Diamond abrasives used in the manufacture of resin bonded abrasives, the traditional products are single crystal particles, most of which (more than 70%) are needle-like, with smooth surface, poorly bonded to the bond, and fall off prematurely during the grinding process, which is not ideal for use. The purpose of this paper is to solve this problem. In this project, a new product of diamond abrasive, CSD (Crumb Structure Diamond), was developed on a six-sided top-press machine by systematic experimental research on the composition and ratio of raw materials, the assembly structure of synthetic blocks, the synthesis process parameters and the regulation mode, using powdered graphite as raw material and iron-based alloy powder as catalyst. Structure Diamond (CSD) abrasive was developed on a six-sided top press. The synthesis pressure and electrical power are basically the same as the process parameters for the synthesis of single crystal diamond, while the synthesis time is shorter, not more than 5 min, and the graphite conversion rate reaches about 80%. The new product is not a needle-like single crystal particle, but a particle of agglomerate structure, and the shape of the particle is equipartite, with rough and uneven surface. CSD abrasives can be used as a new generation of RVD diamond abrasives.
The diamond abrasives used in the manufacture of resin bonded and ceramic bonded abrasives at home and abroad, including the domestic brand RVD, the original De Beers RDA, the American GE RVG, the Russian AC2, the Japanese Tomei IRV and other products, are single crystal diamond particles, irregular in shape, most of the particles are not even isometric (isometric refers to the ratio of the long axis to the short axis size is less than Most of the particles are not even isometric (isometric means the ratio of the long axis to the short axis is less than 1.5), and the needle-shaped particles account for a large proportion. For example, for RVD, the standard stipulates that more than 70% of flake particles are allowed. The particle shape of this type of abrasive is shown in Figure 1.
The use of such abrasives is not ideal, and the following problems mainly exist.
(1) The surface is smooth and the mechanical bonding (engagement) with the bonding agent is not firm. During the grinding process, most of the abrasive grains fall off prematurely before they can fully play their role.
(2) The abrasive grain wears in the direction of the deconstruction surface or at the defects or cracks, and the fracture surface crosses the entire crystal.
(3) The single crystal abrasive grain has few cutting edges and a large cutting edge area, which requires a large grinding force and poor grinding sharpness.
For a long time, people have been seeking solutions to the above problems. Surface plating methods, such as copper, nickel and corundum plating, are used to solve the problem of premature shedding. However, this approach only takes measures from the outside of the particle, but does not solve the problem from the essence of the particle. Later, Be Beers introduced the CDA (now renamed Element Six's PDA321) product, which is an improvement from the particle structure itself. It is self-sharpening, and its sharpness and durability have been significantly improved, thus making it a distinctive product with a worldwide reputation.
The above problem has been noticed in China for a long time, but it has not been solved for decades, and the self-sharpening abrasives similar to CDA have not been developed. After years of efforts, this project finally succeeded in developing a new product of self-sharpening diamond abrasives.
The most significant characteristic of CSD abrasives is their excellent self-sharpening properties. Based on this characteristic, it can also be called Self.Sharpening Diamond.
CSD abrasives are very similar in structure and performance to the SG abrasives that have emerged in the world in recent years, which is a new type of corundum abrasive with excellent performance, microcrystalline polymer structure, good self-sharpening and exponentially longer life than ordinary corundum abrasives.
2 Characteristics of CSD diamond abrasives
2.1 CSD diamond abrasive crystal structure characteristics
The most distinctive feature of CSD abrasive particles is not single crystal particles like ordinary abrasives, but particles composed of multiple small grains. This particle structure is called crumb structure, or granular structure. Each granule contains a number of small particles of different sizes. These small particles are called sub-grains or sub-grains. The size of each sub-grain varies from a few microns to tens of microns. During the grinding process, these sub-grains are shed one after another and the abrasive micro-edges are broken, maintaining multiple sharp cutting edges. This is the reason for the self-sharpening nature of this abrasive.
This agglomeration containing multiple subgrain is caused by local orientation misalignment in some parts of the lattice due to dislocation and impurity accumulation during the crystal growth process.
Under artificial crystal growth conditions, it is difficult to grow coarse-grained single crystal abrasives for a long time. With our new process, coarse-grained abrasives with agglomerate structure can be successfully produced in a short time.
2.2 Particle shape characteristics of CSD diamond abrasives
CSD abrasives are unique in terms of particle shape and surface condition; CSD is an irregularly shaped lumpy particle. Although the shape is irregular, it is not needle-shaped or flaky, but is a relatively uniform three-dimensional size of the isoprene particles, as shown in Figure 2.
As can be seen from Figure 2, the surface of CSD particles is rough and uneven, thus more conducive to the abrasive in the bonding agent to hold firm and effectively prevent premature shedding.
3 Experimental Study on the Preferred Raw Materials of Powdered Graphite and Catalyst Alloy
We were the first in China to consider the option of replacing flake raw materials with powdered raw materials since 1995. This proposal was based on three foreign results. One of the results was the Soviet method of manufacturing diamond polycrystals by direct synthesis. Although this method of manufacturing polycrystals was not successful enough (uneven organization and unstable quality), the graphite conversion rate was high, and synthetic rods were formed with fine-grained diamonds as the main body and containing both catalysts and small amounts of unconverted graphite. Another achievement was the then newly started West German new technology of coarse-grained high-strength diamond synthesis using powdered catalysts. The third new technology was a new Russian method of producing diamond abrasives for resin abrasives directly on a double-sided concave press.
Based on the results of many related new technologies from abroad, we integrated and absorbed the useful parts of them and applied them to the work of synthesizing self-sharpening diamonds. We select the applicable graphite and catalyst alloy raw materials for the requirements of producing self-sharpening diamond, taking into account the domestic conditions.
was established in June 2001, is a national high-tech enterprise specializing in the research and development, production and operation of ultra-precision grinding and polishing materials in China, and is a pioneer in the industry with a number of international and domestic independent intellectual property rights, many years of experience in product technology development and many customer applications.
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