Editorial

2 pages, 175 KiB

Open AccessEditorial

Mechanical Properties and Microstructure of Forged Steels

by Andrea Di Schino

Metals 2021, 11(8), 1177; https://doi.org/10.3390/met11081177 - 24 Jul 2021

Cited by 1 | Viewed by 1618

Forged steels represent a quite interesting material family, both from a scientific and commercial point of view, following many applications they can be devoted to [...] Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)

Research

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17 pages, 8727 KiB

Open AccessEditor’s ChoiceArticle

Effects of Thermomechanical Processing on Hydrogen Embrittlement Properties of UltraHigh-Strength TRIP-Aided Bainitic Ferrite Steels

by Tomohiko Hojo, Yutao Zhou, Junya Kobayashi, Koh-ichi Sugimoto, Yoshito Takemoto, Akihiko Nagasaka, Motomichi Koyama, Saya Ajito and Eiji Akiyama

Metals 2022, 12(2), 269; https://doi.org/10.3390/met12020269 - 31 Jan 2022

Cited by 1 | Viewed by 2164

Abstract

The effects of thermomechanical processing on the microstructure and hydrogen embrittlement properties of ultrahigh-strength, low-alloy, transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steels were investigated to apply to automobile forging parts such as engine and drivetrain parts. The hydrogen embrittlement properties were evaluated by [...] Read more.

The effects of thermomechanical processing on the microstructure and hydrogen embrittlement properties of ultrahigh-strength, low-alloy, transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steels were investigated to apply to automobile forging parts such as engine and drivetrain parts. The hydrogen embrittlement properties were evaluated by conducting conventional tensile tests after hydrogen charging and constant load four-point bending tests with hydrogen charging. The 0.4 mass%C-TBF steel achieved refinement of the microstructure, improved retained austenite characteristics, and strengthening, owing to thermomechanical processing. This might be attributed to dynamic and static recrystallizations during thermomechanical processing in TBF steels. Moreover, the hydrogen embrittlement resistances were improved by the thermomechanical processing in TBF steels. This might be caused by the refinement of the microstructure, an increase in the stability of the retained austenite, and low hydrogen absorption of the thermomechanically processed TBF steels. Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)

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13 pages, 10447 KiB

Open AccessArticle

Air-Hardening Die-Forged Con-Rods—Achievable Mechanical Properties of Bainitic and Martensitic Concepts

by Alexander Gramlich, Robert Lange, Udo Zitz and Klaus Büßenschütt

Metals 2022, 12(1), 97; https://doi.org/10.3390/met12010097 - 04 Jan 2022

Cited by 1 | Viewed by 1713

Abstract

Three air-hardening forging steels are presented, concerning their microstructure and their mechanical properties. The materials have been produced industrially and achieve either bainitic or martensitic microstructures by air-cooling directly from the forging heat. The bainitic steels are rather conservative steel concepts with an [...] Read more.

Three air-hardening forging steels are presented, concerning their microstructure and their mechanical properties. The materials have been produced industrially and achieve either bainitic or martensitic microstructures by air-cooling directly from the forging heat. The bainitic steels are rather conservative steel concepts with an overall alloy concentration of approximately 3 wt.%, while the martensitic concept is alloyed with 4 wt.% manganese (and additional elements), and therefore belongs to the recently developed steel class of medium manganese steels. The presented materials achieve high strengths (YS: 720 MPa to 850 MPa, UTS: 1055 MPa to 1350 MPa), good elongations (A_u: 4.0% to 5.9%, A_t: 12.3% to 14.9%), and impact toughnesses (up to 37 J) in the air-hardened condition. It is shown that air-hardened steels achieve properties close to standard Q + T steels, while being produced with a significantly reduced heat treatment. Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)

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19 pages, 10182 KiB

Open AccessArticle

Redistribution of Grain Boundary Misorientation and Residual Stresses of Thermomechanically Simulated Welding in an Intercritically Reheated Coarse Grained Heat Affected Zone

by Giancarlo Sanchez Chavez, Segen Farid Estefen, Tetyana Gurova, Anatoli Leontiev, Lincoln Silva Gomes and Suzana Bottega Peripolli

Metals 2021, 11(11), 1850; https://doi.org/10.3390/met11111850 - 18 Nov 2021

Cited by 3 | Viewed by 1878

Abstract

A study of the migration of the grain boundary misorientation and its relationship with the residual stresses through time immediately after the completion of a thermomechanical simulation has been carried out. After physically simulating an intercritically overheated welding heat affected zone, the variation [...] Read more.

A study of the migration of the grain boundary misorientation and its relationship with the residual stresses through time immediately after the completion of a thermomechanical simulation has been carried out. After physically simulating an intercritically overheated welding heat affected zone, the variation of the misorientation of grain contours was observed with the electron backscatter diffraction (EBSD) technique and likewise the variation of the residual stresses of welding with RAYSTRESS equipment. It was observed that the misorientation of the grain contours in an ASTM DH36 steel was modified after the thermomechanical simulation, which corresponds to the measured residual stress variation along the first week of monitoring, with compressive residual stresses ranging from 195 MPa to 160 MPa. The changes in misorientation indicate that the stress relaxation phenomenon is associated with the evolution of the misorientation in the microstructure caused by the welding procedure. On the first day, there was a fraction of 4% of the kernel average misorientation (KAM) values at 1° misorientation and on the fourth day, there was a fraction of 7% of the KAM values at 1° misorientation. Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)

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16 pages, 7911 KiB

Open AccessFeature PaperArticle

Cold Formabilities of Martensite-Type Medium Mn Steel

by Koh-ichi Sugimoto, Hikaru Tanino and Junya Kobayashi

Metals 2021, 11(9), 1371; https://doi.org/10.3390/met11091371 - 30 Aug 2021

Cited by 3 | Viewed by 1702

Abstract

Cold stretch-formability and stretch-flangeability of 0.2%C-1.5%Si-5.0%Mn (in mass%) martensite-type medium Mn steel were investigated for automotive applications. High stretch-formability and stretch-flangeability were obtained in the steel subjected to an isothermal transformation process at temperatures between M_s and M_f − 100 °C. [...] Read more.

Cold stretch-formability and stretch-flangeability of 0.2%C-1.5%Si-5.0%Mn (in mass%) martensite-type medium Mn steel were investigated for automotive applications. High stretch-formability and stretch-flangeability were obtained in the steel subjected to an isothermal transformation process at temperatures between M_s and M_f − 100 °C. Both formabilities of the steel decreased compared with those of 0.2%C-1.5%Si-1.5Mn and -3Mn steels (equivalent to TRIP-aided martensitic steels), despite a larger or the same uniform and total elongations, especially in the stretch-flangeability. The decreases were mainly caused by the presence of a large amount of martensite/austenite phase, although a large amount of metastable retained austenite made a positive contribution to the formabilities. High Mn content contributed to increasing the stretch-formability. Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)

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15 pages, 10864 KiB

Open AccessArticle

Influence of Cooling Process Routes after Intercritical Annealing on Impact Toughness of Duplex Type Medium Mn Steel

by Koh-ichi Sugimoto and Hikaru Tanino

Metals 2021, 11(7), 1143; https://doi.org/10.3390/met11071143 - 20 Jul 2021

Cited by 2 | Viewed by 1956

Abstract

To apply the duplex type low-carbon medium-manganese steel to the hot/warm-forging and -stamping products, the influence of cooling process routes immediately after intercritical annealing such as air-cooling (AC) and isothermal transformation (IT) processes on the impact toughness of 0.2%C-1.5%Si-5%Mn (in mass %) duplex [...] Read more.

To apply the duplex type low-carbon medium-manganese steel to the hot/warm-forging and -stamping products, the influence of cooling process routes immediately after intercritical annealing such as air-cooling (AC) and isothermal transformation (IT) processes on the impact toughness of 0.2%C-1.5%Si-5%Mn (in mass %) duplex type medium-Mn (D-MMn) steel was investigated. Moreover the microstructural and tensile properties were also investigated. The AC process increased the volume fraction of reverted austenite but decreased the thermal and mechanical stability in the D-MMn steel, compared to the IT process. The AC process increased the tensile strength but decreased the total elongation. The Charpy V-notch impact value and ductile-brittle transition temperature were deteriorated by the AC process, compared to the IT process. This deterioration of the impact toughness was mainly related to the reverted austenite characteristics and fracture mode. Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)

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14 pages, 7513 KiB

Open AccessArticle

Optimization of Open Die Ironing Process through Artificial Neural Network for Rapid Process Simulation

by Silvia Mancini, Luigi Langellotto, Giovanni Zangari, Riccardo Maccaglia and Andrea Di Schino

Metals 2020, 10(10), 1397; https://doi.org/10.3390/met10101397 - 21 Oct 2020

Cited by 2 | Viewed by 2544

Abstract

The open die forging sequence design and optimization are usually performed by simulating many different configurations corresponding to different forging strategies. Finite element analysis (FEM) is a tool able to simulate the open die forging process. However, FEM is relatively slow and therefore [...] Read more.

The open die forging sequence design and optimization are usually performed by simulating many different configurations corresponding to different forging strategies. Finite element analysis (FEM) is a tool able to simulate the open die forging process. However, FEM is relatively slow and therefore it is not suitable for the rapid design of online forging processes. A new approach is proposed in this work in order to describe the plastic strain at the core of the piece. FEM takes into account the plastic deformation at the core of the forged pieces. At the first stage, a thermomechanical FEM model was implemented in the MSC.Marc commercial code in order to simulate the open die forging process. Starting from the results obtained through FEM simulations, a set of equations describing the plastic strain at the core of the piece have been identified depending on forging parameters (such as length of the contact surface between tools and ingot, tool’s connection radius, and reduction of the piece height after the forging pass). An Artificial Neural Network (ANN) was trained and tested in order to correlate the equation coefficients with the forging to obtain the behavior of plastic strain at the core of the piece. Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)

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11 pages, 6161 KiB

Open AccessArticle

Study of the Effect of Multiple Tempering on the Impact Toughness of Forged S690 Structural Steel

by Luca Pezzato, Claudio Gennari, Dmitry Chukin, Michele Toldo, Federico Sella, Mario Toniolo, Andrea Zambon, Katya Brunelli and Manuele Dabalà

Metals 2020, 10(4), 507; https://doi.org/10.3390/met10040507 - 14 Apr 2020

Cited by 14 | Viewed by 2933

Abstract

During the production of forged metal components, the sequence of heat treatments that are carried out, as well as hot working, remarkably influences mechanical properties of the product, in particular impact toughness. It is possible to tailor impact toughness by varying tempering temperature [...] Read more.

During the production of forged metal components, the sequence of heat treatments that are carried out, as well as hot working, remarkably influences mechanical properties of the product, in particular impact toughness. It is possible to tailor impact toughness by varying tempering temperature and soaking time after hardening treatment, widening the application range of structural steels. In this work, we consider the effects of a second tempering treatment on the microstructural properties and impact toughness of a structural steel EN 10025-6 S690 (DIN StE690, W. n: 1.8931). The steel was first forged and quenched in water after austenitization at 890 °C for 4 h. After quenching different tempering treatments were performed, at 590 °C in single or multiple steps. The effect of these treatments was evaluated both in microstructural terms, by means of optical microscopy, scanning and transmission electron microscopy and X-ray diffraction, and in terms of impact toughness. The mechanical behavior was correlated with the microstructure and a remarkable increase in impact toughness was found after the second tempering treatment due to carbide shape change. Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)

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10 pages, 5546 KiB

Open AccessArticle

Mechanical Properties and Microstructure Characterization of AISI “D2” and “O1” Cold Work Tool Steels

by Mohammed Algarni

Metals 2019, 9(11), 1169; https://doi.org/10.3390/met9111169 - 30 Oct 2019

Cited by 15 | Viewed by 4215

Abstract

This research analyzes the mechanical properties and fracture behavior of two cold work tool steels: AISI “D2” and “O1”. Tool steels are an economical and efficient solution for manufacturers due to their superior mechanical properties. Demand for tool steels is increasing yearly due [...] Read more.

This research analyzes the mechanical properties and fracture behavior of two cold work tool steels: AISI “D2” and “O1”. Tool steels are an economical and efficient solution for manufacturers due to their superior mechanical properties. Demand for tool steels is increasing yearly due to the growth in transportation production around the world. Nevertheless, AISI “D2” and “O1” (locally made) tool steels behave differently due to the varying content of their alloying elements. There is also a lack of information regarding their mechanical properties and behavior. Therefore, this study aimed to investigate the plasticity and ductile fracture behavior of “D2” and “O1” via several experimental tests. The tool steels’ behavior under monotonic quasi-static tensile and compression tests was analyzed. The results of the experimental work showed different plasticity behavior and ductile fracture among the two tool steels. Before fracture, clear necking appeared on “O1” tool steel, whereas no signs of necking occurred on “D2” tool steel. In addition, the fracture surface of “O1” tool steel showed cup–cone fracture mode, and “D2” tool steel showed a flat surface fracture mode. The dimple-like structures in scanning electron microscope (SEM) images revealed that both tool steels had a ductile fracture mode. Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)

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Review

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24 pages, 7714 KiB

Open AccessFeature PaperReview

Recent Progress of Low and Medium-Carbon Advanced Martensitic Steels

by Koh-ichi Sugimoto

Metals 2021, 11(4), 652; https://doi.org/10.3390/met11040652 - 17 Apr 2021

Cited by 11 | Viewed by 3362

Abstract

This article introduces the microstructural and mechanical properties of low and medium-carbon advanced martensitic steels (AMSs) subjected to heat-treatment, hot- and warm- working, and/or case-hardening processes. The AMSs developed for sheet and wire rod products have a tensile strength higher than 1.5 GPa, [...] Read more.

This article introduces the microstructural and mechanical properties of low and medium-carbon advanced martensitic steels (AMSs) subjected to heat-treatment, hot- and warm- working, and/or case-hardening processes. The AMSs developed for sheet and wire rod products have a tensile strength higher than 1.5 GPa, good cold-formability, superior toughness and fatigue strength, and delayed fracture strength due to a mixture of martensite and retained austenite, compared with the conventional martensitic steels. In addition, the hot- and warm-stamping and forging contribute to enhance the mechanical properties of the AMSs due to grain refining and the improvement of retained austenite characteristics. The case-hardening process (fine particle peening and vacuum carburization) is effective to further increase the fatigue strength. Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)

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14 pages, 3460 KiB

Open AccessReview

Low and Medium Carbon Advanced High-Strength Forging Steels for Automotive Applications

by Koh-ichi Sugimoto, Tomohiko Hojo and Ashok Kumar Srivastava

Metals 2019, 9(12), 1263; https://doi.org/10.3390/met9121263 - 26 Nov 2019

Cited by 28 | Viewed by 4591

Abstract

This paper presents the microstructural and mechanical properties of low and medium carbon advanced high-strength forging steels developed based on the third generation advanced high-strength sheet steels, in conjunction with those of conventional high-strength forging steels. Hot-forging followed by an isothermal transformation process [...] Read more.

This paper presents the microstructural and mechanical properties of low and medium carbon advanced high-strength forging steels developed based on the third generation advanced high-strength sheet steels, in conjunction with those of conventional high-strength forging steels. Hot-forging followed by an isothermal transformation process considerably improved the mechanical properties of the forging steels. The improvement mechanisms of the mechanical properties were summarized by relating to the matrix structure, the strain-induced transformation of metastable retained austenite, and/or a mixture of martensite and austenite. Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)

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