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Eglin steel (ES-1) is a high-strength, high-performance, low-alloy, low-cost steel, developed for new generation of bunker buster type bombs, e.g. the Massive Ordnance Penetrator and the improved version of the GBU-28 bomb known as EGBU-28. It was developed in collaboration between the US Air Force and the (Ellwood National Forge Company ). The development of Eglin steel was commissioned to find a low-cost replacement for strong and tough but expensive superalloy steels such as AF-1410, Aermet-100, HY-180, and HP9-4-20/30. A high-performance casing material is required so the weapon survives the high impact speeds required for deep penetration. The material has a wide range of other applications, from missile parts and tank bodies to machine parts. The material can be less expensive because it can be ladle-refined. It does not require vacuum processing. Unlike some other high-performance alloys, Eglin steel can be welded easily, broadening the range of its application. Also, it uses roughly half as much nickel as other superalloys, substituting silicon to help with toughness and particles of vanadium carbide and tungsten carbide for additional hardness and high-temperature strength. The material also involves chromium, tungsten, and low to medium amounts of carbon, which contribute to the material's strength and hardness. ==Properties== At room temperature, ES-1's yield (tensile strength before deformation) is 224,500 PSI (1547 MPa), ultimate strength (breaking point) is 263,700 PSI (1818 MPa). At 900°C, yield is 193,900 PSI (1337 MPa), and ultimate strength is 246,700 (1701 MPa). Rockwell hardness is 45.6 (455 HV10). For toughness, the Charpy notch impact is 56.2 foot-pounds (76 J) at room temperature, and 42.7 ft-lbs (58 J) at -40F (-40°C).〔U.S. Patent No. 7,537,727 B2, Accessed July 16, 2009, column 3, Table 55〕 ES-1 is a balance of cost, tensile strength, high temperature tensile strength and toughness. By varying the heat treatment to include water or liquid nitrogen quenching, or omitting the normalization heat-treat to permit work hardening, properties can be improved.〔U.S. Patent No. 7,537,727 B2, Accessed July 16, 2009, column 7, line 5.〕 ES-5, with an economical air and water quench,〔U.S. Patent No. 7,537,727 B2, Accessed July 16, 2009, column 6, line 65〕 provides 244,800 PSI of yield, and 291,900 PSI ultimate yield.〔U.S. Patent No. 7,537,727 B2, Accessed July 16, 2009, column 5, line 1〕 By comparison, ordinary structural steel yields at 36,000 PSI, 4150 "ordnance" steel (used in high-quality military gun barrels) at 75,000. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Eglin steel」の詳細全文を読む スポンサード リンク
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