The paper presents the research results concerning the chromium-nickel-molybdenum duplex cast steel GX2CrNiMoCuN 25-6-3-3 grade. The aim of studies was the description of the influence of hyperquenching temperature Tp i.e. 1100, 1125 and 1150℃ on microstructure and mainly mechanical properties i.e. tensile strength UTS, yield strength YS, hardness HB, elongation EL and impact energy KV of duplex cast steel GX2CrNiMoCuN 25-6-3-3 grade. The range of studies included ten melts which were conducted in foundry GZUT S.A. Based on the obtained results was confirmed that application of hyperquenching process guarantees the elimination of brittle s phase in the microstructure of studied duplex cast steel. Moreover on the basis of conducted statistical analysis of the researches results is concluded that with the decrease in hyperquenching temperature increases ductility and amount of austenite, while decreases strength and amount of ferrite in studied duplex cast steel GX2CrNiMoCuN 25-6-3-3 grade.