Improvement of the Method for the High-Carbon Wire Rod Pearlite Grain Grade Identification

The main characteristics of metal long products quality include mechanical properties, depending on the microstructure state. The key indicator for evaluation the micro-structure of high carbon steel can be considered the 1st grain grade lamellar pearlite Bfp. For the currently used pearlite dispersion method, according to GOST 8233-56, it is characterized by the subjectivity of the view fields choice for the microstructure evaluation, that reduces the quality of the obtained results. The study purpose was to improve the method of high-carbon steel wire rod microstructure estimation, to reduce the error magnitude in determining the 1st grain grade lamellar pearlite. The experiments were carried out on samples of high-carbon steel wire rod with a carbon content of 0,58 – 0,77 %. The pearlite dispersion was evaluated in 27 view fields, located on mutually perpendicular diagonals of the sample cross section. The study results showed the possibility of reducing the error in determining the estimated value of the high-carbon steel wire rod microstructure pearlite dispersion. Microstructure evaluation in the five view fields should be carried out, taking into account the weight coefficients, determined by the ratio of the zones length, occupied by pearlite with a certain percentage of the 1st grade grain pearlite to the wire rod radius. The proposed method of the microstructure evaluation increases assessment accuracy, without complication of its implementation process.