WO2004113583A1

WO2004113583A1 - Diamond grit having high sintering properties, method of manufacturing the same and sintered tool using the same

Info

Publication number: WO2004113583A1
Application number: PCT/KR2004/001337
Authority: WO
Inventors: Seung-Woo Nam; Tae-Song Kwon; Hyun-Min Nah
Original assignee: Iljin Diamond Co., Ltd.
Priority date: 2003-06-20
Filing date: 2004-06-04
Publication date: 2004-12-29
Also published as: KR20040110607A; KR100489547B1

Abstract

Disclosed is diamond grit for use in tools, such as wheel tools, a method of manufacturing the same and a sintered tool using the same. The diamond grit of the current invention includes a first coating layer composed of at least one selected from among Ti, Cr and Zr, and a second coating layer composed of 30 wt% or less of Cr with the remainder being Cu and inevitable impurities and formed on the first coating layer, and is advantageous in terms of high sintering properties with a copper-based alloy matrix, such as bronze or brass. Further, the sintered tool formed of the diamond grit has a high retention force on the grit. Thus, even though such a tool is used for longer periods, it has a low grit detachment rate and an extended service life, while increasing tool performances, such as cutting efficiency.

Description

DIAMOND GRIT HAVING HIGH SINTERING

PROPERTIES, METHOD OF MANUFACTURING THE

SAME AND SINTERED TOOL USING THE SAME

Technical Field

[1] The present invention relates, in general, to diamond grit for use in tools such as wheel tools, and more particularly, to diamond grit having superior sintering properties with a copper-based alloy matrix, such as bronze or brass, and a method of manufacturing the same and a sintered tool using the same.

Background Art

[2] Generally, diamond, a material having the greatest hardness and heat conductivity, has been widely applied to cut and grind stones, concrete, asphalt, ceramic products, etc. For this, the diamond grit is used in the form of a tool sintered with a matrix metal, such as Co, Cu, Ni, Fe, W and Sn.

[3] However, of the matrix metal, Cu does not form carbides through a reaction with diamond. Hence, in cases of using a copper-based matrix, such as bronze or brass, the diamond grit is lower in bonding strength with the matrix. Thereby, upon manufacturing sintered tools, since the diamond grit has very low sintering properties with the matrix metal, the resultant sintered tools decrease in retention force of the matrix metal on the diamond grit. To overcome the problems, research for diamond grit coated with a metal element, such as Ti, Cr and Zr, is under studying to increase the bonding strength of the diamond grit with the copper-based matrix.

[4] Although the coated diamond grit has higher bonding strength with the copper- based matrix than that of unooated diamond grit, limitations are imposed on increasing the bonding strength of the coated diamond grit. This is because the copper-based matrix metal has the sintering temperature conditions lower than 800 ° C, whereas Ti requires a thermal treatment at 800 ° C or higher for long periods under vacuum to be securely bonded with Cu. Hence, if the copper-based matrix metal is sintered at 800 ° C or higher, the matrix metal is over- sintered, and as well, grit particles extremely grow, resulting in inferior performances of tools. Consequently, the conventional diamond grit having a coating layer is disadvantageous in terms of limitations in increasing sintering properties with the copper-based matrix metal. Disclosure of Invention Technical Problem

[5] Accordingly, it is an object of the present invention is to alleviate the problems encountered in the related art, and to provide diamond grit having high sintering properties with a copper-based alloy matrix, by further including another coating layer composed of Cu and Cr in addition to a conventional coating layer.

[6] Another object of the present invention is to provide a method of manufacturing such diamond grit.

[7] Still another object of the present invention is to provide a tool formed of the diamond grit which is sintered with a copper-based alloy, having advantages of superior tool performance and long service life.

Technical Solution

[8] To achieve the above objects, the present invention provides diamond grit, including a first coating layer composed of at least one selected from among Ti, Cr and Zr, and a second coating layer composed of 30 wt% or less of Cr with the remainder being Cu and inevitable impurities and formed on the first coating layer.

[9] Further, the present invention provides a method of manufacturing diamond grit having high sintering properties with a copper-based alloy matrix, including forming a first coating layer composed of at least one selected from among Ti, Cr and Zr on diamond grit, forming a second coating layer composed of 30 wt% or less of Cr with the remainder being Cu and inevitable impurities on the first coating layer, and thermally treating the diamond grit having the first coating layer and the second coating layer at 800-950 ° C under vacuum.

[10] Furthermore, the present invention provides a tool made of the diamond grit, which is sintered with a copper-based alloy.

Description of Drawings

[11] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[12] HG. 1 is a graph showing service lives of tools (wheels) each formed of conventional diamond grit and diamond grit of the present invention; and

[13] HG. 2 is a graph showing grit detachment rates of tools each formed of conventional diamond grit and diamond grit of the present invention.

Mode for Invention

[14] Based on the present invention, diamond grit includes a first coating layer composed of at least one selected from among Ti, Cr and Zr, and a second coating layer composed of 30 wt% or less of Cr with the remainder being Cu and inevitable impurities and formed on the first coating layer. As such, the second coating layer has 0.3-10 wt% of Cr, and the diamond grit has an average size of 10-1000 m m.

[15] The metal component, such as Ti, Cr and Zr, functions to form carbides on the diamond to be bonded with the diamond. Further, the above metal component has high bonding strength with a matrix metal, and thus, is used to maintain a retention force on the diamond grit required for sintered tools. However, the diamond grit having a conventional coating layer made of Ti, Cr and Zr has limitations for increasing sintering properties with a copper-based alloy matrix.

[16] With the intention of solving the above problem, a second coating layer composed of Cu and Cr is additionally formed on a first coating layer as the conventional layer, whereby sintering properties with the copper-based matrix can be further increased.

[17] In such cases, Cu is a basic component in the copper-based alloy matrix. Thus, when the second coating layer is formed to have Cu, the bonding strength between the copper-based alloy matrix and the diamond grit having the same metal to the above alloy matrix can be further increased.

[18] In addition, Cr has larger evaporation enthalpy than that of Cu, and can produce a nucleus more stable than Cu. Thus, a predetermined amount of Cr is added to Cu, whereby the Cu layer grows centering the nucleus of Cr and the coating layer becomes denser. At this time, if Cr is used in the amount exceeding 30 wt%, the bonding strength with the copper-based matrix metal decreases. Eventually, it is preferred that the second coating layer has 30 wt% or less of Cr. On the other hand, for the formation of the denser coating layer, the amount of Cr in the second coating layer should be not less than 0.3 wt%. Also, the size of the diamond grit is in the range of 10-1000 m m, which is an average size of commercially available diamond grit.

[19] Meanwhile, such diamond grit is manufactured by forming the first coating layer composed of at least one selected from among Ti, Cr and Zr on the diamond grit, forming the second coating layer composed of 30 wt% or less of Cr with the remainder being Cu and inevitable impurities on the first coating layer, and thermally treating the diamond grit having the first and second coating layers at 800-900 ° C under vacuum.

[20] The first coating layer and the second coating layer are formed by means of a general process, for instance, sputtering chemical vapor deposition, or PVD (Physical Vapor Deposition).

[21] After the formation of the coating layers, the metal component contained in the coating layer forms carbides along with the diamond grit, thereby securely bonding the coating layer with the diamond grit. Further, the thermal treatment process is performed at predetermined temperatures to induce mutual diffusion and bonding of the metal components so as to strengthen the bonding between the coating layers.

[22] Particularly, the thermal treatment process is preferably carried out at 800-950 ° C, in which the thermal treatment temperature not lower than 800 ° C is required for mutual diffusion of the metal components, while the temperature not higher than 950 ° C is required to prevent re-graphitization by metal impurities in the diamond grit.

[23] Moreover, to prevent the addition of impurities and to obtain the desirable coating layer, the above thermal treatment process is performed in a vacuum atmosphere of 10 - torr or less.

[24] A better understanding of the present invention may be obtained through the following examples which are set forth to illustrate, but are not to be construed as the limit of the present invention.

[25] EXAMPLE 1

[26] Onto diamond grit having an average size of 400 m m (40/50 mesh), a first coating layer composed of Ti was formed to have 0.3 wt% based on the weight of the diamond grit, by means of a DC magnetron sputtering process. Subsequently, a second coating layer composed of Cu-0.3wt% Cr was formed on the first coating layer to have 0.2 wt% based on the weight of the diamond grit by means of the same process as above.

[27] Specifically, a titanium target was mounted to a target holder, and diamond grit was placed into a sputtering device, in which a vacuum atmosphere of 5x10 torr or less was made by use of a mechanical pump and a diffusion pump. Then, Ar having high purity of 99.999% was introduced into the device until the pressure therein reached

-3

1x10 torr. Then, through the application of DC power (1.2A x 400V), the first coating layer was sputter-deposited on the diamond grit. [28] Thereafter, a target composed of Cu-0.3wt% Cr was mounted to the target holder, and the second coating layer of Cu-Cr alloy was deposited on the first coating layer, according to the above procedure. [29] The thus formed diamond grit having the first and second coating layers was thermally treated at 900 ° C for 1 hour in a high vacuum atmosphere of 5x10 torr or less, to manufacture desired diamond grit. [30] The diamond grit was mixed with 60% bronze-40% cobalt powders, and compressed at high temperatures of 770 ° C to make a segment, which was then welded to a shank having a diameter of 16 inch, to manufacture a tool (wheel). [31] EXAMPLES 2 to 4 [32] Tools were manufactured in the same manner as in Example 1, with the exception that the target composition of the second coating layer was changed to have 2, 10 and 30 wt% of Cr, thus obtaining diamond grit.

[33] COMPARATIVE EXAMPLES 1 AND 2

[34] Tools were manufactured in the same manner as in Example 1, with the exception that diamond grit without a coating layer and diamond grit having only a coating layer of Ti-0.3wt% Cr (first coating layer) were used.

[35] By use of the thus manufactured tools, granite was cut under conditions of a circumferential speed of 28 m/s, a depth of cut of 30 mm and a transporting speed of 3 m/ min. At this time, service lives and grit detachment rates of the above tools were measured. The results are given in HGS. 1 and 2.

[36] From HGS. 1 and 2, it can be found that the tools formed of the diamond grit having the coating layers of the present invention have a longer service life and a lower grit detachment rate, compared to the tools of Comparative Examples.

Industrial Applicability

[37] As described above, the present invention provides diamond grit, a method of manufacturing the same and a sintered tool using the same. The diamond grit of the present invention has superior sintering properties with a copper-based alloy matrix, such as bronze or brass. Further, the tool made of the inventive diamond grit which is sintered with a copper-based alloy has a high bonding strength between the diamond grit and the matrix metal (that is, a high retention force on the grit). Thus, even though such a tool is used for longer periods, it has a low grit detachment rate and an extended service life, while increasing tool performances, such as cutting efficiency.

[38] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

[1] 1. A diamond grit having high sintering properties with a copper-based alloy matrix, comprising: a first coating layer including at least one selected from among Ti, Cr and Zr; and a second coating layer including 30 wt% or less of Cr with the remainder being

Cu and inevitable impurities and formed on the first coating layer. [2] 2. The diamond grit according to claim 1, wherein the second coating layer has

0.3-10 wt% of Cr. [3] 3. The diamond grit according to claim 1, wherein the diamond grit has an average size of 10-1000 m m. [4] 4. A method of manufacturing diamond grit having high sintering properties with a copper-based alloy matrix, comprising: forming a first coating layer including at least one selected from among Ti, Cr and Zr on diamond grit; forming a second coating layer including 30 wt% or less of Cr with the remainder being Cu and inevitable impurities on the first coating layer; and thermally treating the diamond grit having the first coating layer and the second coating layer at 800-950 ° C under vacuum. [5] 5. The method according to claim 4, wherein the thermally treating of the diamond grit is performed under 10 torr or less. [6] 6. A tool made of the diamond grit of any one of claims 1 to 3, which is sintered with a copper-based alloy.