Carbon shaft

Huettner [141] discusses the role of carbon fiber composites in state-of-the-art ceramics in surgery, such as reinforced carbon shaft endoprosthesis, and finds that cfrp is suitable for the construction of endoprosthesis shafts having high static and dynamic strength. Claes [142] describes experimental investigations on hip prostheses with carbon fiber reinforced carbon shafts with ceramic heads, finding cfrp more suitable than stainless steel. 

A carbon shaft weighs about 40% less than a conventional steel shaft, which allows the golf club designer to add weight to the club head and achieve a greater driving distance, yet still save some weight. 

Huettner W, Carbon-fibre-reinforced carbon shaft-endoprosthesis - state of the art Ceramics in Surgery, Proc. 2nd Int. Symp, on Bioceramics, Lignano Sabbiadoro, Italy, 16-19 June, 1982, Vincenzini P ed., Amsterdam, Elsevier, 225, 1983. 

In addition to the principal equations discussed, several others occur which may be of importance, including calcination of calcium carbonate (limestone), which takes place in the upper shaft at 800—870°C,... 

The description given apphes to DR processes that are based on the use of gaseous reductants ia shaft furnaces, batch retorts, and fluidized beds. In the processes that use sohd reductants, eg, coal (qv), the reduction is accomphshed to a minor extent first by volatiles and reduciag gases that are released as the coal is heated and then by CO that is formed by gasification of fixed carbon contained ia the coal char with CO2. Reductioa by sohd carboa and coal volatiles ia kilns is insignificant. 

Low Temperature Carbonization. The Lurgi Sptlgas process was developed to carbonize brown coal at relatively low temperatures to produce tars and oils (Fig. 5). A shaft furnace internally heated by process-derived fuel gas (Spblgas) is used. The product can range from a friable coke breeze to hard lump coal depending on the quality of the briquettes used in the feed. The briquettes, made in normal extmsion presses, break down into smaller sizes during carbonization. 

Fig. 5. Diagram of large Lurgi Spblgas carbonization plant A, coal conveyor B, movable distributor C, coal bunker D, drying zone E, connecting shafts ...

Ferrous foundries consist of two types steel foundries in which electric furnaces (EAF and induction) are used, and iron foundries in which hot-blast cupolas and/or electric furnaces are used. Electric furnaces use virtually 100% scrap charges. Cupolas are shaft furnaces which use preheated air, coke, fluxes, and metallic charges. Scrap is over 90% of the metallic charge. Cupolas accounted for about 64% of total iron foundry scrap consumption in 1994 and electric furnaces accounted for about 34%. The balance was consumed by other furnaces, such as air furnaces. Iron foundry products have a high carbon content and the scrap charge usually contains a high percentage of cast iron or is used in combination with pig iron. 

Sophisticated stmctural analysis techniques make it possible to determine both the amount and exact orientation of reinforcement that the product wQl need to meet the critical stresses in actual service. Hybrid reinforcement systems containing different fiber compositions with different properties are being increasingly used. For example, hybrid carbon and glass fiber automotive drive shafts are in commercial use. 

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). 

The high elastic modulus, compressive strength, and wear resistance of cemented carbides make them ideal candidates for use in boring bars, long shafts, and plungers, where reduction in deflection, chatter, and vibration are concerns. Metal, ceramic, and carbide powder-compacting dies and punches are generahy made of 6 wt % and 11 wt % Co ahoys, respectively. Another apphcation area for carbides is the synthetic diamond industry where carbides are used for dies and pistons (see Carbon). 

Raw Materials. The basic raw materials limestone and coke or coal (qv) should be high quaHty. Limestone should contain a minimum of 95—97% CaCO and a maximum of 1.5% MgCO, 1—1.5% Si02, 1% Fe202 plus AI2O2, and 0.006% phosphoms (see Lime and limestone). The limestone is first converted to lime in a rotary or vertical shaft kiln. The lime is screened to eliminate fines that interfere with the evolution of carbon monoxide in the smelting process. 

Graphites (natural or synthetic) are black semireinforcing fillers used almost exclusively in rotary shaft seal applications where surface lubricity and abrasion resistance must be enhanced (see Carbon, natural graphite). 

Wear and increased leakage from the glands are common. Carbon rings may need replacement after I or 2 years of operation. A unit with labyrinth packing may never need packing replacement. This depends upon operation. If a unit is started quickly with a temperature bow in the shaft, the result is a rub in the labyrinth, and then all packing may need replacement. 

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