PSI - Issue 33

Jesús Toribio et al. / Procedia Structural Integrity 33 (2021) 1209–1214 Jesús Toribio / Procedia Structural Integrity 00 (2021) 000–000

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2

This article studies the presence and evolution of inclusions in pearlitic steel throughout a real process of cold drawing. Special attention is paid to the generation and evolution of the micro-cracks that occurs around the inclusions when the steel wire goes through the different dies of drawing; such micro-cracks can have an influence on the steel’s behavior in fracture. The study of the inclusions has been carried out from the characterization of the same through the analysis of their chemical composition, as well as a quantitative morphological study.

2. Materials and methods

For the study of the evolution of the inclusions in progressively drawn pearlitic steel, the following wires have been used: initial hot rolled bar and the wires from the second, fourth, sixth and seventh steps (E0, E2, E4, E6 and E7 respectively) of the cold drawing process. Fig. 1 shows the true stress vs . true deformation curves ( σ − ε ) obtained in these studies for all the wires analyzed in the present work.

1.6 2.0

1.2

0.00 0.02 0.04 0.06 0.08 0.10 E7 E6 E4 E2 E0

0.8

σ (GPa)

0.4

0.0

ε Fig. 1. True stress vs . true deformation ( σ − ε ) of steels. Longitudinal cuts were performed in the samples (Fig. 2a). These sections were embedded in a phenolic resin, thermally hardened by means of a hot compression assembly, as shown in Fig. 2b.

(a)

(b)

Fig. 2. Preparation of pearlitic steel samples: (a) longitudinal cutting, (b) mounted in resin.

The next step is the mechanical preparation, grinding and polishing of the samples. This step aims to achieve a specular surface on which a chemical attack can be performed to reveal the microstructure of the steel.