LYCOS RETRIEVER 
Boron: Boron Carbide
built 629 days ago
Boron is a strong carbide and nitride-forming element and increases strength in quenched and tempered low carbon steels through the formation of martensite and the precipitation strengthening of ferrite. Boron-containing killed carbon steels are available as low-cost replacements for the high-carbon and low-alloy steels used for sheet and strip. The low carbon boron containing steels have better cold-forming characteristics and can be heat treated to equivalent hardness and greater toughness for a wide variety of applications, such as tools, machine components, and fasteners. Boron is added to fully killed steel to improve hardenability. The amount added is a range of 0.0005 to 0.003%. It is most effective in low carbon steels.
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Ceralloy® 546 Boron Carbide is the lightest technical ceramic material (2.5 g/cm³) as well as the hardest (second only to diamond). This fully dense boron carbide is produced by hot pressing and is characterized as follows:
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Boron forms compounds directly with fluorine, chlorine, bromine, oxygen, sulfur, and carbon. Boron carbide, which is almost as hard as diamond, is formed when boron and carbon are heated together in an electric furnace. Although the properties of boron and most of its compounds are those of a non-metal, the element is unusual in that in boron phosphate it behaves like a metal.
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Boron carbide is the Defense Department's material of choice for body armor. It is the third hardest material on earth, yet it's extremely lightweight. But it has an Achilles heel that piqued the interest of Georgia Tech Professor of Materials Science and Engineering Robert Speyer five years ago.
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Boron ... forms important compounds with two other elements, carbon and nitrogen. Boron carbide (B4C) and boron nitride (BN) are important compounds because of their hardness. In fact, boron nitride may be the hardest substance known. Both compounds have very high melting points: 2,350°C (4,300°F) for boron carbide and more than 3,000°C (5,400°F) for boron nitride.
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Boron Carbide