COMPOSITION OF ABRASIVE WHEELS
Abrasives for use in the production sector must be secured or designed as different tools and formulations, including as abrasive cutting and grinding wheels.
Cut-off wheel for metal is made of brown aluminum oxide* on bakelite bond which gives strength to cutoff wheel and prevents spreading of fragments in case of jamming or damaging of the wheel.
Stainless steel cutoff wheel for metal differs from the usual cutoff wheel for metal by its composition: iron, sulfur and chlorine are excluded from the alloy. This type of cutoff wheels avoids contamination of the cut material during processing. Cutoff wheels differ by the outer diameter, disk thickness and diameter of the bore. Cutoff wheel diameter influences the depth of cut; the disk thickness is selected depending on the thickness of the metal for cutting. Cutoff wheels are mounted on cutting machines with a special nut and bore which is pressed with metal ring - to increase the wheel strength.
Cutoff wheel for stone is made of black silicon carbide** on bakelite bond. The alloy used in the manufacture of cutoff wheels for stone gives the wheel high hardness and strength when cutting concrete constructions, refractory bricks, natural and artificial stone.
Grinding wheel is composed of brown aluminum oxide* on bakelite bond. The maximum speed of this type of wheels is 80 m/s. Grinding wheel is used for cleaning and stripping of products made from different grades of steel. It prevents contamination of the working surfaces of products and micro-cracking.
Bakelite bond consists of bakelite - the synthetic resin made of carbolic acid and formaldehyde. Wheels on this bond are durable, flexible, allow for large circumferential speed, but are destroyed by alkaline coolants. To avoid this, it is recommended to impregnate the wheel with paraffin. The disadvantage of bakelite bond is that it loses strength when heated above 180 C. In order to reduce roughness of processed surfaces the abrasive tools on bakelite bond are sometimes filled with graphite.
Bakelite bond reduces heating of components, provides for high-grades of surface finish, and has higher strength as compared to the ceramic one and increases in size under constant load.
* Aluminum oxide or fused corundum (Al2O3) is a crystalline aluminum oxide obtained from bauxite clay containing about 60% of aluminum. It is referred to as the fused corundum due to the technology of its production in electric arc furnaces.
The purity percentage of aluminum oxide (94–99%) and degree of its hardness makes it one of the varieties of grain used for manufacture of grinding or cutoff wheels or other abrasive tools for processing of wood or metals.
** Silicon Carbide (SiC) is the result of synthesis of oil with natural quartz sand in electric furnaces heated to the temperature higher than 2,000 C. Under these conditions the mixture is crystallized to form silicon carbide. Silicon carbide has solid grains with an ordered crystalline structure which has particularly high cutting capacity allowing to effectively process paints and varnishes, putties, ceramics and stone, iron and titanium, as well as rubber and various polymers.