EP2653265A1 - Abrasive agent and grinding tool - Google Patents

Abstract

Abrasive comprises a base body and abrasive particles applied to the surface of the base body, where the base body has a multicellular structure. Independent claims are also included for: (1) producing an abrasive, comprising providing the multicellular base bodies, coating the base body with binder, and coating the base body with abrasive particles; (2) a grinding tool comprising a substrate, a binder for abrasive, and an abrasive, where the substrate comprises a woven fabric, a knitted fabric or paper, film or nonwoven; and (3) a bonded grinding tool, comprising binder and abrasive.

Description

The invention relates to an abrasive with a base body and applied to the surface of the body abrasive grain. The invention further provides a method for producing such an abrasive article and a grinding tool, in which abrasive article according to the invention is used.

Abrasive materials on the underlay are subject to wear during use, which limits the service life. Decisive for this is the decreasing sharpness of the grinding tool. The cause is primarily a change in the cutting edge geometry, for example, caused by a breakage of abrasive grain, a breakage of abrasive grain from the binder or a wear of the abrasive grain in the form of a continuous Abtrag (plateau formation) and clogging of the abrasive coating by material deposits. When using the grinding tool, this wear manifests itself in decreasing material removal and increasing heat development, but also in a changing grinding pattern. By adjusting the process parameters of the wear can be compensated conditionally, so that in many applications a sufficiently consistent quality machining can be reached. Regardless, however, the tool life is reached when the blades are truncated. Especially in industrial machining processes The then required tool change means a significant reduction of the process efficiency. This applies in particular to the machining processes with which a defined surface structure and roughness is to be obtained.

There have been various attempts in the past to delay the dulling of the grinding tool, such. For example, by a tool structure that provides multiple layers of abrasive grain, which are used in staggered time.

This principle has been realized in different ways. Thus, for example, several layers of binder and abrasive grain have been applied to one another on top of one another. Disadvantage of this structure are the high surface bearing components with the associated heat development, which arise after the wear of the first grain layer. Also, the relatively flat surface structure has no chip spaces, so that a compression of abrasion and clogging of the tool surface is favored. This not only limits the service life of the tool, but also reduces the surface quality of the workpiece to surface defects.

Another method provides agglomerates consisting of several abrasive grains to be applied to the substrate. This method has the advantage, in comparison to the first-mentioned method, that in the course of the grinding process, new abrasive grain bound in the agglomerate continuously engages without a binder layer having to be removed over a large area. A similar approach is followed with defined structured grinding tools, where the abrasive grain is embedded in a bonding matrix.

It is also known ( DE OS 23 48 338 ) to sprinkle a hollow sphere on the substrate instead of an abrasive grain or an agglomerate, on whose outer surface there is a layer of abrasive grain fixed by means of a binder. While at the beginning of the operation initially the abrasive grain fixed on top of the hollow sphere comes into engagement, the sphere opens in the further course of the insert and is removed continuously. Along with this process, the abrasive grain bonded to the outer surface is successively used. An advantage of this tool design is not only in the vertical single-layer structure. The opening of the hollow ball causes in the course of use an approximately constant support share. As a consequence, grinding can be carried out with a hollow ball grinding tool over a long period of time with approximately constant removal rate, the same heat development and the same surface finish. The cutting geometry thus has over the entire life of the tool comparable features. The hollow sphere can be obtained according to this prior art by expanding vinyl chloride / ethylene copolymers. Also known is another method. Accordingly, polystyrene balls are coated with a binder-abrasive grain mixture, wherein the binder consists of a high temperature resistant, inorganic material. This makes it possible to heat the balls to temperatures of about 500 ° C and thus subject the polystyrene core of a pyrolysis with predominantly volatile reaction products. In a subsequent step, the binder must be cured at even higher temperatures. As a result, will a hollow grain ball obtained with a hard burned surface and bonded abrasive grain.

The invention is based on the object to provide an abrasive of the type mentioned, which can be easily manufactured and used in many ways.

The invention solves this problem in that the base body of the abrasive has a multi-cellular structure.

First, some terms used in the invention are explained.

An abrasive is used for machining material on the machined workpiece. The main body carries the abrasive grain, which causes the actual material removal.

According to the invention, the basic body has a multicellular structure. This means that the volume enclosed by it is interspersed with a multiplicity of walls or wall structures which subdivide this volume into smaller cavities (pores or cells). The individual cells may be partially completely closed, in part, they may be due to only partially closed wall structures in conjunction with adjacent cells.

The invention has recognized that such a basic body has a number of advantages. On the one hand, the cell structure causes a strength of the body, in particular during the processing of the coating with binder, but it also stabilizes the abrasive grain during the grinding process. especially when the body undergoes no significant additional stabilization through multiple coating and / or heat treatment. Due to the size and type of the pores, the microporous basic bodies have a comparatively low density, so that a continuous vertical removal with the aim of releasing as yet unconsumed abrasive grain is possible without difficulty. Accordingly, the carrying percentage and thus the heat development of the grinding tool increases only insignificantly after the opening of the body.

The invention has further recognized that the use of a multicellular basic body has a number of further advantages over the use of hollow spheres of the prior art ( DE OS 23 48 338 ) owns.

The hollow spheres of the prior art are opened at an early stage of the grinding process. Although it has been shown that the open hollow spheres do not increase the supporting portion of the tool surface and generate chip space, the chips can not be removed from the half-opened hollow body. Rather, these densify in the course of the grinding process in such a way that the supporting portion of the tool surface is increased and markings can arise with the quality of surface defects on the workpiece surface.

In addition, damage to the abrasive grain hollow body may occur in the production process, which leads to a filling of these hollow bodies with the Nachleimsystem used in the further course of production. In the grinding process, the thus filled hollow body can not open and causes Surface defects and or premature end of life.

The multicellular structure used according to the invention avoids these disadvantages. An open at the beginning of the grinding process body has due to its porous structure no space for receiving chips and abrasion.

The main body according to the invention is preferably made of a glass, in particular it may be a so-called foam glass body. Suitable glasses are, for example, soda lime silicate glasses. The preparation of such preferably substantially spherical base body is familiar to the expert and described for example in FIG DE 39 41 732 A1 . DE 195 22 460 A1 . DE 103 60 819 A1 . EP 484 643 A1 and EP 1 723 087 B1 , These references are also incorporated herein by reference. Suitable basic bodies made of glass with a multicellular structure are commercially available, for example, from Dennert Poraver GmbH under the trade name Poraver®.

The use of such glass body in the context of the invention has the further advantage that an environmentally friendly production of the abrasive is possible. The known in the prior art production of vinyl chloride / ethylene hollow spheres requires due to the processing of vinyl chloride a lot of effort in occupational and environmental protection. In the production of hollow spheres based on polystyrene the same applies (complex labor and environmental protection) in particular in the pyrolysis of the polystyrene core with the resulting volatile pyrolysis products.

The average size of the abrasive body is according to the invention preferably 0.1 to 2 mm, more preferably 0.2 to 1 mm, more preferably 0.3 to 0.5 mm. In particular, the invention makes it possible to provide abrasive bodies of small sizes (for example about 300 μm or 300-500 μm), which are required for the increasingly demanded abrasive tools with a coating thickness of the order of magnitude of 600 μm. Multicellular bodies are readily available in any size and are commercially available. By contrast, in the prior art (based on hollow spheres), the production of such small abrasive body is not readily possible. In the production of vinyl chloride / ethylene copolymer spheres, their size can not be controlled with sufficient accuracy by the process control. In the prior art, therefore, the obtained balls must be screened and only the part with a suitable size spectrum can be used. Furthermore, for reasons of stability, very small hollow spheres require a relatively thick binder layer for the application of abrasive grain, but this thick binder layer makes it difficult to break up in the course of the grinding process. On the other hand, the multicellular bodies of the present invention inherently have higher stability and, therefore, require only a correspondingly thinner binder layer even at a small size.

The pore size of the main body is preferably between 1 and 200 microns (determined on SEM-typefaces). The density of the main body is preferably in the range between 0.1 and 1 g / cm ³ . This density range allows for a sufficient strength, in particular in the production of the abrasive, when applied to a grinding tool and in the application and on the other hand in the course of the Grinding process a continuous removal of the porous body, so that continuously still unused abrasive grain comes into contact with the workpiece surface. At a density in this range, further increase the supporting content and thus the heat of the grinding tool after opening the abrasive body and in the course of its continuous removal only slightly.

The compressive strength of a single body (before its coating with abrasive grain) is preferably from 0.2 to 6 N. Body of smaller size, for example in the size range 0.25 to 0.5 mm, according to the invention, a compressive strength of 0.2 to 1.6 N and accordingly larger bodies, for example in the size range of 1 to 2 mm, can have a compressive strength of 1.1 to 6 N.

To determine the compressive strength of the individual body, a single body is placed on a steel plate. With the help of an attached stamp, the granules are compressed by means of a test press until they break. The required force is given as the compressive strength of the main body in [N]. The data given represents the mean value of 30 individual measurements.

For a sufficient stability, in particular in the further processing of base body to abrasive and abrasive to grinding tool, it can according to the invention to the compressive strength of the bed of bodies arrive. The compressive strength of such a bed of basic bodies according to the invention is preferably between 1 and 4 N / mm ² , more preferably 1.5 to 3 N / mm ² . Again, it may again be preferred if the compressive strength varies depending on the size of the body. For basic bodies in the range 0.1 to 0.3 mm, for example, a compressive strength of the bed of about 2.8 N / mm ^{2 may be} preferred, with a size range between 0.25 and 0.5 mm about 2.6 N / mm ² , at a size range of 0.5 to 1 mm about 2 N / mm ² and in a size range of 1 to 2 mm about 1.6 N / mm ² . The compressive strength of the bed is determined on the basis of DIN EN 1355-2. To determine the compressive strength of the bed, 1 l of the base body is filled into a steel cylinder and compacted. With the aid of an attached punch, the granules in this cylinder are compressed by 20 mm by means of a test press. The required force is given as the compressive strength of the bed in [N / mm2].

The abrasive grain on the surface of the base body may preferably have a grain size between P40 and P2500, preferably between P60 and P180 or P180 and P500 (FEPA standard). The stated values can be combined as desired to areas according to the invention. For example, corundum or silicon carbide can be used as the abrasive grain.

The shape of the abrasive is determined primarily by the shape of the multi-cellular body. This is based on the fact that the main body relative to the abrasive grain has a significantly larger volume and the abrasive grains are mounted on the circumference of the body and thereby can cause no significant change in the shape of the abrasive. The size ratio of the diameter (abrasive grain / body) is preferably less than 1: 6. In the determination according to the FEPA standard 43-D-1984, the average abrasive grain diameter dk50 is determined and in the size ratio to the diameters of the multicellular Basic body set. The diameters of the multicellular basic body are derived from the manufacturer's classification (Dennert Poraver GmbH).

1. a) Bereitstellen der multizellularen Grundkörper,
2. b) Beschichten des Grundkörpers mit Bindemittel,
3. c) Beschichten des Grundkörpers mit Schleifkorn.

The invention further provides a process for producing an abrasive article according to the invention, comprising the steps of:

1. a) providing the multicellular basic bodies,
2. b) coating the base body with binder,
3. c) coating the base body with abrasive grain.

As binders, suitable organic or inorganic binders of the prior art may be used.

After coating the base body with abrasive grain, it is possible to dry according to the invention. It is preferred if, in addition to the drying, to temperatures above 200 ° C, preferably to temperatures of 400 to 1000 ° C, more preferably 800 to 1000 ° C, heated. The binder is further solidified, in particular calcined, and reaches its maximum strength. The abrasive grain is firmly bound to the surface of the body, also solidified binder can contribute to the resistance of the finished abrasive body against pressure and shear loads.

As part of such a thermal treatment may optionally occur a thermally induced change in the multicellular structure in the interior of the body. It is possible by using basic bodies of one According to heat-resistant material to maintain the stability of the multicellular structure even at these high temperatures. This is useful for abrasives for applications with high grinding forces.

The invention further provides a grinding tool with a backing, a binder for abrasives and an abrasive according to the invention. The pad may comprise a woven, knitted or paper. In addition, a capping agent may be applied to the abrasive. The grinding tool may be formed, for example, as a grinding belt, sandpaper, or the like.

Fig. 1

eine mikroskopische Aufnahme eines Grundkörpers mit multizellularer Struktur;

Fig. 2

eine mikroskopische Aufnahme eines erfindungsgemäßen Schleifwerkzeugs nach einer Anwendungsdauer, die etwa der halben Standzeit entspricht;

Fig. 3 und 4

Schleifleistung (Abtrag) und Rauhtiefe erfindungsgemäßer Schleifwerkzeuge.

Embodiments of the invention will be described below. Show it:

Fig. 1

a micrograph of a body with multicellular structure;

Fig. 2

a micrograph of a grinding tool according to the invention after an application period which corresponds to about half the life;

3 and 4

Grinding performance (removal) and roughness depth of grinding tools according to the invention.

Examples 1-4 Production of abrasive bodies

The production of the abrasive body according to the invention is carried out by coating a multicellular body with binder and abrasive grain. The basic body used is glass body Poraver® from Dennert Poraver GmbH. Fig. 1 shows a micrograph of a such basic body with multicellular structure. The size ranges used are given in Tab. 1, which lists the constituents of the abrasive bodies. Table 1 example 1 Example 2 Example 3 Example 4 Basic body Poraver from Dennert [kg] 30 (d = 0.7-1.0 mm) 30 (d = 0.7-1.0 mm) 30 (d = 0.5-1.0 mm) 30 (d = 0.5-1.0 mm) Binder CM 025 [kg] 33 (3x11) * 33 (3x11) * 33 (3x11) * 33 (3x11) * Abrasive grain NK P400 [kg] 90 (3x30) * 90 (3x30) * Abrasive grain SiC P180 [kg] 90 (3x30) * 90 (3x30) * drying * 3x 20 min, 176 ° C 3x 20 min, 176 ° C 3x 20 min, 176 ° C 3x 20 min, 176 ° C hardening - - - 10 min, 920 ° C - - - 10 min, 920 ° C * a three-step coating process was chosen.

Tab. 2 describes the composition of organic and inorganic binders. The binder with the type designation CM 025 is used to apply abrasive grain to the base body. The GL 414 binder is used to apply abrasive to a backing to make a grinding tool (see examples below). The binder NL 592 serves as a covering binder for the grinding tool. Organic binders, eg. B. based on phenolic, epoxy, melamine or polyurethane resins can also be used instead of an inorganic binder for anchoring abrasive grain on the multicellular body. Tab. 2 type designation CM 025 GL 414 NL 592 Refractory binder FFB 32 [kg] 64, 4 Sound GWE [kg] 33.9 Emulan A [kg] 1.79 0.253 0.6 Phenolic resin SF [kg] 50.505 60.0 Omyacarb 4-BG [kg] 26.936 50.0 Calcium carbonate Type 442 [kg] 16.835 25.0 IRON OXYGEN BLACK 316 [kg] 4 Water [kg] 5,471 25.5 Internal type designation description source (1) Refractory binder FFB 32 Momoaluminiumphosphatlösung Chemetall GmbH (2) Sound GWE fire clay Adolf Gottfried Tonwerke GmbH (3) Emulan A. Nonionic emulsifier BASF SE (4) Phenol resin SF Watery Resol Momentive GmbH (5) Omyacarb 4-BG Ground chalk Omya GmbH (6) Calcium carbonate Type 442 Felled chalk Magnesia GmbH (7) IRON OXYGEN BLACK 316 Fe304-color pigment Bayer AG

For the preparation of the abrasive first base body and binder CM 025 are mixed together. A forced mixer "Zyklos" from the company Schwelm is used. As soon as the basic bodies are completely wetted, the abrasive grain is added and distributed homogeneously. The product is dried by means of a belt dryer at about 176 ° C. After drying, the product is classified by means of a vibrating wire. The top wire has a mesh size of 1600 μm, the bottom wire of 840 μm. The residue on the bottom wire is fed to this coating process two more times and dried in each case. Are obtained separated, scatterable and free-flowing abrasive balls. The curing by heating (Examples 2 and 4) takes place only once after the last coating process.

The abrasives differ by use different abrasive grain, namely normal corundum P400 (Examples 1 and 2) and silicon carbide (Examples 3 and 4). The abrasives of Examples 1 and 3 are merely dried, those of Examples 2 and 4 additionally solidified (fired) by heat treatment.

Examples 5 - 8 Production of abrasive belts

Table 3 below shows the constituents of abrasive belts according to the invention. Example 5 Example 6 Example 7 Example 8 carrier Paper (300 g / m ² ) Paper (300 g / m ² ) X2623 / 1 (310 g / m ² ) X2623 / 1 (310 g / m ² ) base binder GL 414 (85 g / m ² ) GL 414 (93 g / m ² ) GL 414 (160 g / m ² ) GL 414 (150 g / m ² ) abrasive Example 2 (122 g / m ² ) Example 1 (106 g / m ² ) Example 4 (220 g / m ² ) Example 3 (191 g / m ² ) deck binder NL 592 (245 g / m ² ) NL 592 (245 g / m ² ) NL 592 (360 g / m ² ) NL 592 (328 g / m ² )

Example 5

A paper support (width 400 mm, 300 g / m ² ) was coated with the GL 414 base binder and subsequently sprinkled with the abrasive of Example 2. The flow rate was 5 m / min and the basis weight of the base binder was 85 g / m ² , that of the abrasive 122 g / m ² .

After a residence time of 90 minutes in a loop drier at 90 ° C., the residual (covering binder) of the type NL 592 with a basis weight of 245 g / m ^{2 was} applied (throughput speed 5 m / min). After drying in a loop dryer (180 min, 130 ° C) and the Flexen (flex system from IM & T, transverse flexure with smooth rod, 1.5 bar, 15 m / min) were made with sanding belts of dimensions 150 mm x 2500 mm (straight film joint on impact, 70 °).

Example 6

The procedure was as in Example 5 with the following deviations:

Scattered is an abrasive of Example 1 at 106 g / m ² ; the base binder GL 414 is applied at 93 g / m ² and the top binder NL 592 at 245 g / m ² .

Example 7

The procedure was as in Example 5 with the following deviations:

The backing used is a cotton fabric X2623 / 1 (Holstein textile finishing, cotton twill weave with a thread count of 32.5 / 19.0 (warp / weft) threads / cm ² with a thread count of 50/36 (warp / weft) TEX, which is solidified with a finish of a skin glue / latex mixture), (310 g / m ² ). An abrasive of Example 4 at 220 g / m ² is scattered; The base binder GL 414 is applied at 160 g / m ² and the top binder NL 592 at 360 g / m ² .

Example 8

The procedure was as in Example 5 with the following deviations:

The backing used is a cotton fabric X2623 / 1 (310 g / m ² ). An abrasive of Example 3 is sprinkled with 191 g / m ² ; the base binder GL 414 is applied at 150 g / m ² and the top binder NL 592 at 328 g / m ² .

Example 9

With the abrasive belts of Examples 5 and 6 grinding tests are carried out under the following conditions: grinder: Surface grinding machine from Niederberger, type NCS-P Supporting disc: grooved, hardness 60 ° Shore power consumption: 2 A Belt speed: 26 m / s Workpiece feed: 10 m / min Workpiece: Flat steel, material number 1.4301 according to DIN 17007 (3 mm x 50 mm x 1000 mm)

Fig. 2 shows the surface of a grinding belt according to the invention after an application period which corresponds to approximately half the service life. Visible are open grain-covered bodies, in this case abrasives, with a porous internal structure, but no accumulation of abrasion.

FIG. 3 shows the result of the grinding tests. It can be seen that the removal rate is significantly higher for an inventive abrasive belt of Example 5, in which the abrasive was additionally heat-treated after drying. The thick printed lines show Example 5 and the thin Example 6.

Grinding tests are carried out under the same conditions with the abrasive belts of Examples 7 and 8, but titanium (material number 3.7164 according to DIN 17007, dimensions: 4 mm × 100 mm × 1000 mm) is used as the workpiece. FIG. 4 shows the result of the grinding tests. It can be seen that the removal rate is significantly higher for an inventive abrasive belt of Example 7, in which the abrasive was additionally heat-treated after drying. The thick printed lines show Example 7 and the thin lines show Example 8.

Claims (15)

Abrasive having a base body and abrasive grain applied to the surface of the base body, characterized in that the base body has a multi-cellular structure. Abrasive according to claim 1, characterized in that the base body is a foam glass body. Abrasive according to claim 1 or 2, characterized in that the base body is substantially spherical. Abrasive according to one of claims 1 to 3, characterized in that the average size of the abrasive body is 0.1 - 2 mm, preferably 0.2 - 1 mm, more preferably 0.3 - 0.5 mm. Abrasive according to one of claims 1 to 4, characterized in that the pore size of the base body is between 1 and 200 microns. Abrasive according to one of claims 1 to 5, characterized in that the density of the base body is between 0.3 and 1 g / cm ³ . Abrasive according to one of claims 1 to 6, characterized in that the compressive strength of a base body is 0.2 - 6 N. Abrasive according to one of claims 1 to 7, characterized in that the compressive strength of a Batch of the body 1 - 4 N / mm ² , preferably 1.5 - 3 N / mm ² . Abrasive according to one of claims 1 to 8, characterized in that abrasive grain has a grain size between P150 and P1000, preferably between P180 and P500. Abrasive according to one of claims 1 to 9, characterized in that abrasive grain comprises corundum or silicon carbide. Process for producing an abrasive according to one of Claims 1 to 10, characterized by the following steps: d) providing the multicellular basic bodies, e) coating the base body with binder, f) coating the base body with abrasive grain. A method according to claim 11, characterized in that the abrasive is heat treated, preferably at temperatures of 400-1000 ° C, preferably 800-1000 ° C. Abrasive tool comprising a backing, a binder for abrasives and an abrasive, wherein the backing preferably comprises a woven, knitted or paper, film or nonwoven, characterized in that it comprises abrasive according to one of claims 1 to 10. Bound abrasive tool, characterized in that it comprises binder and abrasive according to any one of claims 1 to 10. Grinding tool according to claim 13 or 14, characterized in that it additionally comprises a capping agent.

Images