本发明公开了一种大线能量焊接用钢板及其制备方法，所述制备方法包括冶炼、模铸、热处理、控轧控冷工序。本发明钢板中形成大量细小弥散的含有Ti、Zr、Mg的夹杂物粒子，焊接过程中，高温阶段钉扎晶界，细化晶粒，低温阶段诱发针状铁素体，阻碍冲击裂纹的扩展，使钢板具有良好的焊接性能；钢板屈服强度≥360MPa，抗拉强度≥490MPa，断面收缩率≥70%，纵向‑40℃低温冲击功≥250J；200KJ/cm线能量焊接条件下热影响区‑40℃低温冲击功≥50J,300KJ/cm线能量焊接条件下热影响区‑40℃低温冲击功≥80J。

The invention discloses a steel plate for high heat input welding and a preparation method of the steel plate. The preparation method comprises the following working procedures of smelting, die casting, heat treatment and controlled rolling and controlled cooling. According to the steel plate for the high heat input welding and the preparation method of the steel plate, a large number of slight dispersed inclusion particles containing Ti, Zr and Mg are formed in the steel plate, in the welding process, grain boundary is pinned in the high-temperature stage, grains are refined, acicular ferriteis caused to happen in the low-temperature stage, the expansion of impact cracks is prevented, and the steel plate has good welding performance; the yield strength of the steel plate is greater thanor equal to 360 MPa, the tensile strength is greater than or equal to 490 MPa, the shrinkage rate of a cross section is greater than or equal to 70%, and the longitudinal minus 40 DEG C low-temperature impact work is greater than or equal to 250 J; and the heat affected zone minus 40 DEG C low-temperature impact work under 200 KJ/cm heat input welding condition is greater than or equal to 50 J, and the heat affected zone minus 40 DEG C low-temperature impact work under 300 KJ/cm heat input welding condition is greater than or equal to 80 J.