Editorial

2 pages, 179 KiB

Open AccessEditorial

Special Issue on Recent Trends in Advanced High-Strength Steels

by Ricardo Branco, Filippo Berto and Andrei Kotousov

Appl. Sci. 2021, 11(15), 6914; https://doi.org/10.3390/app11156914 - 27 Jul 2021

Viewed by 1264

Advanced high-strength steels play an essential role in many industries and engineering applications because of their excellent combination of mechanical properties important for design, e [...] Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

Research

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7 pages, 846 KiB

Open AccessFeature PaperCommunication

Cyclic Plasticity of the As-Built EOS Maraging Steel: Preliminary Experimental and Computational Results

by Barry Mooney, Dylan Agius and Kyriakos I. Kourousis

Appl. Sci. 2020, 10(4), 1232; https://doi.org/10.3390/app10041232 - 12 Feb 2020

Cited by 9 | Viewed by 2921

Abstract

This short communication offers a preliminary view on ongoing research conducted on the as-built EOS maraging steel 300. The material’s cyclic elastoplastic characteristics under strain-controlled loading have been investigated experimentally. Specimens fabricated under two primary orientations, horizontally and vertically to the build plate, [...] Read more.

This short communication offers a preliminary view on ongoing research conducted on the as-built EOS maraging steel 300. The material’s cyclic elastoplastic characteristics under strain-controlled loading have been investigated experimentally. Specimens fabricated under two primary orientations, horizontally and vertically to the build plate, have been tested. The obtained stress–strain hysteresis loops exhibited symmetry, with the vertical specimen showing a higher plastic strain energy dissipation capability than the horizontal specimen. Modelling of the material’s elastoplastic behaviour was performed with a commonly used kinematic hardening rule, combined with both isotropic and anisotropic yield functions and elasticity moduli. The obtained simulations of the hysteresis loops, from the implementation of these two plasticity models, indicate the advantage of the anisotropic modelling approach over the isotropic approach. The anisotropic plasticity model describes in a more representative way the inherent elastic and plastic anisotropy of the as-built material. Further research is underway to explore the low cycle fatigue performance of this additively manufactured metal. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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13 pages, 10386 KiB

Open AccessArticle

Influence of Chromium Content on the Microstructure and Mechanical Properties of Thermomechanically Hot-Rolled Low-Carbon Bainitic Steels Containing Niobium

by Mohammed Ali, Tun Nyo, Antti Kaijalainen, Jaakko Hannula, David Porter and Jukka Kömi

Appl. Sci. 2020, 10(1), 344; https://doi.org/10.3390/app10010344 - 02 Jan 2020

Cited by 10 | Viewed by 3214

Abstract

The effect of chromium content in the range of 1 wt.%–4 wt.% on the microstructure and mechanical properties of controlled-rolled and direct-quenched 12 mm thick low-carbon (0.04 wt.%) steel plates containing 0.06 wt.% Nb has been studied. In these microalloyed 700 MPa grade [...] Read more.

The effect of chromium content in the range of 1 wt.%–4 wt.% on the microstructure and mechanical properties of controlled-rolled and direct-quenched 12 mm thick low-carbon (0.04 wt.%) steel plates containing 0.06 wt.% Nb has been studied. In these microalloyed 700 MPa grade steels, the aim was to achieve a robust bainitic microstructure with a yield strength of 700 MPa combined with good tensile ductility and impact toughness. Continuous cooling transformation diagrams of deformed and non-deformed austenite were recorded to study the effect of Cr and hot deformation on the transformation behavior of the investigated steels. Depending on the cooling rate, the microstructures consist of one or more of the following microstructural constituents: bainitic ferrite, granular bainite, polygonal ferrite, and pearlite. The fraction of bainitic ferrite decreases with decreasing cooling rate, giving an increasing fraction of granular bainite and polygonal ferrite and a reduction in the hardness of the transformation products. Polygonal ferrite formation depends mainly on the Cr content and the cooling rate. In both deformed and non-deformed austenite, increasing the Cr content enhances the hardenability and refines the final microstructure, shifting the ferrite start curve to lower cooling rates. Preceding austenite deformation promotes the formation of polygonal ferrite at lower cooling rates, which leads to a decrease in hardness. In hot-rolled and direct-quenched plates, decreasing the Cr content promotes the formation of polygonal ferrite leading to an increase in the impact toughness and elongation but also a loss of yield strength. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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15 pages, 6848 KiB

Open AccessArticle

Failure Analysis on a Collapsed Flat Cover of an Adjustable Ballast Tank Used in Deep-Sea Submersibles

by Fang Wang, Mian Wu, Genqi Tian, Zhe Jiang, Shun Zhang, Jian Zhang and Weicheng Cui

Appl. Sci. 2019, 9(23), 5258; https://doi.org/10.3390/app9235258 - 03 Dec 2019

Cited by 1 | Viewed by 2933

Abstract

A flat cover of an adjustable ballast tank made of high-strength maraging steel used in deep-sea submersibles collapsed during the loading process of external pressure in the high-pressure chamber. The pressure was high, which was the trigger of the collapse, but still considerably [...] Read more.

A flat cover of an adjustable ballast tank made of high-strength maraging steel used in deep-sea submersibles collapsed during the loading process of external pressure in the high-pressure chamber. The pressure was high, which was the trigger of the collapse, but still considerably below the design limit of the adjustable ballast tank. The failure may have been caused by material properties that may be defective, the possible stress concentration resulting from design/processing, or inappropriate installation method. The present paper focuses on the visual inspections of the material inhomogeneity, ultimate cause of the collapse of the flat cover in pressure testing, and finite element analysis. Special attention is paid to the toughness characteristics of the material. The present study demonstrates the importance of material selection for engineering components based on the comprehensive properties of the materials. Full article

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9 pages, 2245 KiB

Open AccessArticle

High-Temperature Mechanical Properties of 4.5%Al δ-TRIP Steel

by Dayu Chen, Heng Cui and Rudong Wang

Appl. Sci. 2019, 9(23), 5094; https://doi.org/10.3390/app9235094 - 25 Nov 2019

Cited by 8 | Viewed by 2342

Abstract

The high-temperature mechanical properties of a 4.5% Al-containing δ-transformation-induced plasticity (TRIP) steel were studied by using the Gleeble 3500 thermomechanical simulator. The zero ductility temperature (ZDT) and the zero strength temperature (ZST) were measured, and the brittle zones were divided. The phase transformation [...] Read more.

The high-temperature mechanical properties of a 4.5% Al-containing δ-transformation-induced plasticity (TRIP) steel were studied by using the Gleeble 3500 thermomechanical simulator. The zero ductility temperature (ZDT) and the zero strength temperature (ZST) were measured, and the brittle zones were divided. The phase transformation zone was determined by differential scanning calorimetry (DSC). The temperature of the phase transformation and the proportion of the phase were calculated by the Thermo-Calc software. The ZDT and the ZST of the 4.5% Al-containing δ-TRIP steel are 1355 and 1405 °C, respectively. The first brittle zone and the third brittle zone of the steel are 1300–1350 °C and 800–975 °C, respectively. The reason for the embrittlement of the third brittle zone of the 4.5% Al-containing δ-TRIP steel is that the α-ferrite formed at the austenite grain boundary causes the sample to crack along the grain boundary under stress. The ductility of the 4.5% Al-containing δ-TRIP steel decreases first and then increases with the increase of the α-ferrite. When the proportion of the α-ferrite reaches 37%, the reduction of area (RA) of the 4.5% Al-containing δ-TRIP steel is reduced to 44%. The 4.5% Al-containing δ-TRIP steel has good resistance to the high-temperature cracking. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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28 pages, 18145 KiB

Open AccessArticle

Crack Initiation and Propagation Fatigue Life of Ultra High-Strength Steel Butt Joints

by Markus J. Ottersböck, Martin Leitner, Michael Stoschka and Wilhelm Maurer

Appl. Sci. 2019, 9(21), 4590; https://doi.org/10.3390/app9214590 - 29 Oct 2019

Cited by 22 | Viewed by 5129

Abstract

The division of the total fatigue life into different stages such as crack initiation and propagation is an important issue in regard to an improved fatigue assessment especially for high-strength welded joints. The transition between these stages is fluent, whereas the threshold between [...] Read more.

The division of the total fatigue life into different stages such as crack initiation and propagation is an important issue in regard to an improved fatigue assessment especially for high-strength welded joints. The transition between these stages is fluent, whereas the threshold between the two phases is referred to as technical crack initiation. This work presents a procedure to track crack initiation and propagation during fatigue tests of ultra high-strength steel welded joints. The method utilizes digital image correlation to calculate a distortion field of the specimens’ surface enabling the identification and measurement of cracks along the weld toe arising during the fatigue test. Hence, technical crack initiation of each specimen can be derived. An evaluation for ten ultra high-strength steel butt joints reveals, that for this superior strength steel grade more than 50% of fatigue life is spent up to a crack depth of 0.5 mm, which can be defined as initial crack. Furthermore, a notch-stress based fatigue assessment of these specimens considering the actual weld topography and crack initiation and propagation phase is performed. The results point out that two phase models considering both phases enable an increased accuracy of service life assessment. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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13 pages, 2344 KiB

Open AccessArticle

Fatigue Crack Growth in Maraging Steel Obtained by Selective Laser Melting

by Fernando Antunes, Luís Santos, Carlos Capela, José Ferreira, José Costa, Joel Jesus and Pedro Prates

Appl. Sci. 2019, 9(20), 4412; https://doi.org/10.3390/app9204412 - 18 Oct 2019

Cited by 22 | Viewed by 3685

Abstract

Selective Laser Melting (SLM) is an additive manufacturing technology, ideal for the production of complex-shaped components. Design against fatigue is fundamental in the presence of cyclic loads, particularly for these materials which typically have significant porosity, high surface roughness and residual stresses. The [...] Read more.

Selective Laser Melting (SLM) is an additive manufacturing technology, ideal for the production of complex-shaped components. Design against fatigue is fundamental in the presence of cyclic loads, particularly for these materials which typically have significant porosity, high surface roughness and residual stresses. The main objective here is to study fatigue crack growth (FCG) in the 18Ni300 steel obtained by SLM. Typical da/dN-ΔK curves were obtained in C(T) specimens, indicating that cyclic plastic deformation may be the controlling mechanism. A complementary analysis, based on plastic CTOD range, showed a relatively low level of crack tip plastic deformation, and consequently a reduced level of plasticity induced crack closure. The curve da/dN versus plastic CTOD range is clearly above the curves for other materials. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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16 pages, 4585 KiB

Open AccessArticle

The Effect of Tempering on the Microstructure and Mechanical Properties of a Novel 0.4C Press-Hardening Steel

by Oskari Haiko, Antti Kaijalainen, Sakari Pallaspuro, Jaakko Hannula, David Porter, Tommi Liimatainen and Jukka Kömi

Appl. Sci. 2019, 9(20), 4231; https://doi.org/10.3390/app9204231 - 10 Oct 2019

Cited by 28 | Viewed by 8537

Abstract

In this paper, the effects of different tempering temperatures on a recently developed ultrahigh-strength steel with 0.4 wt.% carbon content were studied. The steel is designed to be used in press-hardening for different wear applications, which require high surface hardness (650 HV/58 HRC). [...] Read more.

In this paper, the effects of different tempering temperatures on a recently developed ultrahigh-strength steel with 0.4 wt.% carbon content were studied. The steel is designed to be used in press-hardening for different wear applications, which require high surface hardness (650 HV/58 HRC). Hot-rolled steel sheet from a hot strip mill was austenitized, water quenched and subjected to 2-h tempering at different temperatures ranging from 150 °C to 400 °C. Mechanical properties, microstructure, dislocation densities, and fracture surfaces of the steels were characterized. Tensile strength greater than 2200 MPa and hardness above 650 HV/58 HRC were measured for the as-quenched variant. Tempering decreased the tensile strength and hardness, but yield strength increased with low-temperature tempering (150 °C and 200 °C). Charpy-V impact toughness improved with low-temperature tempering, but tempered martensite embrittlement at 300 °C and 400 °C decreased the impact toughness at −40 °C. Dislocation densities as estimated using X-ray diffraction showed a linear decrease with increasing tempering temperature. Retained austenite was present in the water quenched and low-temperature tempered samples, but no retained austenite was found in samples subjected to tempering at 300 °C or higher. The substantial changes in the microstructure of the steels caused by the tempering are discussed. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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17 pages, 4499 KiB

Open AccessArticle

Effect of Intercritical Quenching Temperature of Cu-Containing Low Alloy Steel of Long Part Forging for Offshore Applications

by Yuta Honma, Gen Sasaki and Kunihiko Hashi

Appl. Sci. 2019, 9(8), 1705; https://doi.org/10.3390/app9081705 - 25 Apr 2019

Cited by 6 | Viewed by 2959

Abstract

In our previous study, intercritical quenching from the dual-phase region of ferrite and austenite regions, which is called lamellarizing (L) treatment, brought a clear improvement of balance between the strength and toughness of Cu-containing low alloy steel based on American Society for Testing [...] Read more.

In our previous study, intercritical quenching from the dual-phase region of ferrite and austenite regions, which is called lamellarizing (L) treatment, brought a clear improvement of balance between the strength and toughness of Cu-containing low alloy steel based on American Society for Testing and Materials (ASTM) A707 5L grade. Moreover, the results imply that the reverse transformation behavior during L treatment is very important in order to optimize the L treatment temperature. Hence, the purpose of this paper is to clarify the mechanism by which L treatment improves the mechanical properties in terms of reverse transformation behavior. Additionally, offshore structures require good weldability, because the structures generally have a lot of weld joints. Therefore, weldability was also investigated in this study. The investigation revealed that coarse Cu precipitates are observed in the not-transformed α phase, so the strength tendency in relation to the L treatment temperature is relevant to the area ratio of the not-transformed α phase and the transformed γ phase during L treatment. From the in situ electron back scatter diffraction (EBSD) results, it is believed to be possible to enhance the mechanical properties of Cu-containing low alloy steel by controlling the area ratio of the reverse-transformed gamma phase and selecting the appropriate L treatment temperature. Furthermore, the long part forging of Cu-containing low alloy steel has a good weldability, since the maximum hardness of the heat-affected zone (HAZ) is less than 300 HV, and the HAZ of steel has a good crack tip opening displacement (CTOD) property with less than 2.3 kJ/mm of heat input of GTAW. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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13 pages, 12049 KiB

Open AccessArticle

Numerical Study of the Effect of Inclusions on the Residual Stress Distribution in High-Strength Martensitic Steels During Cooling

by Chao Gu, Junhe Lian, Yanping Bao, Wei Xiao and Sebastian Münstermann

Appl. Sci. 2019, 9(3), 455; https://doi.org/10.3390/app9030455 - 29 Jan 2019

Cited by 37 | Viewed by 4453

Abstract

In high-strength martensitic steels, the inclusions significantly affect the material performance especially in terms of fatigue properties. In this study, a numerical procedure to investigate the effect of the inclusions types and shapes on the residual stresses during the cooling process of the [...] Read more.

In high-strength martensitic steels, the inclusions significantly affect the material performance especially in terms of fatigue properties. In this study, a numerical procedure to investigate the effect of the inclusions types and shapes on the residual stresses during the cooling process of the martensitic steels is applied systematically based on the scanning electronic microscopy (SEM) and energy dispersive spectrometer (EDS) results of different types of inclusions. The results show that the maximum residual stress around the interface between Mg-Al-O inclusion and the matrix is the largest, followed by TiN, Al-Ca-O-S, and MnS when the inclusions are assumed as perfect spheres for simplicity. However, these results are proved to be 28.0 to 48.0% inaccurate compared to the results considering actual shapes of inclusions. Furthermore, the convex shape of inclusion will lead to stress concentration in the matrix while the concave shape of inclusion will lead to stress concentration in the inclusion. The residual stress increases with the increase of inclusion edge angle. The increase rate is the largest for TiN inclusions on the concave angle, which leads to extreme stress concentration inside TiN inclusion. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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23 pages, 5469 KiB

Open AccessArticle

Integrating the Shape Constants of a Novel Material Stress-Strain Characterization Model for Parametric Numerical Analysis of the Deformational Capacity of High-Strength X80-Grade Steel Pipelines

by Onyekachi Ndubuaku, Michael Martens, J. J. Roger Cheng and Samer Adeeb

Appl. Sci. 2019, 9(2), 322; https://doi.org/10.3390/app9020322 - 17 Jan 2019

Cited by 6 | Viewed by 3404

Abstract

Pipelines typically exhibit significant inelastic deformation under various loading conditions, making it imperative for limit state design to include considerations for the deformational capacity of pipelines. The methods employed to achieve higher strength of API X80 line pipe steels during the plate manufacturing [...] Read more.

Pipelines typically exhibit significant inelastic deformation under various loading conditions, making it imperative for limit state design to include considerations for the deformational capacity of pipelines. The methods employed to achieve higher strength of API X80 line pipe steels during the plate manufacturing process tend to increase the hardness of the pipe material, albeit at the cost of ductility and strain hardenability. This study features a simple and robust material stress-strain characterization model, which is able to mathematically characterize the shape of a diverse range of stress-strain curves, even for materials with a distinct yield point and an extended yield plateau. Extensive parametric finite element analysis is performed to study the relationship between relevant parameters and the deformational capacity of API X80 pipelines subjected to uniform axial compression, uniform bending, and combined axial compression and bending. Nonlinear regression analysis is employed to develop six nonlinear semi-empirical equations for the critical limit strain, wherein the shape constants of the material model are adapted as dimensionless parameters. The goodness-of-fit of the developed equations was graphically and statistically evaluated, and excellent predictive accuracy was obtained for all six developed equations. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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17 pages, 16359 KiB

Open AccessArticle

Effects of Temperature and Time of Isothermal Holding on Retained Austenite Stability in Medium-Mn Steels

by Adam Grajcar, Paweł Skrzypczyk and Aleksandra Kozłowska

Appl. Sci. 2018, 8(11), 2156; https://doi.org/10.3390/app8112156 - 04 Nov 2018

Cited by 18 | Viewed by 3219

Abstract

Effects of isothermal holding time and temperature on the stability of retained austenite in medium manganese bainitic steels with and without Nb microaddition were investigated. The amount of retained austenite for various variants of thermomechanical processing was determined by X-ray diffraction. Relationships between [...] Read more.

Effects of isothermal holding time and temperature on the stability of retained austenite in medium manganese bainitic steels with and without Nb microaddition were investigated. The amount of retained austenite for various variants of thermomechanical processing was determined by X-ray diffraction. Relationships between processing conditions and microstructure were revealed using light microscopy and scanning electron microscopy techniques. The isothermal holding temperatures changed from 500 to 300 °C and the time was from 60 to 1800 s. The optimal time and temperature of isothermal holding for all the investigated steels were 400 °C and 300 s, respectively. The relationships between the Mn content, amount of retained austenite, and carbon enrichment of the retained austenite (RA) were observed. The noticeable effect of Nb microaddition on the amount of retained austenite was not observed. In general, the carbon content in RA was slightly lower for the steels containing Nb. The optimum gamma phase amount was up to 18% for the 3% Mn steels, whereas it was c.a. 13% for the steels with 5% Mn. It was found that the morphology of blocky/interlath retained austenite depends substantially on the isothermal holding temperature. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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13 pages, 7294 KiB

Open AccessArticle

Fracture Toughness of Hybrid Components with Selective Laser Melting 18Ni300 Steel Parts

by Luis M. S. Santos, Joel De Jesus, José M. Ferreira, José D. Costa and Carlos Capela

Appl. Sci. 2018, 8(10), 1879; https://doi.org/10.3390/app8101879 - 11 Oct 2018

Cited by 18 | Viewed by 3211

Abstract

Selective Laser Melting (SLM) is currently one of the more advanced manufacturing and prototyping processes, allowing the 3D-printing of complex parts through the layer-by-layer deposition of powder materials melted by laser. This work concerns the study of the fracture toughness of maraging AISI [...] Read more.

Selective Laser Melting (SLM) is currently one of the more advanced manufacturing and prototyping processes, allowing the 3D-printing of complex parts through the layer-by-layer deposition of powder materials melted by laser. This work concerns the study of the fracture toughness of maraging AISI 18Ni300 steel implants by SLM built over two different conventional steels, AISI H13 and AISI 420, ranging the scan rate between 200 mm/s and 400 mm/s. The SLM process creates an interface zone between the conventional steel and the laser melted implant in the final form of compact tension (CT) samples, where the hardness is higher than the 3D-printed material but lower than the conventional steel. Both fully 3D-printed series and 3D-printed implants series produced at 200 mm/s of scan rate showed higher fracture toughness than the other series built at 400 mm/s of scan rate due to a lower level of internal defects. An inexpressive variation of fracture toughness was observed between the implanted series with the same parameters. The crack growth path for all samples occurred in the limit of interface/3D-printed material zone and occurred between laser melted layers. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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Review

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15 pages, 4886 KiB

Open AccessReview

Welding Capabilities of Nanostructured Carbide-Free Bainite: Review of Welding Methods, Materials, Problems, and Perspectives

by Aleksandra Królicka, Andrzej Ambroziak and Andrzej Żak

Appl. Sci. 2019, 9(18), 3798; https://doi.org/10.3390/app9183798 - 11 Sep 2019

Cited by 12 | Viewed by 2792

Abstract

This article presents state-of-the-art welding methods and the weldability aspect of steels, particularly high-carbon nanobainitic (NB) steels, without carbide precipitates (CFB—carbide-free bainite). On the basis of research conducted to date, all welding methods with parameters and weld metals for NB CFB are presented. [...] Read more.

This article presents state-of-the-art welding methods and the weldability aspect of steels, particularly high-carbon nanobainitic (NB) steels, without carbide precipitates (CFB—carbide-free bainite). On the basis of research conducted to date, all welding methods with parameters and weld metals for NB CFB are presented. It was found that the process parameters significantly affected the mechanical properties of the welds, which were determined primarily by the properties of the low-temperature heat-affected zone. The microstructures of welded joints in the heat-affected and fusion zones are also described. The general requirements for welding processes, as well as problems and perspectives for further research, are presented. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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