D6AC AlloySpecialty Alloys - High-Strength Alloy SteelsNominal Analysis0.46 C, 0.25 Si, 0.75 Mn, 1.10 Cr, 0.60 Ni, 1.00 Mo, 0.10 V, Bal. FeA medium carbon, low alloy, ultra high-strength steel primarily used for high strength structural applications requiring strength levels up to 280,000 psi. This alloy provides a high yield strength to tensile strength ratio, combined with good ductility. A tough and fibrous fracture is exhibited to as low as -210F (-134°C) in impact testing; also the notch toughness is excellent. It has been selected for fracture toughness critical applications at a variety of strength levels. The deep hardening characteristics has enabled the production of relatively large sections.D6AC Vac-Arc steel is produced by consumable electrode vacuum arc remelting process to impart cleanliness and preferred ingot structure, which in turn improves transverse mechanical properties.
美國于60 年代初開始研制D6AC，由AISI 4340 鋼改進而成，被廣泛用于制造戰術和戰略導彈發動機殼體及飛機結構件。到了70 年代中期，D6AC 逐漸取代了其它合金結構鋼，成為一種制造固體火箭發動機殼體的專用鋼種。美國新型地空導彈“愛國者”，小型導彈“紅眼睛”，大中型導彈“民兵”、“潘興”、“北極星”、“大力神”等，美國航天飛機的φ3.7m助推器殼體也采用D6AC 鋼制造。D6AC 還曾用于制造F-111飛機的起落架和機翼軸等。
標準：
ASTM A29/A29M-04
化學成分：
碳 C ：0.38～0.43
硅 Si：0.15～0.35
錳 Mn：0.60～0.90
硫 S ：允許殘余含量≤0.040
磷 P ：允許殘余含量≤0.035
鉻 Cr：0.60～0.90
鎳 Ni：1.65～2.00
銅 Cu：允許殘余含量≤0.025
鉬 Mo：0.20～0.30
力學性能：
抗拉強度 σb (MPa)≥1280(100),
伸長率 δ5 (%)≥12,
斷面收縮率 ψ (%)≥55,
沖擊功 Akv (J)≥78,
沖擊韌性值 αkv (J/cm2)≥98(10)
熱處理規范：
淬火850℃,油冷;回火600℃,水冷、油冷。
交貨狀態：以熱處理（正火、退火或高溫回火）或不熱處理狀態交貨，交貨狀態應在合同中注明。
