Overview of Coated Abrasives and Application Advantages and Disadvantages

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Coated abrasives are tools made by bonding abrasives to flexible materials like cloth or paper using adhesives (glues), making them suitable for grinding and polishing.

These include various forms such as rolls, sheets, belts, discs, and customized-shaped products. These can be made from substrates like cloth, paper, or non-woven fabric,

They are used extensively in metal, wood, ceramics, plastics, leather, rubber, and non-metallic materials like paint and putty for grinding, polishing, and sanding.

Components of Coated Abrasives

Coated abrasives comprise three main elements: the substrate, the abrasive, and the adhesive.

1. Substrate: This forms the carrier for the abrasive and adhesive and is the primary determinant of the abrasive's flexibility. Substrate materials for coated abrasives include paper, cloth, steel paper, composite substrates, non-woven fabric, polyester films, and more. These substrates must undergo specialized treatment to enhance their physical and mechanical properties, ensuring they meet the requirements for adhesive bonding and grinding processes. Substrate treatments can be categorized into non-water-resistant and water-resistant treatments, with further variations like soft treatment, high-permeability treatment, oil-resistance treatment, and anti-static treatment based on the specific grinding requirements.

2. Abrasive: The abrasive is a material with high hardness and strength, essential for manufacturing abrasive tools or direct grinding and polishing. Abrasives can be categorized into two main types: natural and synthetic. Abrasives must possess certain essential properties such as adequate hardness, strength, suitable fracturing characteristics, self-sharpening ability, and chemical or thermal stability.

3. Adhesive: The adhesive bonds the abrasive to the substrate, providing the abrasive tool with its shape and strength. Adhesives in coated abrasives typically consist of substrate treatment agents, base adhesives, and additional adhesives.

- Substrate Treatment Agents: These agents aim to improve the physical and mechanical properties of the substrate, ensuring proper adhesive bonding and grinding performance. Depending on the specific requirements of the product, substrate treatment can be either water-resistant or non-water-resistant and the treatment agents should be aligned accordingly.

- Base Adhesives: Base adhesives form the coating that bonds abrasives to the substrate.

- Additional Adhesives: Additional adhesives are applied over the already bonded abrasive grains to further enhance their bonding strength, ensuring the abrasive grains withstand the pressures and impacts during grinding without detaching from the substrate.

Common Varieties of Abrasives Used in Coated Abrasives

1. Brown Fused Alumina (A, WA): Composed primarily of α-Al2O3, brown fused alumina exhibits a brown or brownish-red appearance. It boasts high hardness, good toughness, and the ability to withstand substantial pressure. Its important features include resistance to high temperatures and corrosion, while also having excellent chemical stability. Brown fused alumina is widely used in the grinding of high-tensile-strength metals like carbon steel, hard bronze, alloy steel, and malleable cast iron.

2. White Fused Alumina (A, WA): White fused alumina, also primarily composed of α-Al2O3, but appears white in color. It possesses higher hardness than brown fused alumina but is more brittle with better sharpness. It is mainly used for fine and precision grinding of hardened steel, and alloy steel, as well as for thread and gear grinding. It also finds applications in precision casting and advanced refractories.

3. Silicon Carbide (C, GC): Silicon carbide comes in two main varieties: black and green. It primarily consists of SiC and appears black in color. It is characterized by high hardness, brittleness, and excellent sharpness. Silicon carbide does not react with acidic substances but can be decomposed by alkaline oxide melts. Black silicon carbide, with its higher hardness and greater brittleness compared to brown fused alumina, is suitable for processing low tensile strength metals and nonmetallic materials like gray cast iron, brass, lead, and aluminum, as well as hard, brittle nonmetallic materials such as glass and ceramics.

Green silicon carbide, which is purer, harder, and more brittle than black silicon carbide, is suitable for machining hard and brittle materials like hard alloys, optical glass, and agate, and is widely used for precision grinding of gauges, cutting tools, and molds, as well as for honing various cylinders.

4. Zirconia Alumina (ZA): Zirconia alumina consists mainly of α-Al2O3 and AI2O3-Zr eutectic crystals. It appears grayish white or grayish brown and exhibits excellent toughness and wear resistance. It is suitable for high-speed heavy-load grinding and the machining of difficult-to-machine metal materials such as cast steels and alloy steels and is particularly well suited for the grinding of titanium alloys, heat-resistant alloys, and stainless steel.

The Classification of Coated Abrasives

Coated abrasives can be categorized based on the substrate, abrasive, and adhesive into several different varieties, each with distinct properties and uses.

Common classification methods include:

1. Based on the Substrate and Use: Coated abrasives can be divided into dry abrasive cloth, waterproof abrasive cloth, dry abrasive paper, and waterproof abrasive paper. Our company's abrasive cloth generally falls under dry abrasive cloth.

2. Based on the Adhesive and Substrate Treatment: Coated abrasives are categorized into animal glue-bound coated abrasives, resin-bound coated abrasives, all resin-bound coated abrasives, and waterproof coated abrasives.

3. Based on Abrasive Material and Grit Size: Abrasive material indicates the type and performance of the abrasive, while abrasive grit size denotes the size and distribution of abrasive grains. Different abrasive materials and grit sizes correspond to different coated abrasive varieties.

4. Based on Sand Density: Sand density refers to the density of abrasive grains on the surface of coated abrasives. Coated abrasives are classified into dense sand (CL) with a density of 100% and sparse sand (OP) with a density of 50%-70%.

5. Based on Product Shape: Coated abrasives can be categorized by product shape into sheet-shaped (Y), roll-shaped (J), belt-shaped (D), disc-shaped (P), and special-shaped (T).

While numerous classification methods exist, the combination of "adhesive and substrate treatment" coupled with "classification by product shape" is a practical approach that generally meets the requirements.

Applications of Coated Abrasives

Coated abrasives are known for their flexible, high-efficiency, and cold-cutting characteristics. They find widespread application in:

1. Large flat and thin plates, including the processing of metal strips.

2. Mass production of various metal and non-metal workpieces.

3. Shaping, grinding, and polishing of complex-shaped workpieces.

4. External cylindrical grinding, curved surface grinding, and internal cylindrical grinding of various diameter metal tubes, bars, and rolls.

5. Substituting polishing wheels for polishing, especially with flap wheels or drum-type sleeves.

6. For large-scale projects such as hulls, casings, ships, bridges, and more, used in weld seam grinding, burr removal, and extensive rust removal. These operations are efficient, convenient, and safe.

Advantages and Disadvantages of Coated Abrasives

Coated abrasives offer several advantages:

- Flexibility: Coated abrasives are highly flexible, allowing them to conform to complex workpiece shapes. This makes them suitable for various applications, including precision grinding.

- Efficiency: They are known for their efficiency in cold cutting, enabling fast material removal and reducing workpiece heat buildup.

- Wide Application Range: Coated abrasives can be used on a wide range of materials, including metals, woods, ceramics, plastics, leather, rubber, and nonmetallic substances like paint and putty.

- Controlled Material Removal: The flexibility of coated abrasives allows for controlled material removal, making them ideal for precision work.

However, there are also some limitations:

- Wear and Tear: Coated abrasives, especially when subjected to heavy-duty use, can wear out relatively quickly. Frequent replacements of sanding belts or discs may be necessary.

- Dust and Debris: The sanding process generates dust and debris, which can pose health hazards if not managed properly. Adequate dust extraction or personal protective equipment may be required.

- Initial Cost: While the initial cost of coated abrasives is typically lower than other abrasive methods, the need for frequent replacements can increase long-term costs.

Coated abrasives are versatile tools that play a crucial role in various industries. Their flexibility and efficiency make them indispensable for a wide range of grinding tasks.

However, users should be aware of the different types of abrasive products available, and each product's strengths and limitations, and select the correct product according to the required project to ensure safe and effective use.