Eutectoid Pearlitic Steel Research Articles

Effect of Cold Drawing Deformation on Themicrostructure and Evolution of Texture of Near Eutectoid Pearlitic Steel

Effect of Cold Drawing Deformation on Themicrostructure and Evolution of Texture of Near Eutectoid Pearlitic Steel

Effect of cold drawn deformation on microstructure and texture evolution of near eutectoid pearlitic steel

Исследовано влияние холодного волочения на эволюцию микроструктуры и текстуры стальной проволоки околоэвтектоидного состава. Проанализирован микромеханизм процесса деформации стали. Смоделирована эволюция текстуры стали во время волочения с использованием вязкопластической самосогласованной модели (VPSC) и успешно подтверждена экспериментальными результатами. Обнаружено, что благоприятные перлитные колонии, пластинки которых ориентированы вдоль оси проволоки, утоняются и образуют волокнистую структуру. В отличие от этого, ламели, ориентированные перпендикулярно оси проволоки, подвергаются изгибу и перекручиванию в процессе совмещения с осью проволоки. Кристаллографическая текстура б011с была получена после волочения проволоки из исходных текстур б111с и б110с стали. Моделирование VPSC проиллюстрировало относительную значимость скольжения {112}б111с по сравнению с традиционно используемым скольжением {110}б111с. Кроме того, моделирование VPSC показало наличие приблизительно пяти — шести активных систем скольжения (AVACS), которые позволяют поддерживать совместимость деформаций в поликристаллических материалах.

Hydrogen-Assisted Microdamage of Eutectoid Pearlitic Steel in the Presence of Notches: The Tearing Topography Surface

This paper studies the hydrogen-assisted microdamage (HAMD) in fully-pearlitic steel. A detailed analysis is provided of the HAMD region in axisymmetric round-notched samples of high-strength eutectoid pearlitic steel under hydrogen embrittlement environmental conditions. The microscopic appearance and evolution of the hydrogen affected region is analyzed from the initiation (sub-critical) to the fracture (critical) situations. The use of very distinct notched samples and their associated stress distributions in the vicinity of the notch tip allows for a study of the key role of the triaxial stress state on hydrogen diffusion and micro-cracking (or micro-damage). The microscopic appearance of the hydrogen-affected zone (the so-called tearing topography surface) resembles micro-damage, micro-cracking or micro-tearing at a micro- or nano-scale due to hydrogen degradation, thus affecting the notch tensile strength and producing hydrogen embrittlement. A micromechanical model is proposed to explain these hydrogen effects on the material on the basis of the lamellar micro- and nano-structure of the pearlitic steel.

Effect of Austenitization Treatment on Texture Inheritance Characteristics of Near Eutectoid Pearlitic Steel

Effect of Austenitization Treatment on Texture Inheritance Characteristics of Near Eutectoid Pearlitic Steel

Microstructure and mechanical properties of directed energy deposited U75V/15–5PH structurally graded material

In this study, 15–5 precipitation hardening (PH) martensitic steel powder was successfully deposited on U75V eutectoid pearlitic steel to form structurally graded material (SGM) using directed energy deposition (DED) technology. Microstructure evolution mechanism and mechanical properties of U75V/15–5PH SGM were investigated systematically. Results show that the microstructural transition zone (MTZ) is formed above the fusion line due to the dilution effect of eutectoid pearlitic steel. The phase composition of MTZ consists of martensite, retained austenite, and carbides, which is distinct from that of directed energy deposited 15–5PH steel. MTZ possesses the highest microhardness owing to the solid solution strengthening and second phases strengthening of carbon elements provided by eutectoid pearlitic substrate. Special intrinsic thermal cycles of DED lead to the formation of heat affected zone (HAZ) below the fusion line, in which the spheroidization phenomenon of lamellar cementite occurs. The spheroidization degree of lamellar cementite in HAZ is exacerbated with increasing distance from the fusion line. Compared with wrought U75V substrate, the lower tensile strength of SGM is mainly attributed to the weak phase boundaries strengthening of granular pearlite at the bottom of HAZ.

Drawing-Induced Evolution of Inclusions in Cold-Drawn Pearlitic Steel

This article focuses on the analysis of the evolution of inclusions present in eutectoid pearlitic steel subjected to a real cold drawing process. To this end, wires belonging to different stages of the manufacture chain were studied, starting from an initial hot rolled bar (not cold drawn at all). In addition to the information obtained through visual inspection, a quantitative analysis of the microdefects generated by these inclusions was carried out. The analysis was performed using materialographic techniques, scanning electron microscopy (SEM) and the image analysis program (AnaliSYS 3.1®).

Evolution of non-metallic inclusions with cold drawing in progressively cold drawn eutectoid pearlitic steel wires

This article focuses on the analysis of the evolution of inclusions present in eutectoid pearlitic steel subjected to a real cold drawing process. To this end, wires belonging to different stages of the manufacture chain were studied, starting from an initial hot rolled bar (not cold drawn at all). In addition to the information obtained through visual inspection, a quantitative analysis of the micro-defects generated by these inclusions has been carried out. The analysis has been performed using materialographic techniques, scanning electron microscopy (SEM) and the image analysis program (AnaliSYS 3.1®)..

Triaxiality effects on hydrogen-assisted micro-damage (HAMD), notch tensile strength and hydrogen embrittlement of pearlitic steel

This paper offers a detailed analysis of the hydrogen-assisted micro-damage (HAMD) region in axisymmetric round-notched samples of high-strength eutectoid pearlitic steel under hydrogen embrittlement environmental conditions. Emphasis is placed on the microscopic appearance and the evolution of such a microscopic topography from the initiation (sub-critical) to the fracture (critical) point. The use of very different notched geometries —with the subsequent various triaxial stress distributions in the vicinity of the notch tip— allows an analysis of the influence of stress state on hydrogen diffusion and micro-cracking. In all cases, the microscopic appearance of the hydrogen-affected zone resembles micro-damage, micro-cracking or micro-tearing due to hydrogen degradation, thereby affecting the notch tensile strength and producing hydrogen embrittlement.

Influence of Microstructure on Strength and Ductility in Fully Pearlitic Steels

This article deals with the relationship between the microstructure and both strength and ductility in eutectoid pearlitic steel. It is seen how standard mechanical properties and fracture micromechanisms are affected by heat treatment and the resulting microstructure in the material. The yield stress, the ultimate tensile strength and the ductility (measured by means of the reduction in area) exhibit a rising trend with the increasing cooling rate (associated with smaller pearlite interlamellar spacing and a lower pearlitic colony size), while the strain for maximum load shows a decreasing tendency with the afore-said rising cooling rate. With regard to the fracture surface, its appearance becomes more brittle for lower cooling rates, so that the fracture process zone exhibits a larger area with observable pearlite lamellae and a lower percentage of microvoids.

Role of the microstructure on the mechanical properties of fully pearlitic eutectoid steels

This paper analyses how the microstructure of an eutectoid pearlitic steel affects its conventional mechanical properties (obtained by means of a standard tension test) and the associated micromechanisms of fracture. Results show how the yield strength, the ultimate tensile strength (UTS) and the ductility, increase as the continuous cooling rate rises, whereas on the other hand the strain at UTS decreases. The fracture surface exhibits more brittle features when the continuous cooling rate decreases, in such a manner that in the fracture process zone an increasing area appears where the pearlite lamellae can be detected and less regions of microvoids are observed.

Effects of manufacturing-induced residual stresses and strains on hydrogen embrittlement of cold drawn steels

Cold drawn wires of eutectoid pearlitic steel are widely used for prestressing concrete structures that usually work in harsh environments, so that stress corrosion cracking of prestressing steel is a problem of major technological concern. In this paper a previous model developed by the authors is applied to analyse the influence of the residual stress-and-strain profiles after cold drawing on the hydrogen embrittlement susceptibility of prestressing steel wires. Numerical results show the relevant role of both residual stress and strain field in hydrogen diffusion in this material

Microstructure Characteristics of Eutectoid Pearlitic Steel after Equal Channel Angular Pressing at Room Temperature

An ultrafine microduplex structure was successfully produced through equal channel angular pressing (ECAP) at ambient temperature. According to the morphological characteristics of cementite lamellas, the deformed pearlite consists of shear break lamella, locally thinned lamella and irregularly bent lamella. The proportion of locally thinned lamella and irregularly bent lamella has increased with the pass number of ECAP. In addition, the deformed pearlitic ferrite became a supersaturated solid solution of carbon due to the partial dissolution of cementite during ECAP.

XRD analyses on dissolution behavior of cementite in eutectoid pearlitic steel during cold rolling

The changes of lattice parameter and carbon content of cold-rolled pearlitic ferrite ( α) in eutectoid pearlitic steels were studied with X-ray diffraction (XRD) analysis. The effects of rolling reduction and alloying elements on the dissolution of cementite ( θ) were discussed. In the present work, it was observed that XRD peaks of pearlitic α shift to smaller angle side after cold rolling with respect to that of the as-transformed state. The lager the cold-rolling reduction is, the more significant the shift of α peaks, and the larger its lattice parameter. The addition of Cr or Mn can accelerate the dissolution of the pearlitic θ during cold rolling with the effect of Cr more pronounced, but the influence of Si is not so evident.

Relationship between microstructure and strength in eutectoid steels

Abstract This paper analyzes the influence of the microstructural changes undergone by eutectoid pearlitic steels during continuous cold drawing on their yield strength. To this end, samples from a real manufacturing process (wire drawing) were studied, and consideration was given to the microstructure evolution as the drawing progresses up to the final commercial product which is heavily drawn and has undergone severe straining. It is seen that the pearlite interlamellar spacing (decreasing with cold drawing) influences clearly the improvement of yield strength (increasing with cold drawing, which is the final aim of manufacturing), although a relationship of the Hall–Petch type cannot be fitted in this case, probably because cold drawing produces not only an increasing closeness of the pearlitic packing, but also a microstructural orientation in the material.

Effect of cold drawing on environmentally assisted cracking of cold-drawn steel

The fracture behaviour in air and aggressive environments of two eutectoid steels in the forms of hot-rolled bar and cold drawn wire has been compared to elucidate the consequences of cold drawing on their susceptibility to environmentally assisted cracking (EAC) in aqueous environments. Cold drawing produces a microstructural effect on the material: a preferential orientation of the pearlite lamellae aligned parallel to the cold-drawing direction, resulting in anisotropic properties with regard to fracture behaviour in air and aggressive environments. The main consequence is the change in crackpropagation direction approaching that of the wire axis (cold-drawing direction or main average orientation of the pearlite lamellae) and producing a mixed-mode state. The results reported provide insight into the macro- and micro-mechanical effects of cold drawing on the fracture and EAC-behaviour of eutectoid pearlitic steels.

A study on the microstructure and fracture process of a pearlitic steel by means of EDC technique

An investigation of the microstructure and the microprocess of fracture of an eutectoid pearlitic steel has been carried out by means of electron-diffraction-contrast (EDC) and other analytical techniques. The nature of the dislocations in pro-eutectoid ferrite and ferrite in pearlite was determined. The character of interface conjunction between ferrite and cementite was discussed. The fracture process of pearlitic steel has been analysed crystallographically.

共析パーライト鋼の延性支配因子

共析パーライト鋼の延性支配因子