DE2900007A1 - ABRASIVES AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Description

COHAUSZ &. FLORACK

PATENT LAW OFFICE SCHUMANNSTR. 97. D-4000 DÜSSELDORF

Telephone: (0211) 6833 46 Telex: 08586513 cop d

PATENT LAWYERS:
Dipl.-tng. W. COHAUSZ ■ Dipl.-Ing. R. KNAUF · Dr.-Ing., Dipl.-Wirtsch.-Ing. A. GERBER Dipl.-Ing. HB COHAUSZ

THE CARBORUNDUM COMPANY
Niagara Falls, New York 14302
(United States of America)

Abrasives
and its method of manufacture

The invention relates to an abrasive consisting of a rapidly cooled aluminum oxide and zirconium dioxide containing melt, and a process for its production.

Alumina has long been used as the preferred abrasive. It owes this position to its easy position Availability, its toughness and its hardness. Although harder substances, like diamond, are known and called Highly effective abrasives used have not been commercially competitive until recently Materials available as abrasives with overall properties superior to those of aluminum oxide.

Attempts have been made to combine alumina with other oxides such as zirconia to form an abrasive with better properties than alumina. These attempts met with some success, if at least 10% zirconia melted with alumina

32 346
U / -

909828 / 08B7

and the zirconia-alumina melt rapidly to the Was brought to freeze.

In US Pat. No. 3,156,545 it is described that an abrasive with a removal rate equal to that of aluminum oxide is comparable by rapidly cooling a mass of aluminum oxide, zirconium dioxide and a substantial amount, e.g. 15-60% by volume a glass former, such as silicon dioxide, to form a vitreous matrix in which the zirconium dioxide and Alumina particles are embedded, can be obtained. However, the obtained abrasive had an average no higher steel removal rate than aluminum oxide.

Other abrasives based on zirconium dioxide and aluminum oxide are described in later US patents and were constructed from high purity alumina and zirconia manufactured. The products known from these patents perform much better than Abrasives for aluminum oxide.

For example, U.S. Patent 3,181,939 describes high strength abrasives by fusing them together from 10 to 60% by weight of zirconia with ct-alumina and rapid cooling of the melt can be obtained. According to information in this patent specification the abrasives obtained be suitable for cleaning steel, for which a high strength is required. However, ot-aluminum oxide is used to make these abrasives of high purity - usually at least 99.8% by weight - necessary, as well as the purity of the zirconium dioxide should preferably be at least 99%.

According to U.S. Patents 3,891,408 and 3,893,826, abrasives are made with the best abrasives and abrasives Polishing properties obtained when the ratio of the

909828/0857

Zirconium dioxide is chosen for aluminum oxide so that When a melt cools down rapidly, a eutectic structure is formed from this mixture. In both patents stipulates that high purity alumina and zirconia should be used.

It has now been found that contrary to the US patents 3,181,939, 3,891,408, and 3,893,826 teach highly effective alumina-zirconia abrasives from easily available impure raw materials such as bauxite as a source of aluminum oxide and baddeleyite as a source of zirconia. Surprisingly, it was even found that the Alumina-zirconia abrasives made from impure raw materials in some cases, at least in one respect or another, that of pure alumina and zirconia are superior to abrasives obtained. It was also found that in contrast to the U.S. Patent 3,893,826 teaches abrasives should contain at least 0.8, better still at least 1.1% intentionally added silicon dioxide. The proportion of the However, silicon dioxide should not exceed about 3% by weight of the mass.

The abrasive according to the invention thus consists of a fused mixture of zirconium dioxide, Bauxite and, if necessary, silicon dioxide, which is from a substantially homogeneous molten state within has been solidified within a maximum of 3 minutes, better still within a maximum of 1 minute. The finished one Abrasive contains 25 to 50, better 35 to 50% by weight of zirconium dioxide, 49.2 to 74.2, better 49.2 to 64.2 % By weight of aluminum oxide and 0.8 to 2.5, better still 1.1 to 2.4% by weight, silicon dioxide.

The abrasive can be used for the production of coated abrasives as well as for the production of abrasives ,

-A-

909828/0857

especially bonded grinding wheels are used will.

As mentioned, the abrasive consists of particles of a rapidly cooled melt of bauxite and zirconium dioxide. Particle size can range from 6 to 900 grit as published by the U.S. Department of Commerce on April 12, 1965 published commercial standard CS 271-65. A grain size between 6 and 180 is advantageous and preferably between 14 and 80.

Bauxite and zirconia become essentially one homogeneous melt melted together. Bauxite and zirconium dioxide are used in such an amount that that the product after the melt has solidified 49.2 to 64.2% by weight of aluminum oxide, 35 to 50% by weight of zirconium dioxide and contains 0.8 to 2.5 weight percent silica. Cheaper is a product that is 50.5 to 58.9 Contains weight percent alumina, 40 to 45 weight percent zirconia, and 1.1 to 2.4 weight percent silica. Advantageous the product contains up to 2.5 wt .-%, better between 0.25 and 2 wt .-% titanium dioxide. Preferably the product contains between 0.25 and 1.6% by weight of titanium dioxide. The most favorable silicon dioxide content is 1.3 to 2.0 wt%.

The abrasive is made from uncleaned calcined or only partially cleaned bauxite, i.e. a Alumina obtained by melting and reducing calcined bauxite with metallic iron and coal has been obtained. When using unpurified calcined bauxite, the bauxite-zirconium dioxide melt Iron and carbon to remove the iron oxide and some of the silicon dioxide and Titanium dioxide can be added. "Bauxite" here means unpurified calcined bauxite, partially purified To understand bauxite or synthetic bauxite.

909828/0857

Bauxite is a beneficial source of alumina because it is easier to clean than making pure alumina and it usually contains enough silica and titania to introduce the required amounts of these materials into the abrasive. The bauxite used in the manufacture of abrasives generally contains 3 to 4.5% by weight of titanium dioxide, 3 to 8% by weight of silicon dioxide and 3 to 10% by weight of iron oxide (Fe ₂ O ₃ ).

Synthetically produced bauxite can also be used; H. a bauxite made by combining pure alumina with the desired impurities such as silica and titanium dioxide, and has such a composition that it can be used as a substitute for natural ones Bauxite can serve.

When using partially purified bauxite, the mixture is typically 0.1-0.5 before melting % By weight particulate charcoal added. If you use unpurified bauxite, more coal, about 2 to 5 Wt .-%, added together with about 5 to 10 wt .-% metallic iron. The amount of coal to be added and the iron to be added depends on the iron oxide, silicon dioxide and titanium dioxide content of the bauxite. the Any person skilled in the art can easily calculate the amounts of iron and coal required in each case. Any particulate Coal is suitable; petroleum coke is often used. During the smelting and reduction with coal in the presence of metallic iron, excess titanium, silicon and iron are deposited and removed from the Melt removed. After melting, the mixture contains when using unpurified or partially purified Bauxite usually has the desired proportions of silicon dioxide and titanium dioxide. Iron in the form of oxide or of an alloy can remain in the melt in small amounts - up to 1.5% by weight.

909828/0857

/ -Jf.

Should the bauxite not contain enough silica or titania to produce the required silica or titanium dioxide content, the melt can have the missing proportions of silicon dioxide or titanium dioxide can be added. .

Baddeleyite is best used as zirconium dioxide usually 95 to 99% by weight of zirconium dioxide, 0.3 to 3 Contains wt .-% silica, 0.5 to 2 wt .-% titanium dioxide and 0.5 to 2 wt .-%. Contains compared to bauxite Baddeleyite has lower proportions of silicon dioxide, titanium dioxide and iron oxide than unpurified bauxite. Under "zirconium dioxide" are here baddeleyite (zircon earth), the zirconium dioxide "bubbles" formed when zirconium minerals are melted and to understand purified zirconia.

The only contaminants in the finished abrasive which, in the presence of large amounts, can potentially have an adverse effect are alkali and alkaline earth metal oxides such as calcium oxide, magnesium oxide and sodium oxide. However, even these contaminants do not appear to have an adverse effect on the abrasive when their total content is less than 1% by weight. In the case of advantageous compositions of the abrasive, the total proportion is less than 0.5% by weight. In practice, the abrasives produced by melting bauxite and baddeleyite together generally contain less than 0.5% by weight of calcium oxide (CaO), magnesium oxide (MgO) and sodium oxide (Na ₂ O).

The melt from the mixture becomes within a maximum of 3 minutes, better within a maximum of 1 minute cooled from the time of the onset of solidification to complete solidification. The "time of the beginning Solidification "is the point in time at which part of the melt has been cooled down to a temperature below the solidification temperature permanently solidified. Which he-

- 7 -

909828/085?

2300007

The hardening temperature of a eutectic aluminum oxide-zirconium dioxide mixture, ie a mixture which contains about 42% by weight of zirconium dioxide and about 58% by weight of aluminum oxide, is about 1700 ^° C. and is about higher with higher proportions of aluminum oxide or zirconium dioxide.

To achieve the best results, the solidification time, i. H. the time to complete solidification, at most 1 minute, ideally not more than 20 seconds from the time when it begins to solidify.

Any suitable method can be used to rapidly cool the melt. For example, the melt can be poured onto a bed of steel balls 45 mm in diameter or smaller. Balls with a diameter of about 20 mm are advantageous. The melt can also be rapidly cooled by pouring it onto small chunks of about 7 mm diameter or smaller of an already solidified melt or by pouring it into a thin layer about 20 mm thick or less on a steel plate. It can be assumed that any cooling process in which the melt is on a heat-dissipating body with high thermal conductivity, ie of more than about 0.2 W / cm. ⁰ C (0.05 cal / cm-s. ° C) at about 1200 ⁰ C, from a distance of less than 20 mm, better less than 5 mm, is useful. Heat-dissipating bodies that have a lower thermal conductivity, such as chunks of an already solidified melt, can be used if the thickness of the poured-on melt is significantly smaller, i.e. less than 7 mm, better less than 3 mm, for the mentioned chunks of already solidified melt.

Suitable heat-dissipating materials not only have a high thermal conductivity, but also a sufficient one high melting point. Steel is therefore, and because of its low cost and easy procurement

f-n-

a particularly suitable heat dissipating material. Another technically useful heat dissipating material is for example cast iron. Examples of other good heat-dissipating substances, but not for reasons of cost Primarily to be considered are: chromium, nickel, zirconium and their alloys. A high specific Heat from the heat dissipating material is also desirable.

After solidification, the product obtained is comminuted to the desired grain size. This shredding will usually by crushing in a jaw crusher and subsequent fine crushing in a hammer or roller mill.

For the production of the abrasive is according to the procedure according to the invention a thoroughly mixed particle mixture of 35 to 50 wt .-% zirconium dioxide and 50 to 65% by weight of bauxite melted together. The grain size of the zirconium dioxide, bauxite and possibly other components is not particularly critical and can be of 50 mm down to 1 μπι range, provided only all components have approximately the same grain size. The most favorable grain size is between 0.075 and 10 mm. The mixture must contain so much silicon dioxide that the product after solidification is 0.8 to 2.5% by weight silicon dioxide contains. The silica in the mixture is usually supplied by the bauxite or baddeleyite, which also introduces the zirconia. The particle mixture is made by mixing bauxite and zirconium dioxide particles, the latter in the form of baddeleyite. The particles containing alumina and zirconia can also be mixed simultaneously with silica and titania containing particles, if one Addition of additional silica or titanium dioxide is desirable. Usually there is an admixture of additional silicon dioxide or titanium dioxide

909828/0857

290000?

required, but between 1.1 and 2.5% by weight of silicon dioxide and up to 2.5% by weight of the total weight can be used of bauxite and zirconium dioxide are added, provided that the silicon dioxide and titanium dioxide content in each case does not exceed 3% by weight, better in each case 2% by weight. Mixtures of bauxite with Up to 50% by weight of purified alumina in particulate form can also be used as the alumina source will.

After mixing, the particle mixture is melted, usually at a temperature above 1800 ^° C. After melting, the melt is cooled so that it solidifies completely within 3 minutes, better within 1 minute, of the start of solidification. The best time to set is less than 20 seconds. After cooling and solidifying, the product is crushed to make the abrasive. As mentioned, the comminution of the product is usually carried out by crushing it in a jaw crusher and then fine comminuting it in a hammer or roller mill.

It was found that the zirconia in the obtained abrasive was 10 to 25% in the tetragonal crystal form occurs and that the average length of the primary alumina and zirconia crystals, if any are available, is over 60 μΐη. Of the The diameter of the primary crystals is 30 to 60 μια. The distance between the zirconium dioxide particles in the eutectic is usually between 2.5 and 5.0-10 m (2500 and 5000 A).

The abrasive obtained by the process can be used to produce new types of abrasive on substrates and novel bonded abrasive media can be used. The performance of these products is not at all Applications of those known alumina-zirconium

- 10 -

909828/0857

290000? - ψ-

superior to dioxide abrasives, but these products have better properties for at least some applications. Above all, the bonded grinding tools include grinding wheels. For preparing such bonded abrasive body is, the particulate abrasives having a suitable synthetic resin, in particular phenolic resins t such as phenol-formaldehyde, resorcinol-aldehyde resins and cresol-aldehyde resins, or amine-aldehyde resins such as urea-aldehyde and melamine-formaldehyde Resins, bound. The bonded abrasive articles obtained have abrasive properties which are superior to those of alumina and at least equal to those of known abrasives made from essentially pure alumina and zirconia.

Abrasives on a flexible base made from the abrasive grain according to the invention have abrasive properties, the - at least for belt sanding - known abrasives on aluminum oxide backing or alumina-zirconia are superior. This higher performance is in view of the silica content of at least 0.8, better 1.1 wt .-%, surprisingly, since according to the information in the US patent 3 891 408 that from purified starting materials, in particular pure alumina, manufactured abrasives less than 1 wt%, most preferably less than 0.3 wt% silica should contain.

Any suitable backing such as paper, cotton fabric, Polyester cloth or fiber mat. The backing and binding agent should be very durable because It has surprisingly been found that the abrasive grain has a longer service life than the durability of the backing or the binder. The binder used to bind the abrasive grit to the backing is best

- 11 -

909828/0857

290QQQ7

Az-

a thermosetting synthetic resin, e.g. a phenol-formaldehyde synthetic resin .

Surprisingly, it was also found that the abrasive properties of bonded abrasive articles thereby Can be further improved that the abrasive grain according to the invention with up to 60 wt .-%, preferably with 5 to 60% by weight of another abrasive grain such as alumina or partially purified bauxite / is mixed.

The invention is explained in more detail using the examples below. Unless otherwise noted, all parts are and percentages are parts by weight or percentages by weight.

EXAMPLE 1

49.8% by weight of partially purified, particulate bauxite containing about 1.2% by weight of silicon dioxide and about 2.9% by weight of Contained titanium dioxide, 49.8% by weight "zirconium dioxide bubbles", which contained about 10.5% by weight of alumina, about 3.5% by weight of silicon dioxide and about 0.9% by weight of titanium dioxide, and about 0.4 wt% calcined petroleum coke were mixed in a Patterson-Kelly twin-V mixer for 10 minutes.

About 39 kg of the mixture was placed in a 150 kW AC electric oven equipped with two electrodes 43 cm in diameter and 36 cm in height melted. The melt was poured into a mold with steel balls of about 20 mm in diameter was filled. The mold had a diameter of about 500 mm and a height of about 150 mm.

The raw abrasive, i.e. H. the solidified melt was placed by hand on an inclined table on which the Balls could roll away from the solidified melt, separately.

- 12 -

909828/0857

The raw abrasive was crushed in an Allis Chalmers 457mm χ 254mm economy roll crusher. The raw product was passed through the roll crusher four times, and with each pass the nip became narrowed in a ratio between 2: 1 and 3: 1. After four passes, the abrasive grain was sieved off and the screen overflow is returned to the roll crusher.

The abrasive grain was then passed through a 900 rpm Pennsylvania hammer mill three times and thereafter classified.

The abrasive grain thus obtained contained about 1.4 wt .-% silicon dioxide, about 1.6 wt% titanium dioxide, about 43 wt% zirconia, and about 0.5 wt% impurities. Of the The remainder was alumina.

EXAMPLE 2

The procedure of Example 1 was repeated, but instead of the bauxite being essentially pure tabular Aluminum oxide and only 0.1% by weight of petroleum coke were used, as only very little silicon dioxide and iron were present. The abrasive grain obtained contained 0.24% by weight silica.

EXAMPLE 3

The procedure of Example 1 was repeated except that the following changes were made: There were a much larger furnace and a mold about 2.1 m in diameter and 2.1 m high were used. Was used unrefined calcined bauxite together with metallic iron and coal. Zirconium dioxide was not added, nor did the mold contain steel balls. An impact crushing was not made. As a result it was

- 13 -

909828/0857

- 13 -

obtained a brown aluminum oxide abrasive grain.

EXAMPLE 4

The procedure of Example 3 was repeated, but using the abrasive to increase its bulk density was subjected to impact crushing.

EXAMPLE 5

That obtained by following the procedures of Examples 1, 2 and 3 Abrasive grain was used to make abrasive belts used, which were then checked. The procedure was as follows:

By electrostatically coating a layer of conventional brown aluminum oxide grain of the grain size 36, produced according to the method of Example 3 and applied to the finished fabric by sprinkling, A double-coated coated abrasive was produced using a test grain of grain size 36.

The fabric chosen as the base consisted of a conventionally finished, heat-bonded polyester fabric in a 4: 1 satin weave with approximately 41 χ 16 threads / cm ² and a weight per unit area in the finished state of approximately 1.8 g / m ² .

To glue the abrasive grain, a binder was used which was made up of a commercially available one-step, liquid phenolic resin with a formaldehyde / phenol ratio of about 1: 1 and ground limestone with a medium Grain size between 17 and 25 μπι consisted. The mixing ratio of liquid phenolic resin and limestone was 1: 1.

- 14 -

909828/0857

The binder lubricant was ^{heated to about 32 °} C. and applied to the substrate with the aid of a customary roller coating process. The layer thickness of the binder was about 1.2 g / m ² .

With the aid of a conventional grinding belt production device, the aluminum oxide abrasive grain obtained by the method of Example 3 was then ^{applied in a layer thickness of about 1.8 g / m 2} by sprinkling. Immediately thereafter, the test grain was electrostatically applied to the damp web in a layer thickness of about 2.0 g.

The backing coated with abrasive was then ^{heated to 80 °} C. for one hour and to 93 ^° C. for two hours on a rack. After drying, a size with a layer thickness between 1.5 and 1.75 g / m ^{2 was} applied using a customary roller coating method. The size consisted of the 1: 1 phenolic resin-filler mixture already used as a binder, but instead of the limestone, unbuffered synthetic cryolite with an average grain size of 25 μm was used. The coated material was then dried and cured at 107 ⁰ C by heating for one hour at 66 ⁰ C, five hours of heating to 80 ⁰ C and 16stündiges heating.

After curing, the material was trimmed at the edges and bent at right angles to the edge for ease of use to facilitate the production of sanding belts. With the help of known methods, the material was made Sanding belts with the dimensions 50 mm χ 3350 mm are produced. These were carried out on a high-performance upright grinding belt testing machine tested using cold-rolled steel ASI 1018 as the material. At this Testing, the abrasive belt is placed in the usual way, and a workpiece with the dimensions 25 mm 25 mm 914 mm

- 15 -

909828/0857

was arranged so that the square area is just below the horizontal diameter of the pressure roller plant.

The grinding belt to be tested was guided over a pressure roller with a diameter of 356 mm ^{at a surface speed of I280 m 7 IrUn.} A feed force of 280 N was exerted on the workpiece. The amount of material removed after grinding for 30 seconds was determined and recorded by weighing the steel rod before and after grinding. The process was repeated until the material removal was 20 g or less per grinding interval. The total removal determined for the individual test tapes is compiled in Table 1.

Table 1 Tested abrasive grain Material removal

Example 1 (Bauxite-SrO ₂ ^ 383 ^ g

Example 2 (Al ₂ O ₃ -ZrO ₂ '1934 g

Example 3 (bauxite ^ 850 g

This test clearly shows the superior material removal performance of the abrasive grain according to the invention in belt grinding.

Example 6

ıcın mold cavity for producing a cup wheel with the dimensions I52 mm χ 51 mm χ 16 mm was filled with a mixture consisting of 83 wt .-% of the abrasive grain prepared according to the procedure of Example 4 with a particle size distribution of 50 wt -..% of .. grain size 14, 25 wt -% of the grain size 16 to 25 wt -% of the grain 2o; 2.9 wt -.% Of a liquid phenolic resin having a resin solids content of 72 to 76 weight -.%, A viscosity of 0.325 Pa.s to 0,4o5 F325 to 4O5 cP) and a gel time 12-38 minutes at 121 ° C; 4.55 wt -.% Overall of

909828/08 ¹ I.

230000? At-

powdered phenolic resin with a softening point of 80 to 90 ⁰ C, a curing time on a hot plate of 150 ⁰ C of 45 to 55 s, a flow path on an inclined plate at 125 ⁰ C of 26 to 34 mm and a hexamethylenetetramine content of 8, 6 to 9.2 wt%; 4.55% by weight of a powdered phenolic resin modified with polyvinyl butyral with a melting point of 105 to 108 ^° C., a flow path on an inclined plate at 125 ^° C. of 12 to 17 mm and a hexamethylenetetramine content of 6.1 to 7, 2 wt%; and 5.0% by weight of powdered fluorspar.

The mixture was compression molded with such a high pressure that a molded body with a density of 2.74 g / cm ^{3 was} obtained, which was then cured for 9 hours at a temperature of about 180 ^{° C.}

EXAMPLE 7

The procedure of Example 6 was repeated except that the abrasive of Example 4 was mixed in was replaced that of 50 wt .-% of the obtained by the method of Example 1 abrasive with one grain 14, 25 wt .-% of the abrasive obtained by the method of Example 1 with a grain size of 16 and 25 % By weight of the 20 grit abrasive obtained by the method of Example 1.

EXAMPLE 8

The procedure of Example 6 was repeated except that the abrasive of Example 4 was mixed in was replaced, 50 wt .-% of the abrasive obtained by the method of Example 1 with one grain 14, 25% by weight of the abrasive material of grit 16 and obtained by the method of Example 1 25 wt .-% from the according to the method of Example 4

- 17 -

909828 / 0857-

20 grit abrasives.

EXAMPLE 9

The grinding wheels made by the procedures of Examples 6, 7 and 8 were rated for performance through use on a Chicago pneumatic grinder. Model CP 3490, with a speed of 6000 rpm at an air pressure of 6.2 to 6.9 bar tested. The grinding machine was held by hand for 30 minutes in such a position that the grinding wheel could grind a cast steel block.

The grinding wheel and block were checked before and after the 30 minute test weighed for material removal and abrasive consumption ascertain. The results are shown in Table 2.

Table 2

TESTED
GRINDING WHEEL METAL REMOVAL
PER MINUTE WEIGHT RATIO
g METAL / g DISC Example 6 (Al ₂ O ₃ ) 16.3 g 8.7 Example 7
(Bauxite-ZrO ₂ ) 27.9 g 10.9 Example 8
(Bauxite-ZrO ₂ /
Al ₂ O ₃ mixture) 27.9 g 13.4

This example shows that the abrasive according to the invention had a higher performance on the grinding wheels tested Material removal rate as aluminum oxide results and, surprisingly, to increase the grinding wheel service life can be combined with aluminum oxide without impairing the grinding performance.

909828/0857

Claims (1)

2900Ü07 Claims 1 "Abrasives, consisting of particles of a rapidly cooled, A melt containing aluminum oxide and zirconium oxide, characterized in that it consists of 25 to 50% by weight of zirconium dioxide, 49.2 to 74.2% by weight of aluminum oxide and 0.8 to 2.5% by weight of silicon dioxide and the essentially homogeneous melt has been cooled within a maximum of 3 minutes from the start of solidification to complete solidification » 2 "Abrasive according to claim 1, characterized in that it 35 to 50 wt.% zirconium dioxide and 49, 2 to 64, 2 wt.% Contains aluminum oxide, 3 "Abrasive according to claim 2, characterized in that it Contains 40 to 45% by weight of zirconium dioxide. 4 ", abrasive according to one of claims 1 to 3, characterized in that it contains 1, 1 to 2, 5% by weight , preferably 1, 3 to 2, % by weight of silicon dioxide" 5. Abrasive according to one of claims 1 to 4, characterized in that it contains up to 2.5% by weight of titanium dioxide, Abrasive according to Claim 5, characterized in that it contains 0.25 to 2% by weight, preferably 0.25 to 1.6% by weight of titanium dioxide contains. 7. Abrasive according to one of claims 5 or Q _3, characterized in that at least part of the titanium dioxide comes from bauxite, 346 - 2 - 909828/0857 2900ÜÖ7 8 "Abrasive according to one of claims 1, 2 and 4, characterized characterized in that the aluminum oxide and at least part of the silicon dioxide comes from bauxite, A method for making an abrasive article according to any one of claims 1 to 8, characterized in that a thoroughly mixed mixture of particles from 35 to 50 wt _o - melted% bauxite, the melt within a maximum of 3 minutes from the start -% zirconia and 50 to 65 percent " the solidification is cooled to complete solidification and the product is comminuted. 10. The method according to claim 9, characterized in that the Melt has solidified within a maximum of one minute, preferably within 20 seconds, from the start of solidification. 11. The method according to claim 9, characterized in that the mixture of bauxite and zirconium dioxod before. Melting 1, 1 to 2.5% by weight of the mixture silicon dioxide is added, "Method according to one of claims 9 to 11, characterized in that that the mixture before melting 0.1 to 0.5% by weight particulate coal is admixed. 13. Use of the abrasive according to claim 1 for the production of a Abrasive on a flexible surface. 14. Use of the abrasive according to claim 1 for producing a bonded abrasive article. 15. Use of the abrasive according to claim 1 for producing a bonded grinding wheel. 909828/0857