Vitrified Diamond Grinding Wheels
- High grinding efficiency
- High abrasion resistance, low abrasive consumption
- Small grinding force, low grinding temperature
- High precision, good surface quality and good shape retention
Vitrified diamond grinding wheels are a kind of circular bonded abrasive with through-hole in the center which made of diamond powder and vitrified (ceramic) bond. It is composed of the diamond layer, transition layer, and matrix.
Vitrified bond compared with resin bond and metal bond
Bond is a kind of material with high bonding ability. It can bond the diamond grains together and play the role of connecting and fixing.
Bond usually has high strength and good heat resistance, and also has proper hardness. The surface roughness of the bond is good, and the filler is economical and the grinding efficiency is high.
There are usually 3 kinds of the bond: resin bond, vitrified bond, and metal bond
The main components of resin bond: resin material, which adds some metals and metal oxide powder, conventional abrasive powder, and etc.
The main components of the vitrified bond: some mineral raw materials and vitrified material with the low melting point, and the composition is more and complex. Its raw materials mainly include 3 parts: Part 1 is plasticity raw materials, such as loess, clay, bentonite, and etc. Part 2 is barren raw materials, such as fluorite, quartz and etc. Part 3 is accelerating melting raw materials, such as borax glass, talc, feldspar, and etc.
The main components of metal bond: some metal powder or alloy powder.
3 Kinds of Bond Performance
Good elasticity can be made into complex shape for abrasive, good polishing performance, poor heat resistance, poor acid and alkali resistance, poor holding for abrasive grains
Abrasive has good self-sharpening, not block, less dressing after one dressing, high grinding efficiency, low grinding temperature, and low grinding roughness.
polycrystalline diamond, and Cubic Boron Nitride tools, PDC, finish polishing optical glass
Good shape of retention, good chemical stability, good heat resistance, good water resistance, good oil resistance, good acid and alkali resistance, good holding for abrasive grains
Longer service life than that of resin bond, sharp cutting, and high efficiency. It does not heat and blocks easily, easy to control machining accuracy and easy to dress.
PCD and PCBN tools, tungsten carbide, engineering ceramic
High strength, good toughness, good durability, good holding for abrasive grains, poor self-sharpening
Abrasives have high strength, good wear resistance, and long service life. Can withstand heavy load, easy to block and difficult to dress.
Glass, ceramic, stone
Thin abrasive layer, high abrasive grains density, sharp grinding, no dressing, short life
Used in complex geometry of abrasive
Applications of the vitrified diamond grinding wheels
Mainly used in wafer (semiconductor silicon and solar wafer), polycrystalline diamond compact (PDC), diamond polycrystalline (PCD), diamond cutting tools, cubic boron nitride (CBN), tungsten steel (cemented carbide), new engineering structural ceramics, crystals, rare earth materials (magnetic materials) and other high hard brittle materials machining.
Superhard material tools include monocrystalline diamond tools, Pcd/Pcbn insert, chemical vapor deposition(CVD) coated tools, and etc. When grinding monocrystalline diamond tools and PCD/PCBN insert, the grinding efficiency of the vitrified diamond grinding wheels are much higher than that of metal bond and resin bond diamond grinding wheel under the same conditions. Poor self-sharpening of the metal bond diamond grinding wheel causes low grinding efficiency and great damage to edges of polycrystalline diamond, Cubic Boron Nitride inserts.
Resin bond has good self-sharpening, but the holding of abrasive grains is small, so its processing efficiency is low and mostly used in finish polishing. There are some small pores that can hold chips and reduce the blockage in the vitrified diamond grinding wheels. The holding force of bond to the diamond is greater than that of the resin bond, and the grinding efficiency is higher.
Vitrified bond diamond grinding wheel is used for rough grinding, finish grinding and super-finish grinding of ceramic sleeve pin for optical fiber and telethon.
Used for silicon wafer: The surface of the high-performance silicon wafer has high smoothness, good dimensional accuracy, and the surface of the silicon wafer is clean without harmful impurities after grinding wheel machining.
For silicon carbide, silicon nitride, and other engineering ceramic:
The engineering ceramics have higher toughness and hardness. Resin bond diamond wheel has the insufficient abrasive holding force and has more abrasive consumption. While metal bond diamond grinding wheel is difficult to dress and has poor self-sharpening because of the too big force of bonding diamond. Vitrified diamond wheels have good performance and suitable for engineering ceramic.
Structure of vitrified diamond grinding wheels
The working layer plays the role of grinding for the wheel. It mainly consists of diamond grains, bond, and pore. It is usually thin, and its performance directly determines that of the vitrified wheel.
The matrix mainly carries the working layer and fixes the grinding wheel on grinders. Different bond has different matrix material. For example, the metal bond mostly use high-grade spring steel, and resin bond mostly uses bakelite or aluminum alloy, and the vitrified bond mostly uses aluminum alloy as bond material.
Transition layer mainly consists of bond and some other materials. It is between the working layer and the matrix and combines them closely.
Grinding layer organization of vitrified diamond grinding wheels
It mainly consists of diamond abrasive, vitrified bond and pore.
Diamond abrasives: According to the types and grades of diamond, its performance is different and the applied environment is different. Nowadays, the main types of diamond abrasives in China are MBN, RVD, SMD, DMD, ScD, M-SD, and etc. RVD type abrasive is mostly used for vitrified bond.
Vitrified bond: It mainly plays the role of connecting and fixing diamond grains and ensure the strength and shape structure of the wheel.
1 Vitrified bond has high strength and good bonding with diamond grains. It can avoid diamond grains falling off early when grinding and make the grinding wheel fully play the role of grinding.
2 Vitrified diamond wheels have high strength and mostly used in high-speed grinding. There are often some sudden loads and impact forces. High strength can avoid danger or machine damage as far as possible.
3 The bond can ensure the abrasives are made into different shapes under certain technology conditions, which is suitable for manufacturing technology of diamond wheel.
4 The bond has high-temperature resistance and chemical stability.
The pore is an important component of the vitrified bond diamond grinding wheels. It also plays a key role in the structure and performance of the wheel.
In the grinding process, the wheel can generate a large amount of heat because of high-speed rotation and movement, and the pores on the wheel are full of grinding fluid and coolant, so they can cool for the wheel. In addition, there is waste debris in the grinding process, and easily block the contact surface of the wheel and the workpiece, which affect the normal grinding process. These pores in the wheel can hold the debris, greatly improve the grinding efficiency of tools.
There are 2 main ways to obtain pore in a vitrified bond grinding wheel.
1 Add some pure forming material such as CaCO3, coke breeze, naphthalene, walnut shell granule, and etc.
2 The sintering temperature or the bond is not enough, there will be pores. But this way can cause the strength of wheel decrease.
Diamond Grinding Wheels Specification