Methodology of High-Carbon Wire Rod Perlite Grain Grade Identification

Abstract

The quality of the high-carbon rod is determined by mechanical properties, which depend on microstructure characteristics, in particular the perlite grain grade. The existing technique for determining the perlite dispersion has the main drawback - the subjectivity of choosing the five worst view fields for evaluation, which reduces the accuracy of the determination results. The article presents the results of a study aimed at increasing the objectivity and accuracy of the evaluation of high-carbon wire rod perlite grain grade. An improved technique for determining the high-carbon wire rod perlite grain grade – Pgg with five view fields is proposed. The cross-section of the rod sample is considered as an inhomogeneous area from the perlite dispersion point of view, which is divided into three annular zones with different levels of perlite dispersion. Selection of five view fields is carried out as follows: one from the center of the central zone, two fields in the second - an intermediate zone and two fields in the outer zone. Statistical analysis of the experimental data showed that all view fields should be located on the same diagonal. The location of the view fields is fixed and is unchangeable for all samples under study. The technique described in the article is an effective tool for analyzing the structure of high-carbon steel wire rod.

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

“…During evaluation of a particular sample microstructure, the arithmetic average of all values determined on 27 fields of each diagonal was used as the resulting value taken as the baseline. Using the previously presented method, the estimated average arithmetic value of pearlite dispersity over five fields of view located on the diagonal in different zones of the sample cross section was calculated (Tables 3, 4) [11]. Calculations showed good convergence of results.…”

“…The correctness of these characteristics determination causes the stability of the metal products production and its subsequent operation. The proposed methods and techniques are aimed to improve accuracy, objectivity and reduce energy and human resources [1][2][3][4][5][6][7][8][9][10][11].…”

“…Highlighting such characteristic of high carbon wire rod quality as the quantity of 1st grain grade lamellar pearlite, it is necessary to note the greatest susceptibility to the subjectivity of its value due to the method used for its determination. At the same time, the accuracy of microstructure assessment is predetermined both by the professionalism of the research laboratory personnel and the methods used [11,12]. Thereby, in this research, the pearlite dispersity determination method, presented in GOST 8233-56, was considered as the basic method, which regulates the samples production and testing (evaluation) [12].…”

“…up to 1st grade is calculated. The calculation results are fixed and compared with the reference structures listed in GOST 8233-56 [11].…”

“…The drawback of a basic method is the subjectivity of the five worst view fields random selection. Previously, it was proposed to reduce the probability of inaccurate results by application of more regulated method of view fields selection in the cross-sectional plane of the billet [11]. We suppose that the maximum objectivity in the microstructure evaluation is possible when the entire cross-sectional area of the profile is examined.…”