Carbon, Carbides, and Carbonates

Much useful information on these and other solvents will be found in the booklet Synihtiic Oryanic Chemicals issued by the Carbide and Carbon Chemicals Corporation. 

Nitrogen and carbon are the most potent solutes to obtain high strength in refractory metals (55). Particulady effective ate carbides and carbonitrides of hafnium in tungsten, niobium, and tantalum alloys, and carbides of titanium and zirconium in molybdenum alloys. 

Company (Bayway, New Jersey). This was followed in 1921, by the start-up of isopropyl alcohol production in Clendenin, West Virginia, by the Carbide and Carbon Chemicals (Union Carbide) Corporation. The Shell Oil Company began production in the 1930s at Dominguez, California (55). These three companies are the principal domestic manufacturers as of the mid-1990s. 

Carbon, Carbides, and Nitrides. Carbon (graphite) is a good thermal and electrical conductor. It is not easily wetted by chemical action, which is an important consideration for corrosion resistance. As an important stmctural material at high temperature, pyrolytic graphite has shown a strength of 280 MPa (40,600 psi). It tends to oxidize at high temperatures, but can be used up to 2760°C for short periods in neutral or reducing conditions. The use of new composite materials made of carbon fibers is expected, especially in the field of aerospace stmcture. When heated under... 

H. E. Smith, The Effect ofTetramethylorthosilicate on the Eyes, Carbide and Carbon Chemicals Industrial EeUowship 274-1, Mellon Institute, Pittsburgh, Pa. 

A wide range of cutting-tool materials is available. Properties, performance capabilities, and cost vary widely (2,7). Various steels (see Steel) cast cobalt alloys (see Cobalt and cobalt alloys) cemented, cast, and coated carbides (qv) ceramics (qv), sintered polycrystalline cubic boron nitride (cBN) (see Boron compounds) and sintered polycrystalline diamond tbin diamond coatings on cemented carbides and ceramics and single-crystal natural diamond (see Carbon) are all used as tool materials. Most tool materials used in the 1990s were developed during the twentieth century. The tool materials of the 1990s... 

High Speed Steels. Toward the latter part of the nineteenth century, a new he at-treatment technique for tool steels was developed in the United States (3,17) that enabled increased metal removal rates and cutting speeds. This material was termed high speed steel (HSS) because it nearly doubled the then maximum cutting speeds of carbon—low alloy steels. Cemented carbides and ceramics have since surpassed the cutting speed capabiUties of HSS by 5—15 times. 

A hard, mst-resistant shaft of at least 0.25 micrometer finish is usually required. Common shaft surfaces are hardened tool steel, chrome plate, high strength bronze, and carbide and ceramic overlays. Test results over a broad speed range from 0.05 to 47 m/s (10 to 9200 fpm) iadicate that a coefficient of friction of 0.16—0.20 and a wear factor of 14 X 10 m /N(70x 10 ° in. min/ft-lb-h) are typical for dry operation of weU appHed grades of carbon—graphite (29). 

Boron and carbon form one compound, boron carbide [12069-32-8] B C, although excess boron may dissolve ia boron carbide, and a small amount of boron may dissolve ia graphite (5). Usually excess carbon appears as graphite, except for the special case of boron diffused iato diamonds at high pressures and temperatures, eg, 5 GPa (50 kbar) and 1500°C, where boron may occupy both iaterstitial and substitutional positions ia the diamond lattice, a property utilized ia synthetic diamonds (see Carbon, diamond, synthetic). 

Calcium Carbide and its Derivatives. Although hydrocarbon-based acetylene production has become mote important, eady manufacture of acetylene was based on manufacture of the iatermediate, calcium carbide [73-20-7J, CaC2. This ionic acetyUde is produced by reaction of lime and carbon ia electric-arc furnaces (16). 

Group 5 (3), diamondlike carbides and (3), volatile nonmetallic carbides. A line through the box, eg, 0, indicates no carbide formation however, there may be some solubiUty of carbon in the melt. A question mark, eg, Ac , indicates the possibiUty of a carbide. 

Iron carbide (3 1), Fe C mol wt 179.56 carbon 6.69 wt % density 7.64 g/cm mp 1650°C is obtained from high carbon iron melts as a dark gray air-sensitive powder by anodic isolation with hydrochloric acid. In the microstmcture of steels, cementite appears in the form of etch-resistant grain borders, needles, or lamellae. Fe C powder cannot be sintered with binder metals to produce cemented carbides because Fe C reacts with the binder phase. The hard components in alloy steels, such as chromium steels, are double carbides of the formulas (Cr,Fe)23Cg, (Fe,Cr)2C3, or (Fe,Cr)3C2, that derive from the binary chromium carbides, and can also contain tungsten or molybdenum. These double carbides are related to Tj-carbides, ternary compounds of the general formula M M C where M = iron metal M = refractory transition metal. 

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