Abstract：The increase in the size of LNG-tanks leads to mandatory requirement of strengthening of 9Ni steel plates which enables the thickness of the wall without being increased. The strength of the 9Ni steel is markedly increased by the Cu addition due to precipitation of finely dispersed Cu particles. A 9Ni steel with 1.25 pct (mass fraction) copper addition was proposed. The experimental steel plates were processed by controlled-rolling and direct-quenching (DQ). The DQ treated plates were further heat treated, respectively, by 1) QLT, i.e., quenching from austenite (γ) single phase (Q) followed by reheating and quenching from two phase (α+γ) region (L) and tempering (T), and 2) DQ-LT, i.e., quenching from α+γ region and tempering after the controlled rolling. The thermal conditions of the CGHAZ in the QLT treated samples were simulated. The mechanical properties of the CGHAZ and fractographs were examined. The microstructures were analyzed employing optical microscope (OM), scanning electronic microscope (SEM) and transmission electronic microscope (TEM). The volume fraction of austenite was detected by XRD technique. Tensile properties were tested at room temperature while the Charpy V notch impact energy (AKV) was measured at a cryogenic condition of -196℃. The volume fraction of austenite in the QLT (tL=635℃) treated steel was 13.5%. The yield strength (Rp0.2) reached 718MPa, the AKV was 130J. Sufficient cryogenic toughness (AKV at 66J) was achieved in the CGHAZ by double-pass welding operations.
张怀征，刘东升. 热处理工艺对高强度含铜9Ni钢组织和性能的影响[J]. 钢铁, 2011, 46(7): 79-85.
HANG Huai-zheng,LIU Dong-sheng. Effect of Heat Treatment on Microstructure and Mechanical Properties of an High Strength Copper Containing 9Ni SteelZ. Iron and Steel, 2011, 46(7): 79-85.
2011, Vol. 46 
