The grinding wheel is an indispensable tool for grinding. The appropriate selection of the grinding wheel is an important condition that affects the grinding quality and grinding cost. Our company produces a series of surface grinders, which need to be equipped with different grinding wheels to adapt to the surface processing of various workpieces. In order to facilitate the selection of users and the company's designers and craftsmen, this article focuses on the selection of grinding wheels for surface grinders and summarizes the selection of commonly used grinding wheels for different workpiece materials for your reference (see attached table).

There are many types of grinding wheels, with various shapes and sizes. Due to the different abrasives, bond materials and manufacturing processes of the grinding wheels, various grinding wheels have different working properties. Each type of grinding wheel has a certain scope of application based on its own characteristics. Therefore, when grinding, a suitable grinding wheel must be selected according to the specific conditions (such as the material properties of the workpiece to be ground, heat treatment method, workpiece shape, size, processing form and technical requirements, etc.). Otherwise, improper selection of the grinding wheel will directly affect the processing accuracy, surface roughness and production efficiency. The basic principles for grinding wheel selection are listed below for reference.

1. Selection of ordinary grinding wheels

1. Selection of abrasives The selection of abrasives mainly depends on the workpiece material and heat treatment method.

a. When grinding materials with high tensile strength, choose abrasives with high toughness.

b. When grinding materials with low hardness and high elongation, use brittle abrasives.

c. When grinding materials with high hardness, choose abrasives with higher hardness.

d. Choose abrasives that are not prone to chemical reactions in the materials being processed.

The most commonly used abrasives are brown corundum (A) and white corundum (WA), followed by black silicon carbide (C) and green silicon carbide (GC). The remaining commonly used abrasives are chromium corundum (PA) , single crystal corundum (SA), microcrystalline corundum (MA), zirconium corundum (ZA).

Brown corundum grinding wheel: Brown corundum has high hardness and high toughness, and is suitable for grinding metals with high tensile strength, such as carbon steel, alloy steel, malleable cast iron, hard bronze, etc. This abrasive is suitable for grinding It has good performance and wide adaptability. It is often used for rough grinding to remove larger margins. It 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 its toughness is lower than that of brown corundum. During grinding, the abrasive grains are easily broken, so the grinding heat is small and it is suitable for precision grinding. The cost of quenched steel, high carbon steel, high speed steel and grinding wheels for grinding thin-walled parts is higher than that of brown corundum.

Black silicon carbide grinding wheel: Black silicon carbide is brittle and sharp, with a higher hardness than 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. It has sharp abrasive grains and good thermal conductivity. It is suitable for grinding hard and brittle materials such as cemented carbide, optical glass, and ceramics.

Chrome corundum grinding wheel: suitable for grinding tools, measuring tools, instruments, threads and other workpieces with high surface processing quality requirements.

Single crystal corundum grinding wheel: suitable for grinding stainless steel, high-vanadium high-speed steel and other materials with high toughness and hardness, as well as workpieces that are prone to deformation and burns.

Microcrystalline corundum grinding wheel: suitable for grinding stainless steel, bearing steel and special ductile iron, etc., used for form grinding, plunge grinding and 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 selection of particle size mainly depends on the surface roughness and grinding efficiency of the workpiece to be ground.

Particle size refers to the particle size of the abrasive, and its size is expressed by the particle size number (see Table 1).

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 roughness of the ground workpiece is better, but less productive. On the premise of meeting the roughness requirements, coarse-grained grinding wheels should be used as much as possible to ensure higher 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 particle size should be used. For example, when grinding the same plane, the end face of the grinding wheel should be ground with a coarser grain size than the peripheral grinding of the grinding wheel.

The applicable range of grinding wheels with different particle sizes (see Table 2).

3. The choice of hardness mainly depends on the workpiece material to be ground, grinding efficiency and machined surface quality.

Hardness refers to the ease with which the abrasive grains of a grinding wheel fall off under the action of external force. In order to adapt to the grinding requirements of different workpiece materials, grinding wheels are manufactured into different hardness levels (see Table 3).

If the grinding wheel is too hard, the blunt abrasive grains will not fall off easily, the grinding wheel will be easily clogged, the grinding heat will increase, the workpiece will be easily burned, the grinding efficiency will be low, and the surface quality of the workpiece will be affected; If the grinding wheel is chosen too soft, the abrasive grains will fall off while they are still sharp, which increases the loss of the grinding wheel and easily loses the correct geometric shape, affecting the accuracy of the workpiece. Therefore, the selection of grinding wheel hardness should be appropriate and should also be comprehensively considered based on factors such as the contact area between the grinding wheel and the workpiece, the shape of the workpiece, the grinding method, 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, and when grinding hard materials, choose a soft grinding wheel;

b. When grinding soft and tough non-ferrous metals, the hardness should be softer;

c. When grinding materials with poor thermal conductivity, a softer grinding wheel should be selected;

d. When end face grinding is compared with circumferential grinding, the hardness of the grinding wheel should be softer;

e. Under the same grinding conditions, the hardness of the resin bonded grinding wheel is higher than that of the ceramic bonded grinding wheel. 1~2 small steps higher;

f. When the grinding wheel rotation speed is high, the hardness of the grinding wheel can be selected 1~2 small steps softer;

g. Grinding with coolant is better than The hardness of the grinding wheel during dry grinding is 1 to 2 small steps higher.

4. The selection of bonding agent should be considered based on conditions such as grinding method, usage speed and surface processing requirements.

The most commonly used grinding wheel bonds are ceramic bond (V) and resin bond (B).

Ceramic bond is an inorganic bond with stable chemical properties, good heat resistance, corrosion resistance, and large porosity. The grinding wheel made with this bond has high grinding efficiency, low wear, and can be used more efficiently. It maintains the geometry of the grinding wheel well and has the widest range of applications. Suitable for grinding ordinary carbon steel, alloy steel, stainless steel, cast iron, carbide, non-ferrous metals, etc. However, vitrified bonded grinding wheels are relatively brittle and cannot withstand severe vibrations. Generally it can only be used at speeds within 35 meters/second.

Resin bond is an organic bond. The grinding wheel made by this bond has high strength, certain elasticity, low heat resistance, good self-sharpening, easy production and short process cycle. It can manufacture grinding wheels with working speeds higher than 50 m/s and very thin grinding wheels. Its application scope is second only to ceramic bonding agent, and it is widely used in rough grinding, rough grinding, cutting off and free grinding, such as grinding steel ingots and deburring castings. It can manufacture high-speed, high-finish grinding wheels, heavy-duty, cutting-off and various special requirements grinding wheels.

5. The selection of tissue mainly considers the pressure on the workpiece, grinding method, workpiece material, etc.

The structure refers to the percentage of the grinding wheel volume occupied by the abrasive grains in the grinding wheel. The grinding wheel structure grade is divided into 62% of the abrasive grain volume percentage as the "0" structure. For every 2% decrease in the abrasive grain volume, the structure increases by one size, and so on, up to 15 sizes. The larger the number, the looser the organization (see Table 4).

A grinding wheel with a tight structure can grind a better workpiece surface, while a grinding wheel with a loose structure can ensure that the grinding debris is accommodated during the grinding process due to the large gaps and avoid clogging of the grinding wheel.

Usually when rough grinding and grinding softer metals, the grinding wheel is easy to clog