MANUFACTURING METHOD OF Ni CONTAINING STEEL PLATE

To provide a manufacturing method of Ni containing steel plate which is excellent in a low temperature toughness after plastic-strained even when P content exceeds 0.001 mass%.SOLUTION: In the manufacturing method of the present invention, a steel containing a predetermined chemical composition and balance being Fe and unavoidable impurities is hot rolled and then subjected in this order to a quenching step for quenching from a quenching temperature of 800°C or higher and 820°C or lower, an intermediate heat treatment step for cooling at an average cooling rate of 5°C/sec or more to a finish cooling temperature of 200°C or lower after holding at a heating temperature of 690°C or higher and 710°C or lower and a tempering step for tempering at a tempering temperature of 570°C or higher and 600°C or lower, and a parameter H defined by the heating temperature and holding time at the intermediate heat treatment step and the heating temperature and holding time at the tempering step is set to 1.73×10or more and 1.96×10or less.SELECTED DRAWING: Figure 1 【課題】Ｐ含有量が０．００１質量％を超える場合であっても、塑性歪付与後の低温靱性に優れるＮｉ含有鋼板の製造方法を提供する。【解決手段】本発明の製造方法は、所定の化学成分組成を含み、残部がＦｅおよび不可避的不純物である鋼を、熱間圧延した後、８００℃以上８２０℃以下の焼入れ温度から焼入れする焼入れ工程、６９０℃以上７１０℃以下の加熱温度で保持後に、２００℃以下の冷却終了温度まで５℃／秒以上の平均冷却速度で冷却する中間熱処理工程、および５７０℃以上６００℃以下の焼戻し温度で焼戻しする焼戻し工程、をこの順で含み、中間熱処理時の加熱温度および保持時間、ならびに焼戻し時の加熱温度および保持時間によって規定されるパラメータＨを１．７３×１０−６以上１．９６×１０−６以下とする。【選択図】図１