 is pulled from a wire store, not shown on the figures, several loopes around two mutual paralell rolls 3, which are placed on a distant from each other.

The wire 2 thereby constitute a track of paralell wires at the upper side of the cutting-machine 1 as well as at is lower side. A plurality of cutting edges 4 are arrang¬ ed in contact with the wire track on the lower side of the cutting-machine, from which metal fibres 5 are cutted at the movement of the wire. The cutting edges 4 are in¬ dicated dotted on figure 2. The metal fibres 5 after that are brought together in a track 5.1 which is advanced and compressed by help of a couple of rolls 6. The cutting edges 4 extend mainly in a right angle to the wire 2 and show a saw-toothed edge, which gives the separated metal fibres 5 a triangular cross section.

A liquid containing oxide forming additives in an emulsion is added to the string 2 by help of four pads 7, in contact with the track of wires 2, partly at each roll 3 and partly at the upper track of wires. The pads 7 are constituted by felted cloth and are connected to a supply pump 8 through pipes 9. The supply pump 8 is con¬ nected to a liquid container 10 by another pipe 11. The compressed track of metal fibres 5 is convo¬ luted on to a mandrel 12,. as shown on figure 3, to a hol¬ low cylinder 13, which is proposed to be compressed to a ring-shaped object. The ring-shaped object e.g. can con¬ stitute a gasket supposed to be arranged in an exhaust system to a conbustion engine, e.g. an engine to a car.

The outer diameter of mandrel 12 corresponds to the inner diameter of the hollow cylinder 13 and the object. The outer diameter of the hollow cylinder 13 corresponds to the outer diameter of the object, and its lenghts is de- fined of the width of the metal fibre track 2. The amount of metal fibres in the hollow cylinder 13 is correspon¬ ding by weight of the amount required to give the com¬ pressed object a desired density. Practically this will be achieved by compressing the metal fibre track 5.1 to a desired weight per lenght unit and convoluting a desired lenght of the track 5.1 on to the mandrel 12.

The hollow cylinder 13 of metal fibres 2 after

that is placed in a compression die 14 according to fi¬ gure 4, which is constituted by a die 15, in the center of which a post 16 is arranged in a central recess. A cylindrical casing 17 is arranged concentrically to the post 16 and fixed by a supporting ring on the die 15. The hollow cylinder 13 of metal fibres 5 is placed in the ring-shaped gap, which is constituted between the post 16 and the casing 17. A cylindrical force plug 18 is brought into the ring-shaped gap to compress the hollow cylinder 13 to a semi-finished product 19 according to figure 4. The shape of the semi-finished product 19 is defind of the shape of the form of the die 15 and the forcing plug 18.