The invention discloses steel 18MnMoNbR for a
pressure vessel. The steel 18MnMoNbR comprises the following chemical components in percentage by weight (wt%): 0.16-0.20% of C, 0.25-0.45% of Si, 1.35-1.45% of Mn, 0.5-0.6% of Mo, less than or equal to 0.015% of P, less than or equal to 0.005% of S, 0.015-0.040% of Als, 0.030-0.040% of Nb, 0.010- 0.020% of Ti and the balance of Fe and other residual elements, wherein the carbon equivalent of the chemical components is less than or equal to 0.04. Furthermore, the invention provides a process for producing an steel 18MnMoNbR plate with a thickness of 100mm. Due to the processes of pretreating molten iron by adopting the KR method,
smelting by a converter, blowing
argon, carrying out LF refining, carrying out VD refining,
casting a die, heating, controlling rolling and cooling, cooling a
pile and carrying out heat treatment, the content of harmful elements such as P and S which can affect the
toughness of the steel 18MnMoNbR plate in steel can be controlled on the basis of guaranteeing the components of the steel 18MnMoNbR. In addition, by strictly controlling the
heating cycle of the rolled steel, strictly controlling finishing rolling temperature, the reddening temperature and the
cooling speed in the rolling process and cooling the steel-plate
pile slowly, all the performance indexes of the steel 18MnMoNbR plate with the thickness of 100mm can meet the standard requirements.