The invention provides an X65 hot-rolled steel plate for a marine riser and a preparation method. The X65 hot-rolled steel plate is prepared from, by weight, 0.03%-0.05% of C, 0.10%-0.30% of Si, 1.10%-1.35% of Mn, smaller than or equal to 0.007% of P, smaller than or equal to 0.0008% of S, 0.01%-0.05% of Alt, 0.04%-0.06% of Nb, 0.008%-0.018% of Ti, 0.20%-0.40% of Ni, 0.15%-0.30% of Cr, 0.10%-0.20%of Mo, smaller than or equal to 0.004% of N and the balance Fe and unavoidable
impurity elements. The preparation method comprises the steps that
continuous casting blanks with the thickness rangingfrom 300 mm to 500 mm are adopted, differential temperature rolling is adopted for steel blank rough rolling, three-stage rolling is adopted for finish rolling, and then fine and squashed hardened
austenite grains are obtained;
steel plates are cooled after being rolled, and then fine ferrites and a small amount of
acicular ferrite structure are obtained, wherein the initial
cooling temperature ranges from 760 DEG C to 780 DEG C, and the final
cooling temperature ranges from 200 DEG C to 300 DEG C. The X65 hot-rolled steel plate has the advantages of being large in wall thickness, high in strength, low in
yield ratio, excellent in low-temperature
toughness, fracture resistance and
acid resistance and capable of reducing the fracture and
corrosion risks of marine risers.