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Advances in High-Strength Low-Alloy Steels
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Advances in High-Strength Low-Alloy Steels

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 39386

Special Issue Editors

Dr. Zhenjia Xie

E-Mail Website
Guest Editor
Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China
Interests: processing–microstructure–property correlation; precipitation engineering; grain boundary engineering; retained austenite; TRIP effect; TMCP and heat treatment; thermodynamic calculation; phase-field modeling; big-data mining; machine learning
Special Issues, Collections and Topics in MDPI journals
Dr. Xueda Li

E-Mail Website
Guest Editor
School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao 266580, China
Interests: HSLA steels; physical metallurgy during welding; steel corrosion and protection in oil & gas industry
Special Issues, Collections and Topics in MDPI journals
Dr. Xiangliang Wan

E-Mail Website
Guest Editor
Department of Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China
Interests: phase transformation; thermo-dynamical calculation; microstructural characterization; grain refinement; strengthening and toughening mechanisms in high strength low alloy steels
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

High-strength low-alloy steels are a kind of metal material with a large quantity and wide application. With the development of society and economy, as well as the strengthening of human awareness of environmental protection, more stringent requirements have been put forward for the performance of high-strength low-alloy steels. The performance not only pursues higher strength but also develops functional coupling materials, such as earthquake resistance, weather resistance, fire resistance, crack arrest, and so on. According to the different application requirements, new materials and new processes are emerging. Research and design methods are constantly innovating. Big data science and data mining, machine learning, and artificial intelligence are being used in the design and development of high-strength low-alloy steels. In view of these, this Special Issue entitled “Advances in High-Strength Low-Alloy Steels” has been launched. The purpose of this Special Issue is to organize information about the breakthrough of new material properties of high-strength low-alloy steels, new material and new technology, innovation in material characterization and theory, as well as the application of big data and artificial intelligence in the development and production of high-strength low-alloy steels.

Dr. Zhenjia Xie
Dr. Xueda Li
Dr. Xiangliang Wan
Guest Editors

Manuscript Submission Information

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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

  • processing–microstructure–property correlation
  • precipitation engineering
  • grain boundary engineering
  • retained austenite
  • TRIP effect
  • TMCP and heat treatment
  • thermodynamic calculation
  • modeling
  • big data mining
  • machine learning

Published Papers (20 papers)

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20 pages, 7913 KiB  
Article
Quenched and Tempered Steels Welded Structures: Modified Gas Metal Arc Welding-Pulse vs. Shielded Metal Arc Welding
by Houman Alipooramirabad, Neville Cornish, Rahim Kurji, Anthony Roccisano and Reza Ghomashchi
Metals 2023, 13(5), 887; https://doi.org/10.3390/met13050887 - 3 May 2023
Cited by 1 | Viewed by 1757
Abstract
Quench and tempered (Q&T) steels are widely used for a diverse range of applications, particularly in the mining and defence industry, where wear and unconventional loading are common. Furthermore, they are particularly prone to hydrogen assisted cold cracking (HACC), imposing a more careful [...] Read more.
Quench and tempered (Q&T) steels are widely used for a diverse range of applications, particularly in the mining and defence industry, where wear and unconventional loading are common. Furthermore, they are particularly prone to hydrogen assisted cold cracking (HACC), imposing a more careful selection of consumables and requiring a comparably higher welder skill level to fabricate defect-free structures. Therefore, the cost of fabrication of welded structures is higher when the more preferred welding technique of shielded metal arc welding, SMAW, is employed. The introduction of the modified pulsed arc mode of depositions, a variation to pulsed arc deposition, has improved the productivity rates and can be utilised by welders with a greater skill variations. In this study, full-strength butt welds of Q&T steel (AS/NZS 3597 Grade 700), with the thickness of 20 mm, are fabricated under a high level of restraint using both conventional SMAW and modified pulse gas metal welding (GMAW-P). The study investigated the economic feasibility of the two deposition modes and the propensity to cracking for the welded joints under high restraint conditions. Utilising the modified GMAW-P resulted in 63% and 88% reduction in the ‘Arc-On’ time and the total normalised fabrication time, respectively. However, strict controls must be implemented, due to the increased propensity to lack of fusion-type defects, to optimise the welding procedure and mediate for such defects if GMAW-P is to provide a techno-economically beneficial alternative to conventional SMAW when welding Q&T steels. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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19 pages, 10494 KiB  
Article
Production of a Non-Stoichiometric Nb-Ti HSLA Steel by Thermomechanical Processing on a Steckel Mill
by Cleiton Arlindo Martins, Geraldo Lúcio de Faria, Unai Mayo, Nerea Isasti, Pello Uranga, Jose Maria Rodríguez-Ibabe, Altair Lúcio de Souza, Jorge Adam Cleto Cohn, Marcelo Arantes Rebellato and Antônio Augusto Gorni
Metals 2023, 13(2), 405; https://doi.org/10.3390/met13020405 - 16 Feb 2023
Cited by 5 | Viewed by 1557
Abstract
Obtaining high levels of mechanical properties in steels is directly linked to the use of special mechanical forming processes and the addition of alloying elements during their manufacture. This work presents a study of a hot-rolled steel strip produced to achieve a yield [...] Read more.
Obtaining high levels of mechanical properties in steels is directly linked to the use of special mechanical forming processes and the addition of alloying elements during their manufacture. This work presents a study of a hot-rolled steel strip produced to achieve a yield strength above 600 MPa, using a niobium microalloyed HSLA steel with non-stoichiometric titanium (titanium/nitrogen ratio above 3.42), and rolled on a Steckel mill. A major challenge imposed by rolling on a Steckel mill is that the process is reversible, resulting in long interpass times, which facilitates recrystallization and grain growth kinetics. Rolling parameters whose aim was to obtain the maximum degree of microstructural refinement were determined by considering microstructural evolution simulations performed in MicroSim-SM® software and studying the alloy through physical simulations to obtain critical temperatures and determine the CCT diagram. Four ranges of coiling temperatures (525–550 °C/550–600 °C/600–650 ° C/650–700 °C) were applied to evaluate their impact on microstructure, precipitation hardening, and mechanical properties, with the results showing a very refined microstructure, with the highest yield strength observed at coiling temperatures of 600–650 °C. This scenario is explained by the maximum precipitation of titanium carbide observed at this temperature, leading to a greater contribution of precipitation hardening provided by the presence of a large volume of small-sized precipitates. This paper shows that the combination of optimized industrial parameters based on metallurgical mechanisms and advanced modeling techniques opens up new possibilities for a robust production of high-strength steels using a Steckel mill. The microstructural base for a stable production of high-strength hot-rolled products relies on a consistent grain size refinement provided mainly by the effect of Nb together with appropriate rolling parameters, and the fine precipitation of TiC during cooling provides the additional increase to reach the requested yield strength values. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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8 pages, 2238 KiB  
Article
First-Principles Study of B Segregation at Austenite Grain Boundary and Its Effect on the Hardenability of Low-Alloy Steels
by Jingliang Wang, Xiang Yang, Rongtao Qian, Xuequan Rong, Zhenjia Xie and Chengjia Shang
Metals 2022, 12(12), 2006; https://doi.org/10.3390/met12122006 - 23 Nov 2022
Cited by 3 | Viewed by 1241
Abstract
Addition of B is beneficial for the hardenability of low-alloy steels and the effect is further improved when combined with the addition of Mo. While experiments demonstrated that Mo reduces the M23(C,B)6 precipitation and indicated an interaction between the alloying [...] Read more.
Addition of B is beneficial for the hardenability of low-alloy steels and the effect is further improved when combined with the addition of Mo. While experiments demonstrated that Mo reduces the M23(C,B)6 precipitation and indicated an interaction between the alloying elements at the grain boundary, the underlying mechanism remains unclear. In the present study, the segregation behavior of B and its interaction with C and Mo at an austenite grain boundary were investigated using first-principles calculations. It was demonstrated that B has a strong tendency to segregate to the grain boundary and leads to a remarkable reduction in grain boundary energy, which is considered to be responsible for the improvement in hardenability. A strong attractive interaction between B and Mo was revealed, consistent with the experimentally observed co-segregation. The partitioning energies of Mo and B from grain boundary into borocarbide were calculated, and it was found that Mo can suppress the precipitation by increasing the partitioning energy of B and destabilizing the M23(C,B)6 phase. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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23 pages, 16781 KiB  
Article
Strength-Toughness Balance and Hydrogen Embrittlement Susceptibility of a Precipitation-Strengthened Steel Adopted Tempering Process
by Ning Zhao, Yanlin He, Li Lin, Rendong Liu, Qiangqiang Zhao and Weisen Zheng
Metals 2022, 12(9), 1534; https://doi.org/10.3390/met12091534 - 16 Sep 2022
Viewed by 1601
Abstract
Two steels with different nickel (Ni) content were investigated to reveal the role of Ni on strength-toughness balance and hydrogen embrittlement susceptibility. Although they were similar in microstructure, i.e., nano-particles were precipitated on martensitic laths, different mechanical behaviors were exhibited. After tempering, the [...] Read more.
Two steels with different nickel (Ni) content were investigated to reveal the role of Ni on strength-toughness balance and hydrogen embrittlement susceptibility. Although they were similar in microstructure, i.e., nano-particles were precipitated on martensitic laths, different mechanical behaviors were exhibited. After tempering, the yield strength of 3.5 Ni steel reached a peak at 500 °C, while that of 2.5 Ni steel kept a downward trend, indicating that precipitation strengthening was significant in 3.5 Ni steel. Combined with thermodynamic and kinetic analyses, it was shown that when the Ni content increased, the rich-copper (Cu) precipitation transformation driving force would be enhanced and the reverse of austenite transformation accelerated to improve its stability. Moreover, the increase of Ni content also induced the increase in high-angle grain boundaries (HAGBs), which could inhibit crack propagation. Under the comprehensive effects of strengthening and ductility mechanism, 3.5 Ni steel exhibited excellent cryogenic toughness. Although it was not possible to obtain the ideal balancing of strength-toughness for the steel with lower Ni content, its hydrogen embrittlement susceptibility is satisfying. The results showed that the increase of grain boundary density caused by the grain refinement of 2.5 Ni steel is the key factor for its lower hydrogen embrittlement sensitivity index. Moreover, with the reduction of Ni content, the decrease of HAGBs and the increase in Σ11 boundary were conducive to reducing hydrogen-assisted cracking, while the residual Fe3C in 3.5 Ni steel would deteriorate the hydrogen embrittlement resistance. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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14 pages, 8530 KiB  
Article
Influence of ICCGHAZ on the Low-Temperature Toughness in HAZ of Heavy-Wall X80 Pipeline Steel
by Chao Fu, Xueda Li, Haichuan Li, Tao Han, Bin Han and Yong Wang
Metals 2022, 12(6), 907; https://doi.org/10.3390/met12060907 - 26 May 2022
Cited by 5 | Viewed by 1572
Abstract
Low-temperature embrittlement in the heat-affected zone (HAZ) of heavy-wall X80 weld joints is a primary challenge for arctic oil & gas exploitation. In this paper, the influence of intercritically reheated coarse-grained HAZ (ICCGHAZ) on the low-temperature toughness of the weld joint in a [...] Read more.
Low-temperature embrittlement in the heat-affected zone (HAZ) of heavy-wall X80 weld joints is a primary challenge for arctic oil & gas exploitation. In this paper, the influence of intercritically reheated coarse-grained HAZ (ICCGHAZ) on the low-temperature toughness of the weld joint in a 22 mm thick X80 spiral submerged arc welded pipe was studied through instrumented Charpy V-notch impact test at −80~20 °C and corresponding fracture surface characterization. The results indicated that the influence of ICCGHAZ on the overall toughness of the weld joint is related to temperature. At temperatures below −45 °C, individual and tiny martensite-austenite (MA) constituent debonding can trigger cleavage fracture–which was proved to be nucleation-controlled–and the probability of embrittlement of the ICCGHAZ increases. At temperatures higher than −45 °C, only relatively large or closely distributed MA constituent in ICCGHAZ satisfies the conditions to trigger propagation-controlled cleavage fractures, and the influence of ICCGHAZ on the overall toughness is not remarkable. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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11 pages, 2825 KiB  
Article
Study of Surface Temperature Distribution for High-Temperature U75V Rail Steel Plates in Rolling Process by Colorimetry Thermometry
by Dongdong Zhou, Feng Gao, Junjian Wang and Ke Xu
Metals 2022, 12(5), 860; https://doi.org/10.3390/met12050860 - 17 May 2022
Cited by 3 | Viewed by 1924
Abstract
Surface temperature is a critical operating parameter that influences the phase transition time and rolling quality of U75V rail steel plates in the rolling process. There is still no extensive online detection system for the surface temperature of rail steel plates due to [...] Read more.
Surface temperature is a critical operating parameter that influences the phase transition time and rolling quality of U75V rail steel plates in the rolling process. There is still no extensive online detection system for the surface temperature of rail steel plates due to the hazardous environment, incorrect surface emissivity, and complex backgrounds. In this paper, online surface temperature detection equipment based on multi-spectral photography was built for high-temperature rail steel plates in the rolling processes. Then, the emissivity model for a high-temperature environment, colorimetric thermometry, and noise filtering methods were investigated to improve the accuracy of the temperature detection results of rail steel plates. Finally, the surface temperature of the U75V rail steel plate during three rolling passes could be calculated online point by point, and the greatest error was approximately 0.82% due to the blackbody calibration experiments. The results not only have a positive effect on understanding the temperature declination process of low-alloy rail steel plates during the rolling process, but could also benefit the control of the cooling rate and optimize the rolling model during rolling passes. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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14 pages, 6048 KiB  
Article
Effect of Prior Cold Reduction of C–Si–Mn Hot-Rolled Sheet on Microstructures and Mechanical Properties after Quenching and Partitioning Treatment
by Yuanyao Cheng, Gang Zhao, Deming Xu and Siqian Bao
Metals 2022, 12(5), 799; https://doi.org/10.3390/met12050799 - 5 May 2022
Viewed by 1149
Abstract
This paper studies the microstructures and mechanical properties of quenching and partitioning (Q&P) samples prepared with 35% and 75% cold reduction sheets at an annealing temperature of 810 °C (intercritical temperature). The results indicate that prior cold reduction could significantly influence the ferrite [...] Read more.
This paper studies the microstructures and mechanical properties of quenching and partitioning (Q&P) samples prepared with 35% and 75% cold reduction sheets at an annealing temperature of 810 °C (intercritical temperature). The results indicate that prior cold reduction could significantly influence the ferrite recovery and recrystallization during intercritical annealing, which changes the size and distribution of the ferrite and retained austenite in the Q&P samples. Compared with the 75%—Q&P sample, the 35%—Q&P sample had smaller recrystallized ferrite and retained austenite grains, a higher volume fraction of retained austenite, and a more uneven size distribution of retained austenite. The 35%—Q&P sample presented better total elongation and a higher product of strength and elongation (PSE) than the 75%—Q&P sample. The higher total elongation was related to the higher content and uneven size distribution of retained austenite for they strengthened the TRIP effect and improved the uniform elongation of the sample. The results proved that Q&P steel prepared with a cold-rolled sheet with lower reduction exhibits a better combination of strength and plasticity due to the fact that lower reduction can delay the growth rate of austenite and recrystallized ferrite grains during the intercritical annealing stage. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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14 pages, 5416 KiB  
Article
Fracture Analysis of Ultrahigh-Strength Steel Based on Split Hopkinson Pressure Bar Test
by Shihong Xiao, Xiaosheng Luan, Zhiqiang Liang, Xibin Wang, Tianfeng Zhou and Yue Ding
Metals 2022, 12(4), 628; https://doi.org/10.3390/met12040628 - 6 Apr 2022
Cited by 5 | Viewed by 1921
Abstract
Impact loading is an important cause of fracture failure of ultrahigh-strength steel parts during service. Revealing the fracture mechanism of ultrahigh-strength steel under impact loading has important reference significance for the material preparation, part design, and manufacturing of such steel. Based on the [...] Read more.
Impact loading is an important cause of fracture failure of ultrahigh-strength steel parts during service. Revealing the fracture mechanism of ultrahigh-strength steel under impact loading has important reference significance for the material preparation, part design, and manufacturing of such steel. Based on the split Hopkinson pressure bar (SHPB) test, the mechanical response characteristics of 45CrNiMoVA steel under impact loading were analyzed, and the true stress–true strain curves under a high strain rate (103 s−1) were obtained. It was found that under the simultaneous action of forward and tangential loading forces, a severe plastic deformation layer with a thickness of 20–30 μm was generated in the near impact-loading end face, which is the main cause for crack initiation and propagation. Under the condition of a high strain rate, the plastic flow stress of 45CrNiMoVA steel was characterized by the equilibrium of strain hardening and strain softening, and its impact fracture toughness decreased by 43.6%, resulting in increased quasi-cleavage fracture. Hence, severe surface plastic deformation during 45CrNiMoVA steel machining should be avoided, as it may lead to early failure. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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14 pages, 6770 KiB  
Article
Investigation of Through-Thickness Residual Stress, Microstructure and Texture in Radial Forged High-Strength Alloy Steel Tubes
by Weisheng Xu and Jin Zhang
Metals 2022, 12(4), 622; https://doi.org/10.3390/met12040622 - 4 Apr 2022
Cited by 2 | Viewed by 1733
Abstract
Gradient variations of through-thickness residual stress, microstructure and texture greatly affect the performance of cold radial forged tubes. In this work, the through-thickness distribution of residual stress was measured based on the Debye ring. The microstructure was characterized with the electron backscattering diffraction [...] Read more.
Gradient variations of through-thickness residual stress, microstructure and texture greatly affect the performance of cold radial forged tubes. In this work, the through-thickness distribution of residual stress was measured based on the Debye ring. The microstructure was characterized with the electron backscattering diffraction technique. The texture was measured by the X-ray diffractometer. The influence of microstructure and texture on the strength and anisotropy of forged tubes with different thickness reductions was analyzed. The results show that the residual stress varies gradually from compressive to tensile from the outer to inner surface. The microhardness of the outer surface is lower than the inner. The dislocation density and low-angle grain boundary fraction are the smallest in the one-third thickness. The dislocation density and low-angle grain boundary fraction increase gradually from the one-third thickness to the inner surface. The main texture components of the forged tube include {111}<110>, {001}<110> and {114}<110>. Texture {111}<110> deflects gradually toward {114}<110>, {112}<110> and {110}<110> from the external tube to the internal tube. The gradient variation of strength mainly resulted from the difference of the dislocation density. The difference of strength along the radial direction is reduced with a larger thickness reduction. This work has important significance for improving the performance of high-strength alloy steel tubes processed by cold radial forging. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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7 pages, 10538 KiB  
Article
Formation of Widmanstätten Ferrite and Grain Boundary Ferrite in a Hypereutectoid Pearlitic Steel
by Sixin Zhao, Na Min and Wei Li
Metals 2022, 12(3), 493; https://doi.org/10.3390/met12030493 - 14 Mar 2022
Cited by 4 | Viewed by 2163
Abstract
Accompanied by the formation of pearlite, Widmanstätten ferrite (WF), grain boundary ferrite and cementite are often found to nucleate at the prior austenite grain boundary during isothermal heat treatment. A hypereutectoid pearlitic steel transformed isothermally at temperatures ranging from 607 to 707 °C [...] Read more.
Accompanied by the formation of pearlite, Widmanstätten ferrite (WF), grain boundary ferrite and cementite are often found to nucleate at the prior austenite grain boundary during isothermal heat treatment. A hypereutectoid pearlitic steel transformed isothermally at temperatures ranging from 607 to 707 °C was investigated to clarify the evolution of different phases. At 607 °C, WF grains, which had a Kurdjumov–Sachs orientation relationship with the remaining austenite, were found to be aligned with the grain boundary. At 707 °C, lath WF grains, which were arranged parallel to each other, were at a certain angle to the grain boundary. The formation of pearlite showed two-stage kinetics in the dilatometer curve, and the grain boundary’s abnormal structure was suppressed. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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14 pages, 6008 KiB  
Article
Experimental and Simulation Study on the Effect of Reduction Pretreatment on the Void Healing of Heavy Plate
by Zhen Ning, Xue Li, Hongqiang Liu, Qingwu Cai and Wei Yu
Metals 2022, 12(3), 400; https://doi.org/10.3390/met12030400 - 25 Feb 2022
Cited by 4 | Viewed by 1271
Abstract
In addition to eliminating voids in a billet, the reduction pretreatment (RP) process can refine the austenite structure after reheating and can deform the residual voids, which affect the void healing behavior during insulation before rolling, and then can affect the final quality [...] Read more.
In addition to eliminating voids in a billet, the reduction pretreatment (RP) process can refine the austenite structure after reheating and can deform the residual voids, which affect the void healing behavior during insulation before rolling, and then can affect the final quality of the steel plate. In this study, the effect of the RP process on the evolution of voids in billets and steel plates was investigated by experimental and numerical simulation. RP and non-RP billets were reheated and rolled into 60 mm-thick steel plates, respectively, and the evolutionary behavior of voids within the plates was analyzed using ultrasonic flaw detection methods. Finite element method (FEM) and phase-field method (PFM) were used to investigate the mechanism behind improving the quality of steel plates under the RP process. The simulation results show that, in addition to directly closing the voids through plastic deformation, the RP process can promote the diffusive healing behavior during insulation before rolling by refining the reheated austenite organization and by increasing the curvature of the void surface. Due to the reduction in voids inside the steel plate, the impact energy of the RP steel plate is higher. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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8 pages, 6230 KiB  
Article
The Effects of Prior Austenite Grain Refinement on Strength and Toughness of High-Strength Low-Alloy Steel
by Xiucheng Li, Guangyi Lu, Qichen Wang, Jingxiao Zhao, Zhenjia Xie, Raja Devesh Kumar Misra and Chengjia Shang
Metals 2022, 12(1), 28; https://doi.org/10.3390/met12010028 - 24 Dec 2021
Cited by 19 | Viewed by 2834
Abstract
The effects of prior austenite grain (PAG) refinement on the mechanical properties of bainitic/martensitic steels not only come from itself, but also have more complex effects by affecting the substructure formed by coherent transformation. In this study, the samples of a low-alloy steel [...] Read more.
The effects of prior austenite grain (PAG) refinement on the mechanical properties of bainitic/martensitic steels not only come from itself, but also have more complex effects by affecting the substructure formed by coherent transformation. In this study, the samples of a low-alloy steel were water quenched from different austenitizing temperatures and the bainitic/martensitic microstructures with different PAG sizes were obtained. Electron back-scattered diffraction was used to characterize the microstructure and different types of boundaries were identified and quantitatively analyzed. The tensile tests and series temperature Charpy impact tests of different heat treatment were also carried out and comprehensively analyzed with microstructure characterization works. The results show that the uniform refinement of prior austenite grain can increases the density of packet boundary and block boundary, which leads to microstructure refinement with higher density of high-angle grain boundaries with misorientation >45°. The contribution of this microstructure refinement to toughness is significant, but its contributions to strength and elongation are relatively limited. Compared to uniform refined PAG, if the PAGs are mixed crystal, the density of block boundary will be reduced, which leads to a lower density of the high-angle boundary with misorientation >45° and the positive effects of microstructure refinement on toughness improvement are weakened. The observation of fracture surface of impact specimens indicates that refining the PAG can delay the tendency of brittle fracture with the decrease in test temperature, and even in the case of brittle fracture, the cleavage facet of the fracture surface is relatively smaller. This result also verifies that PAG refinement can effectively improve toughness by inhibiting cleavage fracture. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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13 pages, 7371 KiB  
Article
Effect of Vanadium and Strain Rate on Hot Ductility of Low-Carbon Microalloyed Steels
by Siying Song, Junyu Tian, Juan Xiao, Lei Fan, Yuebiao Yang, Qinpan Yuan, Xiaolong Gan and Guang Xu
Metals 2022, 12(1), 14; https://doi.org/10.3390/met12010014 - 22 Dec 2021
Cited by 4 | Viewed by 2094
Abstract
Hot tensile tests were conducted in this study to investigate the effect of strain rate (10−3 and 10 s−1) and vanadium content (0.029 and 0.047 wt.%) on the hot ductility of low-carbon microalloyed steels. The results indicate that a hot [...] Read more.
Hot tensile tests were conducted in this study to investigate the effect of strain rate (10−3 and 10 s−1) and vanadium content (0.029 and 0.047 wt.%) on the hot ductility of low-carbon microalloyed steels. The results indicate that a hot ductility trough appears at a low strain rate (10−3 s−1) because of the sufficient time for ferrite transformation and the growth of second particles, but it disappears at a high strain rate (10 s−1). The hot ductility is improved with the increase in strain rate at 700 °C or higher temperatures. In addition, with the increase in vanadium content, the large amounts of precipitate and increased ferrite transformation result in poor hot ductility of steels fractured at a low temperature range (600~900 °C). However, when the steel is fractured at a high temperature range (1000~1200 °C), more vanadium in the solid solution in the austenite inhibits the growth of parental austenite grains and results in grain refinement strengthening, slightly improving the hot ductility. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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16 pages, 5552 KiB  
Article
Enhancement of Uniform Elongation by Temperature Change during Tensile Deformation in a 0.2C TRIP Steel
by Noriyuki Tsuchida and Stefanus Harjo
Metals 2021, 11(12), 2053; https://doi.org/10.3390/met11122053 - 18 Dec 2021
Cited by 2 | Viewed by 2357
Abstract
It is important to control the deformation-induced martensitic transformation (DIMT) up to the latter part of the deformation to improve the uniform elongation (U.El) through the TRIP effect. In the present study, tensile tests with decreasing deformation temperatures were conducted to achieve continuous [...] Read more.
It is important to control the deformation-induced martensitic transformation (DIMT) up to the latter part of the deformation to improve the uniform elongation (U.El) through the TRIP effect. In the present study, tensile tests with decreasing deformation temperatures were conducted to achieve continuous DIMT up to the latter part of the deformation. As a result, the U.El was improved by approximately 1.5 times compared with that in the tensile test conducted at 296 K. The enhancement of the U.El in the temperature change test was discussed with the use of neutron diffraction experiments. In the continuous DIMT behavior, a maximum transformation rate of about 0.4 was obtained at a true strain (ε) of 0.2, which was larger than that in the tensile test at 296 K. The tensile deformation behavior of ferrite (α), austenite (γ), and deformation-induced martensite (α′) phases were investigated from the viewpoint of the fraction weighted phase stress. The tensile test with a decreasing deformation temperature caused the increase of the fraction weighted phase stress of α and that of α′, which was affected by the DIMT behavior, resulting in the increase in the work hardening, and also controlled the ductility of α and α′, resulting in the enhancement of the U.El. Especially, the α phase contributed to maintaining high strength instead of α′ at a larger ε. Therefore, not only the DIMT behavior but also the deformation behavior of γ, α, and α′ are important in order to improve U.El due to the TRIP effect. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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13 pages, 8702 KiB  
Article
Effect of Ce Content on Microstructure-Toughness Relationship in the Simulated Coarse-Grained Heat-Affected Zone of High-Strength Low-Alloy Steels
by Yuxin Cao, Xiangliang Wan, Feng Zhou, Yong Wang, Xinbin Liu, Kaiming Wu and Guangqiang Li
Metals 2021, 11(12), 2003; https://doi.org/10.3390/met11122003 - 11 Dec 2021
Cited by 2 | Viewed by 1816
Abstract
The study aimed to identify a moderate degree of Ce addition to improve the toughness in the simulated coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steels, based on the effect of the Ce content on particle characteristics, microstructure and impact toughness. Three steels [...] Read more.
The study aimed to identify a moderate degree of Ce addition to improve the toughness in the simulated coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steels, based on the effect of the Ce content on particle characteristics, microstructure and impact toughness. Three steels with 0.012 wt.%, 0.050 wt.% and 0.086 wt.% Ce content were subjected to 100 kJ/cm heat input in their thermal welding cycles. The particles and microstructures in the simulated CGHAZ of each steel were characterized and the impact-absorbance energy levels were measured at −20 °C. The results indicated that Ce2O2S inclusion compounds were gradually modified to CexSy-CeP and CeP with the increasing of the Ce content. A higher fraction of acicular ferrite was formed in the 0.012 wt.%-Ce-treated steel due to the lower mismatch between Ce2O2S and α-Fe. Furthermore, a lower fraction of M-A constituent was obtained in the 0.012 wt.%-Ce-treated steel. As a result, superior toughness and a typical amount of ductile fracture were detected in the simulated CGHAZ of the 0.012 wt.%-Ce-treated steel. Compared with the 0.012 wt.%-Ce-treated steel, a smaller prior austenite grain was observed in the 0.086 wt.%-Ce-treated steel because of the segregation of CeP at the grain boundary. However, the larger size and density of CeP led to poor toughness in the CGHAZ of the 0.086 wt.%-Ce-treated steel. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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16 pages, 6671 KiB  
Article
The Influence of Temperature on the Microstructure and Properties of Nb-V-Ti-Mo Complex Microalloyed High-Strength Fire-Resistant Steel
by Xin Wang, Zhaodong Li, Shitong Zhou, Runnong Chen, Guangjie Da, Qilong Yong, Zhongmin Yang, Junchang Shen, Chengjia Shang and Qingyou Liu
Metals 2021, 11(11), 1670; https://doi.org/10.3390/met11111670 - 20 Oct 2021
Cited by 5 | Viewed by 2041
Abstract
Nb-V-Ti-Mo complex microalloyed high-strength fire-resistant steel was obtained through two-stage hot rolling and laminar cooling. The results showed that the microstructure of the steel included bainite ferrite and martensite-austenite constituent (i.e., MA) islands. The experimental steel displayed high strength at room temperature, with [...] Read more.
Nb-V-Ti-Mo complex microalloyed high-strength fire-resistant steel was obtained through two-stage hot rolling and laminar cooling. The results showed that the microstructure of the steel included bainite ferrite and martensite-austenite constituent (i.e., MA) islands. The experimental steel displayed high strength at room temperature, with a yield strength (YS) of 617 MPa and tensile strength of 813 MPa (elongation = 18.5%). As the temperature increased to 700 °C, the high-temperature yield strength gradually decreased. Electron backscatter diffraction (EBSD) was used to analyze the experimental steels at different temperatures. The grain sizes did not grow significantly. A small number of nanoprecipitates with an average diameter of 29.2 nm were distributed in the matrix of the as-rolled specimen. Upon increasing the temperature, the number of fine nanoprecipitates gradually increased, resulting in a gradual decrease in their average diameter, reaching a minimum of 19.4 nm at 600 °C. The Orowan equation explained well the precipitation strengthening effect of the nanoprecipitates that formed at a high temperature. At both room temperature and 300 °C, the Ashby work hardening theoretical curves were consistent with the experimental true stress-strain curves. Dynamic recovery and recrystallization occurred at 600 °C, which caused the experimental true stress-strain curve to deviate from the calculated curve. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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16 pages, 6939 KiB  
Article
Deformation Behavior and Constitutive Equation of 42CrMo Steel at High Temperature
by Hongqiang Liu, Zhicheng Cheng, Wei Yu, Gaotian Wang, Jie Zhou and Qingwu Cai
Metals 2021, 11(10), 1614; https://doi.org/10.3390/met11101614 - 11 Oct 2021
Cited by 9 | Viewed by 1856
Abstract
High-temperature reduction pretreatment (HTRP) is a process that can significantly improve the core quality of a billet. The existing flow stress data cannot meet the needs of simulation due to lack of high temperature data. To obtain the hot forming process parameters for [...] Read more.
High-temperature reduction pretreatment (HTRP) is a process that can significantly improve the core quality of a billet. The existing flow stress data cannot meet the needs of simulation due to lack of high temperature data. To obtain the hot forming process parameters for the high-temperature reduction pretreatment process of 42CrMo steel, a hot compression experiment of 42CrMo steel was conducted on Gleeble-3500 thermal-mechanical at 1200–1350 °C with the rates of deformation 0.001–10 s−1 and the deformation of 60%, and its deformation behavior at elevated temperature was studied. In this study, the effects of flow stress temperature and strain rate on austenite grain were investigated. Moreover, two typical constitutive models were employed to describe the flow stress, namely the Arrhenius constitutive model of strain compensation and back propagation artificial neural network (BP ANN) model. The performance evaluation shows that BP ANN model has high accuracy and stability to predict the curve. The thermal processing maps under strains of 0.1, 0.2, 0.3, and 0.4 were established. Based on the analysis of the thermal processing map, the optimal high reduction process parameter range of 42CrMo is obtained: the temperature range is 1250–1350 °C, and the strain rate range is 0.01–1 s−1. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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14 pages, 15283 KiB  
Article
Determination of Critical Transformation Temperatures for the Optimisation of Spring Steel Heat Treatment Processes
by Velaphi Jeffrey Matjeke, Josias Willem van der Merwe and Nontuthuzelo Lindokuhle Vithi
Metals 2021, 11(7), 1014; https://doi.org/10.3390/met11071014 - 24 Jun 2021
Cited by 4 | Viewed by 2564
Abstract
Bogie spring performance can be improved by using the exact heat treatment process parameters. The purpose of the study is to determine the critical transformation temperatures and investigate the effect of the cooling rates on microstructural and mechanical properties. The precise determination of [...] Read more.
Bogie spring performance can be improved by using the exact heat treatment process parameters. The purpose of the study is to determine the critical transformation temperatures and investigate the effect of the cooling rates on microstructural and mechanical properties. The precise determination of the required cooling rates for the particular grade of steel is important in order to optimise the heat treatment process of heavy-duty compression helical spring manufacturing. A traditional heat treatment system for the manufacture of hot coiled springs requires heating the steel to homogenize austenite; then, it is decomposed to martensite by rapid cooling. By analyzing the transition properties by heating and differing cooling rates, this analysis examines the thermal behaviour of high strength spring steel. Using the dilatometer and differential scanning calorimeter, scanning electron microscope, optical microscope, and hardness checking, critical transition temperatures and cooling rates of three springs steels were measured. Although the thermal transformation of materials has been researched for decades using dilatometers, not all materials have been characterized. The research offers insights into the critical transformation temperatures for the defined grades of spring steel and the role of cooling rates in the material’s properties. Mechanical properties are influenced by the transition data obtained from the dilatometric analysis. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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14 pages, 15520 KiB  
Article
A Comparative Study of Acicular Ferrite Transformation Behavior between Surface and Interior in a Low C–Mn Steel by HT-LSCM
by Xiaojin Liu, Guo Yuan, Raja. Devesh Kumar Misra and Guodong Wang
Metals 2021, 11(5), 699; https://doi.org/10.3390/met11050699 - 24 Apr 2021
Cited by 2 | Viewed by 1742
Abstract
In this study, the acicular ferrite transformation behavior of a Ti–Ca deoxidized low carbon steel was studied using a high-temperature laser scanning confocal microscopy (HT-LSCM). The in situ observation of the transformation behavior on the sample surface with different cooling rates was achieved [...] Read more.
In this study, the acicular ferrite transformation behavior of a Ti–Ca deoxidized low carbon steel was studied using a high-temperature laser scanning confocal microscopy (HT-LSCM). The in situ observation of the transformation behavior on the sample surface with different cooling rates was achieved by HT-LSCM. The microstructure between the surface and interior of the HT-LSCM sample was compared. The results showed that Ti–Ca oxide particles were effective sites for acicular ferrite (AF) nucleation. The start transformation temperature at grain boundaries and intragranular particles decreased with an increase in cooling rate, but the AF nucleation rate increased and the surface microstructure was more interlocked. The sample surface microstructure obtained at 3 °C/s was dominated by ferrite side plates, while the ferrite nucleating sites transferred from grain boundaries to intragranular particles when the cooling rate was 15 °C/s. Moreover, it was interesting that the microstructure and microhardness of the sample surface and interior were different. The AF dominating microstructure, obtained in the sample interior, was much finer than the sample surface, and the microhardness of the sample surface was much lower than the sample interior. The combined factors led to a coarse size of AF on the sample surface. AF formed at a higher temperature resulted in the coarse size. The available particles for AF nucleation on the sample surface were quite limited, such that hard impingement between AF plates was much weaker than that in the sample interior. In addition, the transformation stress in austenite on the sample surface could be largely released, which contributed to a coarser AF plate size. The coarse grain size, low dislocation concentration and low carbon content led to lower hardness on the sample surface. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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Review

Jump to: Research

28 pages, 13958 KiB  
Review
In Situ Observation of Solidification and Crystallization of Low-Alloy Steels: A Review
by Yong Wang, Qiang Wang and Wangzhong Mu
Metals 2023, 13(3), 517; https://doi.org/10.3390/met13030517 - 3 Mar 2023
Cited by 3 | Viewed by 1961
Abstract
Crystallization during the solidification process of steels is of vital importance for controlling the quality of final products. This paper summarizes the in situ characterization research activities of crystallization behaviors of low-alloy steels during the solidification process. The results obtained using high-temperature confocal [...] Read more.
Crystallization during the solidification process of steels is of vital importance for controlling the quality of final products. This paper summarizes the in situ characterization research activities of crystallization behaviors of low-alloy steels during the solidification process. The results obtained using high-temperature confocal laser scanning microscope (HT-CLSM) are critically reviewed, and other relevant methodologies, i.e., either classical method using differential scanning calorimetry (DSC) or large-scale facility (LSF), are also briefly mentioned. The evolution of the crystallization front from a planar to a cellular and further to a dendritic one, and subsequential microstructure evolutions, i.e., delta-ferrite (δ) formation from the liquid, austenite (γ) transformation and decomposition, are mainly discussed. The current review aims to highlight the state-of-the-art research outputs obtained by the novel in situ characterization techniques, and the obtained knowledge aims to shed light on the further development of the quality low-alloy steel products by controlling the processing and structure correlation. Full article
(This article belongs to the Special Issue Advances in High-Strength Low-Alloy Steels)
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