Bainite (English spelling)

Japanese: ベイナイト（英語表記）bainite

The structure that appears when steel is quenched from the high austenite region to a certain temperature range (lower than A ₁ point and higher than A _r ″ point) and held for a certain time (→ TTT curve, transformation of steel). The temperature range and holding time vary depending on the type of steel, but for eutectoid carbon steel, it is 200 to 500 °C, 10 seconds (high side) to several hours (low side). Bainite has a typical structure that is unique and consists of iron carbide and ferrite with a specific composition. It has slightly different appearances under a microscope at the high and low temperature ends of the temperature range, with the former being feather-like and called high-temperature bainite, and the latter being needle-like and called low-temperature bainite. It has good mechanical properties, being hard and tough. The austenite → bainite transformation is said to occur in a temperature range intermediate between the austenite → ferrite, pearlite transformation that occurs with sufficient diffusion, and the martensite transformation that occurs without diffusion, and includes both diffusionless and diffusional transformations. Unlike martensite, it has the advantage of being usable without tempering. It is named after EC Bain, a researcher of isothermal transformation of steel.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

鋼を高温のオーステナイト域から一定の温度領域 ( A₁ 点より低く A_r ″点より高い) に急冷し，一定時間保持すると現れる組織 (→TTT曲線 ,　鉄鋼の変態 ) 。その温度領域と保持時間は鋼種によって異なるが，共析炭素鋼では 200～500℃，10秒 (高温側) ～数時間 (低温側) である。ベイナイトの代表的な組織は特異組成の鉄炭化物とフェライトから成る特殊なもので，温度領域の高温側と低温側では顕微鏡下でやや異なる様相をもち，前者は羽毛状で高温ベイナイト，後者は針状で低温ベイナイトという。硬くて靭性のあるよい機械的性質をもつ。オーステナイト→ベイナイト変態は，十分な拡散を伴って生じるオーステナイト→フェライト，パーライト変態と，拡散を伴わないで生じるマルテンサイト変態の中間的な温度領域において無拡散変態，拡散変態双方を含んで生じるとされている。マルテンサイトと異なり焼戻さずに使用できる利点がある。名称は鋼の恒温変態の研究者 E.C.ベインにちなむ。

出典　ブリタニカ国際大百科事典小項目事典ブリタニカ国際大百科事典小項目事典について　情報

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