Subdividing coated abrasives is an essential requirement to enhance the quality and diversity of these grinding tools. Coated abrasive belts were initially developed by industrially advanced countries in Europe during the 1960s. It wasn't until the early 1990s that China developed its own AP(Abrasive Paper)belts. With advancements in science, technology, and industrialization, the range of abrasive materials used in coated abrasives has expanded from just three varieties–brown corundum, white corundum, and silicon carbide–to nearly twenty different types with varying densities and particle shapes.
It is well-known that coated abrasives from developed countries in Europe, America, and Japan are more expensive than their Chinese counterparts. The reasons behind this price difference lie in their broader applicability, higher grinding efficiency, and moderate wear resistance, making these products more favored and sought-after by the market and customers. As per Hubei Yuli's General Manager, ShanYu Li, in"Development and Prospect of Coated Abrasives in China, "while the domestic coated abrasive market sales amount to approximately 2.5 billion yuan, imported products consistently hold a share of around 1 billion yuan, and their sales remain stable with relatively higher prices.
Selecting Different Types of Abrasives:
1. Abrasive Variety Selection:
There are various abrasive types to choose from, including brown corundum, sintered brown corundum(blue and red), iridium-coated corundum, white corundum, semi-brittle corundum, zirconium corundum, ceramic abrasives, hollow ball abrasives(aluminum oxide-based), plate-shaped corundum abrasives, sintered corundum abrasives, composite abrasives(aluminum oxide-based), mixed abrasives, silicon carbide(black and green), and combined abrasives of nitrides and carbides.
To make the right abrasive choice, understanding the characteristics of each type is essential:
a.Brown Corundum Abrasives:
Brown corundum is the earliest and most widely used abrasive in coated abrasives. It comes in two production methods: dumping furnace(method)and melting furnace(method).The former results in multiple crystalline aggregates with small crystal sizes and a high glass content in the grain boundaries, leading to poor toughness, high brittleness, easy detachment of abrasive grains, and excellent self-sharpening.The latter, however, produces fewer crystalline aggregates with larger crystal sizes and less glass content. Consequently, it exhibits better toughness, lower brittleness, and superior wear resistance. Properly shaped and with the right density, brown corundum is suitable for both wood and metal grinding, making it the most widely used abrasive in coated abrasives.
Chinese sintered corundum was introduced into abrasive belts approximately 15 years later than its foreign counterparts. It took nearly a decade to progress from concept to product experimentation and around five years from trial use to continuous use, meaning that only a few companies have been using sintered corundum since 2005. Currently, there are only two colors in continuous monthly usage of over 100 tons each(red and blue). Sintered corundum changes its color due to the influence of titanium oxide(TiO2)during the firing process.TiO2, when present in a brown corundum particle, causes it to turn blue when exposed to an oxidizing atmosphere. The toughness strength peaks just before the brown corundum turns blue(below 1300 degrees Celsius), appearing light blue at 1300 degrees Celsius and bluish-grey at 1400 degrees Celsius.
Mixed abrasives involve combining two or more types of abrasives with similar particle sizes and shapes in varying proportions. For example, 80-85%brown corundum mixed with 10%white corundum and 10%silicon carbide, or 80%brown corundum mixed with 10%semi-brittle corundum and 10%zirconium corundum. Different characteristics of abrasive materials in the mixed state can produce varying grinding effects, resulting in complementary advantages. Such mixed abrasives can improve grinding efficiency while reducing abrasive costs.
How to Choose Abrasives:
1. Selection of Abrasive Density:
Different abrasive densities yield different grinding effects. High-density abrasives(shaped abrasives)have been in use for sanding belts for the past ten years in foreign markets.
2. Selection of Abrasive Particle Shape:
The shape of the abrasive particles directly influences the abrasive density and grinding effects. Twenty years ago, foreign sanding belts primarily used pointed, flaky, and elongated abrasive particles for grinding softer materials such as wood and leather. However, with the advent of new materials and their applications, the grinding and wear resistance requirements have evolved. Different materials like steel, iron, copper, aluminum, stainless steel, stone, wood, leather, alloys, etc., have varying characteristics and necessitate abrasives with different toughness and particle shapes to achieve optimal grinding results.
3.Selection of Sanding Density(Amount of Sanding):
The sanding density of abrasive belts affects the grinding effects significantly. Even if the same abrasive material is used, the combination of abrasive+density+particle shape+appropriate sanding amount is necessary to display reasonable grinding results. In the long run, transforming mindsets, improving the grade of abrasives, extending the lifespan of coated abrasive tools, raising product prices, reducing environmental pollution, and moving away from low-grade and low-price vicious competition will be the key directions for future development.
The subdivision of coated abrasives is critical in enhancing their quality and diversity. As the coated abrasive industry continues to evolve with scientific and technological advancements, selecting the right abrasive material becomes crucial. Understanding the characteristics of each abrasive type enables manufacturers and users to optimize their grinding processes for various materials, thereby achieving improved efficiency and performance. As China's coated abrasives industry strives to match the standards set by its foreign counterparts, continuous research and development, adoption of advanced technologies, and a focus on quality will undoubtedly pave the way for a brighter and more competitive future.
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