The technical problem of diamond CBN grinding wheel is here!
1. Choose the right grinding wheel
For different workpiece materials and different processing requirements, different grinding wheels should be selected. Even if the same workpiece material is ground, the grinding ratio of different grades of grinding wheels may be 2 to 5 times different, so choose a suitable grinding wheel.
Diamond grinding wheel is the best abrasive tool for grinding non-metallic materials with high hardness and brittleness such as cemented carbide, optical glass, ceramics, gems and stone. But because diamond is easy to be carbonized 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 is not decomposed at high temperature like diamond, namely oxidation and graphitization. It is chemically inert with iron group elements. High thermal conductivity (46 times that of corundum), and long life of the grinding wheel made with it (up to several tens to hundreds of times that of corundum grinding wheel), which is an alternative to corundum grinding wheel for grinding hardened steel, high-speed tool steel, and bearing steel , Stainless steel, heat-resistant steel, titanium alloy and other high hardness and toughness metal materials are the best abrasive tools.
The bonding agent of super abrasive grinding wheel includes resin, metal, ceramic, electroplating and brazing. Resin bond grinding wheels are mainly used for sharpening measuring tools, hole grinding, cylindrical grinding and surface grinding; metal bond grinding wheels are used for cut-in grinding, optical curve grinder forming grinding, sharpening single-edged tools, and grinding small drills. 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, the dressing is easy, the service life of the grinding wheel is long, and because the ceramic bond itself has good chemical stability, It is resistant to heat, oil, acid and alkali, and can be adapted to various grinding fluids. The grinding cost is low, so it has become the first choice for high-efficiency and high-precision grinding; electroplated grinding wheels are suitable for high-speed precision grinding and profile grinding. It is also suitable for high-efficiency grinding of holes (wet grinding) and use on coordinate grinding machines; brazed grinding wheels are suitable for ultra-high-speed grinding.
The technical problem of diamond CBN grinding wheel is here!
It must be pointed out that due to different manufacturing processes, different grades of abrasives have different crystal and particle shapes, and have different strength, thermal stability and crushing characteristics. It should be based on the type of bonding agent, the material of the workpiece and the grinding method. Choose different abrasives. For example, ceramic bond grinding wheels used for high-efficiency and high-precision grinding can choose high-strength and sharp-shaped abrasives.
The surface of the super-hard grinding product has metal-plated clothing (the metal-plated layer can strengthen and toughen, slow down thermal shock, and act as a bridge between the abrasive particles and the bonding agent, which can improve the performance of the grinding wheel) and non-plated metal clothing. Types 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 coats, such as RVD-Cu and CBN-Cu; wet grinding uses nickel coats, such as RVD-Ni, CBN-Ni. At present, plating metals have developed from nickel and copper to titanium, tungsten alloys, non-metallic ceramics, etc., from single coating to composite coating, and from abrasive coating to micropowder coating.
The technical problem of diamond CBN grinding wheel is here!
The concentration of the hard abrasive grinding wheel cannot be selected too low. A high concentration can bring a high grinding ratio. The super-hard abrasive grinding wheel with a concentration of 200% is actually an ordinary grinding wheel with super-hard abrasives as auxiliary materials. Generally, it is not recommended Named. At present, high-speed and high-efficiency grinding all use higher concentration, and the concentration of ceramic bond CBN grinding wheel is high. The concentration of ceramic bond CBN grinding wheel is generally more than 125%, such as imported ceramic CBN grinding wheel. The concentration is generally 175%~200%.
The hardness level of the grinding wheel indicates the holding force of the bond to the abrasive. The uniform and stable hardness of the grinding wheel and the reasonable choice of the hardness level are important prerequisites for ensuring the grinding quality. Foreign super-hard abrasive grinding wheels generally have 3 to 7 hardness grades to choose from. However, the super-hard grinding wheels produced in my country are not marked with hardness grades, and the corresponding standards are not specified in GB6409. Therefore, the quality is not easy to guarantee, which brings inconvenience to users. Supplement and perfect.
Second, use grinding fluid correctly
The technical problem of diamond CBN grinding wheel is here!
Dry or wet grinding can be used when grinding with super-hard abrasive wheels. However, the use of wet grinding can not only extend the life of the grinding wheel, but also prevent the workpiece from grinding burns. Different grinding fluids will cause the grinding ratio of the grinding wheel to differ several times, even ten times. The degree of mechanical wear, chemical erosion and thermal damage of the grinding wheel in the grinding process is closely related to the cooling effect. But be careful when using CBN grinding wheel for wet grinding, because CBN will react with water vapor and oxygen in the air at high temperature to produce ammonia and boric acid (BN+3H2O→H3BO3+NH3). This reaction is called hydrolysis and will accelerate The grinding wheel is worn. Therefore, water-soluble oils or aqueous solutions with extreme pressure additives are often used in use to weaken the hydrolysis. When wet grinding with different grinding fluids, the relative life of CBN grinding wheels is different. The life of the grinding wheel cooled by pure oil is the longest, the life of the grinding wheel cooled by water-soluble oil is the second, and the life of the grinding wheel cooled by water plus anti-rust additives is the lowest.
Conclusion
Although the production of artificial super-hard abrasives in my country started late, it has developed rapidly. In 1997, the annual output of artificial diamonds in my country reached about 500 million carats, and the annual output of CBN was 8 million carats. At present, a complete technical system has been preliminarily formed, such as super-hard abrasives, special grinding fluids, special dressing technologies and devices, and special grinding machines. At present, China has been able to produce RVD, CBN and metal-plated high-grade abrasive products, such as "metal matrix ceramic CBN grinding wheels", "65m/s ceramic bond CBN grinding wheels", etc. The varieties and specifications of super-hard abrasive grinding wheels have formed a series, exceeding The maximum diameter of the hard abrasive grinding wheel can reach φ750mm (the φ1100mm grinding wheel is being trial-produced), the maximum operating speed can reach 80m/s, and the development of a high-speed grinding wheel of 125m/s has created conditions for the popularization and use of super-hard abrasive grinding wheels.
It is foreseeable that with the widespread use of super-abrasive grinding wheels, it will definitely promote the transformation and development of the grinding machine manufacturing industry, and the development of high-efficiency and high-performance grinding machines will further promote the use of super-abrasive grinding wheels.
