DD240515A1 - ABRASIVE AGENTS FOR THE PRODUCTION OF GRINDING BODIES - Google Patents

Abstract

The invention relates to Schleifmittelkoernungen for the production of abrasive bodies for general grinding tasks on the basis of ceramic bonded Korundschleifkoerperbruch or Korundschleifkoerperresten (waste material). The aim of the invention is to extend the scope of secondary corundum for the production of corundum-based abrasives with low cost and energy expenditure. According to the invention, the object is achieved by obtaining remnants of the waste material, which consist primarily of coagulating the original abrasive composition with a limited layer thickness of surface-adherent ceramic bond matrix and a defined degree of division and this secondary corundum is a formulation component for abrasive bodies for general grinding tasks.

Description

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 to TGL8783: 16-100

Binder content: 8-20Ma .-%

Main components of the ceramic binder:

SiO ₂ 50-70% by weight

AI ₂ O ₃ 10-20Ma .-%

B ₂ O ₃ 0-4Ma .-%

CaO ca.3Ma .-%

Na ₂ O + 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 articles 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.

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 processes use flux acids as solubilizers in various forms: the first type 2-10% by weight hydrofluoric acid at 60 ° C. and the second type a 15-30% strength by weight 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.

Object of the invention

It is the object of the invention to use secondary corundum grains for the production of corundum-based abrasive articles 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 according to the invention in that the secondary corundum grains consist 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 averages below V6 to Vio of the diameter of the original corundum grain and for the grain size> 0.5 mm on average below Ve to Vio of half the 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 particle size range below O, 2mm> 90%, for the grain size range 0.2mm to 0.4mm> 75% and for the grain size range is over 0.4mm> 50% and this secondary corundum grain is a formulation component for grinding wheels.

The secondary corundum grain marked with the mentioned properties is a formulation component for ceramic bonded matrix abrasive production for general grinding tasks up to a working speed of 35 m / s. The secondary corundum grain content is up to 50% by mass of the total abrasive grain of the abrasive article formulation. For organic and magnesite bond matrix abrasive articles, the secondary corundum grain content can be increased up to 100 mass%, i. until complete replacement of primary abrasive grain by secondary abrasive grain.

The invention will be explained below with reference to exemplary embodiments.

embodiments Example 1:

Abrasive disc breakage, normal corundum with ceramic bond and a piece size of <250 x 150 x 150mm is pre-crushed in two stages in a jaw crusher and cone crusher to d 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 ,

Mahiparameter:

Ball size: 60 mm

Ball fill level: 25%

Speed: 80% n _crit .

The following results were obtained (Table I).

Grain class Grain shares Average layer thickness Degree of division

mm% by mass /%

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.d. 98 <0.04 8.0 n.d. 98

From this obtained by mechanical treatment and defined in terms of their properties ' ,

Secondary grits were graded to grain size 32 with a nominal grain size in the main fraction between 0.315-0.400mm by sieving classification according to TGL 8783, and a typical grinder was made for general grinding operations for external cylindrical grinding:

Normal corundum (NK), grit 32, hardness M

NK 32 secondary grain: 43.5% by mass = 50.3%

NK32 primary grain: 43.0 mass% = 49.7% of the abrasive grain

ceramic binder: 13.5Ma .-%

Water glass: 4,7Ma .-%

Pressing pressure: 7.5 MPa

Firing temperature: PK135 (cone drop point)

Properties of the abrasive body with secondary corundum grain of the above composition compared to an abrasive body consisting entirely of primary abrasive grain (with otherwise unchanged formulation) according to Table II:

-3-Table II

properties with secondary corundum without secondary corundum Hardness ¹¹ m / s 5320 5320 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

^1Ϊ The hardness was measured by the determination of the sound propagation 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 mass% 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% of abrasive grain Ma .-% 83.1 57

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

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

Claims (3)

Invention claim: 1. Abrasive grits for the production of abrasive articles for general grinding tasks based on mechanically processed, ceramic bonded Korundschleifkörperbruch and / or Korundschleifkörperresten (waste material), 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 the grain size of <0.5 mm on average below ¹ / 6th to ¹ AO of the diameter of the original Korundkornes and the grain size> 0.5 mm is on average below Vb to Viodes half the diameter of the original Korundkornes and derZerteilungsgrad this Sekundärkorundkörnung over the original grain composition of the abrasive grit for the particle size range below 0.2 mm> 90%, for the particle size range 0.2 mm-0.4 mm> 75% and for the particle size range above 0.4 mm> 50% and this secondary corundum grain size represents a formulation component for grinding wheels. 2. The method according to item!, Characterized in that for the abrasive article production with ceramic bond for general grinding tasks, the secondary corundum grain content of the total abrasive grain to 50 wt .-%. 3. The method according to item 1, characterized in that for the abrasive body production with organic and magnesitic bond of the secondary corundum grain content of the total abrasive grain to 100Ma .-%.