Grinding wheel is an indispensable tool for grinding. Whether the grinding wheel is suitable or not is an important condition that affects the grinding quality and grinding cost. The company produces a series of curved grinding machines, which need to be equipped with different grinding wheels to adapt to the curve processing of various workpieces. In order to facilitate the user to select the grinding wheel in a targeted manner, this paper selects the grinding wheel for the curved grinding machine, and selects the grinding wheel of different workpiece materials for summary.
There are many types of grinding wheels, and there are various shapes and sizes. Due to the different abrasives, binder materials and grinding wheel manufacturing processes, various grinding wheels have different working performances. Each type of grinding wheel has a certain range of application according to its own characteristics. Therefore, when grinding, the appropriate grinding wheel must be selected according to the specific conditions (such as the material properties of the workpiece to be ground, the heat treatment method, the shape and size of the workpiece, the processing form and technical requirements). Otherwise, the machining accuracy, surface roughness and production efficiency will be directly affected by improper selection of the grinding wheel. The basic principles of grinding wheel selection are listed below for reference.
First, the choice of ordinary grinding wheel
1. The choice of grinding wheel mainly depends on the workpiece material and heat treatment method.
a. When grinding materials with high tensile strength, use abrasives with high toughness.
b. When the material has low hardness and high elongation, use a brittle abrasive.
c. When grinding a material with high hardness, use a higher hardness abrasive.
d. Select an abrasive that is not susceptible to chemical reaction by the processed material.
Commonly used abrasives are brown corundum (A) and white corundum (WA), followed by black silicon carbide (C) and green silicon carbide (GC), and the other commonly used are chrome corundum (PA), single crystal corundum (SA), Microcrystalline corundum (MA), zirconium corundum (ZA).
Brown corundum grinding wheel: Brown corundum has high hardness and high toughness. It is suitable for grinding metals with high tensile strength, such as carbon steel, alloy steel, malleable cast iron, hard bronze, etc. This kind of abrasive has good grinding performance and wide adaptability. It is often used to cut a large amount of coarse grinding, which is cheap and can be widely used.
White corundum grinding wheel: The hardness of white corundum is slightly higher than that of brown corundum, and the toughness is lower than that of brown corundum. When grinding, the abrasive grains are easily broken. Therefore, the grinding heat is small, and it is suitable for manufacturing hardened quenched steel and high carbon steel. High-speed steel and grinding wheels for grinding thin-walled parts are more expensive than brown fused alumina.
Black silicon carbide grinding wheel: Black silicon carbide is brittle and sharp, and its hardness is higher than that of white corundum. It is suitable for grinding materials with low mechanical strength, such as cast iron, brass, aluminum and refractory materials.
Green silicon carbide grinding wheel: Green silicon carbide has higher hardness and brittleness than black silicon carbide, sharp abrasive grain and good thermal conductivity. It is suitable for grinding hard and brittle materials such as hard alloy, optical glass and ceramics.
Chrome corundum grinding wheel: suitable for grinding tools, measuring tools, instruments, threads and other workpieces with high surface quality requirements.
Single crystal corundum grinding wheel: suitable for grinding stainless steel, high vanadium high speed steel and other materials with high toughness, high hardness and easily deformed burns.
Microcrystalline corundum grinding wheel: suitable for grinding stainless steel, bearing steel and special ductile iron, etc., used for forming grinding, cutting grinding, mirror grinding.
Zirconium corundum grinding wheel: suitable for grinding Austrian stainless steel, titanium alloy, heat resistant alloy, especially suitable for heavy-duty grinding.
2. The choice of particle size depends mainly on the surface roughness and grinding efficiency of the workpiece being ground.
The particle size refers to the particle size of the abrasive, and its size is represented by the particle size number. When grinding with a coarse-grained grinding wheel, the production efficiency is high, but the surface of the ground workpiece is rough; when grinding with a fine-grained grinding wheel, the surface of the workpiece is ground. Good roughness and low productivity. Under the premise of meeting the roughness requirements, coarse-grained grinding wheels should be used as much as possible to ensure high grinding efficiency. Generally, a coarse-grained grinding wheel is used for rough grinding, and a fine-grained grinding wheel is used for fine grinding.
When the contact area between the grinding wheel and the workpiece is large, a grinding wheel with a coarser grain size is used. For example, grinding the same curve, the grinding of the end face of the grinding wheel is coarser than the grain size selected by the peripheral grinding of the grinding wheel.
3. The choice of hardness depends mainly on the workpiece material being ground, the grinding efficiency and the quality of the machined surface.
Hardness refers to the difficulty of the abrasive wheel falling off under the action of external force. In order to meet the requirements of different workpiece material grinding, the grinding wheel is divided into different hardness grades.
The grinding wheel is selected too hard, the blunt abrasive grains are not easy to fall off, the grinding wheel is easy to block, the grinding heat is increased, the workpiece is easy to burn, the grinding efficiency is low, and the surface quality of the workpiece is affected; the grinding wheel is selected too soft, and the abrasive grain is also off when it is sharp. Increases the wear of the grinding wheel, easily loses the correct geometry and affects the accuracy of the workpiece. Therefore, the choice of the hardness of the grinding wheel should be appropriate. It should also be considered according to the contact area of the grinding wheel and the workpiece, the shape of the workpiece, the way of grinding, the cooling method, the type of bonding agent of the grinding wheel and other factors.
The following grinding wheel hardness selection principles are for reference:
a. When grinding soft materials, choose a harder grinding wheel. When grinding hard materials, choose a soft grinding wheel.
b. When grinding soft and tough non-ferrous metals, the hardness should be selected to be softer; c. Grinding materials with poor thermal conductivity should be selected as softer grinding wheels;
d. When the end face grinding is more than the circumferential grinding, the hardness of the grinding wheel should be selected softer;
e. Under the same grinding conditions, the hardness of the resin bond grinding wheel is 1~2 lower than that of the ceramic bond grinding wheel;
f. When the grinding wheel rotates at a high speed, the hardness of the grinding wheel can be softly 1~2 small;
g. Grinding with coolant is 1~2 less than the hardness of the grinding wheel when dry grinding.
4. The choice of binder should be considered according to the grinding method, the speed of use and the requirements of surface processing.
Commonly used grinding wheel binders are ceramic binder (V) and resin binder (B).
The ceramic bond is an inorganic binder with stable chemical properties, good heat resistance, good corrosion resistance and high porosity. The grinding wheel made of this binder has high grinding efficiency and low wear, and can better maintain the geometry of the grinding wheel. ,Wide range of applications. Suitable for grinding ordinary carbon steel, alloy steel, stainless steel, cast iron, hard alloy, non-ferrous metals, etc. However, the ceramic bond grinding wheel is relatively brittle and cannot be subjected to severe vibration. Generally only use at speeds up to 35 m / s.
The resin binder is an organic binder. The binder has high strength, certain elasticity, low heat resistance, good self-sharpness, simple production and short cycle time. It can manufacture grinding wheels with working speeds higher than 50 m/s and very thin grinding wheels. Its application range is second only to ceramic bonding agents, and it is widely used in rough grinding, rough grinding, cutting and free grinding, such as grinding steel ingots, casting burrs and so on. It can manufacture high-speed, high-gloss grinding wheels, heavy-duty, cutting and grinding wheels with special requirements.
5. The choice of organization mainly considers the pressure, grinding method and workpiece material of the workpiece.
The organization refers to the percentage of the grinding wheel volume occupied by the abrasive grains in the grinding wheel. The division of the grinding wheel is graded at a percentage of 62% of the abrasive grain volume. The volume of the abrasive grain is reduced by 2%, the tissue is increased by one, and so on, with a total of 15 numbers. The larger the number, the looser the organization. The compact grinding wheel can grind out the better surface of the workpiece and organize the loose grinding wheel. Because of the large gap, it can ensure the grinding debris during the grinding process and avoid the blockage of the grinding wheel. When grinding and grinding softer metals, the grinding wheel is easy to block.