Aluminum oxide ( corundum ) used in the coated abrasive and abrasive has a long history , but also a great number of international annual use , the alumina raw material of tungsten carbide and nitride materials in terms of the cheapest , while alumina tool high prices . Carbide cutting tool about the proportion of alumina ( tungsten carbide base ) of the third volume prices , aluminum carbide cutting tool cheaper than this is one of the factors prompting the international aluminum tool development.
The aluminum oxide ( alumina ) ceramic tool is its development of products, fine tip , is a model of modern alumina ceramic , high added value . Al2O3 ( alumina ) powder 4 to 5 yuan / kg, while the price of alumina-based tool from 2000 to 3000 yuan / kg. 2007 sales in Western countries ceramic tools is estimated at over 45 billion U.S. dollars, accounting for about half of the alumina-based ceramic tool . Among the largest output in Japan , followed by the United States , Germany, Britain , etc., while Russia also has a certain production scale . But domestic resources for this material widely , inexpensive , capable of producing high value-added development tools but little could enrich China tungsten resources with emphasis on tungsten carbide cutting tools related.
First, the performance of alumina [PAGE] Modern new ceramic material comprises oxides, carbides , nitrides , borides , silicides, and complex compounds between them. There are works from the use of structural ceramics , functional ceramics , tools and ceramics. Ceramic knives are used to turning or milling metal and alloy tool. Except for the carbide tool that is an oxide ceramic , a nitride . The oxide is the most suitable alumina ( corundum -α-Al2O3) material.
Pure crystalline Al2O3 dozen exist at low temperatures , but are mainly three: the α-Al2O3, β-Al2O3, γ-Al2O3, all crystalline at temperatures over 1600 ℃ above , are converted into high-temperature stable α- Al2O3 ( corundum ) , this change is irreversible . Al2O3 is very low hardness in general , only the α-Al2O3 corundum hardness ( Mohs hardness 9 ) is very high, to make the cutting tool and corundum wear parts .
α-Al2O3 is hexagonal , corundum ( unit cell is sharp rhombohedral ) structure , a = 4.76Å, c = 12.99Å. Density 3.96 ~ 4.01g/cm3, hardness (HV) 3000kg/mm2, Young's modulus 42kg/mm2, thermal conductivity 0.07 cal / ( cm • sec • ℃), the thermal expansion coefficient of 8.5 × 10 ˉ 6 ℃.
Chemical stability of the alumina is a strong reaction with a lot of material is very weak .
Second, the current alumina ceramic cutting tool steel , cast iron, alloy steel and stainless steel and other commonly used carbide-based cemented carbide (WC-Co, WC-TiC-Co). For some special materials also used the highest hardness of diamond and cubic boron nitride (CBN), but their intensity lower than the carbide and diamond cutting tools are not conducive to the steel material , because diamond is easy carbonaceous elements and iron the reaction of iron carbide , leaving the diamond loss, but diamond tools for machining aluminum-silicon alloy has unique advantages. The CBN for many materials , such as iron-based not react to the processing of chilled cast iron, Stellite alloy , heat-resistant nickel-based alloys have better performance. [PAGE]
Alumina and other characteristics are different tool materials : stable alumina chemical properties, particularly good oxidation resistance , even if it is in the cutting edge can be a long red hot cutting , the alumina ceramic tool is particularly suitable for high-speed cutting and heating cutting . Due to the poor wettability of alumina to metal in the majority , it is difficult to bond with a metal (e.g., steel and bonding temperature : aluminum oxide above 1528 ℃, tungsten carbide is 1316 ℃), the cutting performance of the friction coefficient low , low cutting forces , difficult to produce BUE and adhesive wear , so easy to get a high processing light cleansing . Alumina is the most of all the tool material inactive , when you can reduce the spread of the cutting tool wear , Al2O3 dissolution rate in iron than WC 4-5 times lower , thus alumina ceramic cutting tool wear when steel rate than WC -based cemented carbide cutting tools as small as a few times to magnitude . The use of high alumina ceramic cutting tool wear and suitable for high-speed cutting of large machinable features , such as the processing length 7320mm, muzzle diameter of 155mm, 310mm rear end of the barrel diameter steel . Most suitable for processing aluminum metal materials , especially for cutting chilled cast iron or hardened steel , materials used for these fine cars instead of grinding can achieve significant technical and economic benefits . Alumina at high temperatures to maintain a high hardness , cutting speed up to 1300 m / min.
Alumina is currently mainly used for semi-finishing tool and precision machining , precision cutting its accuracy and finish suitable for hard materials to the car instead of grinding , and several times greater processing efficiency , processing costs can be reduced by more than half , so the tool is very popular with alumina people welcome. Many in the German car parts are alumina ceramic tool in turning instead of grinding finishing to complete .
When cutting, ceramic tool can withstand high temperatures 2000 ℃ , and then at 800 ℃ carbide soften . Carbide cutting speed is too high at the time , the temperature of overheating , resulting in severe wear crescent tool damage. High temperature ceramic blade for cutting the high temperature more favorable , since the metal of the workpiece and the plastic tends to soften at high temperatures , and low-energy cutting . Low thermal conductivity of the ceramic high temperature only in the nose , the heat generated by the high-speed cutting with both chip away . Many researchers believe that: alumina ceramic inserts can , and must be 10 times higher than the carbide cutting speed for cutting down the line , in order to truly reflect the advantages of ceramic blades. [