Diamond saw blade is a cutting tool, widely used in the processing of hard and brittle materials such as stone, concrete and ceramics. The diamond saw blade is mainly composed of two parts; the base body and the cutter head. The main body is the main support part of the bonder head, and the cutter head is the part that is cut during use. The cutter head will be continuously consumed during use, while the base body will not, and the cutter head can cut. The role is because it contains diamond, which is currently the hardest substance. It rubs and cuts the processed object in the cutter head. The diamond particles are wrapped in metal inside the cutter head.
During use, the metal carcass is consumed together with the diamond. Generally, the ideal case is that the metal carcass is consumed faster than the diamond so that both the sharpness of the cutter head and the longer life of the cutter head can be ensured.
Classification of Diamond Saw Blades More and more industries use diamond saw blades in the production process. With the integration of the industry, the types of diamond saw blades have become more refined.
one. Manufacturing process classification:
1. Sintered diamond saw blades: divided into cold-pressed sintering and hot-pressed sintering, and pressed and sintered.
2, welding diamond saw blade: high-frequency welding and laser welding two, high-frequency welding through the high-temperature melting of the welding head and the substrate together, laser welding through the high-temperature laser beam to the edge of the blade and the substrate contact to form a metallurgical melting . 3. Electroplated diamond saw blade: The cutter head powder is attached to the substrate by electroplating.
two. Appearance classification:
1. Continuous Edge Saw Blades: Continuous sawtooth diamond saw blades are generally produced by sintering method. Commonly used bronze binders are used as basic carcass materials. Water must be added to ensure the cutting effect, and the type of the slits can be cut with a laser.
2. Blade-type saw blade: Sawtooth disconnection, cutting speed, suitable for dry and wet cutting methods.
3. Turbine-type saw blade: Combining the advantages of the first and second items, the serration continuously exhibits a turbine-like uniform bump, which improves the cutting speed and increases the service life.
Different materials use different types of diamond saw blades. Different powder formulations are suitable for different material properties, and have a direct impact on the quality, effectiveness, qualification rate, and even cost and benefits of the material products.
The factors influencing the efficiency and life of the diamond saw include sawing process parameters, diamond particle size, concentration, and binder hardness. According to the number of energy saw blade speed, sawing concentration, and feed speed.
First, the sawing parameters (1) saw blade linear speed: In actual work, the linear speed of the diamond saw blade is limited by the equipment conditions, saw blade quality and the nature of the sawn stone. From the perspective of the best saw blade life and sawing efficiency, the linear speed of the saw blade should be selected according to the nature of different stone materials. When sawing granite, the blade speed can be selected in the range of 25m to 35m/s. For granites with high quartz content and difficult to saw, the lower limit of the blade speed is appropriate. In the production of granite tiles, the diameter of the diamond saw blade used is small and the line speed can reach 35m/s.
(2) Sawing depth: The sawing depth is an important parameter concerning diamond abrasion, effective sawing, the force condition of the saw blade and the nature of the sawed stone. In general, when the linear speed of the diamond circular saw blade is high, a small depth of cut should be selected. From the present technology, the depth of sawing diamond can be selected between 1 mm and 10 mm. When sawing a granite block with a large-diameter saw blade, the sawing depth can be controlled between 1 mm and 2 mm, and at the same time, the feed speed should be reduced. When the linear speed of the diamond saw blade is large, a large depth of cut should be selected. However, within the allowable range of saw performance and tool strength, it is necessary to take as much cutting concentration as possible to improve cutting efficiency. When there are requirements on the machined surface, small depths of cut should be used.
(3) Feed speed: The feed speed is the feed speed of sawing stone. Its size affects the sawing rate, blade force, and heat dissipation in the sawing area. Its value should be chosen according to the nature of the sawed stone. In general, sawing softer stones, such as marble, can increase the feed speed appropriately. If the feed speed is too low, it is more conducive to improving the sawing rate. Sawing of fine-grained, relatively homogenous granites can be used to properly increase the feed rate. If the feed rate is too low, the diamond blade can be easily ground. However, when sawing coarse and uneven soft and hard granite, the feeding speed should be reduced, otherwise it will cause vibration of the saw blade to cause diamond chipping and reduce the sawing rate. The cutting speed of sawing granite is generally within the range of 9m ~ 12m/min.
Second, other influencing factors (1) diamond particle size: commonly used diamond particle size in the 30/35 ~ 60/80 range. The harder the rock, choose a finer grain size. Because under the same pressure conditions, the finer the diamond, the more conducive to cutting into hard rock. In addition, the general large-diameter saw blade requires a high cutting efficiency, and a coarser particle size, such as 30/40, 40/50, should be selected; the sawing efficiency of a small-diameter saw blade is low, and the rock sawing section is required to be smooth. Use finer particles, such as 50/60, 60/80.
(2) Cone concentration: The so-called diamond concentration refers to the density of diamonds distributed in the carcass of the working layer (ie, the weight of diamond contained in a unit area). "Specification" stipulates that when there are 4.4 carats of diamond per cubic centimeter of work carcass, the concentration is 100%, and when it contains 3.3 carats of diamond, the concentration is 75%. The volume concentration indicates the volume of diamond in the agglomerate, and specifies that the concentration when the volume of diamond accounts for 1/4 of the total volume is 100%. Increasing the diamond concentration is expected to extend the life of the saw blade because increasing the concentration reduces the average cutting force per diamond. However, increasing the depth will inevitably increase the cost of the saw blade, so that there is a most economical concentration, and the concentration increases as the helium cut-off rate increases.
(3) Hardness of cutter head bond: Generally speaking, the higher the hardness of the bond, the stronger its anti-wear ability. Therefore, the hardness of the bonding agent should be high when sawing the rock with high abrasiveness, and the hardness of the bonding agent should be low when sawing the rock with soft material, and the hardness of the binding agent should be moderate when sawing the rock with high abrasiveness and hardness. .
(4) Force effect, temperature effect and abrasion damage: During the process of cutting the stone, the diamond circular saw blade will be subjected to alternating loads such as centrifugal force, sawing force and sawing heat.
Due to the force effect and temperature effect, the worn diamond saw blade was damaged.
Force effect: In the sawing process, the saw blade is subjected to axial force and tangential force. Due to the force acting in the circumferential direction and in the radial direction, the saw blade is wavy in the axial direction and is dished in the radial direction. Both of these deformations will cause the rock face to be not straight, the stone to be wasted, the noise during sawing, and the vibration to increase, resulting in early damage to the diamond agglomerate, and reduced blade life.
Temperature effect: The traditional theory holds that the influence of temperature on the saw blade process mainly manifests itself in two aspects: one is the graphitization of diamond in the agglomeration, and the other is that the diamond and the carcass have a hot enthalpy and cause the diamond particles to fall off prematurely. . New research shows that heat generated during the cutting process is mainly introduced into the agglomerate. Arc zone temperature is not high, generally between 40 ~ 120 °C. However, the temperature of the abrasive grain grinding point is relatively high, generally between 250 and 700°C. The cooling fluid only reduces the average temperature of the arc zone, but has little effect on the temperature of the abrasive particles. Such a temperature does not cause carbonization of the graphite, but it changes the frictional properties between the abrasive particles and the workpiece, and causes thermal stress between the diamond and the additive, resulting in the fundamental bending of the diamond failure mechanism. Studies have shown that the temperature effect is the most influential factor in breaking the saw blade.
Grinding damage: Due to the force effect and temperature, the saw blade will wear out after a period of use. The forms of wear and tear are mainly the following: abrasive wear, partial crushing, large area crushing, shedding, mechanical abrasion in the direction of the cutting speed of the bonding agent. Abrasive wear: The diamond particles and the parts are constantly rubbing, and the edges passivate into a plane, losing the cutting performance and increasing the friction. The heat of sawing will cause a thin graphitized layer on the surface of the diamond particles. The hardness will be greatly reduced and the wear will be aggravated: the surface of the diamond particles will undergo alternating thermal stress, and at the same time, it will withstand the alternating cutting stress, and fatigue cracks will appear and the part will be broken and exposed. The sharp new edges are the ideal wear patterns; large areas are broken: the diamond particles are subjected to impact loading during cutting and cutting, and the more prominent particles and crystal grains are consumed prematurely; shedding: Alternating cutting forces make the diamond The particles are constantly shaken in the binding agent and loosen. At the same time, the wear of the binder itself during sawing and the heat of sawing soften the binder. This reduces the holding power of the binding agent. When the cutting force on the particles is greater than the holding force, the diamond particles will fall off. Either type of wear is closely related to the load and temperature experienced by the diamond particles. Both of these depend on the cutting process and cooling lubrication conditions.
Diamond saw blade manufacturing methods Along with the rapid development of automotive, aerospace and aerospace technologies, the requirements for material properties and processing technologies are increasingly increasing. New materials such as carbon fiber reinforced plastics, particle reinforced metal matrix composites (PRMMC) and ceramic materials are widely used. These materials have properties such as high strength, good wear resistance, and low coefficient of thermal expansion, which determines the very short tool life when machining them. The development of new wear-resistant and stable superhard cutting tools is the subject of many universities, research institutes and companies. Diamond sets mechanical, optical, thermal, acoustic, optical and many other excellent properties in one, has a very high hardness, low friction coefficient, high thermal conductivity, low coefficient of thermal expansion and chemical inertness, is an ideal material for manufacturing tools. This article gives an overview of the development of diamond tool manufacturing methods in recent years.
1. Application Scope (1) Difficult-to-process non-ferrous metal materials When processing non-ferrous metals such as copper, zinc, and aluminum and their alloys, the materials are easy to adhere to the tools, making it difficult to process them. With the low friction coefficient of diamond and small affinity with non-ferrous metals, diamond tools can effectively prevent the metal from sticking to the tool. In addition, due to the large elastic modulus of diamond, the cutting edge deformation during cutting is small, and the small deformation of the cut non-ferrous metal is small, and the cutting process can be completed under a small deformation, thereby improving the quality of the processing surface.
(2) Difficult-to-process non-metal materials processing Hard-to-machine non-metal materials containing a large number of high-hardness particles, such as glass fiber reinforced plastics, silicon-filled materials, and hard carbon fiber/epoxy resin composite materials, the hard spots of the material The tool wears badly and is difficult to machine with carbide tools. The diamond tool has high hardness and good wear resistance, so the machining efficiency is high.
(3) Ultra-precision Machining With the advent of modern integrated technologies, machining has developed in the direction of high precision, and considerable demands have been placed on tool performance. Because of its small friction coefficient, low coefficient of thermal expansion, and high thermal conductivity, it can cut extremely thin chips, and the chips easily flow out. It has a low affinity with other materials and is less likely to generate built-up edge. It has a small heat output, high thermal conductivity, and can avoid heat. Due to the influence of the cutting edge and the workpiece, the cutting edge is not easily passivated, the cutting deformation is small, and a higher quality surface can be obtained.
2. Diamond tool manufacturing methods Currently, there are four main diamond processing methods: thin film coated tools, thick film diamond welding tools, diamond sintered body tools and single crystal diamond tools.
2.1 Thin Film Coated Tools Thin film coated tools are tools made by depositing diamond thin films by chemical vapor deposition (CVD) on a collective material with good rigidity and high temperature properties.
Since thermal expansion of Si3N4 ceramic, WC-Co cemented carbide, and metal W is close to that of diamond, the thermal stress generated during film formation is small, and thus it can be used as a base material of the blade body. In WC-Co cemented carbides, the presence of cohesive phase Co tends to form graphite between the diamond film and the substrate to reduce the adhesion strength. Pretreatment is required to eliminate the influence of Co before deposition (usually by acid etching to remove Co). .
The chemical vapor deposition method uses a certain method to activate the gas containing the C source. Under a very low gas pressure, the carbon atoms are deposited in a certain area, and the carbon atoms form a diamond phase in the process of agglomeration and deposition. Current CVD methods for depositing diamonds mainly include: microwaves, hot filaments, DC arc spraying, and the like.
The advantage of diamond film is that it can be applied to a variety of geometrically complex tools, such as blades with cuttings, end mills, reamers and drill bits; it can be used to cut many non-metallic materials, cutting force is small, deformation is small, The work is smooth, wear is slow, and the workpiece is not easily deformed. It is suitable for fine work with good workpiece materials and small tolerances. The main disadvantage is the poor adhesion of the diamond film to the substrate, and the diamond film tool does not have regrind.
2.2 Diamond Thick Film Welding Tools The manufacturing process of diamond thick film welding tools generally includes: preparation of large-area diamond films; the required shape and dimensions for cutting diamond films into tools; welding of diamond thick films and tool matrix materials; and diamond thick film tools Grinding and polishing of the cutting edge. (1) Preparation and Cutting of Diamond Thick Films A commonly used method for preparing a diamond thick film is a DC plasma jet CVD method. The diamond is deposited on the WC-Co alloy (mirror-finished on the surface) and the diamond film is automatically detached during the cooling of the substrate. This method has a fast deposition rate (up to 930 μm/h) and the lattices are tightly bound to each other, but the growth surface is rough. Diamond film hardness, wear resistance, non-conductivity determines its cutting method is laser cutting (cutting can be carried out in the air, oxygen and argon environment). The use of laser cutting can not only cut the thick diamond film into the required shape and size, but also can cut out the back angle of the tool, with the advantages of narrow slits and high efficiency.
(1) The welding diamond of the diamond thick film cutter has a high interface energy with the general metal and its alloy, so that the diamond cannot be infiltrated by the general low-melting alloy and the weldability is extremely poor. Currently, the weldability between diamond and metal is improved mainly by adding a strong carbide forming element in the copper-silver alloy solder or by metallizing the diamond surface.
1 Active brazing method Solder is generally made of a Ti-containing copper-silver alloy and is not welded with inert flux or vacuum. The commonly used solder composition Ag = 68.8wt%, Cu = 26.7wt%, Ti = 4.5wt%, the common method of preparation is arc melting and powder metallurgy. Ti, as an active element, reacts with C to generate TiC during welding, which improves the wettability and bond strength of diamond and solder. The heating temperature is generally 850°C, holding for 10 minutes, slow cooling to reduce the internal stress.
2 Surface metallization After welding, the metallization of the diamond surface is performed by surface-treating the metal on the surface of the diamond to give it a metallic or metalloid-like behavior. Generally, Ti is plated on the surface of diamond, Ti reacts with C to form TiC, and TiC and Ag-Cu alloy solder have better wettability and bonding strength. At present, the commonly used titanium plating methods include: vacuum physical vapor deposition (PVD, mainly including vacuum evaporation plating, vacuum sputtering plating, vacuum ion plating, etc.), chemical vapor deposition, and powder covering sintering. The PVD method has a low single plating amount, the diamond temperature during plating is lower than 500° C., and the coating and the diamond are physically attached and have no chemical metallurgy. The CVD Ti reacts with diamond to form a strong metallurgical bond. The reaction temperature is high and damages the diamond.
(2) Sharp diamond cutting tools for thick-film diamond tools include: mechanical grinding, hot metal grinding, ion beam, laser beam and plasma etching.
2.3 Diamond Sintering Tool The diamond thick film is rolled to a diamond grain with an average grain size of 32 to 37 μm by rolling and grinding, or a diamond grain is directly produced by a high temperature and high pressure method, and the grain powder is stacked to WC-16 wt% Co. On the alloy, it was then isolated with a Ta foil and sintered at 5.5 GPa and 1500° C. for 60 minutes to form a diamond sintered body. A turning tool made of the sintered body had high wear resistance.
2.4 Single-crystal diamond tools Single-crystal diamond tools usually fix the diamond single crystal on the small cutter head, and the small cutter head is fixed on the turning toolbar with screws or pressure plates. The fixing method of diamond on the small blade head mainly includes: mechanical reinforcement method (flattening the bottom surface of the diamond and the pressure surface, and pressing and fixing on the small blade head with a pressure plate); powder metallurgy method (adding the diamond in the alloy powder, adding Press to sinter in vacuum to fix the diamond on the tip; bonding and brazing (fix the diamond with an inorganic binder or other binder). Because of the great difference in thermal expansion coefficient between diamond and matrix, diamond is easy to loose and fall off.
3. Conclusion At present, there are still some key issues to be solved in the industrialization of diamond, such as high-speed and large-area diamond thick film deposition process, control of grain boundary density and defect density of the diamond film, the low-temperature growth of diamond film, and the combination of diamond film and matrix. Weak and so on. The excellent performance of diamond cutters and the wide development prospect have attracted numerous experts at home and abroad to conduct research, and some have made breakthrough progress. It is believed that diamond tools will be widely applied to modern processing in the near future.
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