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川崎製鉄技報
KAWASAKI STEEL GIHO
Vol. 23(1991) No.2
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高炭素鋼の冷間鍛造性に及ぼす化学成分の影響
Effect of Alloying Elements on Cold Forgeability of 0.53 % C Steel

星野 俊幸(Toshiyuki Hoshino) 天野 虔一(Keniti Amano) 田畑 綽久(Nobuhisa Tabata) 中野 昭三郎(Shozaburo Nakano)
要旨 :
従来,困難とされていた0.53 mass%C鋼の冷間鍛造用鋼への適用を目的として,球状化焼きなまし状態における冷間鍛造性および高周波焼入性に及ぼす合金元素の影響を検討した。(1)Siは,0.1 mass%の微量添加でも変形抵抗を増加させ同時に変形態を低下させる。一方,Mn,CrおよびMoは変形抵抗を上昇させるが,その程度はSiに比較すると小さい。また,Mn,CrおよびMoは,添加量の増加にともなって,炭化物形態を変化させることにより変形態を変化させる。(2)Mn,MoおよびSiは高周波焼入れ後の有効硬化深さを増加させるが,Crは炭化物を安定化することにより低下させる。(3)以上の知見を有効に活用すれば,化学組成の適正化により0.53 mass%C鋼の冷間鍛造用鋼への適用は可能である。
Synopsis :
The effects of alloying elements on both forgeability and hardenability were investigated in order to apply a 0.53-mass% C steel to a cold forging use. Deformation resistance of a spheroidized 0.53-mass% C steel by applying the cold forging was observed to increase with alloying elements in the order of silicon, manganese, chromium and molybdenum. Addition of silicon reduced formability and increased deformation resistance even in the case of small amount of 0.1-mass percentage. The effects of manganese, chromium and molybdenum of formability were closely related to changes in morphology of spheroidized carbides. The hardening depth of the spheroidized steel by the induction hardening was controlled by adjusting the amounts of manganese, molybdenum and silicon. Chromium decreased the hardening depth of spheroidized steel, since chromium atoms were dissolved into cementite during the spheroidizing annealing, resulting in stabilizing the cementite. In this case, the cementite was not fully dissolved in an austenite phase by a rapid induction-heating. The 0.53-mass% C steel can be applied to the cold forging use by optimizing the chemical composition of steel on the basis of these results.
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