一种大线能量焊接EH550MPa级调质海工钢及其制造方法，其成分重量百分比为：C0.06～0.12％，Si，0.02～0.06％，Mn0.7～1.2％，Ti0.006～0.012％，Al0.002～0.010％，Cr0.30～0.50％，Mo0.3～0.4％，V0.03～0.04％，N0.0020～0.0030％，S0.002～0.010％，P≤0.008％，余Fe和不可避免杂质；其中，钢中含Ti夹杂物的平均尺寸在2～3μm之间，此夹杂物密度不小于50个mm²。本发明所述调质海工钢的屈服强度≥550MPa、抗拉强度≥670MPa，母材‑40℃冲击功单个值≥180J，焊接线能量50kJ/cm，100kJ/cm，150kJ/cm的热影响区‑40℃冲击功单个值≥80J。

A large linear energy welding EH550MPa grade tempered marine steel and its manufacturing method, the composition of the weight percentage of: C0.06 ~ 0.12%, Si, 0.02 ~ 0.06%, Mn0.7 ~ 1.2%, Ti0.006 ~ 0.012%, Al0.002 ~ 0.010%, Cr0.30 ~ 0.50%, Mo0.3 ~ 0.4%, the V0.03-0.04%, N0.0020-0.0030%, S0.002-0.010%, P≤0.008%, remaining Fe and unavoidable impurities; wherein the average size of Ti inclusions in the steel is between 2 and 3 μm, and the density of this inclusions is not less than 50 mm2. The tempered marine steel described in the present invention has a yield strength ≥ 550 MPa, tensile strength ≥ 670MPa, the base material -40 ℃ impact work single value ≥ 180J, welding line energy 50kJ/cm，100kJ/cm，150kJ/cm heat-affected zone -40 ℃ impact work single value ≥ 80J.