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Metals
Special Issues
Recent Innovations in Alloy Design and Processing of Microalloyed Steels
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Recent Innovations in Alloy Design and Processing of Microalloyed Steels

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Casting, Forming and Heat Treatment".

Deadline for manuscript submissions: closed (31 October 2021) | Viewed by 8872

Special Issue Editor

Prof. Dr. Hardy Mohrbacher

E-Mail Website
Guest Editor
Department of Materials Engineering (MTM), KU Leuven, 3001 Leuven, Belgium
Interests: microalloyed steel; thermo-mechanical processing; microstructure–property relationships; welding; hydrogen embrittlement; mining; sustainability
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Microalloyed steels have been produced globally by the steel industry for around 50 years at an ever-increasing volume. The metallurgical fundaments of microalloying were established in the 1960s while significant industrial implementation started in the 1970s. Pipeline steels with superior combinations of strength and toughness emerged as the first major application, followed by structural steels and automotive steels. The application of microalloying in steels is relevant to flat products such as plate and strip, long products such as beams and sections, engineering steels, castings, as well as forgings. The well-known metallurgical effects are related to microstructural refinement and precipitation of microalloy particles in the form of carbides or nitrides. Utilizing these mechanisms have allowed designing low-carbon steels with high strength while having excellent weldability and formability.

Over the years, the knowledge on the physical metallurgy of microalloys has been steadily increasing as new characterization techniques have allowed deeper insights into the specific functionality of microalloying elements and their interactions with other alloying elements. This has initiated new applications for microalloys in areas where they have not previously been considered. A prominent example is medium and higher carbon steels, in which microalloying elements are increasingly used for improving the resistance against hydrogen embrittlement. Furthermore, the ongoing quest for more efficient production and manufacturing processes offers new opportunities for microalloying.

This Special Issue invites authors to report on recent innovations in alloy design and processing of microalloyed steels. Contributions should focus on physical metallurgical effects and the interaction with processing and application properties. Reviews reflecting on the state-of-the-art as developed over the more than five decades of microalloying are also welcome.

Prof. Dr. Hardy Mohrbacher
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • microstructural control
  • grain refinement
  • precipitation
  • solute drag
  • segregation
  • hydrogen embrittlement
  • diffusivity
  • recrystallization delay
  • weldability
  • formability

Published Papers (3 papers)

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Research

11 pages, 3425 KiB  
Article
Effect of Hot-Rolled Heavy Section Bars Post-Deformation Cooling on the Microstructure Refinement and Mechanical Properties of Microalloyed Steels
by Monika Banasiak, Andrzej Hornik, Stanisław Szczęch, Janusz Majta, Marcin Kwiecień, Agnieszka Cebo-Rudnicka, Marcin Rywotycki and Krzysztof Muszka
Metals 2021, 11(8), 1284; https://doi.org/10.3390/met11081284 - 14 Aug 2021
Cited by 1 | Viewed by 1708
Abstract
In the industrial practice—especially in the reverse rolling mills—heavy section products with stable mechanical properties (YS, UTS) and ductility (A, Z) but with an impact toughness (KV) at too low levels are often observed. The results presented in the present work concern the [...] Read more.
In the industrial practice—especially in the reverse rolling mills—heavy section products with stable mechanical properties (YS, UTS) and ductility (A, Z) but with an impact toughness (KV) at too low levels are often observed. The results presented in the present work concern the relationship between the parameters of the cooling process of rolled products made of microalloyed steels, with different chemical compositions (such as Al-N, Al-N-V, Al-N-Ti) and their mechanical properties. Special focus was put on the relationship between chemical composition, grain size and impact toughness at subzero temperatures. It is shown, that by introducing the restrictions towards more strict control of the levels of Al, Ti, V, and N, it can be ensured that the final parameters are not that sensitive to process parameters variations which, hence, provides the required mechanical properties and especially impacts on the toughness requirements for a wide range of section products. It was also found that by slight modifications of microalloying elements and proper control of the process parameters, it is possible to replace commonly used normalizing annealing heat treatment after rolling with normalizing rolling. Full article
(This article belongs to the Special Issue Recent Innovations in Alloy Design and Processing of Microalloyed Steels)
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20 pages, 11677 KiB  
Article
Toughness Property Control by Nb and Mo Additions in High-Strength Quenched and Tempered Boron Steels
by Irati Zurutuza, Nerea Isasti, Eric Detemple, Volker Schwinn, Hardy Mohrbacher and Pello Uranga
Metals 2021, 11(1), 95; https://doi.org/10.3390/met11010095 - 5 Jan 2021
Cited by 17 | Viewed by 2898
Abstract
The synergetic effect on hardenability by combining boron with other microalloying elements (such as Nb, Mo and Nb + Mo) is widely known for high-strength medium carbon steels produced by direct quenching and subsequent tempering treatment. The improvement of mechanical properties could be [...] Read more.
The synergetic effect on hardenability by combining boron with other microalloying elements (such as Nb, Mo and Nb + Mo) is widely known for high-strength medium carbon steels produced by direct quenching and subsequent tempering treatment. The improvement of mechanical properties could be reached through optimization of different mechanisms, such as solid solution hardening, unit size refinement, strain hardening, fine precipitation hardening and the effect of carbon in solid solution. The current study proposes a procedure for evaluating the contribution of different microstructural aspects on Charpy impact toughness. First, the effect that austenite conditioning has on low-temperature transformation unit sizes and microstructural homogeneity was analysed for the different microalloying element combinations. A detailed crystallographic characterization of the tempered martensite was carried out using electron backscattered diffraction (EBSD) in order to quantify the effect of unit size refinement and dislocation density. The impact of heterogeneity and presence of carbides was also evaluated. The existing equations for impact transition temperature (ITT50%) predictions were extended from ferrite-pearlite and bainitic microstructures to tempered martensite microstructures. The results show that microstructural refinement is most beneficial to strength and toughness while unit size heterogeneity has a particularly negative effect on ductile-to-brittle transition behaviour. By properly balancing alloy concept and processing, steel having a yield strength above 900 MPa and low impact transition temperature could be obtained by direct quenching and tempering. Full article
(This article belongs to the Special Issue Recent Innovations in Alloy Design and Processing of Microalloyed Steels)
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21 pages, 14679 KiB  
Article
Effect of Nb and Mo Additions in the Microstructure/Tensile Property Relationship in High Strength Quenched and Quenched and Tempered Boron Steels
by Irati Zurutuza, Nerea Isasti, Eric Detemple, Volker Schwinn, Hardy Mohrbacher and Pello Uranga
Metals 2021, 11(1), 29; https://doi.org/10.3390/met11010029 - 25 Dec 2020
Cited by 9 | Viewed by 3397
Abstract
Recently, advanced thermomechanical hot rolling schedules followed by direct quenching are being developed in order to avoid reheating and quenching treatment after hot rolling to eliminate an energy and cost consuming step. The use of boron as an alloying element is a widely [...] Read more.
Recently, advanced thermomechanical hot rolling schedules followed by direct quenching are being developed in order to avoid reheating and quenching treatment after hot rolling to eliminate an energy and cost consuming step. The use of boron as an alloying element is a widely known practice in high strength medium carbon steels to increase the strength due its potential for delaying phase transformation and improving hardenability. In addition, a significant synergetic effect on hardenability could be reached combining B with microalloying elements (adding Nb, Mo or Nb-Mo). With the purpose of exploring the effect of microalloying elements and thermomechanical rolling schedule, laboratory thermomechanical simulations reproducing plate mill conditions were performed using ultra high strength steels micro-alloyed with Nb, Mo, and Nb-Mo. To that end, plane compression tests were performed, consisting of an initial preconditioning step, followed by several roughing and finishing deformation passes and a final quenching step. After fast cooling to room temperature, a tempering treatment was applied. In the present paper, the complex interaction between the martensitic microstructure, the tempering treatment, the addition of microalloying elements, and the resulting tensile properties was evaluated. For that purpose, an exhaustive EBSD quantification was carried out in both quenched as well as quenched and tempered states for all the steel grades and the contribution of different strengthening mechanisms on yield strength was analyzed. Highest tensile properties are achieved combining Nb and Mo, for both quenched (Q) and quenched and tempered states (Q&T), reaching yield strength values of 1107 MPa and 977 MPa, respectively. Higher tempering resistance was measured for the Mo-bearing steels, making the CMnNbMoB steel the one with the lowest softening after tempering. For CMnB grade, the yield strength reduction after tempering of about 413 MPa was measured, while for NbMo micro-alloyed steel, yield strength softening is considerably reduced to 130 MPa. Full article
(This article belongs to the Special Issue Recent Innovations in Alloy Design and Processing of Microalloyed Steels)
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