The production flowsheet of steel 25MnCrNiMoA (/%: 0.25~0.26C

0.22~0.25Si

1.25~1.30Mn

0.008~0.011P

0.002~0.004S

0.45~0.50Cr

0.36~0. 38Ni

0.24~0.26Mo

0.04~0.08Cu

0.025~0.031Alt) is 100t UHP EAF-LF-VD-Φ650mm bloom casting-rolling to Φ120mm products. By observing and analysis on structure at crack area

it is found that there is obvious decarburization and inclusions in structure near the cracks

and multi-ferrite strips exist at end of cracks

it shows that the quality defects of casting bloom are main reason to form surface cracks of round bar of steel 25MnCrNiMoA. With the process measures including controlling [S]≤0.003%

liquid surface fluctuation ≤2mm during casting

casting speed 0.26m/min

overheating extent of liquid 20~30°C，decreasing secondary water rate

straightening temperature of bloom ≥950°C and optimizing ingredient of shielding slag

the surface cracks of hot-rolled products of steel 25MnCrNiMoA are avoided.