Editorial

2 pages, 156 KiB

Open AccessEditorial

Mechanical Behavior of High-Strength, Low-Alloy Steels

by Ricardo Branco and Filippo Berto

Metals 2018, 8(8), 610; https://doi.org/10.3390/met8080610 - 06 Aug 2018

Cited by 17 | Viewed by 3636

High-strength, low-alloy steels are designed to provide specific desirable combinations of properties, such as strength, toughness, formability, weldability, and corrosion resistance.[...] Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

Research

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13 pages, 4782 KiB

Open AccessArticle

Comparative Study of the Uniaxial Cyclic Behaviour of Carbide-Bearing and Carbide-Free Bainitic Steels

by Ricardo Branco, Filippo Berto, Fucheng Zhang, Xiaoyan Long and José Domingos Costa

Metals 2018, 8(6), 422; https://doi.org/10.3390/met8060422 - 05 Jun 2018

Cited by 1 | Viewed by 4152

Abstract

Bainitic steels play an important role in the modern automotive and rail industries because of their balanced properties. Understanding the relationship between the bainitic microstructure features and the fatigue performance is a fundamental ingredient in developing safer and durable products. However, so far [...] Read more.

Bainitic steels play an important role in the modern automotive and rail industries because of their balanced properties. Understanding the relationship between the bainitic microstructure features and the fatigue performance is a fundamental ingredient in developing safer and durable products. However, so far this relationship is not sufficiently clear. Therefore, there is the need to strengthen the knowledge within this field. The present paper aims at comparing the uniaxial cyclic behaviour of carbide-bearing and carbide-free bainitic steels. To meet this goal, fully-reversed strain-controlled tests at various strain amplitudes were performed. After the final failure, fracture surfaces were observed by transmission electron microscopy to relate the bainitic morphology to the fatigue performance. The main findings of this work show that the carbide-free lower bainite has superior fatigue performance compared to the carbide-bearing lower bainite. This is explained by the presence of stable carbides and thick bainite ferrite plates. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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13 pages, 4942 KiB

Open AccessArticle

Evaluation of Failure Pressure for Gas Pipelines with Combined Defects

by Tadas Vilkys, Vitalijus Rudzinskas, Olegas Prentkovskis, Jurijus Tretjakovas, Nikolaj Višniakov and Pavlo Maruschak

Metals 2018, 8(5), 346; https://doi.org/10.3390/met8050346 - 11 May 2018

Cited by 27 | Viewed by 6177

Abstract

The paper presents the study of the influence of mechanical damage on the safe operation of gas transmission pipelines. The main types of pipeline damage with the actual parameters and their influence on the operational parameters are analysed. The damaged fractures of the [...] Read more.

The paper presents the study of the influence of mechanical damage on the safe operation of gas transmission pipelines. The main types of pipeline damage with the actual parameters and their influence on the operational parameters are analysed. The damaged fractures of the section of the pipeline Kaunas (Lithuania)–Kaliningrad (Russia) were investigated in the laboratory. The main operational characteristics and the structure of the pipeline’s metal after the period of long-term operation were determined using various research and experimental methods. The influence of the pipeline’s damage was modelled by using the Finite Element Method and the ANSYS code. The predictions of the failure pressure were made, taking into consideration the actual properties of the pipeline’s metal. Techniques including the hardness and microhardness measurement, chemical analysis, the impact strength test, and metallography analysis with an optical microscope, were used in the experimental study. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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18 pages, 57130 KiB

Open AccessArticle

The Prediction of the Mechanical Properties for Dual-Phase High Strength Steel Grades Based on Microstructure Characteristics

by Emil Evin, Ján Kepič, Katarína Buriková and Miroslav Tomáš

Metals 2018, 8(4), 242; https://doi.org/10.3390/met8040242 - 05 Apr 2018

Cited by 21 | Viewed by 7301

Abstract

The decrease of emissions from vehicle operation is connected mainly to the reduction of the car’s body weight. The high strength and good formability of the dual phase steel grades predetermine these to be used in the structural parts of the car’s body [...] Read more.

The decrease of emissions from vehicle operation is connected mainly to the reduction of the car’s body weight. The high strength and good formability of the dual phase steel grades predetermine these to be used in the structural parts of the car’s body safety zones. The plastic properties of dual phase steel grades are determined by the ferrite matrix while the strength properties are improved by the volume and distribution of martensite. The aim of this paper is to describe the relationship between the mechanical properties and the parameters of structure and substructure. The heat treatment of low carbon steel X60, low alloyed steel S460MC, and dual phase steel DP600 allowed for them to reach states with a wide range of volume fractions of secondary phases and grain size. The mechanical properties were identified by a tensile test, volume fraction of secondary phases, and grain size were measured by image analysis. It was found that by increasing the annealing temperature, the volume fraction of the secondary phase increased, and the ferrite grains were refined. Regression analysis was used to find out the equations for predicting mechanical properties based on the volume fraction of the secondary phase and grain size, following the annealing temperature. The hardening mechanism of the dual phase steel grades for the states they reached was described by the relationship between the strain-hardening exponent and the density of dislocations. This allows for the designing of dual phase steel grades that are “tailored” to the needs of the automotive industry customers. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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14 pages, 34165 KiB

Open AccessArticle

Mechanical Behavior of Two Ferrite–Martensite Dual-Phase Steels over a Broad Range of Strain Rates

by Jiangtao Liang, Zhengzhi Zhao, Hong Wu, Chong Peng, Binhan Sun, Baoqi Guo, Juhua Liang and Di Tang

Metals 2018, 8(4), 236; https://doi.org/10.3390/met8040236 - 03 Apr 2018

Cited by 12 | Viewed by 5726

Abstract

The present study concerns the deformation and fracture behavior of two ferrite–martensite dual phase steels (FMDP660 and FMDP780) with different phase fractions subjected to different strain rate (0.001 s⁻¹ to 1000 s⁻¹) tensile testing. For both steels, the yield strength [...] Read more.

The present study concerns the deformation and fracture behavior of two ferrite–martensite dual phase steels (FMDP660 and FMDP780) with different phase fractions subjected to different strain rate (0.001 s⁻¹ to 1000 s⁻¹) tensile testing. For both steels, the yield strength (YS) monotonically increased with strain rates, whereas the values of ultimate tensile strength (UTS), uniform elongation (UE) and post-uniform elongation (PUE) were maintained stable at the low strain rate range (0.001–0.1 s⁻¹), followed by a significant increase with strain rate at high strain rate levels (0.1–1000 s⁻¹). The FMDP780 steel with a higher fraction of martensite possessed a stronger strain rate sensitivity of tensile strength and elongation (UE and PUE) values at the high strain rate stage, compared with the FMDP660 sample. The change of UTS and UE with different strain rates and phase fractions was highly related to the strain hardening behavior, which was controlled by the dislocation multiplication in ferrite, as validated by transmission electron microscopy (TEM). The fracture surface of the two steels was characterized by dimpled-type fracture associated with microvoid formation at the ferrite–martensite interfaces, regardless of the strain rates. The change of the dimple size and PUE value of the two steels with strain rates was attributed to the effect of adiabatic heating during tensile testing. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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13 pages, 3567 KiB

Open AccessArticle

Precipitation and Grain Size Effects on the Tensile Strain-Hardening Exponents of an API X80 Steel Pipe after High-Frequency Hot-Induction Bending

by Rafael A. Silva, André L. Pinto, Alexei Kuznetsov and Ivani S. Bott

Metals 2018, 8(3), 168; https://doi.org/10.3390/met8030168 - 09 Mar 2018

Cited by 28 | Viewed by 5950

Abstract

This study discusses the use of the Morrison model to estimate the strain-hardening exponent (n) in the presence of precipitation hardening for an API X80 steel pipe. As the grain size becomes larger, high values of n are expected according to [...] Read more.

This study discusses the use of the Morrison model to estimate the strain-hardening exponent (n) in the presence of precipitation hardening for an API X80 steel pipe. As the grain size becomes larger, high values of n are expected according to the Morrison equation. However, the grain size alone is not sufficient to explain the changes of the strain-hardening exponent (n) after hot-induction bending. The vanadium in the ferritic solid solution has an important influence on the decrease of the precipitation hardening, and consequently on the increase of the values of n, despite the refinement of the grain size and high dislocation densities. Therefore, the effects of grain boundaries on the capability to uniformly distribute deformations within the plastic regime become negligible, which limits the application of the Morrison model to estimate the values of n. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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12 pages, 9475 KiB

Open AccessArticle

Effect of Hot Mill Scale on Hydrogen Embrittlement of High Strength Steels for Pre-Stressed Concrete Structures

by Marina Cabrini, Sergio Lorenzi, Tommaso Pastore and Diego Pesenti Bucella

Metals 2018, 8(3), 158; https://doi.org/10.3390/met8030158 - 03 Mar 2018

Cited by 8 | Viewed by 5318

Abstract

The presence of a conductive layers of hot-formed oxide on the surface of bars for pre or post-compressing structures can promote localized attacks as a function of pH. The aggressive local environment in the occluded cells inside localized attacks has as consequence the [...] Read more.

The presence of a conductive layers of hot-formed oxide on the surface of bars for pre or post-compressing structures can promote localized attacks as a function of pH. The aggressive local environment in the occluded cells inside localized attacks has as consequence the possibility of initiation of stress corrosion cracking. In this paper, the stress corrosion cracking behavior of high strength steels proposed for tendons was studied by means of Constant Load (CL) tests and Slow Strain Rate (SSR) tests. Critical ranges of pH for cracking were verified. The promoting role of localized attack was confirmed. Further, electrochemical tests were performed on bars in as received surface conditions, in order to evaluate pitting initiation. The adverse effect of mill scale was recognized. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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7124 KiB

Open AccessArticle

Local Buckling Behavior and Plastic Deformation Capacity of High-Strength Pipe at Strike-Slip Fault Crossing

by Xiaoben Liu, Hong Zhang, Baodong Wang, Mengying Xia, Kai Wu, Qian Zheng and Yinshan Han

Metals 2018, 8(1), 22; https://doi.org/10.3390/met8010022 - 31 Dec 2017

Cited by 17 | Viewed by 5242

Abstract

As a typical hazard threat for buried pipelines, an active fault can induce large plastic deformation in a pipe, leading to rupture failure. The mechanical behavior of high-strength X80 pipeline subjected to strike-slip fault displacements was investigated in detail in the presented study [...] Read more.

As a typical hazard threat for buried pipelines, an active fault can induce large plastic deformation in a pipe, leading to rupture failure. The mechanical behavior of high-strength X80 pipeline subjected to strike-slip fault displacements was investigated in detail in the presented study with parametric analysis performed by the finite element model, which simulates pipe and soil constraints on pipe by shell and nonlinear spring elements respectively. Accuracy of the numerical model was validated by previous full-scale experimental results. Insight of local buckling response of high-strength pipe under compressive strike-slip fault was revealed. Effects of the pipe-fault intersection angle, pipe operation pressure, pipe wall thickness, soil parameters and pipe buried depth on critical section axial force in buckled area, critical fault displacement, critical compressive strain and post buckling response were elucidated comprehensively. In addition, feasibility of some common buckling failure criteria (i.e., the CSA Z662 model proposed by Canadian Standard association, the UOA model proposed by University of Alberta and the CRES-GB50470 model proposed by Center of Reliable Energy System) was discussed by comparing with numerical results. This study can be referenced for performance-based design and assessment of buried high-strength pipe in geo-hazard areas. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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18085 KiB

Open AccessArticle

AISI 304 Welding Fracture Resistance by a Charpy Impact Test with a High Speed Sampling Rate

by Bambang Riyanta, I. N. G. Wardana, Yudy Surya Irawan and Moch. Agus Choiron

Metals 2017, 7(12), 543; https://doi.org/10.3390/met7120543 - 05 Dec 2017

Cited by 3 | Viewed by 7660

Abstract

The purpose of this study was to evaluate fracture resistance in AISI 304. The J-R curve was constructed from data, which resulted from an impact test by Charpy Impact machine equipped with high-speed sampling rate data acquisition equipment. The critical values of fracture [...] Read more.

The purpose of this study was to evaluate fracture resistance in AISI 304. The J-R curve was constructed from data, which resulted from an impact test by Charpy Impact machine equipped with high-speed sampling rate data acquisition equipment. The critical values of fracture resistance in fusion zones (FZ), high temperature heat affected zones (HTHAZ), low temperature heat affected zones (LTHAZ) and unaffected base metals (UBM) were obtained by calculation methods using some formulas and by graphical methods. Laboratory experiments demonstrated the relationships among the values of energy absorption along the impact test with the obstruction of dislocation movement due to the presence of chromium interstitial solute in all zones and chromium rich carbide precipitates in fusion zones and heat affected zones. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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7624 KiB

Open AccessArticle

Characterization of Corrosion Products on Weathering Steel Bridges Influenced by Chloride Deposition

by Vit Krivy, Monika Kubzova, Katerina Kreislova and Viktor Urban

Metals 2017, 7(9), 336; https://doi.org/10.3390/met7090336 - 31 Aug 2017

Cited by 47 | Viewed by 6662

Abstract

The article presents the results of experimental testing of corrosion processes on weathering steel bridges. Two bridge structures spanning various obstacles were selected for the experimental measurement. The tested bridges are situated in the same location and structural solution of these bridges is [...] Read more.

The article presents the results of experimental testing of corrosion processes on weathering steel bridges. Two bridge structures spanning various obstacles were selected for the experimental measurement. The tested bridges are situated in the same location and structural solution of these bridges is similar. Differences in development of corrosion products are mainly affected by the microclimate below the bridge structure. Special attention is paid to a bridge over the motorway which is strongly affected by the deposition of chlorides. The dependences between the measured deposition of chlorides and parameters of corrosion layers (thickness of corrosion products, corrosion rates, and chemical composition) are discussed and evaluated in this article. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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2507 KiB

Open AccessArticle

Microstructural, Mechanical, Texture and Residual Stress Characterizations of X52 Pipeline Steel

by Olivier Lavigne, Andrei Kotousov and Vladimir Luzin

Metals 2017, 7(8), 306; https://doi.org/10.3390/met7080306 - 09 Aug 2017

Cited by 13 | Viewed by 6646

Abstract

In this paper, the microstructural and mechanical properties of a high-strength low-alloy (HSLA) API 5L X52 steel, which is widely utilized in the construction of gas pipelines, were characterized with optical microscopy, electron backscatter diffraction, and standard mechanical tests. The outcomes of these [...] Read more.

In this paper, the microstructural and mechanical properties of a high-strength low-alloy (HSLA) API 5L X52 steel, which is widely utilized in the construction of gas pipelines, were characterized with optical microscopy, electron backscatter diffraction, and standard mechanical tests. The outcomes of these characterizations were used to evaluate the strengthening contributions of the solid solution, grain size, dislocations, and precipitates to the overall strength of the steel. In addition, texture and residual stresses were determined with neutron diffraction. The residual stresses were found to be low in comparison with the expected stresses due to the operating pressure. However, these stresses could contribute to the initiation and propagation of stress corrosion cracking at the outer surface of the pipe. Neutron diffraction results also suggested that the outer surface of the pipe had a texture that is expected to have a low resistance to high pH stress corrosion cracking. Both conclusions were found to be consistent with field observations. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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2752 KiB

Open AccessArticle

Bayesian Correlation Prediction Model between Hydrogen-Induced Cracking in Structural Members

by Taejun Cho, David Joaquin Delgado-Hernandez, Kwan-Hyeong Lee, Byung-Jik Son and Tae-Soo Kim

Metals 2017, 7(6), 205; https://doi.org/10.3390/met7060205 - 05 Jun 2017

Cited by 5 | Viewed by 4632

Abstract

Background: A quantitative model was developed and applied for analyzing the correlation between hydrogen-induced corrosion cracking in both main cable wires and degraded stiffening of the girders of a cable suspension bridge, considering maintenance effects across time and space. Method: Bayesian inference is [...] Read more.

Background: A quantitative model was developed and applied for analyzing the correlation between hydrogen-induced corrosion cracking in both main cable wires and degraded stiffening of the girders of a cable suspension bridge, considering maintenance effects across time and space. Method: Bayesian inference is applied for predicting the correlations among the wires in the main cables owed to hydrogen-induced cracking (HIC) in the cable wires of a steel bridge, by using the improved hierarchical Bayesian models proposed here. Results: The simulated risk prediction under decreased strength of cable wires, due to the corrosion cracking, yields posterior distributions based on prior distributions and likelihoods. The Bayesian inference model can be applied to the design and maintenance of highly corroded and correlated components Data are updated through analyzed information from previous crack steps. A numerical example including not only reliability indices but also probabilities of failure for cable wires, damaged by HIC, is then presented. Compared with a conventional linear prediction model, the one herein developed provides highly improved convergence and closeness to the analyzed data. Conclusion: The proposed model can be used as a diagnostic or prognostic prediction tool for the performance of corroded bridge cable wires with crack propagation, allowing the development of maintenance plans for mechanical components and the overall structural system. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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28582 KiB

Open AccessArticle

Brittle Fracture Behaviors of Large Die Holders Used in Hot Die Forging

by Weifang Zhang, Hongxun Wang, Jingyu Zhang, Wei Dai and Yuanxing Huang

Metals 2017, 7(6), 198; https://doi.org/10.3390/met7060198 - 30 May 2017

Cited by 5 | Viewed by 7981

Abstract

Brittle fracture of large forging equipment usually leads to catastrophic consequences. To avoid this kind of accident, the brittle fracture behaviors of a large die holder were studied by simulating the practical application. The die holder is used on the large die forging [...] Read more.

Brittle fracture of large forging equipment usually leads to catastrophic consequences. To avoid this kind of accident, the brittle fracture behaviors of a large die holder were studied by simulating the practical application. The die holder is used on the large die forging press, and it is made of 55NiCrMoV7 hot-work tool steel. Detailed investigations including mechanical properties analysis, metallographic observation, fractography, transmission electron microscope (TEM) analysis and selected area electron diffraction (SAED) were conducted. The results reveal that the material generated a large quantity of large size polyhedral M₂₃C₆ (M: Fe and Cr mainly) and elongated M₃C (M: Fe mainly) carbides along the martensitic lath boundaries when the die holder was recurrently tempered and water-cooled at 250 °C during the service. The large size carbides lead to the material embrittlement and impact toughness degradation, and further resulted in the brittle fracture of the die holder. Therefore, the operation specification must be emphasized to avoid the die holder being cooled by using water, which is aimed at accelerating the cooling. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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Review

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26 pages, 13859 KiB

Open AccessReview

Distinct Fracture Patterns in Construction Steels for Reinforced Concrete under Quasistatic Loading— A Review

by Fernando Suárez, Jaime C. Gálvez, David A. Cendón and José M. Atienza

Metals 2018, 8(3), 171; https://doi.org/10.3390/met8030171 - 09 Mar 2018

Cited by 8 | Viewed by 4622

Abstract

Steel is one of the most widely used materials in construction. Nucleation growth and coalescence theory is usually employed to explain the fracture process in ductile materials, such as many metals. The typical cup–cone fracture pattern has been extensively studied in the past, [...] Read more.

Steel is one of the most widely used materials in construction. Nucleation growth and coalescence theory is usually employed to explain the fracture process in ductile materials, such as many metals. The typical cup–cone fracture pattern has been extensively studied in the past, giving rise to numerical models able to reproduce this pattern. Nevertheless, some steels, such as the eutectoid steel used for manufacturing prestressing wires, does not show this specific shape but a flat surface with a dark region in the centre of the fracture area. Recent studies have deepened the knowledge on these distinct fracture patterns, shedding light on some aspects that help to understand how damage begins and propagates in each case. The numerical modelling of both fracture patterns have also been discussed and reproduced with different approaches. This work reviews the main recent advances in the knowledge on this subject, particularly focusing on the experimental work carried out by the authors. Full article

(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)

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