There are many methods to manufacture diamond tools, including powder metallurgy sintering method, electroplating (casting) method, high temperature and high pressure method, brazing method, resin bonding method.One of the most widely used is powder metallurgy. Powder metallurgy methods used in the production of diamond tools include cold pressing sintering, impregnation, hot pressing and electric spark sintering.
1.Cold pressing Core sintering process
The main function is to fully mix the prepared powder, through the mold to achieve the product (cutter) blank stamping forming, including dynamic cold pressing and automatic cold pressing to ensure the normal follow-up pressing. At present, oscillating 3D mixer is commonly used in diamond tool industry. The stirring equipment has three modes of motion: rotation, translation and swing, and reversal. The movement trajectory of powder is three-dimensional, which can make the powder mixed evenly in a short time and refine the particles.
Because the powder fluidity is good, the diamond is coated by the powder and distributed more evenly. Thus, the loss of cold pressing die is reduced, and the die life is increased by more than 50%. Improve the production efficiency, for the realization of fully automatic cold press production to create conditions.
The sintering equipment is mainly resistance furnace and hot press, which mainly completes the sintering densification of diamond tools or tool heads.There are three factors affecting sintering: sintering temperature, holding time and holding pressure.
The sintering temperature and holding time mainly depend on the composition of the base material, so that the base alloy can get good melting and sufficient alloying. Sintering temperature and holding time should be appropriate. Too high sintering temperature and too long holding time will cause thermal damage to diamond, increase matrix hardness, reduce wear resistance, loss of a large number of low melting point elements, and affect the cutting performance of saw blade. If the sintering temperature is too low and the holding time is too short, the alloy will not be able to melt completely, resulting in loose tissue and low hardness, thus reducing the service life of the saw blade.
If the pressure is too low, sintered diamond body will not burn in situ; If the pressure is too high, it will increase the abrasive wear and may cause the loss of matrix material.
2. Hot pressing
As pressing and hot pressing is the most widely used method in diamond tool manufacturing, it is considered as a form of activated sintering because it is carried out simultaneously with sintering. At present, medium frequency heating and resistance heating are used. In recent years, the EDM sintering process has been developed.
The characteristics of hot pressing sintering are:
(1) The metal carcass is firmly bonded with diamond. Due to the poor wettability of general alloys to diamond, diamond only inserts in the matrix. Hot pressing method makes the matrix hold the diamond firmly with the help of extrusion friction and plastic flow between the matrix and hard points at high temperature.
(2) The performance of the carcass can vary over a wide range. Due to the simultaneous action of pressure and temperature, the restriction on the type and content of the body material is reduced. In order to adapt to the constantly changing processing objects, the composition and manufacturing process of the body can be adjusted in time, so as to obtain the required performance.
(3) Short sintering time. Because the temperature and pressure are lower than other production methods, the holding time is short. Therefore, the production cycle can be shortened and thermal damage to diamond can be reduced.
In short, because of the unique technological characteristics of hot pressing, it is very suitable to produce diamond tools represented by circular saw blade, impregnated insert and geological drill bit, and it is the most widely used production method at home and abroad.
3. Weld
Welded diamond circular saw blades are welded to connect the segments to the substrate. At present, there are two commonly used forms of welding, one is high-frequency welding, the other is laser welding.
4. Post-processing
Post-processing equipment mainly includes polishing machine, edge cutting machine, stress adjusting machine, painting line, diamond polishing pad, etc. The main work of these equipment is to complete the cutting edge before the finished product, in order to meet the stress requirements and aesthetic requirements of product design.
5.Vacuum Brazed
Some transitional elements (such as Ti, Cr, W, etc.) are coated on the surface of diamond, and carbide is formed on the surface by chemical reaction with them. Through the action of this layer of carbide, diamond, binder and matrix can achieve solid chemical metallurgical bonding through brazing, so as to realize the true metallization of diamond surface, which is the principle of diamond brazing.
6.Electroplating
Electroplated diamond tools binding force strong, high grinding efficiency, the shape error is small and easy to maintain, but work layer is thinner, service life is low, it is mainly used for glass, ceramic, stone, shell, jewelry and jade article, semiconductor materials and hard alloy grinding, edge grinding, nesting, punching, carving, grinding, etc. More details at www.gloriosotools.com.
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