PSI- Issue 9

Jesús Toribio / Procedia Structural Integrity 9 (2018) 317–322

318

2

Author name / Structural Integrity Procedia 00 (2018) 000–000

1. Introduction

High-strength cold drawn pearlitic steels are materials of the highest importance in structural engineering since they are components of prestressed concrete structures, frequently undergoing cyclic (fatigue) loading. This paper reviews previous research by the author in the matter of microstructure-based anisotropic fatigue behavior of hot rolled and cold drawn pearlitic steels and their corresponding fatigue crack paths .

2. Microstructural evolution with cold drawing

Pearlitic microstructures and their evolution during cold drawing have been studied for years, e.g., by Embury and Fisher (1966), Langford (1977) and Ridley (1984). Specific papers were published by Toribio and Ovejero (1997, 1998a, 1998b, 1998c) showing the slenderizing and orientation/alignment (along the wire axis or cold drawing direction) of the pearlitic colonies , as well as increasing orientation/alignment (again along the wire axis or drawing direction) together with densification of the ferrite/cementite lamellae (decrease of interlamellar spacing). As a consequence, whereas the microstructure of the hot rolled pearlitic steel bar is randomly oriented, the fully cold drawn pearlitic steel wire exhibits a markedly oriented microstructure (in the matter of both colonies and lamellae), fully aligned quasi-parallel to the wire axis or cold drawing direction, as shown in Fig. 1. In addition, Toribio et al. (2016) published a recent paper with detailed information on microstructural evolution in pearlitic steels with very different levels of strain hardening and cumulative plastic strain.

Fig. 1. Microstructures of the hot rolled bar (left) and the cold drawn wire (right) in longitudinal sections. Vertical side of the micrograph is always parallel to the wire axis or drawing direction, whereas horizontal side is associated with the radial direction of the cylinders.

50

40

30

β

e

z

β (º)

20

10

0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

ε P

Fig. 2. Angle of the pearlite lamellae and the wires axis, showing a progressive orientation and alignment with the drawing direction.