Heat Treatment Process and Application of High-Strength Steel

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 (30 June 2023) | Viewed by 8984

Special Issue Editor


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Guest Editor
Regional Technological Institute, University of West Bohemia, 301 00 Pilsen, Czech Republic
Interests: high-strength steel; heat treatment; thermomechanical treatment; Q-P steel; TRIP steel; additive manufacturing; semi-solid processing
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Special Issue Information

Dear Colleagues,

High-strength steels usually require heat treatment processes to realize their mechanical properties. Most modern high-strength steels use retained austenite, which occurs in different morphologies and is surrounded by various matrix types, to achieve an excellent combination of strength and ductility. The so-called TRIP effect occurs during the deformation of the retained austenite, resulting in intense strain hardening. Each high-strength steel group requires a typical heat treatment procedure—an intercritical annealing process for TRIP steels whereby a sufficient fraction of retained austenite is stabilised by isothermal holding time in the bainitic transformation region. The Q&P process is another modern method, in which, due to retained austenite’s foil-like nature, the ductility of martensitic steels is significantly improved. For contemporary 3rd-generation steels, such as medium manganese or low-density steels, heat treatment conditions have also been developed for optimal performance. Medium manganese steels also exhibit excellent low-temperature impact toughness. Due to the properties of high-strength steels, which allow for reducing the weight of the final parts, they are used in a wide range of applications. They can be used not only for car body parts but also other transport technology, as well as structural elements such as bridges, mining platforms, etc. In some cases, due to their chemical composition, they can replace materials where mechanical or corrosion properties are activated by a high content of precious alloying elements.

This Special Issue of Metals focuses on different types of high-strength steels, from the development of their chemical composition to the design of heat and thermomechanical processing for different types of applications.

Dr. Hana Jirková
Guest Editor

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Keywords

  • high-strength steels
  • retained austenite
  • intercritical annealing
  • Q-P process
  • medium manganese steels
  • low-density steels
  • martensite

Published Papers (6 papers)

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Research

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19 pages, 18692 KiB  
Article
Experimental and Numerical Process Design for Press Partitioning of the New Q&P Steel 37SiB6
by Christian Illgen, Sven Winter, Rico Haase, Marcus Böhme, Nadja Reiser, Ansgar Hatscher, Verena Psyk, Verena Kräusel and Martin F.-X. Wagner
Metals 2023, 13(8), 1346; https://doi.org/10.3390/met13081346 - 27 Jul 2023
Viewed by 1340
Abstract
Quenching and partitioning (Q&P) heat treatments of low-alloy steels with exceptional property combinations are particularly promising. In this study, we characterize for the first time a new low-alloy steel to be processed using Q&P heat treatments. In combined experimental and numerical studies, we [...] Read more.
Quenching and partitioning (Q&P) heat treatments of low-alloy steels with exceptional property combinations are particularly promising. In this study, we characterize for the first time a new low-alloy steel to be processed using Q&P heat treatments. In combined experimental and numerical studies, we design a novel approach that effectively combines the short cycle times of press hardening with the excellent property profiles of Q&P-treated steels. We identify an appropriate austenization temperature of 950 °C and a portioning temperature of 250 °C for Q&P heat treatments through dilatometric studies. We adjust a number of reference conditions with fractions of 2.1 to 6.3 wt.% of retained austenite, resulting in tensile strengths up to 1860 MPa and elongations to failure up to 7%. Initial numerical designs of the process can identify varying temperature profiles and cooling rates depending on the position in the die. The results show that the geometry of the part plays a minor role, but the die temperature of 200 °C is the dominant factor for successful partitioning directly in the press hardening process. Full article
(This article belongs to the Special Issue Heat Treatment Process and Application of High-Strength Steel)
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15 pages, 13895 KiB  
Article
Influence of Higher Stabilization Temperatures on the Microstructure and Mechanical Properties of Austenitic Stainless Steel 08Ch18N10T
by Tomáš Janda, Štěpán Jeníček, Ludmila Kučerová, Radek Leták, Dagmar Jandová and Hana Jirková
Metals 2023, 13(5), 975; https://doi.org/10.3390/met13050975 - 18 May 2023
Cited by 2 | Viewed by 1168
Abstract
Precipitation strengthening in titanium-stabilized austenitic stainless steels can improve the hot yield strength, as requested, e.g., for nuclear industry applications. The resulting properties depend mainly on the parameters of the heat treatment and previous forming. The influence of the heat treatment parameters on [...] Read more.
Precipitation strengthening in titanium-stabilized austenitic stainless steels can improve the hot yield strength, as requested, e.g., for nuclear industry applications. The resulting properties depend mainly on the parameters of the heat treatment and previous forming. The influence of the heat treatment parameters on the development of the microstructure and mechanical properties was determined for steel 08Ch18N10T (GOST). Solution annealing and stabilization with different temperatures and holds were performed on the steel, which was, in delivered condition, stabilized at 720 °C. Heat-treated samples were subjected to static tensile testing at room temperature and at 350 °C, microstructural analysis using light, scanning electron and transmission electron microscopy focused on precipitates, and HV10 hardness testing. The strengthening mechanism and its dependence on the stabilization parameters are described. The results of the experiment show the influence of the state of the input material on the final effect of heat treatment—repeated heat treatment achieved lower-strength characteristics than the initial state, while almost all modes showed above-limit values for the mechanical properties. Stabilization temperatures of 720 to 800 °C were found to be optimal in terms of the achieved hot yield strength. At higher temperatures, slightly lower strengths were achieved, but at significantly shorter dwell times. Full article
(This article belongs to the Special Issue Heat Treatment Process and Application of High-Strength Steel)
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14 pages, 4371 KiB  
Article
Characteristic Flow Behavior and Processing Map of a Novel Lean Si Spring Steel for Automotive Stabilizer Bars
by Hongbo Pan, Shiwei Li, Jing Ding, Weiming Liu, Yanan Fu, Xiaohui Shen, Hailian Wei, Huiting Wang, Liang Yu and Qiang Fang
Metals 2023, 13(1), 44; https://doi.org/10.3390/met13010044 - 24 Dec 2022
Viewed by 1203
Abstract
The spring steel for automotive stabilizer bars has a great responsibility in that its quality directly affects the stability, safety, and comfort of vehicle operation. The isothermal thermal compression behavior of a novel lean Si spring steel that was used to manufacture an [...] Read more.
The spring steel for automotive stabilizer bars has a great responsibility in that its quality directly affects the stability, safety, and comfort of vehicle operation. The isothermal thermal compression behavior of a novel lean Si spring steel that was used to manufacture an anti-roll bar was investigated with a DIL805A/D quenching thermal dilatometer in this research. A hyperbolic sine type of constitutive model was established, and hot processing maps were produced to evaluate the experimental steel’s hot workability properties. The experimental results suggest that dynamic recrystallization (DRX) preferentially occurs at a low strain rate and high thermal processing temperature, while the processing maps of the experimental steel are susceptible to strain. The instability regions increase as the strain increases. The processing maps’ stable and instable domains should be decided upon comprehensive analysis of the instability criterion, power dissipation efficiency, and strain rate sensitivity index. The optimum parameters of hot processing for the experimental steel at various strains are that the deformation temperature of 1000–1150 °C and the strain rate of 0.1, approximately. Full article
(This article belongs to the Special Issue Heat Treatment Process and Application of High-Strength Steel)
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10 pages, 3969 KiB  
Article
The Influence of Cooling Rate between Ms and Mf on the Mechanical Properties of Low Alloy 42SiCr Steel Treated by the Q-P Process
by Omid Khalaj, Ehsan Saebnoori, Bohuslav Mašek, Ctibor Štadler, Parsa Hassas and Jiří Svoboda
Metals 2022, 12(12), 2081; https://doi.org/10.3390/met12122081 - 04 Dec 2022
Cited by 1 | Viewed by 1417
Abstract
A series of experiments was conducted by quenching and partitioning (Q-P) heat-treated alloys to investigate the effect of cooling intensity on the mechanical properties of low alloy steel 42SiCr. By applying a conventional heat treatment, reasonable high strength can be achieved; however, the [...] Read more.
A series of experiments was conducted by quenching and partitioning (Q-P) heat-treated alloys to investigate the effect of cooling intensity on the mechanical properties of low alloy steel 42SiCr. By applying a conventional heat treatment, reasonable high strength can be achieved; however, the alloys become more brittle. To obtain an optimal balance, advanced heat treatment methods like the Q-P process can be used. It consists of quenching to temperatures between martensite start and martensite finish temperatures and holding, which leads to the stabilization of untransformed austenite by carbon partitioning. The martensitic microstructure is then formed with a small volume fraction of retained austenite embedded on a microscopic scale. The material’s deformability can be significantly improved by using such heat treatment processes. Moreover, to improve advanced high strength properties (AHSS), an additional Q-P process can be applied, which leads to erasing the influence of cold forming as well as enhancement of the mechanical properties. Several combinations of the Q-P process with/without partitioning were performed with various cooling rates for both heat treatment methods. Ultimate Tensile Strength (UTS), Ductility and Hardness (HV10), as well as the microstructure of the alloys, are compared to evaluate the cooling intensity effects. The cooling rate is found not to be a significant factor influencing mechanical properties, which is a crucial point for practical material heat treatment. Full article
(This article belongs to the Special Issue Heat Treatment Process and Application of High-Strength Steel)
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21 pages, 8552 KiB  
Article
Effect of Different Heat Treatments on Tensile Properties and Unnotched and Notched Fatigue Strength of Cold Work Tool Steel Produced by Powder Metallurgy
by Alessandro Morri, Lorella Ceschini and Simone Messieri
Metals 2022, 12(6), 900; https://doi.org/10.3390/met12060900 - 25 May 2022
Cited by 1 | Viewed by 1542
Abstract
The present study investigates the effect of two heat treatments on the microstructure, the tensile and the fatigue properties of a powder metallurgy tool steel that has undergone two heat treatments: quenching and multiple tempering (conventional for powder metallurgy tool steel), and quenching [...] Read more.
The present study investigates the effect of two heat treatments on the microstructure, the tensile and the fatigue properties of a powder metallurgy tool steel that has undergone two heat treatments: quenching and multiple tempering (conventional for powder metallurgy tool steel), and quenching and multiple tempering with an intermediate cryogenic step at −80 °C (new solution). The findings of the research indicated that the new heat treatment promotes the development of a homogeneous distribution of carbides in the martensitic matrix, with an increase of about 10% in tensile strength and about 7% in elongation to failure. This combination of exceptional strength with a high degree of toughness leads to an improvement in the fatigue behaviour of the steel, which exhibits a higher unnotched and notched fatigue strength (about 15% and 25% respectively) and a lower fatigue notch factor (about 15%) compared to conventionally heat-treated steel. These results highlight that the powder metallurgy tool steel, with the new heat treatment, could be a viable option for the production not only of tools and dies, but also for high-performance automotive components, including even those with complex geometries, such as camshafts or crankshafts. Full article
(This article belongs to the Special Issue Heat Treatment Process and Application of High-Strength Steel)
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Review

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24 pages, 7930 KiB  
Review
Effects of Partial Replacement of Si by Al on Cold Formability in Two Groups of Low-Carbon Third-Generation Advanced High-Strength Steel Sheet: A Review
by Koh-ichi Sugimoto
Metals 2022, 12(12), 2069; https://doi.org/10.3390/met12122069 - 01 Dec 2022
Cited by 3 | Viewed by 1643
Abstract
Partial replacement of Si by Al improves the coatability (or galvanizing property) of Si-Mn advanced high-strength steel (AHSS) sheets. In this paper, the effects of the partial replacement on the microstructure, tensile property, and cold formability are reported for the low-carbon third-generation AHSS [...] Read more.
Partial replacement of Si by Al improves the coatability (or galvanizing property) of Si-Mn advanced high-strength steel (AHSS) sheets. In this paper, the effects of the partial replacement on the microstructure, tensile property, and cold formability are reported for the low-carbon third-generation AHSS sheets, which are classified into two groups, “Group I” and “Group II”. The partial replacement by 1.2 mass% Al increases the carbon concentration or mechanical stability of retained austenite and decreases its volume fraction in the AHSSs, compared to Al-free AHSSs. The partial replacement deteriorates the tensile ductility and stretch formability in the AHSSs with a tensile strength above 1.2 GPa. On the other hand, it achieves the same excellent stretch-flangeability as Al-free AHSSs. A complex addition of Al and Nb/Mo further enhances the stretch-flangeability. The cold formabilities are related to the heat treatment condition and microstructural and tensile properties, and the stress state. Full article
(This article belongs to the Special Issue Heat Treatment Process and Application of High-Strength Steel)
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