WO2017050755A1 - Method for the production of open-pore, ceramic-bound abrasive tools - Google Patents

Method for the production of open-pore, ceramic-bound abrasive tools Download PDF

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Publication number
WO2017050755A1
WO2017050755A1 PCT/EP2016/072292 EP2016072292W WO2017050755A1 WO 2017050755 A1 WO2017050755 A1 WO 2017050755A1 EP 2016072292 W EP2016072292 W EP 2016072292W WO 2017050755 A1 WO2017050755 A1 WO 2017050755A1
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Prior art keywords
pore
solid particles
abrasive
grinding
inorganic solid
Prior art date
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PCT/EP2016/072292
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German (de)
French (fr)
Inventor
Matthias Müller
Cristina DIDAVIDE
Original Assignee
Reishauer Ag
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Priority to DE102015115953 priority Critical
Priority to DE102015115953.8 priority
Application filed by Reishauer Ag filed Critical Reishauer Ag
Publication of WO2017050755A1 publication Critical patent/WO2017050755A1/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B24GRINDING; POLISHING
    • B24DTOOLS FOR GRINDING, BUFFING, OR SHARPENING
    • B24D3/00Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
    • B24D3/02Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
    • B24D3/04Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially inorganic
    • B24D3/14Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially inorganic ceramic, i.e. vitrified bondings
    • B24D3/18Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially inorganic ceramic, i.e. vitrified bondings for porous or cellular structure
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B24GRINDING; POLISHING
    • B24DTOOLS FOR GRINDING, BUFFING, OR SHARPENING
    • B24D18/00Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for
    • B24D18/0009Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for using moulds or presses

Abstract

The present invention relates to a method for producing open-pore, ceramic-bound abrasive tools having a pore fraction of between 20 and 80 % by volume, wherein a mixture of abrasive grains (31), binder (32) and pore forming agents is used, the pore forming agents comprising inorganic solid particles, in particular glass-like, crystalline and/or amorphous and/or semi-crystalline inorganic solid particles, with an average particle diameter of between 400 and 2000 μm.

Description

A process for producing open-pored, vitrified

Grinding Tools

TECHNICAL FIELD

The present invention relates to a method for producing open-pored, vitrified bonded abrasive tools and produced by this process grinding tools. STATE OF THE ART

Vitrified bonded abrasive tools are used in the art, in particular for surface machining. To prepare the grinding tools are grinding grains, for example those based on aluminum oxide, silicon carbide, diamond or CBN, is processed with a binder and optionally further additives such as fillers, grinding active substances, pore formers or temporary adhesives to a mixture, which is then required to mold is pressed. The resulting green body is then dried, optionally at appropriate temperatures of the added Porenbildnem freed and then fired ceramic.

Depending on the application, the abrasive tools a specific porosity with the pores to allow efficient use of cooling lubricants and absorption and removal of grinding chips, so that a high material removal with low thermal load of the workpiece is made possible. It is common to the mixture add artificial pore formers where they are substances that can be removed from the green body at low temperatures by evaporation, sublimation or burning. The most famous and still most widely used pore formers for vitrified bonded grinding tools is naphthalene, which can be removed by sublimation is already at about 80 ° C. Not only are the employees at the production sites but also local residents, a disadvantage of the use of naphthalene can be seen especially in the toxicity and especially in the intense and characteristic odor, so harassed by the exhaust air and exposed to health risks. Despite corresponding consuming and expensive protective measures a nuisance and danger to the environment can not be in the use of naphthalene completely

avoid. There have therefore been numerous attempts in the past,

replacing naphthalene by alternative pore former, but this failed often because these alternative materials are not or only insufficiently show the necessary for the production of ceramic-bonded grinding tools beneficial properties, such as low springback after shaping, good mixing performance, low tendency to swell in connection with the liquid

Anfeuchtsystemen, stable homogeneous distribution and low separation tendency in the finished composition, less exothermic and residue-free as possible

Burnout.

In EP 2540445 A1 a method for manufacturing a die bonded-abrasive tool is described, being used as the pore former dicarboxylic acids, and mixtures of dicarboxylic acids and hydrates of the dicarboxylic acids. A disadvantage of this process is that significant volumes of gas are released during the decomposition of the dicarboxylic acids, the mechanical

can cause damage to the green body, which through a time-consuming and

costly temperature control must be avoided. In addition, the dicarboxylic acids must also be granulated with relatively great expense with the addition of binders to be used without problems in the mix for the green body to which the production of grinding tools and expensive additionally complicated.

DE 196 28 820 A1 describes a process for preparing porous ceramic articles, wherein the ceramic compound in the solid state present, not soluble or swellable in bulk, non-deformable Acrylatgläser from polyacrylates or polymethacrylates which are klassierbar in a defined grain size, as burn-out pore formers are added. A disadvantage of the method described in the above document is that the

Combustion and decomposition products of Acrylatglases when burning in a narrow temperature interval are released, thereby to be used for cleaning exhaust gases afterburning will shortly extremely heavily loaded, what the risk of incomplete combustion and thus a

Pollution of the environment entails. In addition, polyacrylates burn not completely odorless, which has a negative effect especially when large amounts are burned abruptly. In addition, there is a danger that by briefly during burnout of the pore former

released large gas volumes forces are generated, whereby the

Grinding tools can be damaged. The German utility model DE 20 2010 015 210 U1 discloses the use of thermoplastic granules as novel pore formers. The signature can be taken from any details which thermoplastic material and how this thermoplastic granulate is to be used. However, it has been found that thermoplastic polymers are usually not completely odor-free process. In addition, the processing of such pore former requires very precise and often complex temperature control, thereby reducing the time and energy for the production of

Grinding wheels increased.

SUMMARY OF THE INVENTION

Thus, there remains a need for a pore-forming agent and a process for producing open-pored grinding tools which overcomes the disadvantages of the prior art.

The object is achieved by a process for the preparation of porous, vitrified bonded abrasive tools having a porosity between 20 and 80 vol.% by the use of a mixture containing abrasive grain, binder and pore-forming agent, wherein inorganic and pore former solid particles having an average particle diameter of between 200 and 2000 are used μηι. Suitable inorganic solid particles are inorganic

Compounds provided that melt upon heating in a temperature range between 200 and 1200 ° C, decompose or volatilize, thereby releasing little or no environmentally harmful emissions.

Here, for example percarbonates can be used as inorganic solid particles which decompose when heated.

However, particularly advantageous is the use of glassy, ​​crystalline and / or amorphous and / or semi-crystalline inorganic solid particles as a pore former, wherein the inorganic solid particles, melted when heated are volatilized or decomposed. When using refractory particles, the melt superimposed on the surface of the surrounding particles, in particular to the abrasive grains, wherein the points at which the inorganic

Solid particles were present, then pores are formed. Of course it is also possible for the inorganic solid particles in

use combination with other pore formers, with a preferred

Embodiment of the present invention provides the combination with thermoplastic polymers, wherein the two different pore formers advantageously supplement. Thus, the inorganic solid particles can be used as needed on its own or in addition to other pore formers. If a combination with other pore formers is used, the mixture advantageously comprises for the preparation of open-cell, ceramic bonded grinding tools at least one thermoplastic polymer as pore former further. By appropriate combinations can be ensured that the

include pore formers that required for the production of ceramic-bonded grinding tools positive properties such as low tendency to swell, homogeneous stable distribution and low resilience during pressing of the mass, low burden on the environment and the workplace, as well as reducing the cost through shortened firing time during the burn-out phase.

A particularly advantageous embodiment of the present invention provides that the pore formers are used in a defined, multimodal grain distribution such that specifically a defined pore space with different pore sizes may be generated in the grinding tool that is optimized for the particular grinding operation, the size of the pores is adapted to generated during the grinding process chips and coolant supplies. The pore formers are used μιτι each as granules with a grain fraction in a particle size range between 50 and 2000th

Preferably, the pore-forming agent have a multimodal particle size distribution with at least a coarse and a fine fraction and at least two

Grain size maxima in the range between 100 and 1000 pm, where the maximum of the finest fraction between 200 and 500 pm, and the maximum is the coarsest fraction between 500 and 1500 pm is located. When using a Porenbildnermischung with a bi-modal particle size distribution of the average grain size d is 5 o of the fine fraction is preferably between 100 and 400 pm and the average grain size d 5 o of the coarse fraction 350 to 1000 pm.

For Porenbildnermischung with a trimodal particle size distribution of the average grain size d 50 of the fine fraction is advantageously between 100 and 300 pm, the average grain size d 50 of the middle fraction between 250 and 450 pm and the average grain size d 50 of the coarse fraction between 400 and 1000 pm.

The present invention is also an abrasive tool with a porosity between 20 and 80 vol.%, Which is prepared using a mixture comprising inorganic solid particles, in particular glassy, ​​crystalline and / or amorphous and / or semi-crystalline solid particles, with a mean particle diameter between includes 400 and 2000 pm as pore formers.

The preparation of porous, ceramic-bonded grinding tools is normally carried out in that the means of bringing the grinding process

Abrasive grains are presented in a defined particle size and first mixed with a powdered binder. The mixture is then added a liquid temporary adhesive, is fixed with the aid of the ceramic binder which is added as a powder to the abrasive grain surface. As a temporary adhesive dextrin can be used for example. Subsequently, the

Pore ​​formers and other additives are added, the pore formers are, as well as the abrasive grains used in solid form in a defined particle size that is adapted to the size of the desired pores and is preferably approximately in the grain size range of the abrasive grains used. Also, the shape of the glassy, ​​crystalline and / or amorphous and / or semicrystalline inventively used as a pore former inorganic

Solid particles is advantageously matched to the shape of the abrasive grains. As other additives, in particular fillers, grinding aids and humectants are employed which serve, inter alia, to adjust the rheology of the mass so that the presses enables to form a homogeneous green body, or is facilitated.

Further advantageous embodiments of the inventive method consist in mixing the Porenbildnermischung prior to introduction in the mass with a temporary adhesive, thus the homogeneity of the abrasive tool can also be improved.

The process for producing the openly porous ceramic-bonded

Grinding tools begins with the preparation of a homogeneous mixture, the abrasive grains, binder and pore-forming agent, wherein as the pore former inorganic solids, especially vitreous, crystalline and / or amorphous and / or semi-crystalline inorganic solid particles having an average

Particle size between 200 and 2000 are used μητι. This mixture is introduced into a pressing mold and pressed to form a homogeneous green body. The green body is then dried and sintered in a temperature range below 1300 ° C.

When using Porenbildnermischungen having a multimodal distribution of the pore former results in grinding wheels, which also has a multimodal

have pore distribution, wherein the pores have an average diameter between 50 and 2000 μιη. It has been found that open-pored, ceramic-bonded grinding tools with a targeted multimodal pore distribution have advantages over the conventional grinding tools, since it is possible in this way to adapt the grinding tool optimal grinding conditions. The advantages are reflected in particular reflected in high

Removal rates combined with a cool finish.

The open-pore, vitrified bonded abrasive tools of the invention have a void content between 20 and 80 vol.% And preferably have a multimodal pore size distribution having at least two pore size maxima in the range 100-000 μιη on.

In an advantageous embodiment of the present invention has the

The abrasive tool is a bi-modal pore distribution the maximum of the fine pores of between 100 and 400 μιη and the maximum of the coarse pores 350-1000 μιη located.

A further advantageous embodiment provides abrasive tools having a multimodal pore distribution before, wherein the maximum of the finest pores between 100 and 300 μιτι, μηη the maximum of the average pore between 250 and 450 and the maximum of the coarsest pores between 400 and 1000 μηι located.

Preferably, the maxima of the pore size distribution apart by at least 100 μιη.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below with reference to the drawings, which are illustrative only and not

are limiting. In the drawings:

Fig. 1 shows an exemplary ceramic bonded abrasive tool;

Figure 2 is a highly schematic flow diagram of a method for manufacturing an open-pored ceramic-bonded grinding tool. and

Fig. 3 is a highly schematic diagram of the structure of an open-cell, ceramic-bonded grinding tool. DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 shows an example of a ceramic bonded abrasive tool in the form of a grinding worm for hard finish machining of gears. The invention is not limited to such grinding worm, but is applicable to any type of vitrified bonded abrasive tools.

In Fig. 2 is a simplified flow diagram for the manufacture of vitrified bonded grinding tool is illustrated. First, abrasive grains, a ceramic binder, a pore-forming agent and, optionally, glue and additives are mixed (step 21). Subsequently, the resulting mass is removed from the mixer, screened, placed in a mold and pressed with a hydraulic press (step 22). The green body thus obtained is optionally dried and fired in an oven (step 23).

The microstructure of a grinding tool manufactured in this way is strong in Fig. 3 in

schematically illustrated. The abrasive grains 31 are connected to bond posts 32 consisting of the ceramic binder. located (3 in the sectional view of Fig. not detectable) therebetween are a plurality of differently sized pores 33. The mixture of abrasive grains 31 bond bridges 32 and pores 33 forms a three-dimensional open network. The shape, size and

Size distribution of the pores 33 is highly dependent on the size of the pore former.

The pores artificially created with Porenbildnem have an irregular shape, which is derived from the geometry of the pore former and the adjacent abrasive grains, but can be approximately described as spherical. Their size can therefore be characterized by their average diameter.

Size specifications for pores always refer below to the

determined by electron microscopy average diameter. The abrasive grains also have an arbitrary, usually irregularly-polyhedral shape, but

is typically well approximated by the spherical description. The abrasive grain size may be described in the usual way by the abrasive grain diameter in the case of mesh sizes smaller than the clear

must be mesh size of the screen. Size specifications for abrasive grains always refer below to the detected by screening abrasive grain size. Similarly, size specifications and size distributions always refer to pore formers to identified by screening sizes. used pore formers

As part of the experimental examples were each glass particles (Example A),

Polyethylene (Comparative Example B) and naphthalene (Comparative Example C) as

Pore ​​formers used. The chosen particle size of the pore former is based on the average diameter of the abrasive grain D K and can therefrom with a typical pore former for each factor F x calculated. To ensure comparability of the examples, the factor Fx = 2.0 ± 1.0 was selected in all cases. This is summarized in Table 1 below.

Table 1: Used pore formers

Figure imgf000010_0001

Making the wheels

For all tested disks were the same as in Table 2

reproduced raw material components used, so that by the grinding test is possible a direct comparison of the individual pore-forming agent, wherein the amounts of the individual components in each case on the abrasive grain (100%) are obtained. table 2

Figure imgf000011_0001

The components were introduced into a drum mixer, and in 23

Mixing steps mixed for about 60 minutes, was to visually recognize a certain homogeneity and flowability of the mass. Subsequently, the mass was removed from the mixer and sieved. The sieved material was placed in a mold and pressed bar form-fitting manner with a hydraulic press at pressures of 90th The green body thus obtained had the dimensions (diameter x height x bore) 280 x 128 x 157 mm and were in an electric furnace up to a maximum temperature of 1200 ° C with a pore-forming agents of each

adapted burning software burned.

In the processing of the masses to firing of the discs no odor was observed in the patterns A and B, while the pattern C already at the mixing and pressing showed the characteristic of the naphthalene extremely strong and unpleasant odor of moth powder and tar. In the

Temperature treatment, initially reacts in the pore former, was the pattern A odorless, in the pattern B wax-like smell was a slight, but not unpleasant determine. The firing of the master disk C was accompanied by an extremely strong odor again.

Grinding Test The finished wheels had the characteristics described in Table 3 below. To test the slices in a first step, the

Grenzzeitspanungsvolumen or the equivalent limiting chip thickness h eq _th until the occurrence of grinding burn, and in a second step the

Grenzzeitspanungsvolumen or the equivalent limiting chip thickness h eq _ determined with respect to the exceeding of the permissible wear limit. Both values ​​are also recorded in the Table 3 below.

table 3

Figure imgf000012_0001

* Overheating limit = maximum achievable equivalent chip thickness h eq _th that, that is applicable without schieifbrandfrei thermomechanical surface layer damage.

** wear limit = maximum achievable equivalent chip thickness h eq _, which is applicable to maintain a predetermined wear criterion. The wheels were tested on a machine Reishauer RZ 260 using Kühiöl and a diamond dresser. As a workpiece, a test wheel was selected from the material 16MnCr5. There was a parallel comparative wheel as a reference (100%) also investigated to exclude possible influence of the batch of workpieces. When grinding burn test was systematic enlargement of the

Axial feed (Z-feed) in otherwise the same average values ​​and

Cutting conditions worked in three stages with three Egalisierhüben, a Schrupphub and a Schlichthub. In this way was in the 2nd stage for the

Schrupphub a uniform delivery are ensured. Of the

Overheating detection was carried out after the Schlichthub (3rd stage) with nital etching.

The wear test was carried out with a comparable technology, being carried in the 2nd stage at Schrupphub variable Z-feed and after the Schlichthub (3rd stage) of the wear was determined in the range of use of the grinding worm during Schrupphubes. When exceeding a

Form deviation of the profile fff> 6 μιη at a given grinding speed, the power limit is reached.

A high wear resistance of the Abrichthäufigkeit is reduced and increases the number of sandable in a dressing cycle workpieces and thus increase productivity. The encountered during processing of the compositions A, B conditions in relation to the odor development, and the mechanical, physical and chemical workability make it clear that the pore formers used are outstandingly suitable as a replacement for naphthalene. In addition, the invention sample A has the advantage that it is much easier to handle than the two control swatches, since the use of inorganic solid particles no complicated firing curve must be driven to the burning out

is considered entraining agent and prevents the making suddenly develop large volumes of gas that can cause damage to the grinding tool. Rather, the glass melts during the sintering process and attaches to the surface of the surrounding particles, while simultaneously at the points at which the glass particles were positioned pores are formed whose size depends on the size of the glass particles used. Here, supporting the

Glass melt not only on the surface of the surrounding particles to, but also penetrates into cracks and capillaries of the grinding tool, whereby the strength of the bond and the entire grinding tool is increased.

Thus, open-pore ceramic-bonded grinding tools works using glassy, ​​crystalline and / or amorphous and / or semi-crystalline inorganic solid particles can be produced much more rapidly as the pore former. The manufacturing cost can due to the lower energy consumption, per unit time, increased throughput and lower Committee in

Production significantly reduced. Another advantage is the

added environmental impact, especially when only inorganic

Solid particles are used as the pore former, that of when burning

Grinding tool not release any odorous or toxic gases.

Due to a targeted use of inorganic solid particles with different particle sizes grinding tools can be obtained with a homogeneous multimodal pore distribution that is optimized both for taking the chips and for flushing the coolant. At the same time, the hardness of the disc can be optimized in this way. The grinding tests have shown that grinding wheels of the invention both the grinding burn test and the wear test equal to perform well or better than the standard or conventional manufactured with naphthalene disc.

Claims

1. A process for producing open-pored, vitrified
Grinding tools with a pore proportion of between 20 and 80 vol.%, Wherein a mixture of abrasive grain, binder and pore-forming agents is used,
characterized, in that
the pore former inorganic solid particles having an average
include particle diameter between 200 and 2000 μιη.
2. The method of claim 1,
dadu rch, in that
exclusively inorganic solid particles are used as pore formers.
3. The method of claim 1,
dadu rch, in that
the inorganic solid particles together with other
Pore ​​formers, in particular thermoplastic polymers, can be used.
4. The method according to any one of claims 1 to 3,
characterized, in that
the inorganic solid particles glassy, ​​crystalline and / or amorphous and / or semicrystalline solid particles.
5. The method according to any one of claims 1 to 4,
characterized, in that
the pore former in a multi-modal distribution with at least a coarse and a fine fraction at least be present, the maximum of the finest fraction is situated between 200 and 500 μηη and the maximum of the coarsest fraction between 500 and 1500 [in located. A process for producing open-pored, vitrified
Abrasive tools according to one of claims 1 to 5, comprising the steps of:
- Preparation of a abrasive grains, binder and pore former
comprehensive homogeneous mixture,
- Entering the mixture into a mold,
- pressing the mixture to form a homogeneous green body,
- drying of the green body and
- sintering of the dried green body at a temperature below 1300 ° C.
The abrasive tool manufactured by using a method according to one of claims 1 to 6,
characterized, in that
the abrasive tool has a porosity of between 20 and 80 vol.%, wherein the pores have an average diameter of between 50 and
2000 μηη have.
Grinding tool according to claim 7,
characterized, in that
the grinding tool has a multimodal pore size distribution having at least two pore size maxima in the range between 100 and 1000 μιτι.
PCT/EP2016/072292 2015-09-22 2016-09-20 Method for the production of open-pore, ceramic-bound abrasive tools WO2017050755A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19628820A1 (en) 1996-07-17 1998-01-22 Zschimmer & Schwarz Gmbh & Co Production of ceramic porous products
US20030194947A1 (en) * 2002-04-11 2003-10-16 Eric Bright Porous abrasive articles with agglomerated abrasives and method for making the agglomerated abrasives
WO2008112899A2 (en) * 2007-03-14 2008-09-18 Saint-Gobain Abrasives, Inc. Bonded abrasive article and method of making
US20100154315A1 (en) * 2008-12-19 2010-06-24 Saint-Gobain Abrasives Inc. Bonded abrasive articles and methods of forming
DE202010015210U1 (en) 2010-11-06 2012-01-13 Peter Sälzer Pore ​​formers made of thermoplastic granules for the manufacture of ceramic grinding wheels
EP2540445A1 (en) 2011-06-29 2013-01-02 Hermes Schleifkörper GmbH Method of manufacturing a tool made from bound abrasive agents

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19628820A1 (en) 1996-07-17 1998-01-22 Zschimmer & Schwarz Gmbh & Co Production of ceramic porous products
US20030194947A1 (en) * 2002-04-11 2003-10-16 Eric Bright Porous abrasive articles with agglomerated abrasives and method for making the agglomerated abrasives
WO2008112899A2 (en) * 2007-03-14 2008-09-18 Saint-Gobain Abrasives, Inc. Bonded abrasive article and method of making
US20100154315A1 (en) * 2008-12-19 2010-06-24 Saint-Gobain Abrasives Inc. Bonded abrasive articles and methods of forming
DE202010015210U1 (en) 2010-11-06 2012-01-13 Peter Sälzer Pore ​​formers made of thermoplastic granules for the manufacture of ceramic grinding wheels
EP2540445A1 (en) 2011-06-29 2013-01-02 Hermes Schleifkörper GmbH Method of manufacturing a tool made from bound abrasive agents

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