For different workpiece materials and different processing requirements, different grinding wheels should be used. Even when grinding the same workpiece material, the grinding ratio of different brands of grinding wheels may differ by 2 to 5 times, so the appropriate grinding wheel should be selected.
Diamond wheels are the best grinding tools for grinding non-metallic materials with high hardness and brittleness, such as cemented carbide, optical glass, ceramics, gemstones and stone. But because diamond is easy to carbonize at 700 ℃ ~ 800 ℃, it is not suitable for grinding steel. The hardness of CBN is slightly inferior to diamond, but its thermal stability is good (it can withstand high temperature of 1300 ℃ ~ 1400 ℃), it does not decompose at high temperature like diamond, ie oxidation and graphitization, chemically inert with iron group elements, The thermal conductivity is high (46 times that of corundum), and the life of the grinding wheel made by it is long (up to tens to hundreds of times of the corundum grinding wheel). It is an alternative to corundum grinding wheel for grinding hardened steel, high-speed tool steel, bearing steel , Stainless steel, heat-resistant steel and titanium alloy and other metal materials with high hardness and toughness.
The bonding agents for super-hard abrasive wheels are resin, metal, ceramic, electroplating and brazing. Resin bond grinding wheel is mainly used for sharpening tool, grinding hole, cylindrical grinding and surface grinding; metal bond grinding wheel is used for plunge grinding, shaping grinding of optical curve grinder, sharpening single-edged tool, grinding small bit The spiral groove is also suitable for electrolytic grinding; the grinding efficiency of the ceramic bond grinding wheel is high, the shape retention is good, the durability is high, it is easy to dress, the service life of the grinding wheel is long, and because the ceramic bond itself has good chemical stability, Heat-resistant, oil-resistant, acid-alkali-resistant erosion, suitable for all kinds of grinding fluids, and low cost of grinding It is also suitable for efficient grinding of holes (wet grinding) and use on coordinate grinding machines; brazed grinding wheels are suitable for ultra-high-speed grinding.
It must be pointed out that different brands of abrasives have different crystal morphology and particle shapes due to different manufacturing processes, but have different strengths, thermal stability and crushing characteristics. According to the type of bonding agent, the grinding workpiece material and the grinding method, Choose different abrasives. For ceramic bond grinding wheels used for efficient and high-precision grinding, high-strength and sharp-shaped abrasives can be used, such as the PDA type (man-made diamond variety) and ABN800 type (CBN variety) produced by DeBeers or other similar properties. Grade.
The surface of the super-hard grinding is also coated with metal coating (the metal coating can play a role in strengthening and toughening, slowing thermal shock and acting as a bridge between the abrasive particles and the bonding agent, which can improve the performance of the grinding wheel) and non-metal coating It should be selected according to different conditions such as the type of bonding agent, workpiece material, dry grinding and wet grinding. Dry grinding generally uses copper clothing, such as RVD-Cu, CBN-Cu; wet grinding uses nickel clothing, such as RVD-Ni, CBN-Ni. At present, the plating metal has developed from nickel and copper to titanium, tungsten alloys, non-metallic ceramics, etc., from a single coating to a composite coating, and from abrasive grain plating to fine powder plating.
The concentration of the hard abrasive grain grinding wheel cannot be selected too low. High concentration can bring high grinding ratio. The 200% concentration super hard abrasive wheel is actually a kind of ordinary grinding wheel with super hard abrasive as auxiliary material, generally not recommended Naming. At present, high-speed and high-efficiency grinding use higher concentration, and the concentration of ceramic bond CBN grinding wheel uses higher concentration for high-efficiency grinding. The concentration of ceramic bond CBN grinding wheel is generally selected to be more than 125%. For example, imported supporting ceramic CBN grinding wheel, its The concentration is generally 175% to 200%.
The hardness level of the grinding wheel indicates the strength of the bond on the abrasive. The reasonable selection of the hardness of the grinding wheel is uniform and stable, and the reasonable choice of hardness is an important prerequisite for ensuring the quality of grinding. Foreign super-hard abrasive wheels generally have 3 to 7 hardness grades to choose from, but the super-hard grinding wheels produced in our country are not marked with hardness grades, and the corresponding standards are not specified in GB6409, so the quality is not easy to guarantee, which brings inconvenience to users and is urgently needed. Supplement and perfect.
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