The Hardness Of The Wheel

Grinding wheel grinding tool is an indispensable tool for grinding, grinding wheel selection is appropriate or not, is the impact of grinding quality, grinding costs an important condition. The company produces a series of surface grinder, need to configure a different grinding wheel to adapt to a variety of workpiece plane machining. In order to facilitate the user and the company design, process personnel selection, this paper for grinding, Grinding Wheel the use of different parts of the workpiece grinding wheel selection for the use of reference (see table).

Many types of grinding wheel, and a variety of shapes and sizes, due to grinding wheel abrasive, binder materials and grinding wheel manufacturing process is different, a variety of grinding wheel has a different performance. Each kind of grinding wheel according to its own characteristics, have a certain scope of application. Therefore, grinding, must be based on specific circumstances (such as grinding the workpiece material properties, Grinding Wheel heat treatment methods, the workpiece shape, size and processing and technical requirements, etc.), use the appropriate wheel. Otherwise it will be due to improper selection of grinding wheel and directly affect the processing accuracy, surface roughness and production efficiency. Grinding Wheel The basic principles of the selection of the grinding wheel are listed below for reference.

First, the choice of ordinary wheel

1. Abrasive selection Abrasive selection depends mainly on the workpiece material and heat treatment methods.

A. Grinding tensile strength of high material, the choice of toughness of the abrasive.

B. Low hardness, elongation of large materials, the use of more brittle abrasive.

C. High hardness of the material, Grinding Wheel the choice of higher hardness of the abrasive.

D. Use abrasives that are less susceptible to chemical reactions.

The most commonly used abrasives are corundum (A) and white corundum (WA), followed by black silicon carbide (C) and green silicon carbide (GC), the rest are commonly used chrome corundum (PA), monocrystalline corundum (SA) , Microcrystalline corundum (MA), zirconia corundum (ZA).

Brown corundum wheel: high hardness of corundum, toughness, suitable for grinding high tensile strength of the metal, such as carbon steel, alloy steel, malleable cast iron, hard bronze, this abrasive grinding performance, wide adaptability, Commonly used in the removal of the larger margin of coarse grinding, cheap, can be widely used.

White corundum wheel: white corundum hardness slightly higher than the corundum, toughness is lower than the corundum, grinding, abrasive grain easily broken, therefore, grinding heat is small, suitable for making refined hardened steel, high carbon steel, High-speed steel and grinding thin-walled parts with the grinding wheel, the cost is higher than the corundum.

Black silicon carbide wheels: black silicon carbide crisp and sharp, hardness than white corundum high, suitable for grinding mechanical strength of low materials, such as cast iron, brass, Grinding Wheel aluminum and refractory materials.

Green silicon carbide wheel: green silicon carbide hardness brittle black silicon carbide high, abrasive abrasive, good thermal conductivity, suitable for grinding carbide, optical glass, ceramics and other hard and brittle materials.

Chrome corundum wheel: suitable for grinding tools, measuring tools, instruments, threads and other surface processing quality requirements of the workpiece.

Single crystal corundum wheel: suitable for grinding stainless steel, Grinding Wheel high vanadium high-speed steel and other toughness, high hardness of the material and easy deformation of the workpiece.

Microcrystalline corundum wheel: suitable for grinding stainless steel, bearing steel and special ductile iron, etc., for forming grinding, cutting into the grinding, mirror grinding.

Zirconia corundum wheel: suitable for grinding Austrian body stainless steel, titanium alloy, heat-resistant alloy, especially for heavy-duty grinding.

2. The choice of particle size depends mainly on the surface roughness and grinding efficiency of the workpiece being ground.

Particle size refers to the particle size of the abrasive, and its size is expressed in particle size

Grinding with coarse-grained grinding wheel, Grinding Wheel the production efficiency is high, but the surface of the workpiece grinding is more rough; with fine-grained grinding wheel grinding, grinding the workpiece surface roughness is better, and the productivity is low. In order to meet the requirements of roughness, should try to use coarse-grained grinding wheel to ensure high grinding efficiency. General coarse grinding when the use of coarse-grained grinding wheel, fine grinding when the use of fine-grained wheel.

When the wheel and the workpiece contact area is large, to use some coarse grinding wheel. For example, grinding the same plane, grinding the end of the grinding wheel with the grinding wheel than the peripheral grinding of the selected size to be thicker.

Different size of the wheel of its scope

3. The choice of hardness depends mainly on the grinding of the workpiece material, grinding efficiency and processing surface quality.

Hardness refers to the grinding wheel in the external force under the action of the degree of wear and tear, in order to meet the requirements of different parts of the workpiece grinding, Grinding Wheel manufacturing grinding wheel into different levels of hardness (see Table 3).

Grinding wheel is excellent, grinding blasting abrasive is not easy to fall off, easy to block the grinding wheel, grinding heat increased, the workpiece easy to burn, grinding efficiency is low, affecting the workpiece surface quality; grinding wheel is too soft, abrasive is still sharp off , Increased wheel wear, easy to lose the correct geometry, affecting the accuracy of the workpiece. Therefore, the choice of grinding wheel hardness should be appropriate, but also should be based on the wheel and the workpiece contact area size, the workpiece shape, grinding, cooling, grinding wheel binder and other factors to consider.

The following principle of choice of hardness of the grinding wheel for reference:

A. Grinding soft materials to choose harder grinding wheel, grinding hard materials will have to choose a soft wheel;

B. Grinding soft and toughness of non-ferrous metals, the hardness should be selected soft;

C. Grinding the poor thermal conductivity of the material should be selected soft grinding wheel;

D. Face grinding than the circumferential grinding, the hardness of the wheel should be selected soft;

E. In the same grinding conditions, the use of resin-bonded grinding wheel than the ceramic binder grinding wheel hardness is 1 to 2 small;

F. Wheel rotation speed is high, the hardness of the wheel can choose soft 1 ~ 2 small;

G. Grinding with coolant is 1 to 2 times higher than that of dry grinding wheel.

4. The choice of binder should be based on grinding methods, Grinding Wheel the use of speed and surface processing requirements and other conditions to be considered.

The most commonly used grinding wheel binder is a ceramic binder (V) and a resin binder (B).

Ceramic binder is an inorganic binder, chemical stability, heat resistance, corrosion resistance, porosity, this combination of grinding wheel manufacturing efficiency, wear is small, can better maintain the geometry of the wheel , The most widely used Suitable for grinding ordinary carbon steel, alloy steel, stainless steel, cast iron, hard alloy, nonferrous metals and so on. However, the ceramic binder grinding wheel brittle, can not be subject to severe vibration. Generally only in 35 m / s or less speed to use.

Resin binder is an organic binder, the combination of the manufacture of high strength wheel, with a certain flexibility, low heat resistance, self-sharpening, easy to produce, short process cycle. Can produce working speed higher than 50 m / s wheel and very thin grinding wheel. Its application range is second only to ceramic bonding agent, widely used in coarse grinding, barren grinding, cutting and free grinding, such as grinding steel ingots, casting burrs and so on. Can manufacture high-speed, high-quality grinding wheel, heavy load, Grinding Wheel cut off and a variety of special requirements of the wheel.

5. The choice of the organization mainly consider the pressure of the workpiece, grinding methods, workpiece materials and so on.

The organization refers to the percentage of the grinding wheel in the grinding wheel. The division of the wheel grade is based on the percentage of the abrasive volume of 62 as "0". The abrasive volume is reduced by 2, and its organization is increased by one, and so on, divided into 15 numbers. The larger the number, the more loose the organization

Tissue tight grinding wheel can produce a better surface of the workpiece, the organization of loose grinding wheel, because the gap is large, can ensure that the grinding process to wear debris, to avoid the wheel clogging. Usually grinding and grinding more soft metal, the grinding wheel is easy to plug, should use the loose structure of the wheel; molding grinding and precision grinding, in order to maintain the geometry of the grinding wheel and get a good roughness, should be used more closely Grinding wheel; grinding machine tool guide and carbide tools, in order to reduce the workpiece thermal deformation, to avoid burning cracks, should adopt loose tissue grinding wheel; grinding heat sensitive materials, non-ferrous metals, non-metallic materials should use more than 12 # Grinding wheel.

6. The shape and size of the selection should be based on grinding conditions and workpiece shape to choose.

Commonly used wheel shape has flat shape wheel (P), single concave grinding wheel (PDA), double concave grinding wheel (PSA), sheet grinding wheel (PB), cylindrical grinding wheel (N), bowl type wheel (BW) Grinding wheel (D1) and so on.

Each grinding machine can use the wheel shape and size have a certain range. In the possible conditions, the outer diameter of the grinding wheel should be selected as large as possible to improve the wheel speed, get higher productivity and workpiece surface quality, wheel width can also get the same effect.

Is the standard grinding wheel writing order: grinding wheel code, size (diameter × thickness × aperture), abrasive, particle size, hardness, organization, bonding agent, the maximum working speed.

Example: P 400 × 150 × 203 A60 L 5 B 35

Second, the choice of diamond wheel

Diamond grinding wheel than boron carbide, silicon carbide, corundum and other abrasive abrasive made of abrasive blade angle sharp, low wear, long life, high productivity, good processing quality, but expensive, and therefore suitable for fine grinding carbide, ceramic , Semiconductor and other high hardness brittle difficult to process materials.

Diamond wheel features include abrasive type, particle size, hardness, Grinding Wheel concentration, binder, wheel shape and size.

Abrasive: widely used artificial diamond (JR), according to its crystal shape and particle strength, divided into various models, according to their specific use selected models.

Particle size: to the workpiece roughness, grinding productivity and consumption of diamond three aspects of comprehensive consideration.

Hardness: only resin binder diamond grinding wheel only "hardness" of this feature. Generally use S (Y1) level or higher.

Bonding agent: There are four commonly used bonding agent, its binding capacity and wear resistance to resin, ceramics, bronze, electroplating metal order, followed by gradually strong. Resin binder diamond grinding wheel grinding efficiency is high, the workpiece roughness is good, for a wide range of self-sharpening good, easy to plug, heat a small, easy to dress, mainly used for refining process. Ceramic binder diamond wheel is mainly used for a variety of non-metallic hard and brittle materials, carbide, superhard materials such as grinding.

Concentration: The concentration of choice should be based on the use of grinding wheel size, bonding agent, shape, processing methods, production efficiency and wheel life requirements. High-strength diamond grinding wheel to maintain the shape of the wheel-shaped strong, low-concentration grinding wheel grinding, the consumption of diamonds is often lower, should be selected as appropriate.

Shape and size: according to the shape of the workpiece, size and machine conditions selected.

Third, cubic boron nitride (CBN) grinding wheel selection

Cubic boron nitride (CBN) grinding wheel cubic boron nitride particles adhere to the ordinary grinding wheel surface is only a thin layer, the abrasive grain toughness, hardness, durability is 100 times the corundum grinding wheel, the most suitable for high hardness, Large, high temperature strength, low thermal conductivity of difficult grinding steel and high-speed or ultra-high-speed grinding. Its scope of application and artificial diamond play a complementary role. Diamond grinding wheel in the grinding carbide and non-metallic materials, has a unique effect, but in grinding steel, especially grinding special steel, the effect is not significant. Cubic boron nitride grinding wheel grinding steel efficiency than corundum grinding wheel to nearly 100 times higher than the diamond grinding wheel five times, but grinding less brittle materials and diamond.

The choice of cubic boron nitride grinding wheel is similar to that of diamond grinding wheel. But in the choice of binder, most of the resin binder, followed by plating, metal bonding agent. Ceramic binder CBN grinding wheel is mainly used for titanium alloy, high speed steel, Grinding Wheel malleable cast iron and other hard processing of ferrous metal grinding, resin binder CBN grinding wheel for grinding ferromagnetic materials, is the ideal choice for processing steel. CBN wheel concentration is generally selected in the 100 to 150 more economical and reasonable, it can not use ordinary cutting fluid, the need for special cutting fluid.

Fourth, the choice of air hole grinding wheel

The perforated grinding wheel has the advantages of being easy to be clogged, high in durability and strong in cutting ability. Applicable to soft metal and plastic, rubber and leather and other non-metallic materials, coarse, fine grinding. At the same time, it has the characteristics of rapid heat dissipation, so in grinding some of the heat-sensitive materials, thin-walled parts and dry grinding process (such as sharpening carbide cutting tools and machine tools, etc.) have a good effect.

The production method of the air hole grinding wheel and the general ceramic bonding agent wheel is basically the same. The difference is that in the ingredients plus a certain amount of pore-forming agent, it is completely volatilized before the grinding wheel or burned, resulting in large pores.

(A), such as black silicon carbide (C), green silicon carbide (GC) and white corundum (WA), etc., the hardness of these abrasives, the high hardness of the abrasive Brittle and sharp, with good thermal conductivity and electrical conductivity; abrasive grain size (36 # ~ 180 #); binder (ceramic binder); hardness (G ~ M grade); shape (flat, cup, bowl or dish Shape, etc.); stomatal size (about 0.7 to 1.4 mm).