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川崎製鉄技報
KAWASAKI STEEL GIHO
Vol. 23(1991) No.4
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自動車外板用焼付硬化型強度冷延鋼板の開発
Development of Bake-Hardening High Strength Cold-Rolled Sheet Steels for Automobile Exposed Panels

佐藤  進(Susumu Satoh) 岡田  進(Susumu Okada) 加藤 俊之(Toshiyuki Kato) 橋本  修(Osamu Hashimoto) 花澤 利健(Toshitake Hanazawa) 恒川 裕志(Hiroshi Tsunekawa)
要旨 :
自動車の軽量化に適する外板用冷延鋼板(表面処理鋼板を含む)として,優れた成形性と焼付硬化性を兼備した新鋼板を検討し,以下の結果を得た。(1)Nb添加極低炭素鋼(Nb(at%)/C(at%)〜1)を830℃以上の高温焼鈍をして急冷すると,深絞り性に好ましい,強い{111}再結晶集合組織と焼付硬化性に有効な固溶Cの両者が得られる。(2)この原理を新高温連続焼鈍ラインに適用し,焼付硬化型超深絞り性冷延鋼板を開発した。(3)この連続焼鈍冷延鋼板に低温塗布型有機塗膜処理を応用し,同様の材料特性を有する有機複合被覆鋼板を開発した。(4)高温焼鈍と急冷の可能な新連続溶融亜鉛めっきラインにより,焼付硬化型超深絞り性合金化溶融亜鉛めっき鋼板を開発した。(5)開発鋼板はフェンダーなどのパネルの薄肉化に適する。
Synopsis :
New cold-rolled sheet steels (including surface-coated sheet steels) with excellent formability and high bake-hardenability suitable for gage-down of automobile exposed panels have been investigated. (1) High temperature annealing above 830℃ and subsequent rapid cooling with a Nb-bearing extra-low C steel (Nb(at%)/C(at%)〜1.0) provide an intense {111} recrystallization texture favorable for deep drawability and some amount of solute C effective in bake-hardenability. (2) This processing principle has been applied to developing extra-deep drawing cold-rolled sheet steels with bake-hardenability by the use of newly developed continuous annealing lines (KM-CAL) capable of high temperature annealing at approximately 900℃. (3) Organic composite coated sheet steels with similar mechanical properties have been developed by applying a new organic film baked at a low temperature to the continuously annealed sheet steels. (4) Hot-dip galvannealed sheet steels with extra-deep drawability and bake-hardenability have been also developed by the newly installed continuous hot-dip galvanizing line capable of high temperature annealing and rapid cooling. (5) These new sheet steels are suitable for gage-down of exposed panels for automobiles such as fenders.
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