Editorial

4 pages, 197 KiB

Open AccessEditorial

Advanced High-Strength Steels by Quenching and Partitioning

by Ilchat Sabirov, María J. Santofimia and Roumen H. Petrov

Metals 2021, 11(9), 1419; https://doi.org/10.3390/met11091419 - 08 Sep 2021

Cited by 1 | Viewed by 1555

Quenched and partitioned (Q&P) steels are recently developed materials with carefully selected chemical compositions and multiphase microstructures resulting from precisely controlled heating and cooling processes [...] Full article

(This article belongs to the Special Issue Advanced High Strength Steels by Quenching and Partitioning)

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13 pages, 5241 KiB

Open AccessArticle

Improving Hydrogen Embrittlement Resistance of Hot-Stamped 1500 MPa Steel Parts That Have Undergone a Q&P Treatment by the Design of Retained Austenite and Martensite Matrix

by Zhou Wang and Mingxin Huang

Metals 2020, 10(12), 1585; https://doi.org/10.3390/met10121585 - 26 Nov 2020

Cited by 3 | Viewed by 2448

Abstract

Hydrogen embrittlement is one of the largest obstacles against the commercialisation of ultra-high strength quenching and partitioning (Q&P) steels with ultimate tensile strength over 1500 MPa, including the hot stamped steel parts that have undergone a Q&P treatment. In this work, the influence [...] Read more.

Hydrogen embrittlement is one of the largest obstacles against the commercialisation of ultra-high strength quenching and partitioning (Q&P) steels with ultimate tensile strength over 1500 MPa, including the hot stamped steel parts that have undergone a Q&P treatment. In this work, the influence of partitioning temperature on hydrogen embrittlement of ultra-high strength Q&P steels is studied by pre-charged tensile tests with both dog-bone and notched samples. It is found that hydrogen embrittlement resistance is enhanced by the higher partitioning temperature. Then, the hydrogen embrittlement mechanism is analysed in terms of hydrogen, retained austenite, and martensite matrix. Thermal desorption analysis (TDA) shows that the hydrogen trapping properties are similar in the Q&P steels, which cannot explain the enhancement of hydrogen embrittlement resistance. On the contrary, it is found that the relatively low retained austenite stability after the higher temperature partitioning ensures more sufficient TRIP effect before hydrogen-induced fracture. Additionally, dislocation recovery and solute carbon depletion at the higher partitioning temperature can reduce the flow stress of the martensite matrix, improving its intrinsic toughness and reducing its hydrogen sensitivity, both of which result in the higher hydrogen embrittlement resistance. Full article

(This article belongs to the Special Issue Advanced High Strength Steels by Quenching and Partitioning)

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17 pages, 5004 KiB

Open AccessFeature PaperArticle

Austenite Reverse Transformation in a Q&P Route of Mn and Ni Added Steels

by Maribel Arribas, Teresa Gutiérrez, Eider Del Molino, Artem Arlazarov, Irene De Diego-Calderón, David Martin, Daniele De Caro, Sudhindra Ayenampudi and Maria J. Santofimia

Metals 2020, 10(7), 862; https://doi.org/10.3390/met10070862 - 29 Jun 2020

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Abstract

In this work, four low carbon steels with different contents of Mn and Ni were heat treated by quenching and partitioning (Q&P) cycles where high partitioning temperatures, in the range of 550 °C–650 °C, were applied. In order to elucidate the effect of [...] Read more.

In this work, four low carbon steels with different contents of Mn and Ni were heat treated by quenching and partitioning (Q&P) cycles where high partitioning temperatures, in the range of 550 °C–650 °C, were applied. In order to elucidate the effect of applying these high partitioning temperatures with respect to more common Q&P cycles, the materials were also heat treated considering a partitioning temperature of 400 °C. The microstructure evolution during the Q&P cycles was studied by means of dilatometry tests. The microstructural characterization of the treated materials revealed that austenite retention strongly depended on the alloy content and partitioning conditions. It was shown that the occurrence of austenite reverse transformation (ART) in the partitioning stage in some of the alloys and conditions was a very effective mechanism to increase the austenite content in the final microstructure. However, the enhancement of tensile properties achieved by the application of high partitioning temperature cycles was not significant. Full article

(This article belongs to the Special Issue Advanced High Strength Steels by Quenching and Partitioning)

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22 pages, 13014 KiB

Open AccessArticle

Temperature Dependence of the Static and Dynamic Behaviour in a Quenching and Partitioning Processed Low-Si Steel

by Florian Vercruysse, Carola Celada-Casero, Bernd M. Linke, Patricia Verleysen and Roumen H. Petrov

Metals 2020, 10(4), 509; https://doi.org/10.3390/met10040509 - 15 Apr 2020

Cited by 12 | Viewed by 2737

Abstract

Because of their excellent combination of strength and ductility, quenching and partitioning (Q & P) steels have a great chance of being added to the third generation of advanced high strength steels. The large ductility of Q & P steels arises from the [...] Read more.

Because of their excellent combination of strength and ductility, quenching and partitioning (Q & P) steels have a great chance of being added to the third generation of advanced high strength steels. The large ductility of Q & P steels arises from the presence of 10% to 15% of retained austenite which postpones necking due to the transformation induced plasticity (TRIP) effect. Moreover, Q & P steels show promising forming properties with favourable Lankford coefficients, while their planar anisotropy is low due to a weak texture. The stability of the metastable austenite is the key to obtain tailored properties for these steels. To become part of the newest generation of advanced high strength steels, Q & P steels have to preserve their mechanical properties at dynamic strain rates and over a wide range of temperatures. Therefore, in the present study, a low-Si Q & P steel was tested at temperatures from −40 °C to 80 °C and strain rates from 0.001 s⁻¹ to 500 s⁻¹. Results show that the mechanical properties are well-preserved at the lowest temperatures. Indeed, at −40 °C and room temperature, no significant loss of the deformation capacity is observed even at dynamic strain rates. This is attributed to the presence of a large fraction of austenite that is so (thermally) stable that it does not transform in the absence of deformation. In addition, the high stability of the austenite decreases the elongation at high test temperatures (80 °C). The additional adiabatic heating in the dynamic tests causes the largest reduction of the uniform strain for the samples tested at 80 °C. Quantification of the retained austenite fraction in the samples after testing confirmed that, at the highest temperature and strain rate, the TRIP effect is suppressed. Full article

(This article belongs to the Special Issue Advanced High Strength Steels by Quenching and Partitioning)

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22 pages, 17509 KiB

Open AccessFeature PaperArticle

Microstructure Evolution and Competitive Reactions during Quenching and Partitioning of a Model Fe–C–Mn–Si Alloy

by Samy Aoued, Frédéric Danoix, Sébastien Y.P. Allain, Steve Gaudez, Guillaume Geandier, Jean-Christophe Hell, Michel Soler and Mohamed Gouné

Metals 2020, 10(1), 137; https://doi.org/10.3390/met10010137 - 16 Jan 2020

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Abstract

The mechanisms behind the carbon enrichment of austenite during quenching and partitioning are still a matter of debate. This work investigates the microstructural evolution during the quenching and partitioning of a model Fe–C–Mn–Si alloy by means of in situ high energy X-ray diffraction [...] Read more.

The mechanisms behind the carbon enrichment of austenite during quenching and partitioning are still a matter of debate. This work investigates the microstructural evolution during the quenching and partitioning of a model Fe–C–Mn–Si alloy by means of in situ high energy X-ray diffraction (HEXRD) atom probe tomography, and image analysis. The ultra-fast time-resolved quantitative information about phase transformations coupled with image analysis highlights the formation of carbide-free BCT bainite, which is formed within a very short range during the reheating and partitioning step. Its transformation rate, which is a better indicator than the intrinsic volume fraction, depends on the quenching temperature (QT). It is shown to decrease with decreasing QT, from 45% at QT = 260 °C to 20% at QT = 200 °C. As a consequence, a significant part of the carbon enrichment observed in austenite can be attributed to bainite transformation. Furthermore, a large part of carbon was shown to be trapped into martensite. Both the formation of Fe_2.6C iron carbides and the segregation of carbon on lath boundaries in martensite were highlighted by atom probe tomography. The energy for carbon segregation was determined to be 0.20 eV, and the carbon concentration on the lath boundaries was obtained to be around 25 at %. Therefore, the carbon enrichment of austenite is the result of competitive reactions such as carbon partitioning from martensite, bainite transformation, and carbon trapping in martensite. Full article

(This article belongs to the Special Issue Advanced High Strength Steels by Quenching and Partitioning)

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12 pages, 3771 KiB

Open AccessArticle

Enhancing the Mechanical Properties of a Hot Rolled High-Strength Steel Produced by Ultra-Fast Cooling and Q&P Process

by Teng Wu, Run Wu, Bin Liu, Wen Liang and Deqing Ke

Metals 2019, 9(9), 958; https://doi.org/10.3390/met9090958 - 31 Aug 2019

Cited by 8 | Viewed by 2585

Abstract

The quenching and partitioning (Q&P) process of advanced high strength steels results in a significant enhancement in their strength and ductility. The development of controlled rolling and cooling technology provides an efficient tool for microstructural design in steels. This approach allows to control [...] Read more.

The quenching and partitioning (Q&P) process of advanced high strength steels results in a significant enhancement in their strength and ductility. The development of controlled rolling and cooling technology provides an efficient tool for microstructural design in steels. This approach allows to control phase transformations in order to generate the desired microstructure in steel and, thus, to achieve the required properties. To refine grain structure in a Fe-Si-Mn-Nb steel and to generate the microstructure consisting of martensitic matrix with embedded retained austenite grains, hot rolling and pressing combined with ultrafast cooling and Q&P process is employed. The slender martensite in hot rolled Q&P steel improves the strength of test steel and the flake retained austenite improves the plasticity and work hardening ability through the Transformation Induced Plasticity (TRIP) effect. Full article

(This article belongs to the Special Issue Advanced High Strength Steels by Quenching and Partitioning)

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17 pages, 4070 KiB

Open AccessArticle

Microstructural Characterization and Mechanical Properties of Direct Quenched and Partitioned High-Aluminum and High-Silicon Steels

by Pekka Kantanen, Mahesh Somani, Antti Kaijalainen, Oskari Haiko, David Porter and Jukka Kömi

Metals 2019, 9(2), 256; https://doi.org/10.3390/met9020256 - 21 Feb 2019

Cited by 21 | Viewed by 3847

Abstract

A new experimental steel containing in weight percent 0.3C-2.0Mn-0.5Si-1.0Al-2.2Cr and 0.3C-1.9Mn-1.0Si-1.0Cr was hot rolled in a laboratory rolling mill and directly quenched within the martensite start and finish temperature range. It was then partitioned without reheating during slow furnace cooling to achieve tensile [...] Read more.

A new experimental steel containing in weight percent 0.3C-2.0Mn-0.5Si-1.0Al-2.2Cr and 0.3C-1.9Mn-1.0Si-1.0Cr was hot rolled in a laboratory rolling mill and directly quenched within the martensite start and finish temperature range. It was then partitioned without reheating during slow furnace cooling to achieve tensile yield strengths over 1100 MPa with good combinations of strength, ductility and impact toughness. Gleeble thermomechanical simulations led to the selection of the partitioning at the temperatures 175 and 225 °C, which produced the desired microstructures of lath martensite with finely divided retained austenite in fractions of 6.5% and 10% respectively. The microstructures were analyzed using light and scanning electron microscopy in combination with electron backscatter diffraction and X-ray diffraction analysis. The mechanical properties were characterized extensively using hardness, tensile and Charpy V impact testing. In tensile testing a transformation induced plasticity mechanism was shown to operate with the less stable, carbon-poorer retained austenite, which transformed to martensite during straining. The auspicious results in respect to microstructures and mechanical properties indicate that there are possibilities for developing tough ductile structural steels through thermomechanical rolling followed by the direct quenching and partitioning route. Full article

(This article belongs to the Special Issue Advanced High Strength Steels by Quenching and Partitioning)

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9 pages, 3434 KiB

Open AccessArticle

Superior Mechanical Properties and Work-Hardening Ability of Ultrafine-Grained Quenched and Partitioned Steels Processed by a Novel Approach Involving Asymmetric Hot Rolling

by Zhengyou Tang, Jianeng Huang, Xingchao Lu, Hua Ding, Dongmei Zhang and Devesh Misra

Metals 2018, 8(11), 872; https://doi.org/10.3390/met8110872 - 25 Oct 2018

Cited by 8 | Viewed by 3153

Abstract

An approach is proposed to enhance the mechanical properties and work-hardening (WH) ability of low-alloy steels. Using asymmetric hot rolling (AHR) and subsequent direct quenching (DQ) prior to the quenching and partitioning (Q&P) process, an ultrafine-grained Q&P steel with excellent combination of tensile [...] Read more.

An approach is proposed to enhance the mechanical properties and work-hardening (WH) ability of low-alloy steels. Using asymmetric hot rolling (AHR) and subsequent direct quenching (DQ) prior to the quenching and partitioning (Q&P) process, an ultrafine-grained Q&P steel with excellent combination of tensile strength of ~1000 MPa and total elongation of ~35% was obtained, which exhibited high WH exponent at higher strain induced by the higher volume fraction and higher stability of film-like retained austenite located between the martensite laths. Full article

(This article belongs to the Special Issue Advanced High Strength Steels by Quenching and Partitioning)

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12 pages, 3602 KiB

Open AccessArticle

A Study of the Optimum Quenching Temperature of Steels with Various Hot Rolling Microstructures after Cold Rolling, Quenching and Partitioning Treatment

by Bin Chen, Juhua Liang, Tao Kang, Ronghua Cao, Cheng Li, Jiangtao Liang, Feng Li, Zhengzhi Zhao and Di Tang

Metals 2018, 8(8), 579; https://doi.org/10.3390/met8080579 - 26 Jul 2018

Cited by 7 | Viewed by 3666

Abstract

Quenching and partitioning (Q&P) processes were applied to a cold-rolled high strength steel (0.19C-1.26Si-2.82Mn-0.92Ni, wt %). The effects of the prior hot-rolled microstructure on the optimum quenching temperature of the studied steels were systematically investigated. The microstructure was analyzed by means of transmission [...] Read more.

Quenching and partitioning (Q&P) processes were applied to a cold-rolled high strength steel (0.19C-1.26Si-2.82Mn-0.92Ni, wt %). The effects of the prior hot-rolled microstructure on the optimum quenching temperature of the studied steels were systematically investigated. The microstructure was analyzed by means of transmission electron microscope (TEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). Compared with the ferrite pearlite mixture matrix, the lower martensite start (Ms) temperature and smaller prior austenite grain size in the cold-rolled martensite matrix are the main reasons for the optimum quenching temperature shifting to a lower temperature in the Q&P steels. We found that an empirical formula that only considers the influence of the alloy composition in the calculation of the Ms temperature will cause a certain interference to the pre-determined optimum quenching temperature of the Q&P steel. Full article

(This article belongs to the Special Issue Advanced High Strength Steels by Quenching and Partitioning)

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