What are the Classifications of Abrasives?

What is an Abrasive Tool?

Abrasives are known as industrial teeth. Abrasives or grinding tools are often used as grinding tools in grinding machine parts to be processed to meet certain technical requirements. Uses include grinding, polishing, sanding, cleaning, cutting, and drilling. Commonly used abrasive mills have cut-off and grinding discs, louver discs, quick-change discs, rolls, bonded wheels, flap rings and sandpaper rings, non-bonded flap wheels, flap wheels, sandpaper rolls and pile rolls, tungsten steel rotary file.

Development of Abrasives:

Abrasives are tools used for grinding, grinding, and polishing. Most of the grinding tools are artificial grinding tools made of abrasives and bonding agents, and natural grinding tools are also directly processed into natural ore rocks. In addition to being widely used in machinery manufacturing and other metal processing industries, abrasive tools are used in the processing of non-metallic materials such as grain processing, paper industry, ceramics, glass, stone, plastic, rubber, and wood.

During the use of the abrasive tool, when the abrasive grains are blunt, due to the partial fragmentation of the abrasive grain itself or the fracture of the bond, the abrasive grains fall off partially or completely from the abrasive tool. And the abrasive on the working surface of the abrasive tool continues to appear new cutting the cutting edge, or new sharp abrasive grains are constantly exposed so that the abrasive tool can maintain the cutting performance for a certain period. The self-sharpening of abrasive tools is a prominent feature of abrasive tools compared with ordinary knives.

Humans have already started to use natural millstones to process tools such as stone knives, stone axes, bone tools, horn tools, and dental tools. Around 1900, the development of artificial abrasives appeared, and various abrasive tools made of artificial abrasives were produced one after another, creating conditions for the rapid development of grinding and grinding machines. Since then, the proportion of natural abrasives in abrasives has gradually decreased.

Abrasives are divided according to their source of raw materials, and there are two types of natural abrasives and artificial abrasives. The natural abrasive tools commonly used in the machinery industry are only whetstones. Artificial abrasives are divided into five categories according to their basic shape and structural features grinding wheels, grinding heads, oilstones, sand tiles, and coated abrasives. In addition, it is customary to classify abrasives as a category of abrasive tools. Bonded abrasives can be divided into ordinary abrasive bonded abrasives and super abrasive bonded abrasives according to the abrasives used. The former is made of ordinary abrasives such as corundum and silicon carbide, and the latter is made of super abrasives such as diamond and cubic boron nitride. In addition, there are some special varieties, such as sintered corundum grinding tools and so on.

Ordinary abrasive bonded abrasives are abrasive tools that consolidate ordinary abrasives into a certain shape and have a certain strength by a binder. It is generally composed of abrasives, bonding agents, and pores. These three parts are often called the three elements of bonded abrasives.

Abrasives Play a Cutting Role in Abrasive Tools:

The binder is a material that consolidates loose abrasives into abrasive tools, and there are two types inorganic and organic. Inorganic binders include ceramics, magnesite, and sodium silicate. Organic binders include resin, rubber, and shellac. The most commonly used of these are ceramic, resin, and rubber bonds.

During the grinding process, the pores play a role in containing and removing chips and can accommodate coolant, which helps to dissipate the grinding heat. To meet some special processing requirements, some fillers, such as sulfur and paraffin, can be impregnated in the pores to improve the performance of the abrasive tool.

What are the Classifications of Abrasives?

• Brown corundum abrasive: The main component is Al2O3, which has medium hardness, high toughness, sharp particles, relatively low price, and is suitable for processing metals with high tensile strength. Both microcrystalline corundum abrasive and black corundum abrasive is its derivatives.
• Brown corundum abrasive: Its hardness is slightly higher than that of brown corundum, but its toughness is poor. It is easy to cut into the workpiece during grinding. It has good self-sharpening, low calorific value, strong grinding ability, and high efficiency. Chrome corundum abrasive is a derivative of it.
• Single crystal corundum abrasive: Its particles are composed of a single crystal and have good multi-edged cutting edges, high hardness and toughness, strong grinding ability, and low grinding calorific value. The disadvantage is that the production cost is high and the output is lower, so the price is higher. Zirconium corundum abrasive is also a crystal compound with slightly lower hardness, finer crystal size, and good wear resistance.
• Black silicon carbide abrasive, green silicon carbide abrasive, cubic silicon carbide abrasive, cerium silicon carbide abrasive: Belong to silicon carbide abrasive, the main component is silicon carbide SiC, high hardness, high brittleness, sharp abrasive grains, good thermal conductivity, Strong abrasiveness, more suitable for processing hard and brittle metal and non-metal products.

What is the Difference Between Ordinary Abrasives and Super Hard Material Abrasives?

• Ordinary abrasives: Refers to abrasives made of the above-mentioned ordinary abrasives. The combination of abrasives can be divided into bonded abrasives and coated abrasives. According to different bonding agents, it can be divided into a series of ceramic abrasives, resin abrasives, rubber abrasives, and magnesia abrasives.
• Super hard material abrasive tools: Mainly use metal powder, metal oxide or CBN, and other super hard materials as fillers, and can also add ordinary abrasives (such as Al2O3, SiC, etc.), resin bond or vitrified bond or metal Abrasives made of binders.

Common Abrasive Bonded Abrasives Feature Items are:

Shape, size abrasives, grain size, hardness, weave, backing, and bonding agents. Abrasive tool hardness refers to the difficulty of the abrasive grains falling off the surface of the abrasive tool under the action of external force, which reflects the strength of the bond to hold the abrasive grains. The hardness of the abrasive mainly depends on the amount of bonding agent added and the density of the abrasive. If the abrasive grains fall off easily, the hardness of the abrasive is low. On the contrary, it means high hardness. The grades of hardness are generally divided into super soft, soft, medium soft, medium, medium-hard, hard, and super hard, and several subgrades can be subdivided from these grades. The methods for measuring the hardness of abrasive tools are the hand awl method. The mechanical awl method, the Rockwell hardness tester method, and the sandblasting hardness tester method.

The hardness of the abrasive tool has a corresponding relationship with its dynamic elastic modulus, which is beneficial to use the audio method to measure the dynamic elastic modulus of the abrasive tool to express the hardness of the abrasive tool. In the grinding process, if the material hardness of the workpiece to be ground is high, the abrasive tool with low hardness is generally used. On the contrary, use abrasive tools with high hardness.

The structure of abrasive tools is roughly divided into three categories: tight, medium, and loose. Each category can be further divided into subdivided numbers, etc., which are distinguished by organization numbers. The larger the organization number of the abrasive tool, the smaller the volume percentage of the abrasive in the abrasive tool, and the wider the gap between the abrasive grains, indicating the looser the organization. Conversely, the smaller the weave number, the tighter the weave. Abrasives with a loose structure are not easy to be passivated during use, and generate less heat during the grinding process, which can reduce heat deformation and burns of the workpiece. Abrasive grains with a tighter structure are not easy to fall off, which is conducive to maintaining the geometric shape of the abrasive. The organization of the abrasive tool is only controlled according to the abrasive tool formula during manufacture and is generally not measured.