Materials scientists are seeking to produce metals with reduced weight and dimensions while maintaining the appropriate mechanical properties. There are several ways to improve the internal structure of metals, such as the ultrasound used to solidify liquid metal (this is a patent of Toyota Motors Company). The homogeneity of the grains and the uniformity of the metal structure affects its mechanical strength.This paper presents the results of investigations into the effects of hot deformation parameters in compression on the austenite grain size in HSLA steel (0.16% C, 0.037% Nb, 0.004% Ti, 0.0098% N). The axisymmetric compression investigations were performed on cylindrical investigation specimens of d=1.2 using the Gleeble 3800 simulator. The strain rate=1s-1÷15.9s-1 and strain degree ε=1.2. Before deformation, the research specimens were austenitized at TA = 1100 ÷ 1250°C. Metallographic observations of the primary austenite grains were conducted with an optical microscope, while the structure of dynamically recrystallized austenite, inherited by martensite, was examined by EBSD technique using a scanning electron microscope