DD240515B1 - ABRASIVE AGENTS FOR THE PRODUCTION OF GRINDING BODIES - Google Patents

Description

original Korundkornes and for the grain size> 0.5 mm on average under - to --- half

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Diameter of the original corundum grain and the degree of division of this secondary corundum grain over the original grain composition of the abrasive body for the grain size range below 0.2 mm> 90%, for the grain size range 0.2mm-0.4mm> 75% and for the grain size range over 0.4mm> 50%.

2. Abrasive grains according to claim 1, characterized in that the secondary corundum grain content in ceramic bond of the total abrasive grain is up to 50Ma .-%.

3. Abrasive grains according to claim 1, characterized in that the secondary corundum grain content with organic and magnesitic bond of the total abrasive grain is 100Ma .-%.

Field of application of the invention

The invention relates to abrasive grains for the production of abrasive articles for general grinding tasks on the basis of mechanically treated, ceramic bound Korundschleifkörperbruch or Korundschleifkörperresten (waste material).

Characteristic of the known technical solutions

It is known that secondary corundum grains are recovered from ceramically bonded corundum abrasive body breakage or corundum abrasive body residues by a mechanical treatment, which, however, are used as abrasive exclusively in loose form or dispersed in a liquid or paste or bound to a substrate. The secondary grains are to a great extent afflicted with different layer thicknesses and proportions of ceramic binding residues and form aggregations with varying degrees of separation. Thus, the reuse of secondary corundum grain for the production of solid abrasive bodies for general grinding tasks is not possible.

The following corundum abrasive fracture or corundum abrasive residue is defined as waste material:

Corundum grain according to TGL8783: 1 & -100

Binder content: 8-20% by mass

Main components of the ceramic binder:

SiO ₂ 50-70% by weight

Al ₂ O ₃ 10-20 mass%

B ₂ O ₃ 0-4Ma .-%

CaO approx. 3% by weight

Na ₂ OH-K ₂ O 5-10 Ma .-%

The degree of division in% defines the fraction of secondary corundum which corresponds to the original grain composition of the abrasive article, i. H. is free of aggregations.

For the production of abrasive bodies from this defined secondary material certain properties are to be maintained in relation to the secondary corundum grain to be obtained in order to produce grinding wheels without loss of quality can.

For example, aggregations represent solid, small units of the original abrasive body of bonded ceramic corundum grains with intact texture. Their content ranges from more than 70% by weight of the secondary corundum grain, depending on the original grain size of the secondary material. The associated high proportion of already fired ceramic binder participates in the binder reaction in an uncontrolled extent in the second fire for abrasive particles from secondary corundum. It comes to hardness deviations, microstructural defects and moreover to re-boiling phenomena that can lead to the destruction of the abrasive structure. The aggregations can degrade the grinding properties.

An expensive, but effective with respect to the separation of the ceramic binder from the secondary corundum grain solution is the chemical treatment, as proposed in the patents DD 122677 and DD 152863. Both chemical methods employ hydrofluoric acids in a different form as a disintegrating agent on: the first font 2-10 wt .-% hydrofluoric acid at 60 ⁰ C and the second reference, a 15-30 wt .-% sodium acid mixture of hydrofluoric acid, sulfuric acid and / or perchloric acid and / or nitric acid at room temperature. Although a quantitative separation of the binder is not necessary, so are the components of the acid mixture, sufficient reaction times, the multiple washing of the secondary corundum and the neutralization of the wash water unavoidable and very complicated starting conditions or process steps.

It is the object of the invention to use secondary grain granules for the production of corundum-based grinding bodies with low cost and energy expenditure.

Explanation of the essence of the invention

The invention has for its object to obtain secondary corundum grain for the production of abrasive articles for general grinding tasks on the basis of ceramic bound Korundschleifkörperbruch and / or Korundschleifkörperresten (waste material). As grinding wheels for general grinding tasks applicable working speeds are understood to 35m / s. This object is achieved in that the secondary corundum grain mainly of grains of the original abrasive composition with surface-adhering portions of a ceramic

Bonding matrix whose layer thickness for the grain size <0.5 mm on average below - to the diameter of the

6 10

original corundum grain and for the grain size> 0.5 mm on average below - to half the diameter of

6 10

original Korundkornes and the degree of division of this secondary corundum compared to the original corundum composition of the abrasive body for the grain size range below 0.2 mm 2: 90%, for the grain size range 0.2 mm to 0.4 mm a 75% and for the grain size range over 0.4mm ä 50%.

The secondary corundum grain marked with the mentioned properties is a formulation component for ceramic bond matrix abrasive dressing for general grinding tasks up to a working speed of 35 m / s. It is essential to the invention that the secondary corundum grain content of the abrasive grains in the case of ceramic bonding amounts to up to 50 mass% of the total abrasive grain. Furthermore, it is essential to the invention that the secondary corundum grain content with organic and magnesitic bonding of the total abrasive grain is 100 mass%, i. it comes to 'complete replacement of primary abrasive grain by secondary abrasive grain.

embodiments Example 1:

Grinding wheel break, IMormalkorund with ceramic bond and a stucco size of <250 χ 150 χ 150 mm is pre-crushed in two stages on my jaw crusher and cone crusher to Ci ₉₀ = 10 mm and a mean grain size of 3 mm and ground in a mill with free-moving grinding media, especially a ball mill ,

grinding parameters:

Ball size: 60 mm

Ball fill level: 25%

Speed: 80% n _knt

The following results were obtained (Table I).

grain class grain portions average layer thickness of division mm Wt .-% μιτι % 0.5-1.0 16.9 24-56 55 0.2-0.5 37.5 21-30 81 0.1-0.2 22.8 10-28 94 from 0.071 to 0.1 5.8 <15 98 0.063 to 0.071 2.4 n.d. 98 0.04-0.063 6.6 n. b. 98 <0.04 8.0 n.d. 98

From this secondary productions obtained by mechanical treatment and defined in terms of their properties, the grain size 32 having a nominal grain size in the main fraction between 0.315-0.400 mm was separated by sieve classification according to TGL 8783 and a typical abrasive body for general grinding operations for external cylindrical grinding was prepared:

Normal corundum (NK), grit 32, hard m

NK32 secondary grain: 43.5 mass% = 50.3%

NK 32 primary grain: 43.0 mass% = 49.7% of the abrasive grain

ceramic binder: 13.5% by mass

Water glass: 4,7Ma .-%

Pressing pressure: 7.5 MPa

Firing temperature: PK135 (cone drop point)

Properties of the grinding wheel with secondary grain diameter of the above composition compared to a grinding wheel consisting entirely of primary grinding grain (with otherwise unchanged formulation) according to Table II.

properties with secondary corundum without secondary corundum Hardness ¹¹ m / s 5320 5 320 Bruchumfangsgeschwindig speed (required at least 63m / s m / s 79 81 relative grinding wheel wear% 100 101 relative cutting relationship % 100 103 relative surfaces roughness% 100 100

"The hardness was measured by the determination of the sound transit time in m / s.

Example 2.

Example 2 relates to the secondary corundum grain and the formulation of Example 1 wherein the ceramic binder is replaced by organic and magnesite binder and the secondary corundum content is 100% by weight of the abrasive grain used (Table III).

Table III

modified formulation components with organic bond with magnesitic compared to Example 1 binding

Grain as Example 1 32/25

Hardness N / O N / O

Binder content Ma.% 16.9 Magnesite 20

MgCl ₂ lye23 Abrasive grain content Ma.% 83.1

This results in the following abrasive properties (Table IV):

Table IV

Seku = secondary corundum

Features organic bond magnesite bond

with Seku without Seku with Seku without Seku

Hard m / s 3500 3 550 - - Bruchumfangsge speed m / s 88 90 - - relative penalty wear% 100 100 100 100 relative cutting relationship % 101 100 100 100 relative surfaces roughness% 100 100 100 100

Claims (1)

1. Abrasive grits for the production of abrasive grains with secondary corundum grain for general grinding tasks based on mechanically processed, ceramic bonded Korundschleifkörperbruch and / or Korundschleifkörperresten, characterized in that the Sekundärkorundkörnung consist of grains of the original abrasive composition with surface-adhering portions of a ceramic bonding matrix whose Layer thickness for grain size <0.5 mm on average below - to - the diameter of the 10