Improve the quality of diamond tools in China from the beginning of technology

China's total stone output, stone export volume and stone consumption have reached the world's first place: there are more than 20,000 stone processing enterprises, nearly 5 million employees, with an annual output of 6 million cubic meters of stone, with an annual output of 120 million square meters, year-on-year With an output value of more than 80 billion yuan and more than 500 advanced production lines, the total import and export volume exceeds 1.2 billion US dollars, making it a veritable stone producing country.

Although China has entered the ranks of major powers in the above aspects, it is not yet a strong country. With the integration of the global economy and China's entry into the WTO, how to make China a powerful country in the production of diamond tools is an important issue facing our counterparts. According to our practice and investigation, we only put forward some views on improving the quality of diamond tools in China.

1. Provide high-strength diamond with stable production performance, coarse particles and good thermal stability for diamond tool manufacturing.
The grade quality, particle size and concentration of diamonds play a decisive role in diamond tools. In China's diamond synthesis, the six-sided top small tonnage high-strength process has matured, the six-face top large tonnage large cavity process has been continuously improved, and the two-side top synthetic diamond has also begun to take shape. The powder catalyst synthesis, carbon, and pyrophyllite block raw materials are continuously produced. perfect. Therefore, for the manufacture of diamond tools in China, high-strength diamond with stable performance, coarse particles and good thermal stability is possible. In addition to the SDA+, SDB, DSN, MBS, and ISD series, DeBeers has launched BKI, BK30, BK60, and BK70 diamonds for the national market. South Korea’s Rijin Corporation has launched the SDS series of diamonds with six-sided top synthesis, which are worthy of China. Learn from peers.

2. Use strong carbide forming elements to improve diamond holding power
A key factor in improving the cutting efficiency and life of diamond saw blades is to increase the holding power of the carcass to the diamond. The carcass has a good grip on the diamond, the diamond will not fall off prematurely, and has the largest protruding height, sharp cutting and high efficiency.

3. Using ultrafine powder and prealloyed powder
In the production of special saw blades, ultrafine metal powders and prealloyed powders should be used. The refinement of the metal powder is advantageous for lowering the sintering temperature and increasing the hardness. The use of pre-alloyed powder prevents premature loss and segregation of low-melting metals, favors the elastic limit and yield strength of sintered products, increases the holding power of diamonds, and reduces sintering temperature and holding time. China Shanghai Materials Institute, Beijing Artificial Crystal Institute, Changsha Metallurgical Materials Institute and Nangong University Powder Metallurgy Institute have done a lot of work in this regard. South Korea's ultra-fine powders and pre-alloyed powders from BASF, UM, INCO, Fum-tungstene, and Kennametal are widely used in the production of high-grade saw blades.

4. Promote granulation process in the production of cutter head
The granulation process has been widely used in China's cemented carbide and ceramic production. In recent years, it has also been widely used and developed in the production of diamond cutter heads. The advantage of powder granulation is that the segregation of diamond is reduced, the distribution is more uniform, the cutting performance of the cutter head is improved, the fluidity of the powder is increased, the application of the volumetric cold press process is made possible, and the ordinary cold press process is better, reducing The harm of dust to workers. The disadvantage is that investment and process procedures are added, and binders are added during granulation, which may have an adverse effect on welding, sintering and carcass performance. The advantages and disadvantages of various granulation methods are shown in the table below.

Disadvantages: need to be cleaned, no diamond, only one metal, large equipment.

Rolling method: Advantages: easy to operate, good paraffin adhesion, spherical. Disadvantages: The granulation process is unstable, contains diamond, and is difficult to granulate. It needs to be sieved.

Extrusion screening method: advantages: fast speed, less binder, easy to operate. Disadvantages: no diamond, need to be screened, shape is not uniform, the pass rate is 20% to 40%.

Manual screening method: advantages: simple, low investment, can contain diamonds, and the production volume is small. Disadvantages: It is difficult to select the binder, the labor required is heavy, and the shape is irregular.

Pressure sieving and rolling method: Advantages: stable process, easy to clean, automatic, diamond-containing, one-time granulation optional. Disadvantages: It is difficult to choose a binder, and more flux is needed.

Low-speed mixing high-speed cutting method: advantages: can be automated, the size of the particle can be artificially controlled. Disadvantages: no diamond, the amount of granulation can not be too small, the pass rate is 70% to 80%.

Germany Feiyu Company introduced GA180 and GA240 granulators, and its granulation process is composed of mixing → adding binder stirring → scraping and sieving → rolling granulation. This method is used to increase the cold pressing speed of the cutter head by 3 times, the die life by 1 time, and the cold press cost by 2/3.

South Korea Dikes Co., Ltd. introduced the CA-10 granulator, which consists of dry mixing with binder, low-speed external stirring (25~28r/min), and high-speed cutting (2300～2800r/min).

In order to granulate, Germany developed GB300, 400, 500 type binder, Korea used Olycox, China's Nanjing Sishangke Trade Development WS-120 granulating agent is a white group globular powder with a density of 1.068g/cm3. The thermal decomposition temperature is 320-350 ° C, and the residual ash after sintering is <0.01%. It has replaced imported binder and has been widely used in various diamond tool factories.

5. Sintering process promotes vacuum protection atmosphere hot pressing sintering process and equipment
Sintering is a key process in the production of diamond saw blades. Its quality will affect the density, hardness and cutting performance of the saw blade. The technical performance of the sintering equipment also affects the production cost, product and quality of the saw blade. Recently, we conducted a survey on the overall sintering furnace of diamond saw blades. The comparative sintering tests were carried out using the same formula powder in several representative furnace types. The results show that:

(1) Hydrogen protection, pressureless sintering, and furnace and bell furnace are suitable for the production of low-grade small-size saw blades, which have a large single output, but the saw blade has a low life;

(2) CSF500 hot-pressing sintering furnace, the furnace temperature distribution is uniform, and the nitrogen-protected pressure-sintered saw blade has high hardness and high density. Sharp and long-lasting when sawing, it can produce high-grade saw blades, and can produce multi-species and multi-species saw blades;

(3) RYL series frequency atmosphere protection hot press sintering furnace has superior design performance and is suitable for mass production of single specification saw blade, but the adaptability to many varieties is poor, and the furnace temperature distribution needs to be further improved;

(4) After the SF500 and ZBRY-2 sintering furnaces are perfected, they are a promising sintering equipment.

6. Diamond wire saw production adopts hot isostatic pressing and high temperature brazing process
In the past ten years, diamond wire saws have been used in quarrying and construction projects to make diamond wire saws from quarry to stone processing plants, from large cutting to finishing, from sheet cutting to processing of shaped products and construction. Engineering a variety of applications, the world's stone cutting accounted for 10% of the share, and there is a growing trend.

There are several main features in the development process:

(1) The bead production method consists of electroplating single layer and double layer metal diamond beading, to hot pressing sintering and high temperature brazing beading, so that the application range of the wire saw is expanded from marble to granite and concrete.

(2) The diameter of the wire saw is reduced from 10 to 12 mm to 6 to 8 mm, which improves the cutting efficiency and reduces material consumption.

(3) The development of the CNC controlled wire saw machine makes it possible to make a multi-wire saw, so that the wire saw machine can enter the plate factory, which can effectively cut the plate and the special-shaped products, and can replace the frame saw and the bridge plate saw machine.

(4) The hot isostatic pressing process is used for beading production to improve the density, hardness, strength and service life of the bead.

Hot isostatic pressing (HIP) is to place the sintered product in a hot isostatic press with an inert gas Ar (argon) as the pressure transmitting medium, the temperature rises to 1320 ~ 1400 ° C, and the gas is thermally expanded to produce 80 ~ 150MPa. Pressure, put the beads in a glass wrap for a certain period of time.

Hot isostatic pressing reduces the porosity of the product and increases density, strength, impact toughness and performance. China's Beijing Iron and Steel Research Institute, Nangong University Powder Metallurgy Institute, Beijing Nonferrous Metal Research Institute, Zhuzhou Cemented Carbide Factory have hot isostatic pressing equipment.

(5) Using a single layer of high temperature brazed diamond beads
The process is a new patented technology introduced by Taiwan's Taiwan Wheel Manufacturing Company (KNIKInc.). The high-temperature brazing beaded diamond arrangement rules are reasonable, the chemical bonding and metallurgical combination are coexisting, and the diamond holding power is strong and outstanding. The diamond usage can be saved by half, the sawing speed is 2 to 4 times that of the ordinary saw blade, the cutting life is equivalent, and the saw blade cost is reduced.