Recent developments in green silicon carbide

Green silicon carbide as an abrasive, silicon carbide production area in our previous two or three decades was a hero, and later as for export purposes and silicon carbide grinding non-development, production volume relative to the black silicon carbide, gradually relegated secondary position.
But its total production is always rising steadily, especially in the late 1990s, the international wire cutting of green silicon carbide powder application process, our green silicon carbide production and exports have increased, but producing regions and manufacturers also limited to the traditional Northeast Mudanjiang, Hun, etc., the Central Plains, Zhengzhou, Pingdingshan, Shandong Tengzhou, linshu and Hubei Danjiangkou, etc., the Northwest Territories and only Qinghai Guide Haiyan and Blackforge change Green furnace of LAI.
Another turn of the century before, not on the use of Sichuan power grid small hydro electricity low (from the 0.08 to 0.15 yuan / KWH), from Shandong, and Fujian in Lianyungang Miannig, ganluo and Johnson and Yaan, etc., to build a batch furnace capacity 6300KVA ~ 2000KVA green silicon carbide smelter home.
So far, China's annual output of green silicon carbide by the reform and opening up to the time of less than three tonnes to seven or eight tons. But the biggest single furnace capacity still hovering at 5000 ~ 6300KVA, smelting process also follows the formation of the sixties and the East China Sea petroleum coke calcination quartz sand as raw material processes.

Garnet evaluation and appreciation

Garnet in color, transparency, clarity, weight and other aspects of its cut quality evaluation standards, excellent product requires pure color beautiful, clean and transparent interior, flawless crack, cut well and have some weight.
(1) Color: The color to be pure and beautiful. Different varieties, different colors, values ??are different. As rare demantoid, chrome vanadium grossular other green varieties if transparent without cracking, high quality and high quality emerald may equal value; red pyrope, orange spessartine, Hessonite also valuable, and maroon, dark red almandine lower value.
(2) Transparency: high quality person should be transparent and clean. Translucent or color depth are often processed into a concave arc in order to increase transparency. While opaque to translucent varieties to check the internal arrangement of inclusions see if processed into cabochon while showing a starlight effect.
(3) Clarity: To no cracks, flaws, especially a lot of dark red almandine. Complete crystal partakers who pay attention to whether the internal structure or folder with black opaque inclusions agglomerate. Such as Vietnam output intact skin only to garnet crystal thin transparent can be utilized for other mineral impurities within the black heart. At present, high-quality garnet mostly irregular silicon carbide grit.
(4) Weight: raw block the bigger the better, rounded shapes to mix better, which can improve the processing yield. Right Demantoid green grossular other high-grade varieties, the price increases exponentially with the weight, usually more than 0.5ct very valuable; while other species with different weight finished their prices changed little, mainly to see required when making jewelry styles and sizes requirements. But a few rare giant crystal or finished products can be regarded as treasures. (5) Cut: To fashionable, proper proportion, polish well. Different varieties of materials to be designed for different styles. High dispersion Demantoid processed into standard round brilliant, in order to fully reflect its fire color; coloration were processed for the double curved to enhance the body color; color depth are processed in order to lighten the color of the concave arc, increasing transparency; has multiple sets of special needles arranged in the direction of the arc-shaped inclusions processing to display the star effect.

Silicon carbide industry's position in the slice

Crystalline silicon photovoltaic feeder line cutting is cutting the biggest market differentiator, and silicon carbide crystal wafer cutting is very important as an accessory, the market demand with the development of photovoltaic industry has maintained a strong growth momentum. However, since entering in May, silicon carbide market prices began to loosen, product demand dropped, companies have been affected to varying degrees. Henan Green foreign filter water treatment materials industry professionals once said: "silicon carbide powder is a tool in the hands of photovoltaic enterprises, who have the best tools, whoever occupies the best cutting opportunities."
It is obvious from this statement in the slice of silicon carbide powder industry position is pivotal. With the rapid development of photovoltaic industry, the industry's growing demand for wafer temperature, the number is growing, while the production of polycrystalline silicon carbide powder as an important accessory, its natural demand is increasing. Domestic silicon carbide powder is mainly divided into black silicon carbide powder and green silicon carbide powder into two categories, the black silicon carbide powder and green silicon carbide powder technology and ingredients are different, resulting in the market demand for these two products is not the same.
At present, mainly dominated by green silicon carbide powder, because it itself determines its characteristics more suitable for photovoltaic, semiconductor crystal silicon material cutting edge parts, so the use of green silicon carbide powder than black silicon carbide powder. Our country is a major exporter of silicon carbide production and, in 2009 total output of 530,000 tons of silicon carbide and more, accounting for 56.3% of the global total, ranking first in the world. 2010 silicon carbide production reached 700,000 ~ 800,000 tons, as of now, 2011 silicon carbide production has reached 30 million to 40 million tons.

About corundum abrasive characteristics and processing technology introduction

Corundum abrasives, white fused alumina, white fused alumina block, abrasive corundum, white corundum sand (WA)
White fused alumina abrasive is alumina as raw materials, high temperature melting together. White, slightly higher hardness than corundum, lower toughness. Made with corundum abrasive for high carbon steel, high speed steel and hardened steel grinding. Corundum abrasive, white corundum abrasive polishing material can be used, but also for precision sand casting, coating materials, chemical catalyst carrier, special ceramics, advanced refractories.
White fused alumina abrasive chemical composition:
Chemical composition size range AI2O3 (%) Na2O (%)
F12 - F80 ≥ 98.5 ≤ 0.50
F90 - F150 ≥ 98.5 ≤ 0.60
F180 - F220 ≥ 98.2 ≤ 0.70
Physical properties of corundum abrasives: Physical property
Basic mineral crystal size μm really infer g/cm3 Bulk density g/cm3 microhardness g/mm2
α-AI2O3 600 ~ 1400 ≥ 3.90 1.5 ~ 1.95 2200 ~ 2300
Corundum abrasive properties: white, hard and brittle than corundum, strong cutting force, good chemical stability, with good insulation. White fused alumina abrasive Scope: do solid structure and coated abrasives, wet or dry spray sand, suitable crystals, the electronics industry and ultra-fine grinding and polishing production advanced refractory. Suitable for machining hardened steel, alloy steel, high speed steel, high carbon steel and other hard hardness, tensile strength greater material. Corundum abrasives can also be used as catalyst, insulators and precision casting sand.

Silicon carbide is the most widely used and most economical product

Silicon carbide (SiC) with quartz sand, petroleum coke (or coal), wood chips as raw material in electric arc furnace smelting. There are also rare in nature, silicon carbide mineral, Moissanite. Silicon carbide, also known as Moissanite.
In contemporary C, N, B and other high-tech non-oxide refractory raw material, silicon carbide is the most widely used and most economical one. Can be called emery or refractory sand. Silicon carbide is quartz sand, petroleum coke (or coal), wood (green silicon carbide production requires add salt) and other raw materials at high temperature in a resistance furnace smelting. At present, China's industrial production is divided into black silicon carbide and silicon carbide green silicon carbide two kinds, both hexagonal crystal, specific gravity of 3.20 ~ 3.25, microhardness 2840 ~ 3320kg/mm2.
SiC as chemical stability, high thermal conductivity, thermal expansion coefficient, good wear resistance, except for the abrasive used, there are many other uses, for example: a special process the silicon carbide powder coating on the turbine impeller or cylinder block wall, can improve the wear resistance and extended service life 1 to 2 times; made for advanced refractory, thermal shock resistance, small size, light in weight, high strength, good energy saving effect. Low-grade silicon carbide (SiC-containing about 85%) is an excellent oxygen scavenger, it can accelerate the speed steel, and facilitate control of chemical composition and improve the quality of steel.
Silicon carbide is also used extensively for production of silicon carbide heating elements.

Corundum: corundum density related presentations

Corundum density:
Density is divided into two, one corundum bulk density, the second is the true density corundum. 
Bulk density:
1.53 ~ 1.99g/cm3, the bulk density of the abrasive and the abrasive grain size, grain size, species, particle shape and other factors are, in general, coarse abrasive bulk density than the fine-grained abrasive, mix size is greater than the bulk density of the abrasive single particle density.
Particle density:
3.95 ~ 4.0g/cm3, in recent years, special casting corundum true density has reached 4.1g/cm3, the true density of the abrasive is the unit volume (excluding the volume of open porosity) contained within the abrasive quality, primary particle size of as follows: 45% to 55%, corundum can rest assure that more than 50%, the basic effect of particle size is an important indicator to ensure the ground, should be properly controlled in the production, but the production speed may slow down.

 

Silicon carbide and corundum abrasives on the characteristics and performance description

1, brown fused alumina:The main chemical composition AL2O3, the bauxite, iron and anthracite from melting in an electric arc furnace. Corundum abrasive color is brown, its color, the name corundum. The abrasive has a certain hardness and toughness, with the strong grinding ability, able to withstand great pressure. With a high temperature, anti-oxidation, anti-corrosion and chemical stability is good. High tensile strength as it applies to the grinding of the material tensile strength, suitable for general steel, high carbon steel, alloy steel, for the processing of hard wood, other abrasives can be used in substitution is insufficient, a universal Abrasive said, is the most widely used kind of abrasive.2, corundum:The main chemical composition of AL3O2 aluminum oxide powder as raw material in electric arc furnace melting together. Color is white, in terms of its color name corundum. Corundum corundum texture purer than brown. Using aluminum oxide powder material, corundum used by the Department of bauxite processing is made in advance, the main physical components (without grinding capacity) by arc melting from the converted. The conversion has strong grinding force.3, black silicon carbide:The main chemical composition of SiC. From petroleum coke, quartz sand, sawdust as raw materials in the resistor formed by the melting furnace. Black silicon carbide color is black, in terms of its color, named for the black silicon carbide. Black silicon carbide is brittle texture than corundum abrasive, hardness hard, its toughness is also inferior to corundum abrasive, than the end of the tensile strength of the material, such as non-metallic materials (various boards such as wooden plywood, particleboard, high school low-density fiberboard , bamboo board, calcium silicate board, leather, glass, ceramics, stone, etc.) and non-ferrous metals (aluminum, copper, lead) and other materials processing is particularly suitable for hard and brittle materials texture is ideal abrasive machining .4, green silicon carbide:The main chemical composition of SiC used in the manufacture of raw materials such as black silicon carbide plus industrial salt production are substantially the same as the reaction agent and accelerator reaction from the resistance furnace. Terms of their color is green so named for the green silicon carbide . green silicon carbide texture than the more pure black, green silicon carbide powder can be made, even higher hardness than black silicon carbide and silicon carbide which uses the same ground outside is more suitable for fine grinding of materials such as grinding thread, measuring tools, etc. in the grinding mill material is more widely used carbide, diamond products of the workpiece. Because green silicon carbide in the manufacturing cost is higher than the black silicon carbide, such as the use of raw materials is not the same on the ratio, plus a salt auxiliary materials as well as differences in processing power and so on, so green silicon carbide products cheaper than Black silicon carbide is higher. Therefore, the selection of green silicon carbide and silicon carbide in comparison, in the non-metallic and non-ferrous materials generally do not use green silicon carbide, green silicon carbide as the main choice and precision grinding carbide grinding, in belt and other coated abrasives green silicon carbide as grinding on the selection of materials for less.5, microcrystalline corundum:The main chemical components of AL2O3, used the same raw materials and corundum, only in the smelting process using rapid cooling process fine crystals obtained results. Fine crystalline corundum corundum mechanical strength than ordinary higher. Made with microcrystalline corundum abrasives commonly used for coarse grinding steel, high toughness titanium-nickel alloy steel and other difficult to grind materials, but rarely used in the manufacture of coated abrasives.