When we produce abrasive for cutting disc or grinding wheel, we must first select the particle size of the abrasive according to the surface quality, processing efficiency, durability, wheel speed, dressing process and other requirements to be achieved by the work piece. So what is the abrasive grain size and how to choose the abrasive grain size? Let’s start to discuss .
Particle size is directly related to the quality of the grinding process, especially the surface roughness. To obtain a satisfactory roughness, the choice of abrasive particle size is very important.
Understand what is “granularity”, then how do we choose the appropriate granularity number in actual production?
This problem is a bit complicated, because in addition to the surface quality of the work piece, processing efficiency, durability, etc., the grinding method (internal grinding, external grinding, end grinding, etc.), dressing process, work piece type, processing technology, etc. will all affect To the choice of granularity number. Let’s briefly talk about it below, and welcome everyone to add.
(1) The selection principle of super-hard abrasives is actually the same as that of ordinary abrasives. Compared with ordinary abrasives, due to the sharpness and non-wearability of super-hard abrasives, the grain size of super-hard abrasives should be finer by 1 to 2 particle size numbers if the same surface roughness requirements are achieved. At the same time, under the premise of satisfying the surface roughness, try to choose a coarser particle size to achieve higher processing efficiency.
(2) Considering the bonding strength of different bonding agents, each bonding agent has its optimal particle size range, too coarse or too fine is not conducive to its grinding process. For general rough and fine grinding operations, resin bond abrasives should be finer than 100/120 (too coarse, resin bond cannot be held, causing the abrasive to fall off prematurely, which is not conducive to grinding); metal bond abrasives should be 70/80 ~230/270; The ceramic bond abrasive tool is in between. In addition, because the resin bond has a certain degree of elasticity and the same roughness requirement, the abrasive particle size can be appropriately selected to be coarser.
(3) When the grinding allowance is large, the grinding depth is large, and coarse grinding is used, preferably coarse grain; when the precision is high, the grinding depth is small, and fine grinding is used, preferably fine grain. In forming grinding, in order to improve the shape retention of the abrasive, the abrasive grain size is finer than that used for general grinding.
(4) If the grinding wheel is finely dressed, coarser grain size abrasive tools can be used to obtain higher grinding efficiency; when grinding cemented carbide, due to the poor thermal conductivity of the material, it is easy to cause burns and cracks, and coarse grain size should be selected; Coarse grain size should be used for flat grinding, cutting, grooving, etc.; high-speed grinding wheels should be finer 1 to 2 grain sizes; thin-walled work pieces and dry grinding are likely to generate heat and cause burns, so coarse grain size should be used.
Table 4 shows the average particle size of diamond and CBN and the number of particles per carat. The number of particles per carat here is very valuable. It is directly related to the area of the work contact surface and the number of abrasive particles involved in the work. Some one who have interested in this can study it. Finally, emphasize the quality control of super-hard abrasive grain size.
As one of the three elements of abrasive tools, the stability of its quality directly determines the stability of the quality of the grinding wheel. The importance of the stability of the quality of the grinding wheel is self-evident. Therefore, every abrasive manufacturer must establish its own set of abrasive inspection system.
The national standard is actually the minimum standard. Each manufacturer of abrasives cannot blindly copy it. Instead, they should establish their own particle size composition standards based on actual needs, and scientifically and reasonably control the particle size of the abrasives in order to stabilize product quality. Of course, the quality inspection of abrasives is not only the particle size composition, but also performance indicators such as impact toughness, bulk density, and single particle strength, which are not explained here.