Solutions for Vacuum Brazing of Diamond Tools

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In recent years, the application of diamond cutting tools in woodworking industry has caused great changes in furniture industry. Furniture manufacturers around the world are replacing carbide with PCD cutters to reduce tool costs and increase productivity.
Today’s furniture mostly uses particleboard, density board and other wear-resistant materials. The wear resistance of diamond cutting tools is 125 times that of cemented carbide. The quality of finished products of diamond cutting tools is much higher than that of cemented carbide cutting tools, and the solid wood processing is far different from that of cemented carbide cutting tools.
Because of its special physical properties, diamond cutting tools show irreplaceable advantages in modern cutting process, and are regarded as one of the most promising tool materials to improve productivity. At present, the application of diamond tools in various materials processing is becoming more and more popular, and it has become an indispensable and important tool in modern industrial intelligent production and processing.
Diamond cutting tools have the advantages of high hardness and wear resistance, low friction coefficient, high elastic modulus, high thermal conductivity, low thermal expansion coefficient, and low affinity with non-ferrous metals. It can be used for precision machining of non-metallic hard and brittle materials such as graphite, high wear resistant materials, composite materials, high silicon aluminium alloy and other tough non-ferrous metal materials.
Brief introduction of diamond cutting tools.
Diamond cutting tools have the advantages of high hardness and wear resistance, low friction coefficient, high elastic modulus, high thermal conductivity, low thermal expansion coefficient, and low affinity with non-ferrous metals. It can be used for precision machining of non-metallic hard and brittle materials such as graphite, high wear-resistant materials, composite materials, high silicon aluminium alloy and other tough non-ferrous metal materials.
There are many types of diamond cutting tools, and their performances are significantly different. The structure, preparation methods and application fields of different types of diamond cutting tools are quite different.

Application of Diamond Tool Types
1. Natural diamond cutting tools
Natural diamond cutting tools are mainly used for precious non-ferrous metals such as copper and copper alloys, gold, silver and rhodium, as well as ultra-precision mirror processing of special parts, such as video disk, optical plane mirror, polyhedron mirror and quadric mirror. But its crystalline anisotropy makes the tool expensive.
Natural diamond is the hardest material in known minerals, which is mainly used to prepare tools and turning tools. The radius of natural diamond tool can reach 0.01-0.002 micron after fine grinding. The cutting edge of the natural single crystal diamond (SCD) tool was enlarged 1500 times and the smooth edge was observed. Ra can reach 4 micron in SCD turning aluminium piston, and 15-50 micron in PCD cutting tool when the surface is rough under the same cutting conditions. Therefore, the mirror surface can be obtained by precision and ultra-precision machining with SCD tool and precision lathe.
With the continuous development of science and technology, synthetic diamond monolithic wafers have been used in the market. High temperature and high pressure (HPHT) diamond wafers and chemical vapor deposition (CVD) diamond wafers. Because of its nature and natural diamond almost no difference, so it is recognized by the market. Among them, high temperature and high pressure synthetic diamond wafers have been recognized by the market for their high cost performance.

2. Artificial Polycrystalline Diamond (PCD) Tools
PCD is a polycrystalline material synthesized by aggregation and sintering of diamond powder with cobalt and other metal binders under high temperature and ultra-high pressure, also known as sintered diamond. Polycrystalline diamond tools are sintered into milling cutters, which are used for milling. The PCD grains are arranged in disorder, isotropic, uniform hardness and graphitization temperature is 550 C. The tool has high hardness, high thermal conductivity, low coefficient of thermal expansion, high modulus of elasticity and low coefficient of friction. The blade is very sharp and so on.
The performance of PCD depends on the content of diamond grain and cobalt. The tool life of PCD is 10-500 times as long as that of WC tool. It is mainly used for turning non-ferrous metals such as aluminium, copper, magnesium and their alloys, cemented carbide, fibre plasticizer with strong wear resistance, metal matrix composites, wood and other non-metallic materials. The cutting speed, feed speed and depth of cutting depend on the material and hardness of the workpiece.

3. PDC Tools for Artificial Polycrystalline Diamond Composites
Artificial polycrystalline diamond composite (PDC) has similar performance and application to PCD cutting tools. It is mainly used in cutting non-ferrous metals, cemented carbide, ceramics, non-metallic materials (plastics, hard rubber, carbon rods, wood, cement products, etc.) and composites, gradually replacing cemented carbide cutting tools. Because there are some residual bonded metals and graphite between diamond particles, the distribution of bonded metals in coalescence or vein shape will reduce tool wear resistance and life. In addition, there is residual solvent metal, which contacts directly with the surface of diamond. The cutting performance of the tool is not stable because of the reduction of the oxidation resistance of PDC and the heat resistance of the tool.
In order to improve the toughness and solderability of PCD blades, PCD and cemented carbide blades are often made into synthetic polycrystalline diamond composite blades (PDC). That is, a layer of 0.5-1 mm thick PCD sintered on the surface of cemented carbide substrate. The bending strength of composite blade is basically the same as that of cemented carbide, and its hardness is close to PCD, so it can be used instead of PCD. The edge sharpness and surface quality of PCD and PDC cutting tools are lower than those of natural diamond cutting tools. At the same time, its machinability is very poor and its grinding ratio is small, so it is difficult to form arbitrarily according to the geometry of the tool head. Using artificial polycrystalline diamond composite sheet can only produce turning tools, but can not produce indexable inserts with chip breaking grooves and milling cutters with complex three-dimensional surface geometry.
Diamond coated cutting tools can be used in high-speed machining because, in addition to the excellent mechanical properties of diamond coated cutting tools, diamond coated cutting tools can be prepared with arbitrary complex shapes for high-speed machining such as Al-Ti alloy aviation materials and difficult-to-machine non-metallic materials such as graphite electrodes.

4. Cubic Boron Nitride Cutting Tools
Cubic boron nitride (PCBN) is not a kind of diamond, but it is the second inorganic superhard material after synthetic diamond. Its hardness is slightly lower than that of diamond. Its thermal stability is good. Its heat resistance can reach 1400-1500 degrees, almost double that of diamond. Cubic boron nitride (PCBN) tools are mainly suitable for processing various ferrous metals and their alloys. All kinds of hardened steel (carbon tool steel, bearing steel, die steel, high-speed steel) pearlite gray cast iron (vanadium-titanium cast iron), cold-hardened cast iron superalloy (nickel-based alloy cobalt-based alloy) and surface spray surfacing welding process. It has long service life, reduces the number of tool changes, compensates the time of shutdown, makes the high efficiency of CNC machine tools and automated production lines more fully play, and can change the traditional. Machining method (i.e. roughing with tool before quenching and finishing with grinding wheel after quenching) can be used for turning (turning instead of grinding) before quenching in a CNC machine tool, which has good economic benefits.
Widespread use of diamond woodworking cutting tools
Woodworking carving cutters, router cutters, gongs, trimmers, woodwork knives, bottom clearing knives, arc knives, flat knives
Mainly used for trimming, engraving and forming of woodworking furniture, cabinet doors, wardrobes, wooden doors, tables and chairs, photo frames, logo wooden brackets, wood flooring, density board, particleboard, anti-betterboard, fireproof board, multi-layer board, bakelite board, fiberboard, melamine veneer, plexiglass, acrylic, cast aluminium, graphite, tungsten steel, ceramics, hard plastics and other materials. Diamond cutting tools are widely used in furniture, cabinets, wooden doors and other woodworking industries. They have high durability-price ratio, 100 times longer tool life and 12 months longer durability without grinding.

But when brazing diamond straight knives, it is difficult to braze. The reasons are as follows.
1. PCD composite is thin, about 1.2 mm. Temperature should not be too high, easy to overheat. PCD is damaged.
That is to say, the brazing temperature should not be too high, and should not exceed 760.
2. After one side of brazing is completed, the other side is heated, which easily leads to the melting of the side that has been brazed.
The uneven heating results in brazing defects.
For the pain point of vacuum furnace brazing diamond straight knife can be used. Avoid the above problems.

Vacuum brazing furnace for diamond woodworking tools has great advantages.
1. Heating uniformity, accurate temperature control, no overheating problem.
2. It can realize batch production and produce more than 200 cutting tools at a time.
3. Easy to operate, and more convenient, a tool with multiple tool heads can also be welded at the same time;
4. Increase strength to ensure consistency of welding.
If you need a vacuum brazing furnace for diamond woodworking tools, you can contact SIMUWU.

Vacuum brazing paste
Low temperature solder paste, which contains active metal titanium, can not be soldered in air or in general protective atmosphere (e.g. nitrogen); it can be soldered in argon protective state, but the requirement is higher and the success is not easy. Containing active filler metal titanium, it can weld single crystal diamond, CVD, PCD, PCBN. It is suitable for most PCD welding (especially PCD with temperature less than 760 degrees), and requires high vacuum (10-2Pa).
Vacuum furnace and low temperature solder paste for diamond woodworking tools, vacuum brazing scheme for diamond PCD woodworking tools.

Vacuum brazing process:
Step 1: Apply ointment
The solder paste is painted on the weld seam manually, the knife head is placed well, and the knife head is fixed in the appropriate position by using the stickiness of the solder paste.
Step 2: Feeding and heating up
The tool is put into the vacuum furnace, and the whole welding process is maintained in the pumping state. When the vacuum degree reaches 10-2 Pa, the temperature begins to rise, holding for 3 minutes at 300 and 500 degrees respectively, holding for 5 minutes when it rises to 20 degrees below the solid point, and then holding for 5 minutes when it rises to the welding temperature. The temperature and holding time can be adjusted according to the power of each vacuum furnace, the number of primary welding parts and the size of the workpiece.
Step 3: Cooling
With the furnace cooling, continue to maintain the state of exhaust, until the temperature in the furnace is below 200 degrees, can not open the furnace to take parts.