EP0820364A1

EP0820364A1 - Grinding tool with a metal-synthetic resin binder and method of producing the same

Info

Publication number: EP0820364A1
Application number: EP97901222A
Authority: EP
Inventors: Markus Fischbacher
Original assignee: Tyrolit-Schleifmittelwerke Swarovski KG
Current assignee: Tyrolit-Schleifmittelwerke Swarovski KG
Priority date: 1996-02-14
Filing date: 1997-02-07
Publication date: 1998-01-28
Anticipated expiration: 2017-02-07
Also published as: EP0820364B1; BR9702077A; DE59708987D1; AT403671B; US6063148A; ATA25396A; WO1997029886A1

Abstract

The invention concerns a grinding tool for machining in particular brittle-hard materials. The bond in the grinder members of the tool is brought about by two components, one component consisting of synthetic resin, such as for example high-temperature thermoplastics or pressure sintered polymer, and a second component consisting of sintered metal with a low melting point. The processing temperature of the two components when they are jointly pressure sintered is the same. The essence of the invention lies in designing the two different binders such that they each have their own cohesive network and their mutual spatial interlacement in the grinding member forms an interpenetrating network. The invention further concerns a method of producing grinding members for grinder tools. The invention combines the advantage of greater binding forces of the metal bond with the advantage of higher elasticity of the synthetic resin bond in a grinding tool.

Description

Abrasive tool with a metal-synthetic resin binder and process for its manufacture

The invention relates to a grinding tool for machining in particular brittle hard materials such as natural and artificial stone, sintered hard metal, ceramic and the like, the grinding tool being constructed in one piece or preferably in several parts from a supporting part and an abrasive body and the grinding tool or whose grinding body is made of high-performance abrasive grain such as diamond, metallic binder, synthetic resin binder and optionally filler.

The invention further relates to a method for producing such a grinding wheel.

Grinding tools of the type mentioned at the outset can be used both in the wet and in the dry grinding process. The fields of application are the processing of natural and artificial stone, preferably with multi-part grinding tools in, for example, grinding and polishing lines for decorative stone materials, in the production and repair grinding of

Tools for machining metal, which consist wholly or partly of hardened tool steel, hard metal or ceramic.

The patent US 3650715 specifies a grinding wheel bond which contains dendritic metal as a filler in polyimide resin. The metal lies as

"clusters of dendritic metal particles", ie as clusters of dendrites. The cited patent suggests highly heat-resistant polyimide resin for use in highly stressed grinding tools, in particular those used in dry grinding. To dissipate the heat generated during grinding and to additionally support the abrasive grains in the synthetic resin bond, copper or silver is preferably added as a filler. As a result, grinding wheels are proposed in which the soft engagement of resin-bonded grinding bodies and the thermal conductivity and Stability of metal bonds in a tool can be aimed for.

A part of the resin-bonded diamond grinding wheels available on the market for high thermal stress or for high surface pressure on the grinding surface is based on the type of bond proposed in US 3650715.

The object of the invention is to provide an improved abrasive article which, using highly heat-resistant synthetic resins and metal alloys as bonding raw materials, enables an improvement in the grinding properties, an increase in the cutting performance and a more economical use of the expensive high-performance abrasive grain contained. Furthermore, it is an object of the invention to provide a method with which such grinding bodies can be produced.

This object is achieved according to the invention in that the grinding wheel is constructed using at least two different binding systems, namely a metallic binder and a synthetic resin binder, in that the different binders are sintered to form a coherent network, in that the different networks have an interwoven spatial network structure and that the abrasive grain and optionally the filler is located within at least one of the different binders and / or in the phase boundary between the different binders.

The two interwoven bond networks extend over the entire grinding wheel, whereas in the case of such tools according to the prior art, the metal component of the bond is present as an accumulation of filler particles in a synthetic resin matrix. It was known that when the sinterability of the metallic component and the synthetic resin component of the bond are adapted to one another, a reliable formation of two networks based on completely different substances can be achieved. The sinterability is characterized by the same sintering temperature during pressure sintering for both network raw materials. Between Abrasive grains and possibly filler particles are embedded in the webs or within the webs of each binding network. During the formation of the two networks during the pressure sintering process, abrasive grains can be enclosed both in the area of the metallic and in the area of the plastic binding part and for later contact with the

Workpiece to be integrated.

According to the invention, the presence of the metal bond portion in the form of an extensive metal mesh achieves a very good support effect in the bond structure, similar to the strengthening effect of reinforcing steel in

Concrete. The synthetic resin network embedded between them, on the other hand, is responsible for the resilience and vibration damping when the abrasive grains enter the brittle hard workpiece surface.

According to the invention, the sinterability of the metal bond component is adapted to that of the respective synthetic resin bond component of the bond. This is done by selecting the alloy composition of the metallic binding component with regard to the pressure softening point and liquid phase formation.

An embodiment of the invention is given if the plastic binder is a high-temperature thermoplastic and a correspondingly low-sintering alloy is selected for the metallic network, which alloy can preferably be bronze with a composition of 60 volume percent copper and 40 volume percent tin. The formation of the two interwoven networks according to the invention is achieved even at the maximum processing temperatures of the high-temperature thermoplastic of 300 ° C.

A further embodiment of the invention is provided if the network of synthetic resin binders is made up of a crosslink-curable pressure sinterpolymer from the group of the polyimides. In this embodiment of the invention, the corresponding metal binding network can also preferably be made of bronze. The associated pressure sintering temperature in this embodiment is 400 to 500 ° C. in order to build up a sintered metal-bound and / synthetic resin-bound spatial network.

US 3650715, for example, provides "melleable metal" in the form of filler accumulations which are embedded in the synthetic resin matrix. The effects according to the invention cannot be achieved by this arrangement. According to the invention, on the other hand, it is provided that the metal component of the binding acts as a supporting reinforcement braid, with the additional advantage that a bronze, especially a brittle bronze, has less tendency to clog the grinding wheel surface or the cutting edges of the grinding grains when it comes into contact with the workpiece this could easily occur with ductile metal.

In addition to the preferred exemplary embodiments, a number of variations of the described basic idea of the invention are possible depending on the raw materials available on the market, in particular depending on the synthetic resin properties.

A further embodiment of the idea of the invention is given if, in adaptation to the relatively low processing temperatures for the synthetic resin bonding network, low-sintering alloys are used, which can then mostly also be ductile or lubricating during grinding, as mentioned above. In this case you only need an inorganic filler like

Silicon carbide, aluminum oxide, heavy spar, quartz, graphite or the like are mixed into the powder for the networks in a preferred comfort fineness of less than 100 μm to promote the brittleness properties.

The invention has recognized that on the basis of the binders known per se, such as high-temperature resins and sintered metal alloys, significant improvements in the construction of abrasive bodies containing high-performance cutting material possible are. The achievable improvements are tied to the manufacturing process. Accordingly, the subject of the invention is also a method for producing an abrasive body with method steps according to the characterizing part of independent claim 8.

The characteristic process steps of the invention can be modified depending on the high-temperature binding resin used, without departing from the inventive concept. When using a high-temperature thermoplastic, a common sintering temperature of more than 300 ° C. is provided for the pressure sintering. When using a pressure sinter polymer from the group of polyimides, the common pressure sintering temperature for the formation of a network of metal bond and one of synthetic resin bond can be increased to approximately 500 ° C. It is essential here that the pressure sintering capacity of the metal binding component is already present at a temperature which is at least 10 ° C. below the respective degradation temperature of the synthetic resin binding component.

The invention makes use of the surprising finding that the joint pressing and unifying or the joint pressure sintering of two binding powders, each of which is completely different in nature, into one

Binding part in the grinding body leads. It is only important to bring the sintering temperature of the metallic binding component closer to the processing temperature of the synthetic resin binding component when using a high-temperature thermoplastic. When using thermosetting pressure sinter polymer, its special processing and curing temperature must also be the basis for the approach of the sintering temperature of the metallic binding component. The determining factor for the common sintering temperature is the processing temperature of the binding resin at which there is still a sufficient distance from the degradation temperature of the resin. This minimum distance was around 10 ° C.

In an embodiment of the manufacturing process according to the invention, the introduction of the sinterability of the metallic binding component to each ne of the synthetic resin binding component is brought about by a bronze powder modified with tin. It was found that additional tin powder with a grain size of 2 to 50 my makes it considerably easier to adapt the sintering conditions to the requirements of plastic bond processing.

If a high-temperature thermoplastic is used as the synthetic resin component for binding the grinding wheel, particularly low, common processing temperatures of 300 ° C. or higher are required in order to ensure the reliable formation of the metal bond network as well. In these cases it has been shown that, as is known per se, bismuth in the presence of copper and tin makes the sinterability capable of sintering by forming particularly low-melting structural components.

Two production examples of grinding wheels according to the invention are described below:

Example I

The grinding pad for one was used for dry grinding of milling cutters equipped with P20 carbide on a Strausack tool grinding machine

D11V9 cup made. A binding powder with 60 volume percent 70/30 copper-tin-bronze type 25 GR from Poudmet / France with an average grain size of 30 my and 40 volume percent high-temperature thermoplastic type "P84HT" from HPP (formerly Lenzing ) / Austria mixed with diamond abrasive grain type RVG-D from General Electric / USA with grain size US-mesh 120/140 in a Turbula mixer. The amount of diamond grain was measured in such a way that a concentration of C75 (3.3 carats per cm 3) was produced in the finished abrasive coating.

The powder resin contained 2% "75F" tin powder from Pometon /

France as a flux or to adjust the sintering ability of the different binding networks to be trained.

All starting materials were dried. The joint pressure sintering was carried out in the abrasive coating mold at 370 ° C. for 20 minutes in a nitrogen atmosphere at a pressure of 20,000 N cm.

The abrasive coating was shaped at 300 ° C and not subjected to post-curing.

Example II

° Bobble head segments were produced to equip station No. 9 of a 24-station Breton machine. Granite slabs of medium machinability were processed in a continuous process on this grinding and polishing line with wet grinding using water as a detergent.

A mixture of 8.5% by volume 5 tin powder of the "75F" type from Pometon / France with an average grain size of 30 μm, 51.5% by volume, 80/20 bronze of the "25GR" type from Fir ¬ ma Poudmet / F rich, with medium grain size of 50 my, 40 volume percent powder resin of the type "Vespel SP1A" from Du Pont / USA with medium grain size of 50 my and diamond abrasive grain of type "MDAS" from De 0 Beers / Germany with the US-Mesh 230/270 grain size, 20 minutes in one

Turbula mixer mixed. The raw materials were pre-dried and mixed without additives. The diamond content for the finished abrasive coating was intended to be C18 (= 0.79 carat / cm2).

5 This abrasive coating mixture was cold pressed in the press mold with 2000 N cm ^"2. The abrasive coating mixture was then sintered in the same press mold at 490 ° C. and a holding time of 20 minutes in a nitrogen atmosphere at 22,000 N cm ^{" 2} . After the pressure sintering, the abrasive coatings were depressurized under a nitrogen atmosphere and at temperatures of 0 300-400 ° C. for 16 hours.

With grinding tools according to the invention, the advantages of metal binding can be largely combined with the advantages of synthetic resin binding in one tool be realized. The higher binding force of the metallic network, together with the elasticity and vibration-damping effect of the synthetic resin bond, occurs simultaneously. The pressure load on abrasive coverings according to the invention can be increased. A good thermal compensation of the grinding temperature takes place through the coherent metallic bond network.

Claims

Grinding tool for processing particularly brittle hard materials such as natural and artificial stone, sintered hard metal, ceramic and the like, the grinding tool being constructed in one piece or preferably in several parts from a supporting part and an abrasive body and the grinding tool or its grinding body made of high-performance abrasive grain such as diamond, metallic binder , Synthetic resin binder and optionally filler is produced, characterized in that

that the metallic binder and the synthetic resin binder are each sintered into a coherent network,

that the metal bond network and the synthetic resin bond network penetrate one another to form an intertwined, coherent, double spatial network and

that the abrasive grain and optionally the filler is located within at least one of the different binders and / or in the phase boundary between the different binders.

Grinding tool according to claim 1, characterized in that the synthetic resin bond network consists of a plastic from the group of high-temperature thermoplastics such as polyamide imides, polyether ether ketones, polyarylsulfones, liquid crystal polymers, polyphenylene sulfides, silicone resins, polyimides and the metal bond network consists of one already at temperatures above of 300 ° C pressure sinterable metal or an alloy of at least two metals from the known group of binding metals such as silver, copper, aluminum, tin, zinc, cadmium, lead, antimony, bismuth.

3. Grinding tool according to claim 1, characterized in that the synthetic resin bond network made of a high-temperature-resistant, crosslinking (Curable) sintered polymer from the group of polyimides and the metal binding network made of a metal which is sinterable at temperatures above 400 ° C. from the known group of binding metals such as silver, copper, aluminum, tin, zinc or an alloy is formed from at least two of these metals.

4. Grinding tool according to one of claims 1 to 3, characterized in that the metal bond network consists of a bronze with 50 to 98 percent by weight copper and 50 to 2 percent by weight tin.

5. Grinding tool according to one of claims 1 to 3, characterized in that the metal bond network consists of brittle bronze with 38-64 weight percent copper and 36-62 weight percent tin.

Grinding tool according to one of claims 1 to 5, characterized in that the metal bond network contains an inorganic filler from the group of carbides, oxides or the like to increase the tendency to brittle fracture with a grain size of preferably at most 100 my.

7. Grinding tool according to one of claims 1 to 6, characterized in that the volume fraction of the metal bond network in the grinding wheel to the volume fraction of the synthetic resin bond network is in a range from 20:80 to 80:20, preferably 30:70.

A process for producing a high-performance abrasive grain and, if appropriate, filler in a bonded abrasive article of a grinding tool according to claim 1, characterized by the process steps: A) dry mixing at least one metallic binding powder and at least one synthetic resin binding powder with the same sintering ability and optionally a filler to form a binding powder;

B) cold-pressing the binding powder after addition of the abrasive grain at room temperature, preferably without a humectant, to give a green body;

C) joint pressure sintering of the metallic binder and the synthetic resin binder of the green body at a sintering temperature of at least 10 ° C. below the degradation temperature of the synthetic resin binder;

D) Sintering the synthetic resin binder and the metallic binder to form a coherent, interwoven spatial network, the abrasive grains and any filler particles present within at least one network, but preferably within both networks and / or in the area of the phase boundary between the two networks.

9. A method for producing an abrasive body according to claim 8, gekennzeich¬ net by pressure sintering together of a high temperature thermoplastic from the group of polyamideimides, polyether ether ketones, polyarylsulfones, Liquididcrystal polymers, polyphenylene sulfides, silicone resins, polyimides and an alloy of at least two metals from the Group of Cu, Sn, Zn, Ag, Pb, Al, Bi at temperatures from 300 ° C to 10 ° C below the degradation temperature of the synthetic resin used and at a pressure of 5000 to 30000 Newtons per square centimeter (N cm ^"2 ) .

10. The method for producing an abrasive body according to claim 8, gekennzeich¬ net by joint pressure sintering of a crosslinking (curable) pressure sintered polymer from the group of polyimides and an alloy at least two metals from the group of copper, tin, zinc, silver, aluminum at a temperature of 400 ° C to 10 ° C below the degradation temperature of the synthetic resin used and a pressure of 5000 to 30,000 Newtons per square centimeter (N cm ^"2 ).

11. The method for producing an abrasive body according to claim 10, marked by chemical curing of the polyimide network formed during the joint pressure sintering at temperatures up to 400 ° C. and for a period of up to 24 hours in the non-pressurized sintering die.

CHANGED REQUIREMENTS

Lbe ⁱ m International Bureau on 23 June 1997 (06/23/97) received initial claims 9 and 10 modified; all other claims unchanged (2 pages)]

(Continued from page 10, claim 8)

A) dry mixing of at least one metallic binding powder and at least one synthetic resin binding powder with the same sintering ability and optionally a filler to form a binding powder;

D) combining the synthetic resin binder and the metallic binder to form a coherent, interwoven spatial network, the grinding grains and the filler particles which may be present within at least one network, but preferably within both networks and / or in the area of the phase boundary between the two networks.

9. The method for producing an abrasive body according to claim 8, gekennzeich¬ net by common Drucksintem a high-temperature thermoplastic from the group of polyamide imides, polyether ether ketones, polyarylsulfones, liquid crystal polymers, polyphenylene sulfides, silicone resins, polyimides and an alloy of at least two metals from the Group of Cu, Sn, Zn, Ag, Pb, Al, Bi in a temperature range starting at 300 ° C and ending 10 ° C below the degradation temperature of the high-temperature thermoplastic used and at a pressure of 5000 to 30000 Newtons per square centimeter ( N cm ^"2 ). 10. The method for producing an abrasive article according to claim 8, gekennzeich¬ net by pressure sintering together a crosslinking (hardenable) pressure sintered polymer from the group of polyimides and an alloy of at least two metals from the group of copper, tin, zinc, silver, aluminum in a temperature range beginning at 400 ° C and ending 10 ° C below the degradation temperature of the pressure sinterpolymer used and at a pressure of 5000 to 30000 Newtons per square centimeter (N cm ^"2 ).

11. The method for producing an abrasive article according to claim 10, characterized by chemical curing of the polyimide network formed during the joint pressure sintering at temperatures up to 400 ° C. and for a period of up to 24 hours in the non-pressurized sintering mold.