Resin-bonded superhard material tools mainly use diamond or cBN as abrasives, resin powder as binder, and add appropriate filling materials. After formula design, weighing and mixing, hot pressing molding, secondary curing, and subsequent processing, etc. Superhard tools made by this process are suitable for different grinding requirements.
Compared with ceramic bonded or metal bonded superabrasives, it has the characteristics of simple manufacturing process, easy availability of raw materials, low cost, etc. It can be used in large quantities of low-quality superabrasives and can process a wide range of objects, such as various difficult-to-machine steel materials, Carbide, glass, ceramics, stone, etc.
Resin superhard abrasives are widely used because they have good self-sharpening properties during the grinding process and are not easily clogged. The ground workpieces have good surface quality and the grinding wheels are easy to dress.
The resin binders used in resin diamond tools are mainly divided into two categories: phenolic resin and polyimide resin. The actual working temperature of phenolic resin diamond tools does not exceed 120°C. Polyimide resin has slightly better heat resistance and can be used in Long-term use at 260℃.
Since polyimide resin is relatively expensive, especially in recent years, scientists have modified phenolic resin so that its actual working temperature can reach above 200°C, so phenolic resin is increasingly used.
Design of resin-bonded diamond tools The design of resin-bonded diamond tools is mainly based on the following five aspects
1 The adhesion must be good. The bonding agent can be evenly distributed on the surface of the abrasive, hold the abrasive grains firmly in the grinding surface, and can be firmly bonded to the base (1), which not only prevents the abrasive from falling off prematurely, but also prevents the separation of the bonding agent and the base body. , to ensure production safety.
2. High grinding efficiency, good wear resistance, and good processing finish (or surface roughness). Because the resin bond is elastic and brittle, it has good self-sharpening properties during grinding and is not easy to clog, but has poor wear resistance. Therefore, when we research and design the bond formula, we must consider both high grinding efficiency and as high wear resistance as possible while ensuring the smoothness requirements. The preparation of the binder is very critical. It is necessary to choose the best ratio of binder to meet both high grinding efficiency and good wear resistance. Only by taking both into consideration can the requirements of grinding processing be ensured, while can achieve the purpose of reducing costs.
3. The heat resistance is better. If the heat resistance of the bond is poor, the abrasive tool will not be able to withstand high temperatures during use and will be consumed quickly. The grinding tool may even be burned, cracked, and de-ringed due to excessive grinding heat. Therefore (1) choose a durable material. Use a binder with good thermal properties and add appropriate fillers to improve its heat resistance; (2) Use coolant for wet grinding as much as possible to improve the durability of the grinding tool; (3) If dry grinding is used, Keep the cutting amount as small as possible to improve the durability of the grinding tool.
4. The strength of the bonding agent must be high. The strength of the bond directly affects the grinding efficiency, wear, workpiece quality and safety performance of the abrasive tool during use. Therefore, it is necessary to understand the factors that affect the bond strength. The main factors that affect the strength of the binder are: (1) The addition of fillers will increase or decrease the strength of the binder. Most fillers can increase the mechanical strength after addition, and increase with the increase in the amount of addition within a certain range. But the wear ratio is reduced. Some fillers, such as graphite and solid molybdenum disulfide, will reduce the strength after adding them, so fillers should be selected reasonably according to the requirements; (2) The molding density of the grinding tool (or the porosity of the grinding tool) will affect the bond strength. If the molding density of the abrasive tool is low, the porosity will be high, and the bond strength will be low. On the contrary, the bond strength will be high. Therefore, the porosity parameters of the grinding tool must be designed reasonably; (3) The hardening temperature and secondary hardening temperature of the grinding tool molding, as well as the heating curve, will affect the bond strength.
5. The hardness of the bond must be appropriate and the wear resistance must be good. The strength of the bond must match the wear rate of the diamond (or CBN) abrasive grains. The abrasive grains cannot fall off prematurely because the bond wears too fast. In that case, the abrasives will not be fully used, resulting in waste.