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Vacuum Brazed Diamond Tools

1.Basic principles of vacuum brazing diamond technology
The basic principle of vacuum brazing diamond technology is to use brazing material containing active elements (such as Ti, Cr, W, etc.), whose melting temperature is lower than the melting temperature of diamond and matrix. In the high-temperature brazing process, active elements are used It chemically reacts with the surface of diamond and forms a layer of carbide. With the help of the transition effect of this layer of carbide, the liquid brazing material wets, spreads, capillary flows, fills gaps, mutually dissolves and diffuses on the surface of diamond and substrate, realizing diamond, The solid chemical metallurgical combination of solder and matrix.

High temperature brazed diamond tools made using brazed diamond technology show incomparable advantages in the following aspects.
(1) The bonding strength is high, and the diamond abrasive is firmly held and does not fall off during use.
(2) The diamond abrasive has a good wetting form. After brazing, it takes on the shape of a “golden pyramid”, resulting in a high exposure of the diamond abrasive. At the same time, the shape between the diamond abrasives presents a “concave” shape, with a large chip-holding space. During use, It is not easy for chips to become clogged and cause tool failure.
(3) The diamond abrasive itself has a high utilization rate, especially when the diamond itself has micro-fragmentation and self-sharpening properties, the life of the tool will be greatly improved, effectively saving resources.
(4) Its strong chemical-metallurgical bonding is suitable for high-load and efficient grinding.
(5) There is no (very little) waste gas, no (very little) waste water, and no (very little) dust during the production process of brazed diamond tools. It is completely green manufacturing and has obvious environmental advantages over other production methods.

2.Diamond tool brazing equipment and processes
Due to the wide variety of diamond tools and their different forms, there are countless derived processes and equipment. However, the current mainstream processes are induction brazing and vacuum brazing.
High-frequency induction brazing has fast heating speed and high brazing efficiency; simple operation and low labor intensity; it can braze various complex shapes and multi-tooth workpieces; when using automatic feeding, atmosphere protection or vacuum induction brazing, the joints have excellent appearance and brazing quality. This method not only has low production cost in one welding, but also the base body can be re-soldered and reused. With the increase in the labor cost of diamond tool manufacturing and the improvement of the quality and stability requirements for diamond tool brazing, the automatic induction brazing process has gradually become the main method for welding diamond cutting tools. The automatic induction brazing of diamond tools can realize automatic tooth separation, It automatically identifies and picks up the cutter head and automatically feeds the soldering pieces. It has the advantages of high welding precision, strong joints, and long service life. One person can operate multiple machines, which greatly reduces labor costs.
Furnace brazing (continuous atmosphere furnace brazing) is mainly used for the production of small saw blades and special-shaped diamond tools. Hydrogen and nitrogen generated by decomposing ammonia are generally used as reducing gases. The heating speed is slow and the temperature is uniform. The brazed joints are beautiful and Reliable quality, bright workpiece surface, high production efficiency, low welding cost, suitable for mass production.
Vacuum brazing generally uses resistance furnace radiation heating, which has high production efficiency and can weld diamond tools with complex structures and large sizes. At present, vacuum brazed single-layer diamond tools are widely used in the manufacturing of solid tools, grinding wheels, stone tools, and glass tools. Vacuum multi-layer diamond tools have good application prospects.

3.Main factors affecting diamond brazing performance
In the preparation process of diamond welding tools, solder powder, gold plating
Diamond type, brazing process parameters (including needle welding temperature, insulation time, brazing atmosphere, etc.) all have a great impact on diamond brazing performance.

3.1 Solder composition
(1) The solder has a suitable melting point.
(2) The brazing material has good infiltration and diffusion effects on diamond.
(3) The solder material should have a stable and uniform composition to reduce segregation and the loss of volatile elements during the brazing process.
(4) It has certain strength, hardness and thermal expansion coefficient.
(5) Avoid large residual stress at the cross section of diamond and solder due to mismatch in physical properties.

3.2 Diamond coating
Diamond coating refers to coating a cloud of affinity metal on the surface of diamond, and forming a strong chemical bond between the coating and diamond, reducing the surface energy of diamond, making it easy to infiltrate with metal bonding agents, and improving the weldability of the diamond surface. Achieve metallurgical bonding between diamond and metal.

3.3 Vacuum brazing process parameters
(1) The process of melting and filling of solder, as well as the chemical metallurgical reaction between the molten solder and the diamond surface, is inseparable from the effects of temperature and holding time.
(2) Brazing atmosphere
Since diamond is prone to graphitization at high temperatures, the diamond brazing process is generally carried out in vacuum or protective atmosphere. However, different brazing atmospheres have different effects on the diamond brazing morphology, intermediate carbide formation, diamond graphitization and grinding. The effects of grain damage patterns, etc. are different.