DE2421830C3 - Abrasive bodies, in particular grinding disks and processes for their manufacture - Google Patents

Description

a) that the vitreous or ceramic binder

(5) is a material whose coefficient of thermal expansion is substantially equal to the coefficient of thermal expansion of the cubic boron nitride (3) contained in the abrasive phase,

b) that the binder versus the cubic boron nitride abrasive particles is essentially inert, and

c) that the layer which forms the phase boundary with respect to the binder is of a different type a chemically produced, thin boron oxide layer firmly adhering to the boron nitride particles

(6), the thickness of which is chosen so that a strong bond between the abrasive particles is promoted on the binder, while on the other hand the thickness of the boron oxide layer is below a strength which the structure and / or the physical properties of the cubic boron nitride.

2. Abrasive body according to claim 1, characterized in that that the abrasive phase, based on its total volume, consists of 10 to 100% by volume of abrasive particles of cubic boron nitride (3) and between 0 and 90% by volume of a second type of abrasive particle (4) exists.

3. Abrasive body according to claim 2, characterized in that the second type of abrasive material (4) has a coefficient of thermal expansion which is substantially equal to the coefficient of thermal expansion of cubic boron nitride (3).

4. Abrasive body according to claim 3, characterized in that the second type of abrasive particle (4) Silicon carbide is included.

5. Abrasive body according to one of claims 2 to 4, characterized in that based on the total volume the abrasive phase consists of 50 vol .-% of boron nitride abrasive particles (3) and 50% by volume of silicon carbide abrasive particles (4) are contained.

6. Abrasive body according to one of claims 2 or 3, characterized in that the abrasive phase as the second type of abrasive particle (4) Wolfranic carbide, titanium carbide, boron carbide, zirconium carbide, Tungsten boride, titanium boride, zirconium boride, tungsten nitride, titanium nitride and / or zirconium nitride contains.

7. A method for producing grinding bodies, in particular grinding wheels, according to one of the claims 1 to 6, one containing at least cubic boron nitride as abrasive particles Abrasive phase with a powdery vitreous or ceramic binder and mixed with an intermediate binder, placed in a mold and twisted into a molded body in this is, whereupon the shaped body is heated to fuse the vitreous or ceramic binder and to bond the abrasive grains of the abrasive phase in the abrasive article, characterized in that the heating is carried out in the presence of oxygen so that on the surface of the cubic boron nitride particles the boron is oxidized and a thin, firmly adhering one Boron oxide layer on the surface of each consisting of cubic boron nitride

ι »Abrasive particles is generated, with the thickness the boron oxide layer is adjusted so that there is a strong bond between the abrasive particles and the binder is promoted, while on the other hand the thickness of the boron oxide layer is below a thickness which corresponds to the structure and / or the physical properties of the cubic boron nitride would change, and that heating up to a temperature up to and including 982 ° C is carried out.

in 8. The method according to claim 7, characterized in that the abrasive particles consisting of cubic boron nitride are exposed to the oxidizing atmosphere before the production of the ceramic bond, and the boron oxide layer

2, is generated.

9. The method according to any one of claims 7 or 8, characterized in that the abrasive phase In addition to the cubic boron nitride, a second type of abrasive particle is admixed whose

κι coefficient of thermal expansion roughly equal to that Is the coefficient of thermal expansion of the cubic boron nitride, and that this abrasive phase with a Binder phase is mixed, which is opposite to the cubic boron nitride and the second abrasive

r, particle type is essentially inert.

10. The method according to claim 9, characterized in that the abrasive phase as the second Abrasive particle type silicon carbide, tungsten carbide, titanium carbide, boron carbide, zirconium carbide,

, in wool ramboride, titanium boride, zirconium boride, tungsten nitride, Titanium nitride and / or zirconium nitride is admixed.

11. The method according to any one of claims 7 to 10, characterized in that it is in the abrasive

4 · -, phase cubic boron nitride and optionally the second type of abrasive particles containing, pressed molded body is ^{fired in the presence of air as an oxidizing atmosphere at a temperature of up to and including 98O 0} C and that the

-, o burning time and the oxidation conditions like that be adjusted so that the formation of excessive amounts of boron oxide on the surface of the cubic Boron nitrides excluded and at the same time the formation of a thin, firmly adhering layer Boron oxide is guaranteed on the surface of the cubic boron nitride.

12. The method according to claim 11, characterized in that a firing temperature between 540 ⁰ C and 870 ⁰ C is maintained.

The invention relates to grinding bodies, in particular grinding wheels with a grinding section in the Abrasive phase at least cubic boron nitride as abrasive particles in a vitreous or ceramic Contains binder, the abrasive particles

have another type of layer on their surface, and a method for producing the same.

Since the development of cubic boron nitride, it has been known in the art to use this cubic boron nitride as an abrasive in grinding wheels. The hardness, strength and other properties of cubic boron nitride have made it a beneficial, albeit expensive, abrasive for use in grinding wheels. Despite its inexpensive nature, cubic boron nitride has proven extremely useful in grinding metals and other hard materials. For example , cubic boron nitride was used in grinding wheels with a metal bond, a bond in synthetic resin and a ceramic bond

When grinding metals and other hard materials, such as metal carbides, it is of particular importance that the grinding wheel have high strength, resistance to thermal shock, resistance to mechanical shock, low wear, good shape retention, free cutting properties (i.e. that it does not become charged with the ground material by sticking it to the grinding wheel), has good grinding efficiency and a good rate of metal removal. All of these properties are of particular importance in a grinding process such as the internal grinding of metal parts. In an internal grinding operation such as grinding a hole in a metal part, for example, it is of particular importance that the grinding wheel maintain its shape for long periods of time while exhibiting good strength, grinding efficiency and metal removal rate. Excessive and / or irregular wear of the grinding wheel leads to dimensional errors outside the tolerance limits and a disadvantageous change in the shape of the workpiece being ground. Similar problems and requirements arise in the contour grinding of metals in which a grinding wheel of a certain shape is used. As with internal grinding, contour grinding with a certain shape grinding wheel requires that the grinding wheel maintain its original shape for extended periods of time while exhibiting good grinding efficiency and a good metal deposition rate. The advantageous properties of grinding wheels listed above are of course of varying importance in all types of grinding processes. In some types of grinding operations, precise retention of the shape of the grinding wheel is not as important as in other types of grinding operations, but all of the grinding wheels must advantageously have those properties which enable them to be used economically with high efficiency.

The known grinding wheels containing the cubic boron nitride in a synthetic resin bond have proven unsatisfactory in practice under the tough conditions of high-precision grinding, kit, for example for internal grinding or contour grinding, because they easily lose their shape and have very poor resistance to high temperatures, which often below severe grinding conditions occur. The other type of known grinding wheels, which contain the cubic boron nitride in a metal bond, are extremely expensive and their use has been limited in practice to the grinding of extremely hard materials, such as components made of metal carbides for machining tools.

The high coefficient of expansion of the metal bond and the great affinity with regard to the loading of abrasive material have made the known grinding disks, which contain the cubic boron nitride in metal bond, unsuitable for use in grinding metal over long grinding times under severe conditions, although still Add to that the poor cutting speeds.

Another type of known grinding wheel that contains the cubic boron nitride in a vitrified bond, have enjoyed very limited practical success in metal grinding; especially if the grinding wheel is exposed to high mechanical and thermal shocks while at the same time changing its shape must adhere to longer periods of time under severe grinding conditions. A destruction of the bond with the the subsequent loss of the cubic boron nitride grinding oaks appear to be the main one Reason for the poor performance of grinding disks, which contain the cubic boron nitride in a vitrified bond, under grinding conditions with high thermal and mechanical shocks. In addition, it is known that those known in the prior art Grinding wheels that contain the cubic diamond in a ceramic bond for many types of metal show a low grinding efficiency and comparatively high grinding pressures or forces require to achieve an abrasive effect.

It is obvious that according to your state of the art A wide variety of binders for cubic boron nitride in grinding wheels have been used to reduce the losses on the comparatively expensive cubic boron nitride abrasive particles. the Coefficients of thermal expansion of the various binders compared to the abrasive particles used have not been exposed.

A grinding body of the type defined at the outset is known from DE-OS 20 56 873, which can contain diamonds or cubic boron nitride as an abrasive. In this known abrasive body, the abrasive particles are also bound by a ceramic matrix. As another type of layer on the surface of the abrasive particles, a metal coating is proposed here, which should amount to 10 to 60% of the total volume of abrasives plus coating. Copper, silver, nickel, cobalt, molybdenum and their alloys are mentioned as being suitable for the covering. It is obvious that such a Delag protects the cubic boron nitrides which are also used in this known grinding body against any contact with oxygen. A conventional glass dressing or a specially composed glass frit is proposed as the binding agent for this known grinding body, which is based on the factors p, according to "Hall"("The Properties of Glass", 2nd Edition, Morey, New York 1954,271,272) have a linear thermal expansion coefficient of 2.84 · 10 ~ ⁶ or 4.28 · 10 ~ ^6. These two glass associations should also contain 11.5 to 26.5% by volume of a metal powder in the known abrasive body, which results in the The coefficient of thermal expansion of the actually used glass bandage is significantly increased. This well-known grinding wheel

thus consists of abrasive particles. which by one Metal covering are protected, in a vitreous bond, whose coefficient of thermal expansion is different from that of the abrasive particles differs, with regard to the mixed properties of the glass bond nothing is said about the abrasive. As is common practice in this area, it has good thermal conductivity in the foreground.

The coating of diamond bodies with a metal, preferably nickel, is also in the CH-PS 4 58 972 mentioned, since nickel is a catalytic one with regard to the synthetic resins in question for embedding plays an important role. The CH-PS 4 58 972 itself relates to a process for the production of cutting or Schieil tools, in which the grains of a cutting or grinding material are embedded in a carrier are. Here one starts from the disadvantageous phenomena in metal embedding and tries to to avoid these disadvantages in that for embedding in a metallic carrier material the cutting or grinding media is a heat-resistant, hard and dense, non-metallic coating is applied. As materials for such, not Metallic layers should above all oxides, carbides, nitrides and borides come into consideration, which by Vacuum vapor deposition on the abrasive grains before they are embedded in the metallic carrier material can be applied. This is intended to make the Sehleifmitlkorncr secure against the harmful reactions between the abrasive and the embedding metal are protected, without affecting the binding of the grains. Alternatively, it is suggested to use the Abrasive grains first apply a thin metallic layer, which is what the non-metallic Layer of greater thickness adjoins. Another alternative provides. individual diamond grains with one three-layer coating, first titanium, then titanium oxide and finally another metallic one Titanium coating. The CH-PS 4 58 972 therefore describes a grinding body with completely enclosed and isolated abrasive particles, which particularly affect the reactivity of the Binder protected s.nd, wherein a metal is used as a binder, so that between the binder and the Abrasive phase there is a significant difference in the coefficient of thermal expansion.

From the US-PS35 76 6! 0, a grinding body, in particular a grinding wheel of the type defined at the outset, is also known, which cüuiäii cubic boron nitride as an abrasive. uc'i uicScP υέιν3ηηΐΐ: Π Grinding wheel SiHu lifting the preferred embodiment with cubic boron nitride in resin bond also provided glass-like or ceramic bonds. As a different type of layer on the surface of the abrasive particles, a borosilicate layer is proposed, which is not only intended to improve the strength of the bond in ceramic bonds, but is also provided as a barrier layer between the binder and the cubic boron nitride (column 3, lines 9 to 14 of U.S. PS). A special glass association is not mentioned here. In order to produce the borosilicate layer on the abrasive particles from cubic boron nitride, it is proposed here to first produce a boron oxide layer by oxidizing the surface of the cubic boron nitride particles. This is to clean the surface of most impurities and leave a thin layer of boron oxide.

As the next step in production, an organosilicon compound is applied in solution by which the main part of the boron oxide formed is removed again, after which the cubic boron nitride together > to be heated with the organosilicon compound to bring about a reaction of the organosilicon compound with the remaining boron oxide, which thereby in the essential to be completely converted into borosilicate. According to this well-known proposal, the

in this way, in situ generated borosilicate layer on the surface of the cubic boron nitride particles result in good bonding of the abrasive particles in the binder. at This known method is therefore the initially generated boron oxide on the surface of the cubic

r> boron nitride by reaction with the organosilicon compound removed again, since this boron oxide layer is only a reaction partner for the organosilicon compound was intended to produce the borosilicate.

jo From US-PS 35 25 600 finally a resin-bonded abrasive body is known in which the abrasive material consists of Al ₂ O ₃ . As with the other materials used as abrasive grains, the abrasive material here is isolated by coating, where-

2-, here the differences in the ion radius and the ion properties between the abrasive and the binding agent should be balanced. In detail the AhOt initially with a first inner coating made of a ceramic silicate material and then with a

jo provided a second coating made of a silicone resin, wherein a synthetic resin is used as a binder. From DE-OS 21 21 320 a method for Surface passivation of diamonds is known, which is used in heavy-duty tools, especially

Γι others in needles for scanning optical disks and Gramophone records, are to be used. According to this known method, the diamond is against hot and cold oxidation protected by a layer of siloxal on its surface, as it is

4 (i has found. That the surface passivation of Diamonds are disadvantageous due to the formation of a boron oxide film

'is. in that boron oxide is hygroscopic at room temperature. The one mentioned here as state of the art Method is to give the diamond low

4- Add amounts of boron so that this is protected from burning after formation of a boron oxide film. For this purpose, boron is added to the volume of the Diamonds or incorporated into its surface.

On a grinding tool, for example a grinding

5 (i disk with cubic boron nitride in ceramic bond, are the conditions set by the practice, that this is free-grinding (i.e., withstands loading), grinds at low grinding pressures, a good one Adhesion between the binder phase and the cubic boron nitride, thereby resulting in a rapid or premature breaking out of the cubic boron nitride grains with the consequence of rapid wear the grinding wheel of losing its shape to withstand mechanical and thermal shocks

bo is tough and has good grinding efficiency. The state of the art known grinding bodies (for example grinding wheels) with cubic boron nitride in ceramic Bond have shown in practice that each

b5 one or more of the properties mentioned above miss.

The invention is therefore based on the object of specifying a grinding wheel of the type defined above,

which is characterized by the fact that it is considerably easier to manufacture in comparison with the relevant state of the art and is also superior to the known grinding wheels with cubic boron nitride in a vitrified bond in terms of its grinding properties ; is.

To solve this problem, the following are given in the case of a grinding wheel of the type mentioned at the beginning Features suggested.

ok

a) that the vitreous or ceramic binder Is material whose coefficient of thermal expansion is essentially equal to the coefficient of thermal expansion of the cubic boron nitride contained in the abrasive phase, ü

b) that the binder versus the cubic boron nitride abrasive particles in the is essentially inert. and

c) that the different layer forming the phase interface with respect to the binder consists of a chemically produced, thin boron oxide layer firmly adhering to the boron nitride particles, the thickness of which is selected in this way. that a strong bond is conveyed between the Schleifmittelicilchen and binders, while on the other hand: is ~, thickness of the Boroxydschicht under a strength which would change the structure and / or the physical properties of cubic boron nitride.

il)

The grinding bodies according to the invention have excellent grinding properties when grinding metals with high resistance to thermal and mechanical shocks and good grinding efficiency with high dimensional stability. r>

Since, according to the invention, the cubic boron nitride is no longer used in the manufacture of such grinding bodies must be completely protected against oxidation by special measures, is also the Production much easier, with a κι at the same time such grinding wheels with the known grinding wheels with regard to its grinding properties is superior to cubic boron nitride in a ceramic bond.

Compared to the entire state of the art, a; achieved by the invention in particular the advantage that. Apart from the excellent grinding properties that result from the experiments described below with reference to special embodiments, such grinding bodies can be produced much more easily, since the other type of layer on the surface of the abrasive particles consisting of cubic boron nitride is only formed by a thin boron oxide layer . The formation of a thin boron oxide layer on the surface is one of the characteristic properties of cubic boron nitride, as already stated in US Pat. No. 3,576,610 (column 2, lines 53 to 55) Susceptibility to surface oxidation is either avoided or the boron oxide already formed is removed again of oxygen almost unavoidable is required.

In an advantageous development according to the invention, the abrasive phase is based on their total volume of 10 to 100% by volume of abrasive particles of cubic boron nitride and between 0 and 90 volume percent of a second type of abrasive particle. These Embodiment offers the advantage that while retaining the advantageous properties mentioned above Depending on the intended use, the comparatively expensive cubic boron nitride can be saved and can be reduced to a limit of 10% of the total volume of the abrasive phase.

Here, it is preferred that the second type of abrasive particle have a coefficient of thermal expansion which is substantially equal to the coefficient of thermal expansion of the cubic boron nitride.

Silicon carbide is preferably contained as the second type of abrasive particle.

A particularly inexpensive composition of an abrasive article according to the invention with excellent Properties can be created based on the total volume of the Abrasive Phase 50% by volume of abrasive particles composed of boron nitride and 50% by volume of silicon carbide existing abrasive particles are included.

In a modified embodiment, it is possible that the abrasive phase as the second Abrasive particle type tungsten carbide, titanium carbide, boron carbide, zirconium carbide, tungsten boride, titanium boride, Contains zirconium boride, tungsten nitride, titanium nitride and / or zirconium nitride.

The invention also relates to a method for producing abrasive bodies, in particular Grinding wheels of the type described above, in which at least cubic boron nitride is used as the abrasive particles containing abrasive phase with a powdery, vitreous or ceramic binder and an intermediate binder mixed, introduced into a mold and in this to form a molded body is pressed, whereupon the shaped body is heated to the vitreous or ceramic binder merge and bond the abrasive grains of the abrasive phase in the abrasive, which characterized in that the heating is carried out in the presence of oxygen, so that on the surface of the cubic boron nitride particles the boron is oxidized and a thin, firmly adhering one Boron oxide layer on the surface of each cubic boron nitride abrasive particle is generated, the thickness of the boron oxide layer is adjusted so that a strong bond between the Abrasive particles and the binder is promoted, while on the other hand the thickness of the boron oxide layer is below a strength which corresponds to the structure and / or physical properties of the cubic Boron nitride would change, and that heating up to a temperature up to and including 982 ° C is carried out.

Further refinements of this method are given in the subclaims.

The thin, firmly adhering boron oxide layer is chemically applied to the surface of the cubic Boron nitride abrasive particles may be formed in the practice of the invention prior to or are formed simultaneously with the manufacture of the grinding wheel and has a thickness such that the boron oxide layer is fully adhered to the cubic boron nitride abrasive particle and the physical Properties or structure of the cubic

Boron nitrides does not change. Furthermore, the thin, firmly adhering boron oxide layer has such a thickness that there is no loosely bound boron oxide which could easily become detached from this layer.

The cubic boron nitride used in practicing the invention is a cubic boron nitride crystalline structure, which has the cubic structure of zinc blende and a hardness that corresponds to the hardness of a Diamond is approximated. The boron nitride cubic crystalline structure is described in US Pat. No. 2,947,617, reference is hereby made to its disclosure content.

Through those used in the preceding and following expression "thermal expansion coefficient" is related to the volume Ausdeh-: - · called expansion coefficient. The definition and the formula for calculating the coefficient of thermal expansion based on the volume can be looked up in the usual specialist books on physics, chemistry, mechanical engineering and process engineering.

Although it is necessary to achieve the advantages associated with the abrasive article according to the present invention may be particularly useful as a second type of abrasive particle in the practice of the invention To use abrasive particles whose coefficient of thermal expansion is the same or almost the same is the same as the coefficient of thermal expansion of cubic boron nitride, can alternatively be used with large Effectively, as the second type of abrasive particles, an abrasive can be used, the particles of which have a Have a coefficient of thermal expansion that is somewhat, if not significantly, the coefficient of thermal expansion of the cubic boron nitride differs.

The abrasive made of cubic boron nitride and the second in combination with the Cubic boron nitride abrasives used in practicing the invention can be any Have mesh fineness, as they are in this field of technology for use in abrasive media in general is known.

Preferably, a continuous ceramic bond should be made without using extremely high temperatures or long firing times. The vitreous or ceramic bonds which are useful in the context of the present invention are vitreous or ceramic bonds which are formed in an oxidizing atmosphere at temperatures up to and including 1000 ^° C. (1800 ^° F). Those skilled in the art can readily make vitreous or ceramic bonds within the scope of the present invention which are useful in practicing the invention. The invention is not concerned with the composition of the various vitreous or ceramic binders useful in the invention.

As a grinding body according to the invention, grinding wheels of the general kind in this field come known shapes in question, such as the usual disc, plate and bowl shapes, as well other forms. In the various forms in question, abrasive bodies should also be used are mentioned and emphasized in which the abrasive particles or grains mainly when are not even arranged exclusively in a circumferential layer, this circumferential layer being the Carries out the grinding process.

The following describes the invention and its practice without any limitation explained in more detail using exemplary embodiments. In the following examples, the amounts given are given in parts by weight, if no other dimension is given.

example 1
composition

Cubic boron nitride
170/200 grit
Black silicon carbide
180 grit
binder
50 wt% solids
containing aqueous
Paraffin wax emulsion

37.88 wt. O / o
34.85 wt%

19.44 wt%
7.83 wt%

The binder used in the above composition had, given as oxides, 2-> essentially the following composition:

K ₂ O 1.0, Na ₂ O 1.0, Al ₂ O j 2.0,
B ₂ Oi 26.0 and SiO ₂ 70.0.
Cubic boron nitride: silicon carbide
κι (volume) = 50:50

Procedure

The cubic boron nitride and the silicon carbide were mixed and then the 50 wt .-%

r> Aqueous paraffin wax emulsion containing solids added and mixed into the mixture of cubic boron nitride and silicon carbide. The binder was then added and thoroughly mixed into the mixture and the resulting mixture

41) was then dried at 40 ⁰ C (105 ° F) in an oven to remove substantially all of the water from the mixture to. After removing from the oven, the dried mixture was crushed by passing it through a 45 mesh sieve. The required amount of the dried particulate mixture was then placed in a convenient mold, the fully assembled mold placed in a press, and the grinding wheel pressed to the required size and shape. The grinding wheel, after being removed from the mold, was then fired in an oxidizing atmosphere (e.g. air) by heating it at a rate of 150 ° C per hour (300 ° F per hour) to a temperature of 830 ° C (1525 ° C) F) was achieved, and by keeping the temperature of 830 ° C (held in 1525 ⁰ F) for three hours.

Example 2
composition

Cubic boron nitride
170/200 grit
Black silicon carbide
180 grit
binder

37.69 wt. O / o
34.68% by weight 0/0
19.83 wt. O / o

50 wt% solids
containing aqueous
Paraffin wax emulsion

7.80 wt%

The binder used in the above composition was expressed as oxides im essentially the following composition:

K ₂ O 1.0, Na ₂ O 1.0, Li ₂ O 0.5, ZnO 2.0, CaO 1.1, MgO 7.2,
Al ₂ Oi 8.7, B ₂ Oi 27.0, and SiO ₂ 51.5. Cubic boron nitride: silicon carbide (volume) = 50:50.

Procedure

The same procedure as in Example 1 was followed.

Example 3 Composition

Cubic boron nitride
170/200 grit
Black silicon carbide
180 grit
binder
50 wt% solids
containing aqueous
Paraffin wax emulsion

35.85 wt. O / o 36.93 wt.%

19.81% by weight 7.41% by weight

The binder used in the above formulation had the same composition as that in Example 2 binders used.

Cubic Boron Nitride: Silicon Carbide (volume) = 47.4: 52.6.

Procedure

The same procedure as in Example 1 was followed.

Example 4 Composition

Cubic Boron Nitride 36.26 wt%

170/200 grit

Black silicon carbide 33.36 wt%

180 grit

Binder 22.88% by weight

50% by weight solids 7.50% by weight

containing aqueous

Paraffin wax emulsion

Black silicon carbide

4 F grit

binder

50 wt% solids

containing aqueous

Paraffin wax solution

33.36 wt%

22.88% by weight 7.50% by weight

The binder used in the above formulation had the same composition as that in Example 2 binders used.

Cubic boron nitride: silicon carbide (volume) = 50:50.

Procedure

The same procedure as in Example 1 was followed.

Example 6
composition

Cubic boron nitride
140/170 grit
Black silicon carbide
170/200 grit
binder
Synthetic resin (phenolic resin)

36.83% by weight 37.94% by weight

20.35 wt% 4.88 wt%

The binder used in the above formulation had the same composition as that in Example 2 used binders.

Cubic boron nitride: silicon carbide (volume) = 50:50.

Procedure

The same procedure as in Example 1 was followed.

Example 5

Composition ^b '

Cubic Boron Nitride 36.26 wt%

170/200 grit

«Ι The binder used in the above formulation had the same composition as the binder used in Example 2.

Cubic boron nitride: silicon carbide π (volume) = 47.4: 52.6.

Procedure

The cubic boron nitride and silicon carbide were intimately mixed together and then the

Ao binder was added and also carefully mixed in, whereupon the synthetic resin 5417 BKP was added and also carefully mixed in. The required amount of the resulting homogeneous mixture was then poured into a suitable

■ The mold was entered, the fully assembled mold was placed in a hot press and the grinding wheel was at a mold temperature of 163 ^; C (325 ⁰ F) pressed. The mold was then ^{cooled to about 132 0} C (275 ° F) and the grinding wheel removed from the mold

• -.Μ withdrawn, whereupon the grinding wheel was then baked, they are heated (1525 ° F) by in an oxidizing atmosphere (ie, air) at a rate of 150 "C (300 ° F) per hour to a temperature of 830 C ^c and then the temperature of

>-> 83O ⁰ C (1525 ⁰ F) was held for three hours.

Example 7
composition

Cubic Boron Nitride 36.83 wt%

140/170 grit

Black silicon carbide 18.97 wt. ^{O /} o

170/200 grit

Black silicon carbide 18.97 wt%

4 F grit

Binder 20.35% by weight

Synthetic resin (phenolic resin) 4.88% by weight

The binder used in the above formulation! had the same composition as that in Example 2 use a binder.

Cubic boron nitride: silicon carbide (Volume) = 47.4: 52.6.

Procedure

The same procedure as in Example 6 was followed.

Example 8
composition

Cubic boron nitride
170/200 grit
Black silicon carbide
180 grit
binder
50 wt% solids
containing aqueous
Paraffin wax emulsion

59.25 wt. O / o 13.63 wt. O / o

19.47 wt% 7.65 wt%

The binder used in the above formulation had the same composition as that in Example 2 binders used.

Cubic boron nitride: silicon carbide (volume) = 80:20.

Procedure

The same procedure as in Example 1 was followed.

Example 9

composition

Cubic boron nitride 15.44 wt%

170/200 grit

Black silicon carbide 56.46 wt%

180 grit

Binder 20.17% by weight

50 wt% solids 7.93 wt%

containing aqueous

Paraffin wax emulsion

The binder used in the above formulation had the same composition as that in Example 2 used binders.

Cubic boron nitride: silicon carbide (volume) = 20:80.

Procedure

The same procedure as in Example 1 was followed.

Example 10 Composition

Cubic Boron Nitride 42.98 wt%

170/200 grit

Black silicon carbide
180 grit
binder
50 wt% solids
containing aqueous
Paraffin wax solution

30.05 wt. O / o

18.08 wt. O / o
8.89 wt.%

The binder used in the above formulation had the same composition as that in Bei game 2 binders used on.

Cubic boron nitride: silicon carbide
(Volume) = 56.8: 43.2.

Procedure

The same procedure as in Example 1 was followed.

Two embodiments of the invention are explained in more detail below with reference to the drawing.

It shows:

F i g. 1 shows a first embodiment of the grinding wheel according to the invention;

F i g. Fig. 2 shows a detail of the grinding wheel according to the invention on a considerably enlarged scale; and

F i g. 3 shows a second embodiment of the grinding wheel according to the invention.

In the drawings, FIG. 1 shows the grinding wheel according to the invention as a highly schematic Grinding wheel 1, which is illustrated in section and around the axis 2 during grinding is rotated. In the sectional view of FIG. 1 is the cubic boron nitride abrasive particles with 3 while the second abrasive particle is denoted by 4. To make a distinction are the cubic boron nitride particles as small crosses and the second type of abrasive particle by small circles illustrated. The abrasive particles 3 and 4 are in the ceramic or vitreous matrix 5 bound and in the embodiment of FIG. 1 over the total cross section of the grinding wheel 1 equally distributed.

In Fig. Figure 2 is a detail of the abrasive article according to the invention as it is in both the embodiment according to FIG. 1 as well as in the embodiment according to FIG. 3 is given. also very schematic and in substantial enlargement illustrated. As Fig .; shows, the abrasive particles 3 have cubic Boron nitride has a thin fes on its surfaces forming the phase interface with the binder 5 adhering layer 6 made of boron oxide.

In Fig. 3 is a second embodiment according to dei Invention also illustrated in the form of a grinding wheel 11, which differs from the one shown in FIG. 1 cause , Illustrative embodiment differs in that the from the abrasive particles 3 and Ί existing abrasive phase only provided in the grinding section forming the peripheral area are, so that the middle ι area of the grinding wheel 11 in terms of diameter exclusively from derr ceramic or vitreous binder 5 is made.

For this 1 Bhilt drawings

Claims (1)

Patent claims: 1. Abrasive bodies, especially grinding wheels, with a grinding section that is in the abrasive phase at least cubic boron nitride as abrasive particles in a vitreous or ceramic binder contain, wherein the abrasive particles have a different layer on the surface, characterized,