Characteristics of self-sharpening diamond abrasives

Characteristics of self-sharpening diamond abrasives

2021-11-09 14:31:00 7

3.1 Graphite selection

Tests were conducted using natural and artificial graphite raw materials, respectively. The test results show that using natural graphite, self-sharpening diamond can be produced, but the yield and quality are unstable due to the unstable composition. With artificial graphite, it is also possible to produce self-sharpening diamonds. It is also possible to produce self-sharpening diamonds by using a mixture of artificial graphite and natural graphite with a small amount of natural graphite added to the artificial graphite.

In order to control the consistency of the technical conditions of the raw material and thus the stability of the product quality, it was decided to use mainly artificial graphite as the graphite raw material for diamond production.

Comparative tests were also carried out on flake and powder raw materials. The test results showed that the conversion rate and single yield of powdered raw material were two times higher than that of flake raw material. Therefore, powdered graphite should be used for the production of self-sharpening diamond, and flake graphite should no longer be used.

3.2 Choice of catalytic alloy garrison

As we all know, artificial diamond usually uses the following kinds of catalysts: De Beers uses cobalt-based alloy catalyst and nickel-based alloy catalyst; G. E company uses nickel-based alloy catalyst; Russia uses nickel-manganese catalyst; China uses nickel-manganese cobalt or nickel-manganese iron catalyst, also used iron-based catalyst. So, what kind of catalyst is the most suitable for producing self-sharpening diamond? We found that the above-mentioned catalysts can produce self-sharpening diamond after testing. However, considering the special requirements for the production of self-sharpening diamond, such as high yield, i.e. high conversion rate, low cost, isometric particle shape and agglomerate crystal structure, without emphasizing the requirement of single crystal, complete crystal shape and high strength index, the use of nickel-based alloy catalyst (nickel-iron catalyst) or iron-based alloy catalyst can meet the requirements, and there is no need to use expensive cobalt-based alloy catalyst.

The purity of the catalyst metal powder and the surface condition are strictly required to ensure that the purity is high enough and the surface is not oxidized. We used imported metal powder and domestic metal powder for comparison tests, the effect is very different, in the same conditions, the yield difference of 30% a 50%.

3.3 The choice of graphite and catalyst ingredients ratio

For powdered graphite and powdered catalyst ratio of two raw materials, we have carried out a substantial adjustment test. The catalyst to graphite weight ratio was tested in a wide range of synthesis from 70:30 to 30:70, respectively. We know that usually flake raw materials produce conventional diamond abrasives with more catalyst than graphite, while the results of the powdered raw material production self-sharpening diamond tests show that the ratio is the opposite. To θ20mm cavity for example, the results of the multi-batch test show that graphite and catalyst weight ratio of 40:60 when. Single production does not exceed 20 carats; while the weight ratio of about 60:40, single production reaches about 30 carats.

4 Experimental study on the assembly method of synthetic rods and synthetic blocks

The main steps of the powdered raw material processing process are as follows.

Dosing → mixing → pre-pressing and forming → vacuum drying → assembling → drying → setting aside.

Compared with the usual synthetic diamond abrasive synthetic rods and synthetic blocks, the synthetic rods and synthetic blocks used for synthesizing self-sharpening diamond were improved in many ways, and the advantages of two-sided top synthetic rods were absorbed, and four kinds of structures were designed and tested for preference. The structure form is shown in Figure 3.

Piece number 1 and 2 is the role of the synthetic rod at both ends of the temperature is not too low; piece number 3 and piece number 5 contact, to avoid piece number 5 and graphite sheet contact, can effectively prevent the steel cap is burned and melted, so as to prevent the "release"; piece number 7 wrapped in the periphery of the synthetic rod, to prevent external media pollution synthetic rod; piece number 8 for the synthetic rod, by the pre-pressed into the Two cylinders are connected up and down, and once pressed into the whole type of synthetic rods, compared with this structure is conducive to the two ends and the middle of a more uniform density.

Such a structure reduces the pressure difference and temperature difference between axial and radial directions, and basically realizes the production of diamond more uniformly in all parts of the whole synthetic bar. This assembly method is the widely used method of powder raw material assembly in China at present.

5 Experimental study of CSD diamond synthesis process parameters

In order to meet the special requirements of synthesizing CSD self-sharpening diamond, the parameters of synthesizing pressure, temperature and time, as well as the parameters and parameter systems, including the starting heating pressure, pausing pressure and holding pressure, the starting heating power, pausing power and synthesizing holding power, as well as the pausing time and holding time during the segmental pressurization process, were selected separately and the system as a whole was optimized and combined. . The test results show that the synthesis process parameters for growing CSD self-sharpening diamond are somewhat different from those for synthesizing conventional diamond abrasives. The main differences are: slightly higher synthesis pressure (P ≈ 5.5 GPa); slightly lower synthesis temperature (t ≈ 1450°C): much shorter synthesis time, the actual growth effective time is about 13 min, and the pause time is correspondingly shorter, between 0 - 60 s; single synthesis time cycle 4 - -5min, including the synthesis before and after the boost and unloading pressure and other auxiliary time included.

Taking 6×10MN six-sided top press θ20mm cavity as an example, the main parameters of synthetic diamond are as follows.

Synthesis pressure (table value): 95--105

Synthesis power (table value): 50--60

Synthesis cycle (min): 4--5

Under the same conditions, if the synthesis time is within 1 minute, the product particle size is mostly in the micron range; if the synthesis) time continues to be extended, the product particle size will go beyond the micron range and grow into a conventional particle size diamond abrasive, but the single output does not increase significantly.

Based on the preferential experimental study of raw and auxiliary materials, assembly methods, and the number of synthesis processes, a multi-batch small batch production was verified using appropriate raw materials and processes, and good results were achieved. Taking θ20mm synthetic rod as an example, the statistical results of six batches of production showed that the single yield of CSD abrasive reached about 30 carats on average, and the graphite conversion rate reached about 80%.

6 Conclusion

The experimental study shows that CSD self-sharpening diamond abrasives can be produced by choosing suitable powdered graphite and catalyst as raw materials, adopting appropriate assembly method and proper synthesis process on a domestic six-sided top press. The particles of this new product are of agglomerated structure, the shape of the particles is equipartite, the surface is rough and uneven, and the bonding force with the bonding agent is strong. During the grinding process, the CSD abrasive is micro-edged and broken, and the grinding is sharp and durable, which is a newer product of RVD and worth promoting.


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