the tools can be coated in the fully hardened and tempered condition without affecting hardness. Tungsten carbide is another effective coating. One technique, developed by Rocklin Manufacturing and called Rocklinizing, deposits 0.0001 to 0.0008 in (0.0025 to 0.0203 mm) of the carbide using a vibrating arcing electrode of the material in a handheld gun. Titanium carbide and titanium nitride are the latest coatings. The nitride, typically 0.0003 in (0.008 mm) thick, has stirred the greatest interest, although the carbide may have advan- tages for press tools subject to high pressure. In just the past few years, all sorts of tools, primarily cutters but also dies, have been tita- nium-nitride-coated, which imparts a gold- or brasslike look. The coating can be applied by chemical vapor deposition (CVD) at 1750 to 1950°F (954 to 1066°C) or by physical vapor deposition (PVD) at 900°F (482°C) or less. Thus, the PVD process has an advan- tage in that the temperature involved may be within or below the tempering temperature of the tool steels so that the coating can be applied to fully hardened and tempered tools. Also, the risk of distor- tion during coating is less. Titanium nitride coaters include Aerobraze, Multi-Arc Vacuum Systems, Scientific Coatings, Star Cutter, Sylvester, and Ti-Coating. Another method being used to pro- long tool life is to subject the tools to a temperature of Ϫ320°F (Ϫ196°C) for about 30 h. The cryogenic treatment, which has been called Perm-O-Bond and Cryo-Tech by Materials Improvement, is said to rid the steel of any retained austenite—thus the improved tool life. Others in this business include Amcry, Endure, and 3X Kryogenics. TRAGACANTH GUM. An exudation of the shrub Astragalus gummifer of Asia Minor and Iran, used in adhesives or for mucilage, for leather dressing, for textile printing, and as an emulsifying agent. To obtain the gum, a small incision is made at the base of the shrub, from which the juice exudes and solidifies into an alteration product, not merely the dried juice. The gum derived from the first day’s incision, known as fiori, is the best quality and is in clear, fine ribbons or white flakes. The second incision produces a yellow gum known as biondo. The third incision produces the poorest quality, a dark gum known as sari. Rainy weather during the incision period may cause a still inferior product. Tragacanth is insoluble in alcohol but is soluble in alkalies and swells in water. Karaya gum from southern Asia is from various species of Sterculia trees, especially S. urens, of India. It is also known as Indian gum, Indian hog gum, and hog tragacanth. The sticky gum is dried, and the chunks are broken and the pieces sorted by color. A single chunk may have colors varying from clear white to dark amber and black. The color is caused by tannin or other impurities. 980 TRAGACANTH GUM Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses The No. 3 grade, the lowest, has up to 3% insoluble impurities. The gum is marketed in flakes and as a white, odorless, 150-mesh powder. The chief constituent is galactan. In general, the gum is more acid than tragacanth and is likely to form lumpy gels unless finely ground. It is widely used as a thickening and suspending agent for foodstuffs, drugs, cosmetics, adhesives, and textile finishes. Gum tragacynth thoroughly mixed with glycerin and water produces a thick paste, tra- gacynth glycerite, a useful excipient to bind tablet masses. For oral ingestion, suspensions of gum tragacynth have been formulated. One such product is a suspension of procaine penicillin. In hair lotion in which there is 10% isopropanol, gum tragacynth is able to withstand the alcohol without precipitation. It is also a thickener of the aqueous phase in oil-in-water systems, resulting in shelf-stable emulsions. Regular as well as low-calorie salad dressings, such as Thousand Island, French, and Roquefort, are such oil-in-water emulsions. The low-calorie versions have higher amounts of gum tragacynth, to provide the body that oil traditionally gives the regular dressing. Tragacynth gums, Type A.10, Type W, and Type L, are pharmaceuti- cal grades in powder form, produced by Meer Corp. The granules of water-soluble gums, such as karaya, tragacanth, and acacia, are swelled by water and dispersed in water in micro- scopic particles to form cells or filamentlike structures which hold the water like a sponge and will not settle out. This type of colloidal dis- persion is called a hydrasol, and when thick and viscous is called a gel. From 2 to 3% of karaya or other gum will form a gel in water. These gums will gel in cold water, while gelatin requires hot water for dissolving. In a gel there is continuous structure with molecules form- ing a network, while in a sol the particles are in separate suspension and a sol is merely a dispersion. Some dispersions, such as albumen, cross-link with heat; others, like guar gum, cross-link with alkalies; still others, like pectin, link with sugar and an acid. Gums with weak surface forces form weak gels which are pastes or mucilage, and a high concentration is needed to produce a solid. Karaya has great swelling power, and is used in medicine as a bulk laxative. Ghatti gum, from the abundant tree Anogeissus latifolia of India, is entirely soluble in water to form a viscous mucilage. It is twice as effective as gum arabic as an emulsifier, but is less adhesive. It comes in colorless to pale-yellow tears of vitreous fracture, called also Indian gum, and is used in India for textile finishing. Aqualized gum, of Glyco Products Co., Inc., is tragacanth or karaya chemically treated to give more rapid solubility. Water-soluble gums are also produced syntheti- cally. Polyox gum, of Union Carbide Chemicals Co., is a polymer of polyethylene oxide containing carboxylic groups giving water solubil- ity when the pH is above 4.0. In paper coating with ammonia, the TRAGACANTH GUM 981 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses ammonia evaporates to leave a water-insoluble, grease-resistant film that is heat-sealing. It is also used in latex paints and in cosmetics. Another water-soluble gum which forms a true gel with a continuous branched-chain molecular network is okra gum, produced as a 200- mesh tan powder. It is edible and is used for thickening and stabilizing foods and pharmaceuticals. It is also used in plating baths for bright- ening nickel, silver, and cadmium plates. It is extracted from the pods of the okra, Hibiscus esculentus, a plant of the cotton family. In the southern states the pods, called gumbo, are used in soups. The refined gum, after extraction of the oils and sugars, contains 40.4% carbon, 6.1 hydrogen, and 2.1 nitrogen, with the balance insoluble cellulose. TRIPOLI. A name given to finely granulated, white, porous, siliceous rock, used as an abrasive and as a filler. True tripoli is an infusorial, diatomaceous earth known as tripolite, and is a variety of opal, or opaline silica. In the abrasive industry it is called soft silica. It is quarried in Missouri, Illinois, eastern Tennessee, and Georgia. Pennsylvania rottenstone is not tripoli, although it is often classified with it. The material marketed for oil-well drilling mud under the name of Opalite, is an amorphous silica. The Missouri tripoli ranges in color from white to reddish, and the crude rock has a porosity of 45% and contains 30% or more of moisture. It is air-dried and then crushed and furnace-dried. Tripoli is used in massive form for the manufacture of filter stones for filtering small supplies of water. Missouri tripoli is also used for the manufacture of foundry parting. Finely ground tripoli, free from iron oxide, is used as a paint filler and in rubber. The grade of tripoli known as O.G. (once ground) is used for buffing composition, D.G. (double ground) for foundry partings, and the air-float product for metal polishes. Tripoli grains are soft, porous, and free from sharp cutting faces, and they give a fine polishing effect. It is the most commonly used polishing agent. The word silex, which is an old name for silica and is also used to designate the pul- verized flint from Belgium, is sometimes applied to finely ground white tripoli employed as an inert filler for paints. Much Illinois fine- grained tripoli is used for paint, and for this purpose it should be free from iron oxide. Rottenstone is a soft, friable, earthy stone of light gray to olive color, used as an abrasive for metal and wood finishing. It resembles Missouri tripoli and is derived from the weathering of siliceous-argillaceous limestone, with generally from 80 to 85% alu- mina, 4 to 15 silica, and 5 to 10 iron oxides. Rottenstone was largely imported from England, but one variety is found in Pennsylvania. It is finely ground and is marketed either as a powder or molded into bricks. The latter form is used with oil on rag-wheel polishing. A 250-mesh powder is used as a filler in molding compounds. 982 TRIPOLI Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses TRISODIUM PHOSPHATE. A white, crystalline substance of composi- tion Na 3 PO 4 и 12H 2 O, also known as phosphate cleaner, used in soaps, cleaning compounds, plating, textile processing, and boiler compounds. The commercial grade is not less than 97% pure, with total alkalinity of 16 to 19% calculated as Na 2 O. The anhydrous trisodium phosphate is 2.3 times as effective as the crystalline form, but requires a longer time to dissolve. Disodium phosphate is a white, crystalline product of composition Na 2 HPO 4 и 12H 2 O used for weighting silk, boiler treatment, cheese making, and cattle feeds. The medicinal, or USP, grade has only seven molecules of water and has a different crystal structure. The commercial grade is 99.4% pure and is readily soluble in water. Trisodium phosphate hemi- hydrate is a granular, crystalline grade from FMC Corp. for degreasing and water conditioning. Monosodium phosphate is made by reacting soda ash with phosphoric acid in molecular pro- portions; it is used in similar applications to the disodium variety. Sodium tetraphosphate, Na 6 P 4 O 13 , contains 39.6% Na 2 O and 60.4 P 2 O 5 . It is the sodium salt of tetraphosphoric acid and is mar- keted in beads that are mildly alkaline and highly soluble in water. The specific gravity is 2.55 and it melts at 1,112°F (600°C). It is used in the textile industry as a water softener and to accelerate cleansing operations. It removes lime precipitation and sludge and saves soap. Quandrafos, of American Cyanamid Co., used to replace quebracho for reducing the viscosity of oil-well drilling mud, is sodium tetraphosphate, containing 63.5% P 2 O 5 . It makes the cal- cium and magnesium compounds inactive, and 0.06% of the mater- ial controls 16.1% of water in reducing viscosity. It also gives smooth flow with minimum water in paper coating and textile printing. Metafos, of the same company, has a higher percentage of P 2 O 5 — 67%—and a lower pH, for use in textile printing where low alkalin- ity is needed. Sodium pyrophosphate, Na 4 P 2 O 7 , is added to soap powders to increase the detergent effect and the lathering. It is also used in oil-drilling mud. The crystalline form, Na 4 P 2 O 7 и 10H 2 O, is very soluble in water and is noncaking, and it is used in household cleaning compounds. Sodium tripolyphosphate, Na 5 P 3 O 10 , is a water-soluble, white powder used as a detergent, a water softener, and a deflocculating agent in portland cement to govern the viscos- ity of the shale slurry without excessive use of water. Large quanti- ties of these phosphates are used in the processing of chemicals, textiles, and paper; and since they are toxic contaminants of ground and surface waters, mill wastes must be deactivated before they are discharged. The use of phosphates in detergents and soap powders has been banned in many areas since they lead to rapid algal growth in surface waters. TRISODIUM PHOSPHATE 983 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses TULIPWOOD. Also called yellow poplar, whitewood, and canary whitewood, the wood of the tree Liriodendron tulipifera of Canada and the eastern United States. The tree grows to a height of 250 ft (76 m) and to diameters of more than 10 ft (3 m). It is used for furni- ture, veneer, millwork, toys, woodenware, boxes, crates, and pulp- wood. Owing to its close texture and even coefficient of expansion, it has been used for expansion blocks in humidity regulators. It is yel- lowish, soft, and durable. The density is about 30 lb/ft 3 (481 kg/m 3 ). The lumber may be mixed with cucumber magnolia, Magnolia acuminata, and evergreen magnolia, M. grandifolia, but magnolia woods are lighter in color. TUNG OIL. A drying oil which has almost double the rapidity of lin- seed oil. It is used for enamels and varnishes; in brake linings, plastic compounds, and linoleum; and for making pigment for India ink. Tung oil is pressed from the seeds of Aleurites montana and A. fordii. The names wood oil and China wood oil are loosely and erro- neously used to designate tung oils, but true wood oil is an oleoresin from the Keruing tree of Malaya used for waterproofing and caulk- ing boats, while tung oil is never from the wood. The oil has a power- ful purgative action, and the Chinese word means stomach. The Chinese tung oil is from the nuts of the tree A. montana, the China wood oil tree, and A. fordii. The latter tree is hardier than A. mon- tana, which requires a hot climate. The American tung oil is from the nuts of the tree A. fordii of the Gulf states, which gives an annual production of about 30 lb (14 kg) of oil per tree. The tree grows to a height of 25 ft (8 m) and bears for 5 years. The seeds, or nuts, contain 50 to 55% oil. This tree is also grown in South Africa and Argentina. The color of tung oil varies from golden yellow to dark brown according to the degree of heat used in extraction. It has a pungent odor resembling that of bacon fat. A good grade of raw tung oil should have a specific gravity between 0.934 and 0.940, a saponification value of 190, and an iodine value of 163. The oil contains about 72% eleostearic acid, which has a very high iodine value, 274, and gives to the oil a greater drying power than is indicated by the iodine value of the oil itself. The oil has the property of drying throughout at a uniform rate, instead of forming a skin as linseed oil does; but it dries flat instead of glossy, like linseed oil, and is inclined to produce a wrinkled surface. It is mixed with rosin, since rosin has great affinity for it, and the two together are suitable for gloss varnishes. In combi- nation with other drying oils, it improves water and alkali resistance, and is used mainly in quick-drying enamels and varnishes. The oil from A. montana, or mu oil, has a higher percentage of eleostearic acid than that from A. fordii. The Japanese tung oil is from the 984 TUlLIPWOOD Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses nuts of the larger tree A. cordata. The oil is superior to Chinese tung oil and is seldom exported. It does not gelatinize as Chinese tung oil does, when heated. It is used in Japan for varnishes, waterproofing paper, and soaps. The saponification value is 193 to 195, iodine value of 149 to 159, and specific gravity 0.934 to 0.940. The kernels of the nuts yield about 40% oil. The tree is grown also in Brazil and thrives in hot climates. Candlenut oil is from the seed nuts of A. moluccana of Oceania and southern Asia. It received its name from the fact that the Polynesians used the nuts as candles to light their houses. The oil is variously known as kukui, kekune, and lumbang, and as an artist’s paint, oil is called walnut oil or artist’s oil. The nut resem- bles the walnut but has a thicker shell. The oil has a specific gravity of 0.923, iodine value 165, and is between linseed and soybean oil in properties. It is high in linoleic and linolenic acids. The variety known as soft lumbang oil, or bagilumbang oil, from the tree A. trisperma of the Philippines, resembles tung oil and is high in eleostearic acid. The chief production of lumbang oil is in the Fiji Islands. The Safflower, Carthamus tinctorius, is grown in California, France, and India, and in the latter country it is grown on a large scale for seeds, which yield up to 35% of the clear, yellowish saf- flower oil used in paints, leather dressings, in the manufacture of nonyellowing alkyd resins, and for foods. The oil has a high content, 73%, of linoleic acid, the highest of essential polyunsaturated acids of any vegetable food oil. It is odorless, with a bland taste, has a specific gravity of 0.915, and an iodine value of 150. Safflower 22, of Pacific Vegetable Oil Corp., is a conjugated paint oil made by isomerizing saf- flower oil. It has a rapid drying rate, color retention, and an ability to produce wrinkled finishes by adjustment of the amount of drier. It can thus replace tung oil. It takes up maleic anhydride readily, and is used for making modified alkyd finishes. Wecoline SF, of Drew Chemical, is a concentrate of safflower fatty acids with 67.3% linoleic acid and only 0.2 linolenic acid, for compounding in coatings. Saff, of Abbott Laboratories, is an emulsion of safflower oil used as a drug to lower blood cholesterol. Refined and deodorized oil shows 2.8 ϫ 10 Ϫ6 lb (1.3 mg) of “cholesterol-equivalent” sterols per 0.22 lb (100 g) of oil. The heads of the plant are dried and used as food colors, for dyeing textiles, and for cosmetic rouge. TUNGSTEN AND TUNGSTEN ALLOYS. A heavy, white metal, symbol W, with a specific gravity of 19.6, a density of 0.697 lb/in 3 (19,290 kg/m 3 ), the highest melting point, 6170°F (3410°C), of all metals and a tensile strength of 50,000 lb/in 2 (345 MPa) at 2500°F (1370°C). Wolframite is the chief ore of the metal tungsten. Its composition is (FeMn)WO 3 . TUNGSTEN AND TUNGSTEN ALLOYS 985 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses 986 TUNGSTEN AND TUNGSTEN ALLOYS When the manganese tungstate is low, the ore is called ferberite; when the iron tungstate is low, it is called hübnerite. The ore is con- centrated by gravity methods to a concentrate containing 60 to 65% tungstic oxide, WO 3 . To extract pure WO 3 from the concentrate, it is fused with sodium carbonate, Na 2 CO 3 , to form sodium tungstate, Na 2 WO 3 , which is dissolved in water. When an acid is added to the solution, the WO 3 precipitates out as a yellow powder. The metallic tungsten is obtained by reduction and is then pressed into bars and sintered. Wolframite occurs usually bladed or columnar in form. It has a specific gravity of 7.2 to 7.5, a Mohs hardness of 5, a black color, and a submetallic luster. It is found in the mountain states, Alaska, China, and Argentina, but it also widely distributed in various parts of the world in small quantities. Chinese wolfram concentrates contain 65% tungstic oxide; the Arizona concentrates contain an aver- age of 67%. California and Nevada concentrates are scheelite contain- ing from 60 to 67% tungstic oxide. The sanmartinite of Argentina is a variety containing zinc. Tungsten has a wide usage in alloy steels, magnets, heavy metals, electric contacts, rocket nozzles, and electronic applications. It is also used for x-ray and gamma-ray shielding and wear-resistant surfaces, electroplates providing Vickers 700 or greater hardness. Tungsten resists oxidation at very high temperatures and is not attacked by nitric, hydrofluoric, or sulfuric acid solutions. Flame-sprayed coatings are used for nozzles and other parts subject to heat erosion. Tungsten alloys are used for weights and counterbalances, radiation shielding, grinding tools, tooling, and high-temperature applications. Copper-tungsten composites and silver-tungsten composites serve as resistance-welding die inserts, electrode facings, electrical contacts, heat sinks, wear surfaces, and electrodes for electrical-dis- charge machining (EDM) and electrochemical machining. Tungsten is usually added to iron and steel in the form of ferro- tungsten, made by electric-furnace reduction of the oxide with iron or by reducing tungsten ores with carbon and silicon. Standard grades with 75 to 85% tungsten have melting points from 3200 to 3450°F (1760 to 1899°C). Tungsten powder is usually in sizes from 200 to 325 mesh, and may be had in a purity of 99.9%. Parts, rods, and sheet are made by powder metallurgy, and rolling and forging are done at high temperature. The rolled metal may have a tensile strength as high as 500,000 lb/in 2 (3,448 MPa) and a Brinell hardness of 290, whereas drawn wire may have a tensile strength to 590,000 lb/in 2 (4,068 MPa). The tungsten powder is used for spray coatings for radia- tion shielding and for powder-metal parts. Tungsten wire is used for spark plugs and electronic devices, and tungsten filaments are used in lamps. Tungsten wire as fine as 0.00018 in (0.00046 cm) is used in Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses TUNGSTEN AND TUNGSTEN ALLOYS 987 electronic hardware, and as thin as 0.0004 in (0.001 cm) for wire EDM. Tungsten whiskers, which are extremely fine fibers, are used in copper alloys to add strength. Copper wire, which normally has a tensile strength of 30,000 lb/in 2 (207 MPa), will have a strength of 120,000 lb/in 2 (827 MPa) when 35% of the wire is tungsten whiskers. Tungsten yarns are made up of fine fibers of the metal. The yarns are flexible and can be woven into fabrics. Continuous tungsten fila- ments, usually 394 to 591 in (10 to 15 m) in diameter, are used for reinforcement in metal, ceramic, and plastic composites. Finer fila- ments are used as cores, or substrates, for boron filaments. The metal is also produced as arc-fused grown crystals, usually no larger than 0.375 in (0.952 cm) in diameter and 10 in (25.4 cm) long, and worked into rod, sheet, strip, and wire. Tungsten crystals, 99.9975% pure, are ductile even at very low temperatures, and wire as fine as 0.003 in (0.008 cm) and strip as thin as 0.005 in (0.013 cm) can be cold-drawn and cold-rolled from the crystal. The crystal metal has nearly zero porosity, and its electrical and heat conductivities are higher than those of ordinary tungsten. The normal electrical conduc- tivity is about 33% that of copper, but that of the crystal is 15% higher. The molecules of tungsten appear as body-centered cubes, but in the pure metal the atoms normally bond uniformly in six direc- tions, forming a double lattice so that each grain forms a true single crystal. At elevated temperatures, tungsten forms many compounds in chemicals and alloys. One tungsten-aluminum alloy is a chemi- cal compound made by reducing tungsten hexachloride with molten aluminum. Tungsten-rhenium alloys, in wire, rod, sheet, and plate from Rhenium Alloys, Inc., include tungsten-26 rhenium, tungsten-25 rhenium and tungsten-5 rhenium. The W-25Re alloy has a density of 0.711 lb/in 3 (19,680 kg/m 3 ) and melts at 5522°F (3050°C). The electri- cal conductivity is 6% IACS, the ultimate tensile strength is 225,000 lb/in 2 (1,551 MPa), the elongation is 10%, and the tensile modulus is 59,460,000 lb/in 2 (410,000 MPa). Mi-Tech Metals Inc. produces series of tungsten-based metals or alloys for various requirements. The HD tungsten Series, for high- density, high-strength applications, contains 90 to 97% tungsten, plus nickel, iron, or copper, or iron and molybdenum. Depending on grade, density ranges from 0.614 to 0.668 lb/in 3 (17,000 to 18,500 kg/m 3 ), hardness is 24 to 32 Rockwell C, ultimate tensile strength is 110,000 to 125,000 lb/in 2 (758 to 862 MPa), tensile yield strength is 80,000 to 95,000 lb/in 2 (552 to 655 MPa), and elongation is 4 to 10%. Also, the tensile modulus is 40 ϫ 10 6 to 53 ϫ 10 6 lb/in 2 (276,000 to 365,000 MPa), electrical conductivity is 13 to 17%, and most grades are slightly magnetic. Typical uses include crankshaft balancing, radia- tion shielding, rotating inertia members, ordnance parts, boring bars Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses 988 TUNGSTEN CARBIDE and grinding quills and dies for die casting, extrusion, and hot upset- ting. A CW tungsten-copper Series, with 68 to 80% tungsten and the balance copper, is used for electrical-discharge and electrochemi- cal machining. Another, 74 tungsten-26 silver, is also used for EDM. Tungsten-copper grades, with 28 to 55% electrical conductivity, are used for resistance welding, resistance-welding electrode facings, flash-butt-welding dies, and hot upsetting dies. Other metals made by the company are copper– or copper alloy–tungsten carbide and Elecon tungsten-copper and tungsten-silver, tungsten carbide–silver, and molybdenum-silver electrical contact metals. There’s also the Thermitech tungsten-copper Series for heat-sink applications. Cobalt-tungsten alloy, with 50% tungsten, gives a plate that retains a high hardness at red heat. Tungsten RhC is a tungsten- rhenium carbide alloy containing 4% rhenium carbide. It is used for parts requiring high strength and hardness at high temperatures. The alloy retains a tensile strength of 75,000 lb/in 2 (517 MPa) at 3500°F (1927°C). Ammonium metatungstate, used for electroplat- ing, is a white powder of composition (NH 4 ) 6 H 2 W 12 O 40 . It is readily soluble in water and gives solutions of 50% tungsten content. Tungsten hexafluoride is used for producing tungsten coatings by vapor deposition. At a temperature of 900°F (482°C) the gas mixed with hydrogen deposits a tungsten plate. Tungsten hexachloride, WCl 6 , is also used for depositing tungsten coatings at that tempera- ture in a hydrogen atmosphere. Smooth, dense tungsten plates can be deposited from tungsten carbonyl, W(CO) 6 , at a temperature of 302°F (150°C). The carbonyl is made by reacting the hexachloride with carbon monoxide. TUNGSTEN CARBIDE. An iron-gray powder of minute cubical crystals with a Mohs hardness above 9.5 and a melting point of about 5400°F (2982°C). It is produced by reacting a hydrocarbon vapor with tung- sten at high temperature. The composition is WC, but at high heat it may decompose into W 2 C and carbon, and the carbide may be a mix- ture of the two forms. Other forms may also be produced, such as W 3 C and W 3 C 4 . Tungsten carbide is used chiefly for cutting tool bits and for heat- and erosion-resistant parts and coatings. Briquetting of tungsten carbide into usable form was first patented in Germany and produced by Krupp Works under the name of Widia metal. It is made by diffusing powdered cobalt through the finely divided carbide under hydraulic pressure, and then sintering in an inert atmosphere at about 2732°F (1500°C). The briquetted material is ground to shape, and the pieces are brazed into tools. They withstand cutting speeds from 3 to 10 times Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses those of high-speed steel, and will turn manganese steel with a Brinell hardness of 550, but are not shock-resistant. Pressed and sintered parts usually contain 3 to 20% cobalt binder, but nickel may also be used as a binder. The compressive strengths may be as high as 700,000 lb/in 2 (4,827 MPa) with rupture strengths to 200,000 lb/in 2 (1,379 MPa) or higher. One of the earliest of the U.S. bonded tungsten carbides was Carboloy, of General Electric Co., used for cutting tools, gages, drawing dies, and wear parts. The sintered materials have been sold under many trade names such as Dimondite, Firthite, and Firthaloy; Armide, of Armstrong Bros. Tool Co.; Wilcoloy; and Borium and Borod, of Stoody Co. But the carbides are now often mixed carbides. Carboloy 608 contains 83% chromium carbide, 2 tungsten carbide, and 15 nickel binder. It is lighter in weight than tungsten carbide, is nonmagnetic, and has a Rockwell A hardness to 93. It is used for wear-resistant parts and resists oxidation to 2000°F (1092°C). Titanium carbide is more fragile, but may be mixed with tungsten carbide to add hardness for dies. Cutanit is such a mixture. Kennametal K601, of Kennametal, Inc., for seal rings and wear parts, is a mixture of tantalum and tungsten car- bides without a binder. It has a compressive strength of 675,000 lb/in 2 (4,654 MPa), rupture strength of 100,000 lb/in 2 (690 MPa), and Rockwell A hardness of 94. Kennametal K501 is tungsten carbide with a platinum binder for parts subject to severe heat ero- sion. Strauss metal, of Allegheny Ludlum Steel Co., is tungsten carbide. Tungsten carbide LW-1 is tungsten carbide with about 6% cobalt binder used for flame-coating metal parts to give high- temperature wear resistance. Deposited coatings have a Vickers hardness to 1,450 and resist oxidation at 1000°F (538°C). Tungsten carbide LW-1N, with 15% cobalt binder, has a much higher rupture strength, but the Vickers hardness is reduced to 1,150. Metco 35C is a fine powder of tungsten carbide and cobalt for flame spraying to produce a wear-resistant coating of carbide in a matrix of cobalt. GPX 9660, of Securamax International, is a tungsten carbide and cobalt coating applied by flame spraying to increase the wear resistance and, to some extent, the corrosion resistance of steel parts. A tungsten carbide and nickel formula- tion, GPX 9657, also increases wear resistance and provides better corrosion resistance. Tungsten carbide chemically bonded to a mod- ified nickel aluminide, developed at the U.S. Department of Energy’s Oak Ridge National Laboratory and patented by Dow Chemical and Martin Marietta Energy Systems, is harder and perhaps more durable than tungsten carbide–cobalt in rock-, coal-, and metal-cutting applications. TUNGSTEN CARBIDE 989 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Materials, Their Properties and Uses [...]... purified natural metal contains only about one part U235 to about 140 parts of U238, and about 100,000 lb (45,360 kg) of uranium fluoride, UF6, must be processed to obtain 1 lb (0.45 kg) of U235F6 Uranium 238, after the loss of three alpha particles of total mass 12, changes to radium 226 The lead of old uranium minerals came from Ra226 by the loss of five alpha particles, and is lead 206, while the lead... drossing A common type metal is composed of 9 parts lead to 1 antimony, but many varieties of other mixtures are also used The antimony content may be as high as 30%, 15 to 20% being frequent A common monotype metal has 72% lead, 18 antimony, and 10 tin Larger and softer types are made of other alloys, sometimes containing bismuth; the hardest small type contains 3 parts lead to 1 antimony A low-melting-point,... Materials, Their Properties and Uses 1002 VALVE ALLOYS typically made of austenitic stainless steels and, for the highest service temperatures, superalloys Valve alloys include 154 1H and 154 7 carbon steels; 3140, 4140H, 5150 H, 8645, B16, and GM-8440 low-alloy steels; Sil 1, Sil XB, 422, and SUH 11M martensitic stainless steels; and 21-2N, 21-4N, 214N+Cb+W, 23-8N, Gaman H, and 302 HQ austenitic stainless... useful to somewhat higher temperatures (1600°F, 871°C) and also provide sulfidation resistance They include Stellite 3 (W100), W110 (MIL 153 45, Alloy 21), Stellite 6 (W120), Stellite 12 (W180), W150, and W170 Stellite 3 has 52% cobalt, 30.5 chromium, and 12.5 tungsten; W150 contains 60 cobalt, 28 molybdenum, and 8 chromium Both alloys have similar Rockwell C hardness: 50 to 60 at room temperature and,.. .Materials, Their Properties and Uses 990 TUNGSTEN STEEL TUNGSTEN STEEL Any steel containing tungsten as the alloying ele- ment imparting the chief characteristics to the steel It is one of the oldest of the alloying elements in steel, the celebrated ancient Eastern... Molding is done with heat and pressure The urea resins are noted for their transparency and ability to take translucent colors Molded parts with cellulose filler have a specific gravity of about 1.50, tensile strength from 6,000 to 13,000 lb/in2 (41 to 90 MPa), elongation 15% , compressive strength to 45,000 lb/in2 (310 MPa), dielectric strength to 400 V/mil (16 ϫ 106 V/m), and heat distortion temperature... energy-absorbing mounts Conathane UC-38 and UC-39, of Conap, Inc., are liquid, two-component, room-temperature-curing resins for prototype parts UC-38 has a tensile strength of 5,000 lb/in2 (34 MPa), 35% elongation, a Shore D hardness of 75, and a low shrinkage to yield precision parts UC-39 features a demold time of only 1 h Thermoplastic polyurethanes (TPUs) include two basic types: esters and ethers Esters... are generally 1300 to 1400°F (700 to 760°C), with spikes as high as 156 0°F (850°C) Exhaust valves are VALVE ALLOYS Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Materials, Their Properties and Uses 1002 VALVE ALLOYS typically made... 22% bismuth, 50 lead, and 28 antimony It will melt at about 310°F (154 °C) Copper, up to 2%, is sometimes added to type Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Materials, Their Properties and Uses ULTRAHIGH-STRENGTH STEELS 993... point at about 5000°F (2760°C), but a low thermal conductivity For fuel use the particles may be coated with about 0.001 in (0.003 cm) of aluminum oxide This coating is impervious to xenon and other radioactive isotopes so that only the useful power-providing rays can escape These are not dangerous at a distance of about 6 in (15 cm), and thus less shielding is needed For temperatures above 2300°F (1260°C) . given at the website. Materials, Their Properties and Uses The No. 3 grade, the lowest, has up to 3% insoluble impurities. The gum is marketed in flakes and as a white, odorless, 150 -mesh powder. The. vegetable food oil. It is odorless, with a bland taste, has a specific gravity of 0. 915, and an iodine value of 150 . Safflower 22, of Pacific Vegetable Oil Corp., is a conjugated paint oil made. website. Materials, Their Properties and Uses those of high-speed steel, and will turn manganese steel with a Brinell hardness of 550, but are not shock-resistant. Pressed and sintered parts usually