Selection and use of the hottest coated abrasives

Selection and use of coated abrasives

1. Basic knowledge of coated abrasives

1.1 definition and structure of coated abrasives

Coated Abrasives: abrasives made by adhering abrasives to flexible substrates with adhesives

the structure of the coated abrasive tool is shown in Figure 1

the three elements of coated abrasive tools: substrate, abrasive and binder, as shown in Table 1

base material: the carrier of abrasive and binder

abrasive: the main body of abrasive tools for grinding and polishing

binder: plays the role of bonding abrasive and substrate, so that the abrasive tools have a certain shape and strength

nine characteristic factors of Coated Abrasives: substrate, substrate treatment, abrasive, particle size, planting sand density, binder, bonding strength, shape and size

1.2 composition of three elements of Coated Abrasives

the "three elements" of Coated Abrasives: substrate, abrasive and binder. Each element has different properties and different types of materials to choose from

(1) classification of substrate

substrate is the carrier of abrasive and binder in abrasive tools. It is the leading factor for the flexibility of coated abrasives, and it is also the main feature different from other abrasives

the types of base materials mainly include paper, cloth, steel paper, composite matrix, non-woven fabric, etc

paper: coated abrasive paper is made of particularly strong and tough fibers, and is made into varieties of different quality and specifications according to different needs. The price of paper is relatively cheap. Generally, there is no need for substrate treatment, and the consumption is large

in the use of coated abrasives, the type of paper is divided by quantity, as shown in Table 2

Table 2 model of abrasive paper coated

model abcdefh quantitative (g/m2)

cloth: fabric formed by using fiber as raw material and spinning to form a certain organization. Cloth is the most widely used in the substrate coated with abrasive tools, with good flexibility and high strength, but it needs strict substrate treatment

different types of cloth are formed due to different tissues. At present, the cloth used for coating abrasive tools mainly includes cotton cloth, blended cloth, polyester cloth, etc

different types of cloth are formed due to different tissues. At present, the tissues of cloth coated with abrasive tools mainly include 1/1, 2/1, 3/1, 4/1, etc. different cloth with different tissues is selected for different coated abrasive tools

in the use of coated abrasives, like paper, cloth is divided by weight. At present, there is no general standard for the weight of cloth, and its classification is shown in Table 3

Table 3 Classification of cloth for coated abrasive tools

model lfj XYS name light cloth light cloth medium cloth heavy cloth thick heavy cloth super heavy cloth

steel paper: it is a substrate with high strength formed by the fusion of multi-layer cotton fibers. It can bear special high mechanical load, with high strength, small elongation and good heat resistance. It is mainly used in the production of steel paper sand discs and special-shaped products. It is selected according to the requirements of coated abrasive tools

composite base: it is composed of paper and cloth, which combines the advantages of paper and cloth. It has high strength and minimal elongation. It is mainly used to make high-speed heavy-duty sand belts, and a small amount of sand discs. Generally, according to the model of cloth base, it is light composite base and heavy composite base

non woven fabric: one or more fibers are bonded or mechanically, so that they have the appearance and performance of cloth without weaving process. They are mainly used to make soft polishing abrasives

(2) types of abrasives

abrasives are the main body of coated abrasives to produce grinding and polishing effects

Abrasives must have these basic properties: certain hardness, certain strength, appropriate fragmentation, and certain physical and chemical stability

Abrasives can be divided into natural abrasives and artificial abrasives. The commonly used abrasive varieties of coated abrasive tools are:

brown corundum (a): the main components are α- AI2O3, which is brown or brown in appearance, has high hardness, good toughness, can withstand great pressure, and has the characteristics of high temperature resistance, corrosion resistance, good chemical stability and so on. It is widely used

white corundum (a): the main component is α- AI2O3, white in appearance, higher in hardness than brown corundum, brittle, lower in toughness than brown corundum, easy to break abrasive, good in sharpness

black silicon carbide (c): the main component is SiC, which is black in appearance, with high hardness, brittleness and good sharpness of abrasive

zirconium corundum (ZA): the main composition is α- AI2O3 and AI2O3 Zr eutectic, which are grayish white or grayish brown in appearance, have good toughness and wear resistance, and are suitable for high-speed heavy load grinding and processing of difficult to grind metal materials

in addition, there are ceramic abrasives, glass sand, garnet, etc

special requirements of coated abrasives on the chemical composition, particle size, particle shape, bulk density, hydrophilicity, etc. the abrasives used for Coated Abrasives should use the special abrasives for coated abrasives, namely P abrasives

(3) classification of binders

binders are used to bond abrasives and substrates, so that Abrasives have a certain shape and strength. The adhesive applied to abrasive tools is generally composed of substrate treatment agent, primer, compound glue, etc

the role of base material treatment agent is mainly to improve the physical and mechanical properties of the base material, ensure good quality of gluing and sand planting, and endow the product with good performance. According to the different use requirements of products, the substrate treatment is divided into non water resistant treatment and water resistant treatment, and the substrate treatment agent should adapt to it

primer is a coating that binds the abrasive to the substrate and plays the role of bonding and fixing the abrasive

compound glue is to coat a layer of adhesive on the fixed abrasive particles to surround the abrasive, so as to further strengthen the bonding strength between the abrasive particles and the substrate, and ensure that the abrasive particles can withstand the extrusion and impact of grinding force and are not easy to fall off during the grinding process

the main factors affecting the bonding strength of coated abrasives are the type and quantity of binder

the binders used for coating abrasive tools mainly include animal glue, synthetic resin, etc. Examples include leather glue, urea formaldehyde resin, phenolic resin, epoxy resin, alkyd resin, etc

animal glue: good bonding performance, easy to use, but not water-resistant, susceptible to moisture

urea formaldehyde resin: it is simple to manufacture, low in cost, and superior to animal glue in bonding performance, moisture resistance and mildew resistance

phenolic resin: it has high bonding strength, good water resistance, acid resistance and weather resistance, especially the use of water-soluble phenolic resin, making it one of the most important adhesives in the abrasive tool industry

epoxy resin and alkyd resin: good bonding performance and water resistance, but organic solvents are required, which is more than the production of water-resistant sandpaper

1.3 classification of coated abrasives

coated abrasives are composed of substrate, abrasive and binder. According to different substrates, abrasives and binders, coated abrasives can be divided into many varieties, with different properties and different uses. Scientific and reasonable classification method of coated abrasives is an important basis for selecting coated abrasives

(1) according to the classification of substrates and use methods

coated abrasives are divided into dry abrasive cloth, water-resistant abrasive cloth, dry abrasive paper, water-resistant abrasive paper

(2) according to the classification of binder and substrate treatment

coated abrasives are divided into four categories: Animal adhesive bonded abrasives, resin bonded abrasives, full resin bonded abrasives, and water-resistant coated abrasives

(3) classification according to abrasive material and particle size:

abrasive material represents the type and performance of abrasive, and abrasive particle size represents the size and distribution of abrasive particles. Different abrasive materials and particle sizes can be divided into different types of coated abrasives. In addition, there is a code for dry abrasive cloth and water-resistant sandpaper, which are still used in the market for different particle sizes

(4) classification according to the density of planting sand:

refers to the density of abrasive particles on the surface of coated abrasive tools. The density of planting sand coated with abrasives is divided into dense planting sand (CL) and sparse planting sand (OP)

(5) classification according to product shape:

Coated Abrasives can be divided into: leaf, roll, strip, disc and special-shaped products according to product shape

which of the many classification methods is more scientific, intuitive and convenient? We think that "classification according to binder and substrate treatment" is reasonable, and then combined with "classification according to product shape", it can basically meet the description of coated abrasives

according to the classification of binder and substrate treatment, it can be divided into four categories: Animal bonded bonded abrasives, resin bonded abrasives, full resin bonded abrasives, and water-resistant coated abrasives

animal adhesive bonded abrasives: code name is g/g. Animal adhesive is used for both primer and compound glue. Low grade substrate treatment agent has poor heat resistance and moisture resistance, but the binder is water-soluble, cheap, simple to make and convenient to use

semi resin bonding Abrasives: code name is r/g, the primer is animal glue, and the compound is synthetic resin adhesive. It is worth making some changes in the treatment of medium and low-grade base materials. Its characteristics are between animal glue and full resin products

all resin bonded abrasive tools: code name is r/r, the base and compound glue are made of bonding resin, high-grade substrate treatment agent (water-resistant or waterproof), high bonding strength, good wear resistance, heat resistance, mainly used in mechanical grinding

water resistant coated abrasives: Code WP, the base material should be treated with water or oil resistance in advance, and the primer and compound glue are made of synthetic resin or paint, which is suitable for use in Water-Quality coolant

1.4 basic knowledge of abrasive belt

abrasive belt is a circular coated abrasive tool. Due to the production of abrasive belt, the coated abrasive tools have realized the transformation from manual application to modern grinding mode

sand belt is divided into jointless sand belt and jointless sand belt

the joint sand belt is divided into single joint, multi joint and spiral joint. The joint forms include lap method and butt method. Butt joint method is divided into straight joint, S-shaped butt joint and embedded joint

2. Basic knowledge of coated abrasive grinding

2.1 grinding points and scope of application of coated abrasive

coated abrasive is a kind of flexible abrasive made of abrasive, substrate and binder. The grinding of Coated Abrasives has elastic and efficient cold cutting grinding points, which are widely used in:

(1) the processing of large flat thick and thin plates, including metal strips

(2) processing of various metal and non-metal workpieces produced in large quantities

(3) forming grinding and polishing of workpiece with complex profile

(4) cylindrical grinding, curved surface grinding, internal grinding, etc. of metal pipes, rods and rollers of various diameters

(5) the use of leaf wheel or cylindrical sand sleeve can replace the polishing of the polishing wheel

(6) disc products are used for weld grinding, deburring and large-area derusting of large shells, boxes, hulls, bridges, etc., which are efficient, convenient and safe

2.2 grinding mechanism of abrasive belt

coated abrasive tools can be understood as multi knife and multi edge tools composed of many abrasive particles

the abrasive particles coated with abrasive tools are evenly distributed on the surface of the substrate, basically single-layer distribution. The special abrasive used in the coated abrasive has high requirements for basic particle content and uniform particle size, which makes the abrasive particles on the surface of the coated abrasive have a good contour arrangement. In particular, the electrostatic sand planting process is adopted in the production of modern coated abrasive tools, which ensures that the sharp angle of abrasive particles faces outward and the abrasive materials are arranged in a directional manner. The fixed pumping arrangement and contour of abrasive particles on the surface of coated abrasives are important factors for coated abrasives to maintain high grinding efficiency and cold grinding

and wheel grinding is that "belt grinding is developed by increasing the vertical load (grinding pressure) on the belt surface, rather than by increasing the belt speed.

the linear speed of the belt is generally in the range of m/s, rarely exceeding 5