The survey results show that China's total stone output, stone export volume and stone consumption have reached the first place in the world: there are more than 20000 stone processing enterprises with nearly 5 million employees, with an annual output of 6 million cubic meters of stone and 0.12 billion square meters of plates. the annual output value exceeds 80 billion yuan, has more than 500 advanced production lines, and the total import and export volume exceeds 1.2 billion US dollars, making it a veritable stone producer.
China is also a large producer of ceramics. In 1999, the total output of all kinds of ceramic tiles was 1.6 billion square meters (33.6 per cent of the world's total output) and the total consumption was 1.3 billion square meters (30.8 per cent of the world's total consumption). The diamond and diamond tool manufacturers have more than 1000, 1999 annual output of diamond has more than 0.75 billion carats, becoming a major producer of diamond. Diamond saw blades have been able to meet domestic demand. Nearly 1/3 of the products are exported, forming a certain competitive strength in the DIY market.
Although China has stepped into the ranks of great powers in the above-mentioned aspects, it is not yet a powerful country. With the global economic integration, China's entry into the WTO, how to make our country become a powerful country in the production of diamond tools, which is an important issue in front of our counterparts. According to our practice and investigation, only to improve the quality of China's diamond tools, put forward some views.?
1. Provide high-strength diamond with stable mass production performance, coarse particles and good thermal stability for diamond tool manufacturing
Diamond grade quality, particle size and concentration of diamond tools have a decisive role. In diamond synthesis in China, the six-sided top small tonnage high-strength process has matured, the six-sided top large tonnage large cavity process has been continuously improved, the two-sided top synthetic diamond has also begun to take shape, powder catalyst synthesis, carbon, pyrophyllite raw material production has been continuously improved. Therefore, for the manufacture of diamond tools in China, it is possible to synthesize high-strength diamond with stable performance, coarse particles and good thermal stability in batches. In addition to SDA, SDB, DSN, MBS and ISD series, foreign diamond companies have DeBeers introduced BKI, BK30, BK60 and BK70 diamonds for the Chinese market. South Korea, Rijin has introduced SDS series diamonds synthesized on six sides, which are worth learning from our counterparts.?
2. The use of strong carbide forming elements to improve the diamond holding force
One of the key factors to improve the cutting efficiency and life of diamond saw blade is to improve the holding force of matrix to diamond. The matrix has a good holding force on the diamond, the diamond will not fall off prematurely, and has a protruding height, sharp cutting, high efficiency.
There are generally three ways to improve the diamond holding force:
(1) improve the mechanical holding force. This is because the metal powder shrinks during sintering to form a compressive stress that holds the diamond. The generation of compressive stress is due to the different thermal expansion coefficients of diamond and matrix metal, due to the volume change caused by crystal formation and growth during sintering. Due to the limited yield strength of the carcass, the resulting compressive stress and mechanical holding force are limited.
(2) the powder to add a small amount of strong carbide forming elements such as Cr, W, Mo, etc., because of its good wettability and affinity to diamond, sintering in the diamond and matrix metal interface to form carbide, to achieve the diamond gold combination, is conducive to the strengthening and improvement of the holding force.
(3) diamond surface coated with a layer of strong carbide to form metal elements such as Cr, Ni, Ti, W and so on. This is the use of more process measures in recent years. For this reason, Yanshan University has specially developed and produced three types of vacuum micro-evaporation titanium plating equipment.?
According to the experimental research and use at home and abroad, the conditions and scope of use of diamond plating technology are:
Apply to high grade diamond, the effect is more obvious;
② The order of increasing the holding force in the pure drill carcass is: Cr-plated> Ti-plated> unplated diamond.
③ MBS-960Cr2 chrome-plated diamond is suitable for Co-based matrix, low-iron low-bronze matrix and WC matrix.
④ MBS-960Ti2 titanium-plated diamond is suitable for drilling bronze-based matrix and iron-based matrix.
⑤ Use tungsten-plated diamond in cutting asphalt, curing concrete (GreenConcrete) and strengthening (reinforced) concrete saw blades.
⑥ Nickel-plated diamond is suitable for resin-bonded grinding wheels, and its use effect is as follows: needle-shaped nickel-plated diamond> nickel-plated diamond> unnickel-plated diamond.
⑦ Silver-plated diamond is suitable for grinding tungsten carbide carbide tools with precision resin bond grinding wheel. Because the price of silver is not very expensive, suitable for high-precision grinding, its thermal conductivity is good, suitable for oil-cooled grinding hard alloy. At the same time, silver is a good lubricant, which can reduce the friction between the grinding wheel and the workpiece, and the heat is not large.
Coating strong carbide forming elements Ti, Ni, W, Cr, etc. to improve the diamond holding force, mainly due:
① plating metal can prevent diamond in a certain temperature, pressure and sintering time under the conditions of oxidation, graphite and iron thermal corrosion. The author of different metal coated diamond TG (thermogravimetric) analysis, found that diamond at about 800 ℃ that is the beginning of weight loss and graphitization. However, Ti, W, TiN and other diamonds began to lose weight and graphitize at 900 ℃, 925 ℃ and 940 ℃ respectively. It shows that diamond plating metal is beneficial to prevent oxidation and graphitization, and can withstand thermal shock and thermal decomposition. It has obvious protective effect on high temperature sintering matrix.
The carbide alloy can be formed at the interface between diamond and matrix under sintering conditions, which is conducive to the chemical bonding and metallurgical combination of diamond and matrix metal, and greatly improves the holding force of matrix to diamond. X-ray analysis of tungsten-plated diamond shows that WC phase has been formed on the surface of diamond.
The static pressure strength of diamond can be increased by 5% ~ 20%.
After the diamond is plated with metal, the friction of the diamond can be improved, and the latter helps to increase the holding force.
3. The use of ultra-fine powder and pre-alloyed powder.
In the production of special saw blades, it is appropriate to use ultra-fine metal powder and pre-alloyed powder. Metal powder refinement is beneficial to reduce the sintering temperature and improve the hardness. The use of pre-alloyed powder can prevent the premature loss and segregation of low melting point metals, which is conducive to the elastic limit and yield strength of sintered products, increase the holding force of diamond, and reduce the sintering temperature and holding time. China's Shanghai Institute of Materials, Beijing Institute of Artificial Crystals, Changsha Institute of Metallurgical Materials and Central South University of Technology have done a lot of work in this area. South Korea, when producing high-grade saw blades, ultra-fine powder and pre-alloy powder from BASF,UM,INCO,Fum-tungstene,Kennametal and other companies are widely used.?
4. Promote the granulation process in the production of cutter heads
The granulation process has been widely used in the production of cemented carbide and ceramics in China, and has also been widely used and developed in the production of diamond segments in recent years. 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 pressing process is possible, and the ordinary cold pressing process is better. Reduce the harm of dust to workers. The disadvantage is that it increases the investment and process procedures, and the binder is added when granulating, which may have an adverse effect on welding, sintering and carcass performance. The advantages and disadvantages of various granulation methods are compared.
