& Grinding is an extremely important mechanical processing method, accounting for more than 30% of the total machining volume. Modern machining places high demands on the surface quality of machined parts, including high precision, low surface roughness values, low residual stresses, and low hardening layers. This has catalyzed the promotion of superhard abrasive tools and CNC grinding machines, accelerating the development of high-speed, efficient, and high-precision grinding processes< br> Ultra hard materials (such as diamond, cubic boron nitride, etc.) grinding tools are advanced tools with extremely excellent performance. According to different grinding requirements, they are divided into different types of binders, mainly resin, metal, ceramic, and electroplating. Among these various diamond grinding tools, diamond grinding tools with various resins as binders account for the vast majority< br> Proportion of diamond grinding tools with different binders in some countries or groups of countries (%)
Resin diamond grinding tools have unique characteristics
1. Obvious advantages
As of 2009, there were about 300 resin diamond grinding tool production enterprises in China that had a certain influence on the domestic and international markets. At present, there are dozens of types of resins or modified resins used as binders for grinding tools (including ordinary grinding tools and superhard material grinding tools) both domestically and internationally, such as phenolic resin, melamine resin, polyimide resin, epoxy resin, furfural resin, phenolic resin, urea formaldehyde resin, polyvinyl alcohol formaldehyde resin, polyester resin, polyimide resin, boron phenolic resin, etc. Among them, phenolic resin has the highest usage and widest application range< br> Compared to diamond grinding tools produced with metal or ceramic binders, resin bonded grinding tools have the following obvious advantages: 1) raw materials are inexpensive and easy to obtain; 2) The initial investment is not high; 3) The operation is not complicated and the production cycle is relatively short; 4) The energy consumption in the production process is relatively low< br> Resin bonded diamond grinding tools can be used in both high efficiency and low surface roughness machining applications, as well as those with lower requirements, such as semi precision grinding, precision grinding, and polishing grinding. The corresponding relationship between diamond particle size and processed surface roughness is shown in the table below< br> The relationship between diamond hardness and machined surface roughness The processing material objects of resin bonded diamond grinding tools are very wide, and more than 80% of hard alloy workpieces worldwide need to be processed using it. Moreover, semiconductor materials, new energy crystal materials, ferrite materials, building ceramic materials, engineering ceramic materials, functional ceramic materials, glass materials, refractory materials, electric carbon materials, non-ferrous metal materials, high quenched hard metal materials, as well as natural and artificial stone materials, can all be processed using resin bonded diamond grinding tools< br> If B-containing diamond or surface modified diamond is used as abrasive particles, resin bonded diamond grinding tools can also process black metals, heat-resistant alloys, etc. It is precisely because of its excellent performance and broad-spectrum applicability that the application fields of traditional SiC and Al2O3 series grinding tools are gradually being eroded, replaced, and surpassed by it< br> 2. Limitations of high temperature applications
However, things always have their two sides, and as organic materials, resins also have obvious shortcomings in their performance: they are difficult to use under high temperature conditions. Taking the most commonly used phenolic resin as an example, its safe working temperature is below 120 ℃, it begins to decompose above 236 ℃, and it will carbonize above 300 ℃. Even if polyimide with good heat resistance is used as the binder, it can only work normally below 260 ℃< br> Usually, the grinding energy during grinding is 20-60J/mm3, and the temperature generated on the surface of the workpiece by grinding can be expressed by the following equation:
In the formula: C - heat capacity; VW - workpiece speed; AP - Grinding depth; F - feed rate; Vs - Grinding wheel speed
Grinding tests have shown that even with a grinding feed rate of 0.02mm, a high temperature of over 400 ℃ will be generated at the contact point between the front end of the grinding tool and the workpiece being machined. Under dry grinding conditions, the local temperature in this area may even reach thousands of degrees< br> This is enough to cause the decomposition and carbonization of phenolic resin, leading to cracking, collapse, and loss of control over diamond abrasive particles in resin bonded diamond grinding tools, resulting in premature detachment of diamond abrasive particles. This proportion can reach over 40% of the total diamond particles, seriously affecting the service life of the grinding tool< br> Furthermore, the high temperature generated by grinding can also erode the surface of the workpiece being ground, resulting in fine cracks. During the use of the workpiece, due to stress concentration, it is likely to fracture at the crack site, directly affecting the machining quality and workpiece life, and posing a safety hazard to personnel and equipment. Thirdly, the high temperature generated by grinding may also cause changes in the local metallographic structure of the workpiece surface. Taking quenched steel as an example, when the temperature exceeds 650 ℃, its metallographic structure will transform from martensite to austenite, which actually affects the performance of the workpiece. The commonly used high-speed, large-scale, and heavy-duty grinding processes in modern grinding are even more difficult for traditional resin bonded diamond grinding tools to handle< br> 3. How to effectively overcome the limitations of heat resistance For a long time, how to improve the heat resistance of resin bonded diamond grinding tools, so that they can work normally under higher temperature conditions, and maximize their strengths and avoid their weaknesses, has been a problem that troubles the industry< br> Many people have attempted to improve the heat resistance of resins themselves, seeking breakthroughs through the synthesis of new resins or research on resin modification, and have also made certain progress. However, as a member of the organic material family, the resin itself has limited room for improving its heat resistance due to its physical and chemical properties. We only need to look at the fact that the upper limit of the heat-resistant temperature of polyphenylene sulfide (PPS) is 400 ℃, and polyphenylene thiazole can only tolerate 500 ℃ to understand. Some people are also working on the formulation of metal powder components in resin binders, hoping to achieve the effect of quickly transferring grinding heat from the "metal bridge" by increasing the proportion of metal components such as Cu powder with good thermal conductivity. Regardless of the effectiveness of this "bridge", the increase in metal powder not only significantly increases the formulation cost, but also changes the microstructure and hardness of resin bonded diamond grinding tools, which will inevitably have a negative impact on their sharpness and self sharpening< br> I am trying to take a different approach. Based on the characteristic that some substances absorb a large amount of thermal energy during phase transition, the resin bonded diamond grinding tool formula components are changed to achieve "self heat dissipation" performance. After experimentation and screening, a breakthrough has indeed been made in improving its heat dissipation performance, and a national invention patent has been obtained: "Strong Heat Dissipation Resin Diamond Grinding Tool" (patent number: ZL01129089.7, international patent main classification number: CO8J 5/14)< br> The resin bonded diamond grinding tool produced using this invention patent always maintains good working condition during grinding, and has outstanding advantages compared to traditional resin bonded diamond grinding tools:
Sharp grinding, no blockage during use, low noise< br> (2) The working layer of the grinding tool has no cracks or "ring detachment" (i.e. the diamond working layer separates from the metal substrate under the action of grinding heat) during operation< br> (3) The surface of the workpiece has no cracks, erosion or changes in metallographic structure< br> (4) The working layer of the grinding tool has high strength and can withstand grinding feed rates more than 10 times higher than traditional resin bonded diamond grinding tools< br> (5) The working layer of the grinding tool is wear-resistant, and its service life is more than 20% longer than that of traditional resin bonded diamond grinding tools with the same specifications, particle size, and concentration< br> Grinding the same workpiece, the grinding cost is more than 15% lower than traditional resin bonded diamond grinding tools with the same specifications, particle size, and concentration< br>