Calcium steels

Beryllium is added to copper to produce an alloy with greatly increased wear resistance it is used for current-carrying springs and non-sparking safety tools. It is also used as a neutron moderator and reflector in nuclear reactors. Much magnesium is used to prepare light nieial allo>s. other uses include the extraction of titanium (p. 370) and in the removal of oxygen and sulphur from steels calcium finds a similar use. 

Calcium carbide has been used in steel production to lower sulfur emissions when coke with high sulfur content is used. The principal use of carbide remains hydrolysis for acetylene (C2H2) production. Acetylene is widely used as a welding gas, and is also a versatile intermediate for the synthesis of many organic chemicals. Approximately 450,000 t of acetylene were used aimuaHy in the early 1960s for the production of such chemicals as acrylonitrile, acrylates, chlorinated solvents, chloroprene, vinyl acetate, and vinyl chloride. Since then, petroleum-derived olefins have replaced acetylene in these uses. 

Calcium hydride is prepared on a commercial scale by heating calcium metal to about 300°C in a high alloy steel, covered cmcible under 101 kPa (1 atm) of hydrogen gas. Hydrogen is rapidly absorbed at this temperature and the reaction is exothermic. 

Mercury spills should be cleaned up immediately by use of a special vacuum cleaner. The area should then be washed with a dilute calcium sulfide solution. Small quantities of mercury can be picked up by mixing with copper metal granules or powder, or with zinc granules or powder. To avoid or minimize spills, some plants use steel trays as pallets so that a spih, whether of mercury or a mercury compound, is contained on the steel tray. 

Synthetic Marble. Synthetic marble-like resin products are prepared by casting or molding a highly filled monomer mixture or monomer—polymer symp. When only one smooth surface is required, a continuous casting process using only one endless stainless steel belt can be used (52,53). Typically on the order of 60 wt % inorganic filler is used. The inorganic fillers, such as aluminum hydroxide, calcium carbonate, etc, are selected on the basis of cost, and such properties as the translucence, chemical and water resistance, and ease of subsequent fabrication (54,55). 

In concrete, triethanolamine accelerates set time and increases early set strength (41—43). These ate often formulated as admixtures (44), for later addition to the concrete mixtures. Compared to calcium chloride, another common set accelerator, triethanolamine is less corrosive to steel-reinforcing materials, and gives a concrete that is more resistant to creep under stress (45). Triethanolamine can also neutralize any acid in the concrete and forms a salt with chlorides. Improvement of mechanical properties, whiteness, and more even distribution of iron impurities in the mixture of portland cements, can be effected by addition of 2% triethanolamine (46). Triethanolamine bottoms and alkanolamine soaps can also be used in these type appUcations. Waterproofing or sealing concrete can be accompUshed by using formulations containing triethanolamine (47,48). 

Piebaked anodes aie produced by molding petroleum coke and coal tar pitch binder into blocks typically 70 cm x 125 cm x 50 cm, and baking to 1000—1200°C. Petroleum coke is used because of its low impurity (ash) content. The more noble impurities, such as iron and siUcon, deposit in the aluminum whereas less noble ones such as calcium and magnesium, accumulate as fluorides in the bath. Coal-based coke could be used, but extensive and expensive prepurification would be required. Steel stubs seated in the anode using cast iron support the anodes (via anode rods) in the electrolyte and conduct electric current into the anodes (Fig. 3). Electrical resistivity of prebaked anodes ranges from 5-6 Hm anode current density ranges from 0.65 to 1.3 A/crn. ... 

Low Cement, Ultra-Low Cement, and No-Cement Castables are classified on the basis of calcium oxide content. These are 1—2.5, 0.2—1.0, and 0.2% CaO maximum, respectively. In the latter case the lime content is not a result of a hydrauHc setting cement constituent but comes from aggregate impurities. The insulating class is also subdivided. This division is shown in Table 14. Refractories used in steel-pouring pits are classified under ASTM C435 (Table 15). 

High purity 50% ferrosihcon containing <0.1% Al and C is used for production of stainless steel and corded wire for tires, where residual aluminum can cause harm fill alumina-type inclusions. These are also useflil in continuous cast heats, where control of aluminum is necessary. High purity grades of 50 and 75% ferrosihcon containing low levels of aluminum, calcium, and titanium are used for sihcon additions to grain-oriented electrical steels, where low residual aluminum content contributes to the attainment of desired electrical properties, eg, significant reduction of eddy currents. 

Calcium—Silicon. Calcium—silicon and calcium—barium—siUcon are made in the submerged-arc electric furnace by carbon reduction of lime, sihca rock, and barites. Commercial calcium—silicon contains 28—32% calcium, 60—65% siUcon, and 3% iron (max). Barium-bearing alloys contains 16—20% calcium, 9—12% barium, and 53—59% sihcon. Calcium can also be added as an ahoy containing 10—13% calcium, 14—18% barium, 19—21% aluminum, and 38—40% shicon These ahoys are used to deoxidize and degasify steel. They produce complex calcium shicate inclusions that are minimally harm fill to physical properties and prevent the formation of alumina-type inclusions, a principal source of fatigue failure in highly stressed ahoy steels. As a sulfide former, they promote random distribution of sulfides, thereby minimizing chain-type inclusions. In cast iron, they are used as an inoculant. 

Redistillation. For certain appHcations, especially those involving reduction of other metal compounds, better than 99% purity is required. This can be achieved by redistillation. In one method, cmde calcium is placed in the bottom of a large vertical retort made of heat-resistant steel equipped with a water-cooled condenser at the top. The retort is sealed and evacuated to a pressure of less than 6.6 Pa (0.05 mm Hg) while the bottom is heated to 900—925°C. Under these conditions calcium quickly distills to the condensing section leaving behind the bulk of the less volatile impurities. Variations of this method have been used for commercial production. Subsequent processing must take place under exclusion of moisture to avoid oxidation. 

Calcium metal is produced in the United States by Pfizer Inc., Canaan, Coimecticut, and in Canada by Timminco Metals, Toronto, Ontario. In France it is produced by Pechiney ElectrometaHurgie. It is also produced in the Commonwealth of Independent States (CIS) and the People s RepubHc of China. Both Pfizer and Timminco supply the various grades in a variety of sizes and forms. In addition, Pfizer suppHes an 80% Ca—20% Mg alloy and a steel-clad calcium wire for use in deoxidation of steel and other metals. Timminco and Pfizer both supply ca 75% Ca—25% Al alloy for use in lead alloying. Timminco also suppHes a 70% Mg—30% Ca alloy for use in lead debismuthizing (18), and calcium particulate products, which are purchased by several companies for the manufacture of cored wire for use in the steel industry. 

An estimate of world calcium consumption in 1986 indicated that lead refining uses 30% alloys, eg, with Pb, Al, and Si, 25% steel treatment, 20% calciothermic reduction, 10% calcium hydride, 10% and miscellaneous usage is 5%. More recent evidence, however, has suggested that increasing consumption of calcium in battery manufacture has made this the most significant use. 

In the United States calcium carbide-based acetylene is mainly used in the oxyacetylene welding market although some continues to be used for production of such chemicals as vinyl ethers and acetylenic alcohols. Calcium carbide is used extensively as a desulfurizing reagent in steel and ductile iron production allowing steel mills to use high sulfur coke without the penalty of excessive sulfur in the resultant steel (see Sulfurremoval and recovery). Calcium cyanamide production continues in Canada and Europe (see Cyanamides). 

Reaction With Sulfur. An important use of calcium carbide has developed in the iron (qv) and steel (qv) industries where the carbide has been found to be an effective desulfurizing agent for blast-furnace iron. Calcium carbide and sulfur present in the molten metal react... 

Calcium carbide is classed as a ha2ardous chemical under Department of Transportation regulations. Domestic shipments are mainly in steel tote bins varying in capacity from 2.5—4.5 t. A small amount continues to be shipped in industrial wide mouth steel dmms of 270 kg capacity. Containers must be marked "Flammable soHd, dangerous when wet" and have the United Nations designation UN 1402. 

The largest use for calcium carbide is in the production of acetylene for oxyacetylene welding and cutting. Companies producing compressed acetylene gas are located neat user plants to minimize freight costs on the gas cylinders. Some acetylene from carbide continues to compete with acetylene from petrochemical sources on a small scale. In Canada and other countries the production of calcium cyanamide from calcium carbide continues. More recentiy calcium carbide has found increased use as a desulfurizing reagent of blast-furnace metal for the production of steel and low sulfur nodular cast iron. 

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