Forming and Heat Treatment of 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 (31 January 2023) | Viewed by 11639

Special Issue Editor


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Guest Editor
Division of Systems Research, Faculty of Engineering, Yokohama National University, Yokohama, Kanagawa 240-8501, Japan
Interests: production engineering; metal forming; formability; advanced high-strength steel; steel sheet; hot stamping; aluminum alloy sheets; forgings
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Special Issue Information

Dear Colleagues,

Although steel is cheap in price, it is not cheap in quality, and it is used widely due to its flexible performance in strength, formability, and function via structure control using plastic deformation or heat treatment. In automobiles, the shift to EVs is rapid, and it is essential to reduce the weight of vehicles without impairing their safety due to the requirement of additional batteries. Multimaterial construction is an attractive potential solution to the issue of weight reduction; however, steel is still considered the most appropriate and useful type of material. The development of ultrahigh-strength steel sheets is thus being accelerated and leading to a continuous improvement of their strength and formability. The tensile strength of ultrahigh-strength steel sheets for cold stamping has reached 1450 MPa. Hot stamping through combined press forming and heat treatment quenching not only improves strength but also reduces springback. Moreover, it is becoming standard practice to produce ultrahigh-strength components, with steel being used not only for structural but also for functional parts. For example, electrical motors require a magnetic core, and magnetic steel sheets can enhance their magnetic characteristics via rolling and heat treatment.

In this Special Issue, research related to steel, such as forming, heat treatment, and thermomechanical processing, is invited.

Prof. Dr. Tomoyoshi Maeno
Guest Editor

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Keywords

  • steel
  • alloy steel
  • high-strength steel
  • sheet
  • tube
  • metal-forming processes
  • manufacturing
  • thermomechanical processing
  • rolling
  • microstructure

Published Papers (5 papers)

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Research

10 pages, 5481 KiB  
Article
Scattering Behavior of Slivers in Shearing of Magnetized Ultra-High-Strength Steel Sheets
by Ryo Yagita and Yohei Abe
Metals 2023, 13(1), 110; https://doi.org/10.3390/met13010110 - 04 Jan 2023
Cited by 1 | Viewed by 1182
Abstract
The changes in the magnetization properties of high-strength steel and ultra-high-strength steel sheets are investigated, and then the sheared edges and the scattering behavior of slivers in shearing of the ultra-high-strength steel sheets are observed. The maximum magnetic flux density of the magnetized [...] Read more.
The changes in the magnetization properties of high-strength steel and ultra-high-strength steel sheets are investigated, and then the sheared edges and the scattering behavior of slivers in shearing of the ultra-high-strength steel sheets are observed. The maximum magnetic flux density of the magnetized sheet is increased with the increasing tensile strength of the sheet. The maximum magnetic flux density in the magnetized blanks decreases, whereas the density in the demagnetized blanks increases. In the sheared edges, the ratio of the fracture surface becomes larger with the increasing tensile strength of the steel sheet. In shearing, the shearing slivers are observed at the time of crack penetration and at the time of punch rise. The mass of the slivers generated from the blank in shearing increases with the increasing tensile strength of the steel sheet. Two-thirds of the generated shearing slivers stick to the blank in the magnetized blank, whereas two-thirds of the slivers in the blank without magnetization scatter to the outside of the die. Full article
(This article belongs to the Special Issue Forming and Heat Treatment of Steel)
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13 pages, 7121 KiB  
Article
Influence of Austenitisation Temperature and Time on Martensitic and Isothermal Bainite Phase Transformation of Spring Steel
by Anže Bajželj and Jaka Burja
Metals 2022, 12(8), 1373; https://doi.org/10.3390/met12081373 - 18 Aug 2022
Cited by 1 | Viewed by 1407
Abstract
The influence of austenitisation temperature and time on the martensitic and isothermal bainite transformation of 51CrV4 spring steel was analysed. Based on the analysis of dilatometric curves, the martensite start temperatures (MS) were determined at different austenitisation temperatures (800–960 °C) and [...] Read more.
The influence of austenitisation temperature and time on the martensitic and isothermal bainite transformation of 51CrV4 spring steel was analysed. Based on the analysis of dilatometric curves, the martensite start temperatures (MS) were determined at different austenitisation temperatures (800–960 °C) and austenitisation times (5–30 min). At a temperature of 800 °C, a partial austenitic transformation occurred, and undissolved chromium carbides were present in the matrix. At higher temperatures, the austenitic transformation was complete, and the temperature MS increased with the austenitisation temperature. The temperature of the isothermal phase transformation has a stronger effect on the bainite transformation, which has different effects on the stability of the austenite and the diffusion processes. The microstructure of isothermal bainite transformation samples at 330, 430 and 520 °C was characterised by optical microscopy and dilatometric curves. Lower bainite was formed at a bainitic transformation temperature of 330 °C, and a combination of upper and lower bainite was characterised at a transformation temperature of 430 °C. In the samples transformed at 520 °C, a smaller proportion of lower bainite formed in addition to the upper bainite and martensite. Some allotriomorphic ferrite formed along the boundaries of the austenitic grains. Full article
(This article belongs to the Special Issue Forming and Heat Treatment of Steel)
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19 pages, 8740 KiB  
Article
Impact Toughness of Spring Steel after Bainite and Martensite Transformation
by Min-Soo Suh, Seung-Hoon Nahm, Chang-Min Suh and No-Keun Park
Metals 2022, 12(2), 304; https://doi.org/10.3390/met12020304 - 10 Feb 2022
Cited by 3 | Viewed by 1985
Abstract
It has been reported that a multiphase microstructure with bainite, martensite, and retained austenite obtained by austempering, or quenching and tempering of spring steel containing Si, Mn, and Cr exhibits high strength and ductility. However, little research has been conducted on the bainite [...] Read more.
It has been reported that a multiphase microstructure with bainite, martensite, and retained austenite obtained by austempering, or quenching and tempering of spring steel containing Si, Mn, and Cr exhibits high strength and ductility. However, little research has been conducted on the bainite formation and impact fracture behavior of next-generation spring steel from the perspective of engineering and industrial applications. The microstructural transformation characteristics of bainite and martensite related to the heat treatment cycle on the maker side were quantitatively analyzed using electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM) analyses. Moreover, the effects and mechanical properties of bainite and martensite formation in response to changes in lath length and width were studied and analyzed. That is, to obtain the mechanical properties of spring steel with the highest quality, tensile and impact specimens, whose microstructure and notch shape change according to the heat-treatment cycle, were prepared and studied. Full article
(This article belongs to the Special Issue Forming and Heat Treatment of Steel)
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10 pages, 4455 KiB  
Article
Effects of Heat Treatment on the Microstructure and Mechanical Properties of a Novel H-Grade Sucker Rod Steel
by Zhi Tong, Guijuan Zhou, Wenyue Zheng, Haining Zhang, Hongyu Zhou and Xiaoran Sun
Metals 2022, 12(2), 294; https://doi.org/10.3390/met12020294 - 08 Feb 2022
Cited by 3 | Viewed by 3563
Abstract
The sucker rod is an extremely important equipment in oil exploitation, but with the deepening and harsh environment of the petroleum well, higher requirements are put forward for the strength and corrosion resistance of the sucker rod. The most commonly used steel for [...] Read more.
The sucker rod is an extremely important equipment in oil exploitation, but with the deepening and harsh environment of the petroleum well, higher requirements are put forward for the strength and corrosion resistance of the sucker rod. The most commonly used steel for H grade sucker rods is 4330 steel. However, it has characteristics such as high cost and relatively low sulfide stress cracking resistance. Thus, a novel sucker rod steel with a composition of 0.2 wt.% Cu and 1.2 wt.% Ni was designed. Normalizing + tempering (NT) and quenching + tempering (QT) heat treatment were optimized to render the mechanical properties of the novel sucker rod steel to reach the H grade. Additionally, effects of heat treatment on the microstructural evolution and mechanical properties of the novel sucker rod steel were investigated by optical microscope, scanning electron microscope and mechanical property tests. The results showed that the microstructure is tempered sorbite and the mechanical properties reach H grade after NT and QT. Specifically, the tensile strength, yield strength, elongation and impact toughness of NT/QT samples reached 1010.58/1124.37 MPa, 875.93/1042.63 MPa, 15.66/11.59% and ~77.48/~111.69 J/cm2, respectively. Furthermore, the finer and more dispersed carbides were observed in the QT sample, which means that the QT sample had better strength and toughness. Full article
(This article belongs to the Special Issue Forming and Heat Treatment of Steel)
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17 pages, 11253 KiB  
Article
Corner Strengthening by Local Thickening and Ausforming Using Planar Compression in Hot Stamping of Ultra-High Strength Steel Parts
by Tomoyoshi Maeno, Ken-ichiro Mori, Hiroki Homma, Ali Talebi-Anaraki and Ryohei Ikeda
Metals 2021, 11(12), 1977; https://doi.org/10.3390/met11121977 - 08 Dec 2021
Cited by 2 | Viewed by 2514
Abstract
Hot-stamped products are widely used for the body-in-white of an automobile as they are lightweight and improve crashworthiness. A hot-stamping process using planar compression was developed to strengthen corners of ultra-high strength parts by local thickening and hardening. In this process, the corners [...] Read more.
Hot-stamped products are widely used for the body-in-white of an automobile as they are lightweight and improve crashworthiness. A hot-stamping process using planar compression was developed to strengthen corners of ultra-high strength parts by local thickening and hardening. In this process, the corners are thickened by compressing the blank in the planar direction with the upper and lower dies while blocking the movement of both edges with stoppers in the latter stage of forming. Thickening of the corners largely heightens the strength of the formed parts. Not only the thickness but also the hardness of the corner was increased by large plastic deformation and die quenching. For a hot hat-shaped part, a 30% increase in thickness and a 530 HV20 hardness around the corners were attained. The bending rigidity and strength of the formed parts thickened by 30% in the corners increased by 25% and 20%, respectively. In addition, the improvements of the part shape accuracy and the sidewall quenchability were obtained. Full article
(This article belongs to the Special Issue Forming and Heat Treatment of Steel)
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