The invention relates to low-cost plastic mold steel with uniform
hardness in a cross section direction and a production method of the low-cost plastic mold steel. The steel comprises the following chemical components in percentage by
mass: 0.40-0.50% of C, 0.70-1.00% of Si, 1.60-2.00% of Mn, less than or equal to 0.015% of P, less than or equal to 0.005% of S, 0.80-1.00% of Cr, 0.010-0.050% of Als, 0.010-0.030% of Ti, 0.0010-0.0020% of B, 0.0030-0.0080% of N and the balance of Fe and inevitable impurities. Meanwhile, the chemical components further need to meet the formula: B= -0.001507 + 0.0455Als + 0.0318Ti + 0.171N. According to the steel,
precious metal elements such as Mo and Cu are not added, only vacuum treatment is adopted for refining
molten steel, the rolling process is not limited, through the production process path of stacking cooling and
tempering after rolling, normalizing heat treatment generally adopted by the plastic mold steel after rolling is omitted, so that the plastic mold steel is produced at low cost; and the steel disclosed by the invention is high in
hardenability, uniform in
hardness distribution along the cross section, and suitable for manufacturing plastic molds which have strict requirements on dimensional accuracy,
surface roughness and the like and have complex cavities.