Influence of Warm Tempforming on Microstructure and Mechanical Properties in an Ultrahigh-Strength Medium-Carbon Low-Alloy Steel

Kimura, Yuuji; Inoue, Tatsuo

doi:10.1007/s11661-012-1391-2

Cited by 52 publications

(82 citation statements)

References 61 publications

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“…Such bimodal carbide particle distributions might be inherited from those in the tempered martensitic structure. 5) The dAV of the transgranular and intergranular carbide particles were measured to be 15 nm and 37 nm at 0.2% C, 16 nm and 42 nm at 0.43% C, and 22 nm and 46 nm at 0.6% C, respectively; they became slightly larger as the carbon content increased. The respective average aspect ratios of the transgranular and intergranular carbide particles were approximately 1.3 and 1.6 in all the TF samples; the transgranular carbides were more spherical than the intergranular carbides.…”

Section: Microstructuresmentioning

confidence: 96%

“…8) The analysis conditions for the FE-SEM/EBSP technique and ρ estimation in the XRD are described in detail elsewhere. 5,9) The integrated intensities of the (110) XRD peaks (Im) were measured on the RD planes for the TF samples, and the ratio of Im to the integrated intensity of the (110) XRD peak (Is), for a standard sample was measured to evaluate the development of the <110>//RD fiber texture. The carbide particle size was measured by transmission electron microscopy (TEM).…”

Section: Microstructural Characterization and Mechanicalmentioning

confidence: 99%

“…The present authors [4][5][6] have developed a warm tempforming (WTF) process in order to achieve the toughening of ultrahigh-strength low-alloy steel bars. When the WTF was performed on medium-carbon low-alloy steels such as 0.39%C-2%Si-1%Cr-1%Mo steel 4,5) and 0.6%C-2%Si-1%Cr steel, 6) using multi-pass caliber rolling at 773 K with a rolling reduction of 78%, UFEG structures with strong <110>//RD fiber textures were formed.…”

Section: Introductionmentioning

confidence: 99%

“…When the WTF was performed on medium-carbon low-alloy steels such as 0.39%C-2%Si-1%Cr-1%Mo steel 4,5) and 0.6%C-2%Si-1%Cr steel, 6) using multi-pass caliber rolling at 773 K with a rolling reduction of 78%, UFEG structures with strong <110>//RD fiber textures were formed. The steels with the UFEG structures demonstrated an inverse temperature dependence of toughness; the Charpy absorbed energy (vE) increased with decreasing test temperature in the subzero temperature range, in which ultrahigh-strength low-alloy steels usually undergo a ductile-to-brittle transition (DBT).…”

Section: Introductionmentioning

confidence: 99%

“…[4][5][6] It was clear that the transverse grain size, the grain shape and the <110>//RD fiber texture in the UFEG structure were the dominant microstructural factors in controlling the delamination. [4][5][6][7] Furthermore, the carbon content may influence the microstructural features of the UFEG structures and the occurrence of delamination for the warm tempformed steels; however systematic investigation on this subject has not yet been conducted.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Carbon Content on Toughening in Ultrafine Elongated Grain Structure Steels

Kimura

Inoue

2015

ISIJ International

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(0.2-0.6)%C-2%Si-1%Cr-1%Mo steels were quenched and tempered at 773 K and deformed by multipass caliber rolling (i.e. warm tempforming) with a rolling reduction of 78%, in order to obtain ultrafine elongated grain (UFEG) structures. The tensile and Charpy impact properties of the warm tempformed (TF) steels were investigated to determine the influence of the carbon content on toughening in the UFEG structures. The TF samples consisted of UFEG structures with strong <110>//rolling direction (RD) fiber textures. The transverse grain size and aspect ratio in the UFEG structure tended to reduce as the carbon content increased, whilst the carbide particle size became slightly larger. The increase in the carbon content resulted in an increase in the yield strength from 1.68 to 1.95 GPa at room temperature; however, it was accompanied by a loss of tensile ductility. In contrast to quenched and tempered samples exhibiting ductile-to-brittle transitions, the TF samples exhibited inverse temperature dependences of the impact toughness. This was due to delaminations, where cracks were observed to branch in the longitudinal direction (//RD) of the impact test bars. The upper-shelf energy of the TF sample was enhanced as the carbon content decreased, and higher absorbed energy was also achieved as delamination occurred at lower temperatures. The delamination was found to be controlled not only by the transverse grain size, the grain shape, and the <110>//RD fiber texture but also by carbide particle distribution in the UFEG structure.

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Section: Microstructuresmentioning

confidence: 96%

Section: Microstructural Characterization and Mechanicalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of Carbon Content on Toughening in Ultrafine Elongated Grain Structure Steels

Kimura

Inoue

2015

ISIJ International

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Strengthen and Toughen the Low‐Alloyed Steel by Direct Tempforming

et al. 2022

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Improving strength without sacrificing toughness is a permanent request for the development of advanced engineering materials. Herein, a novel energy‐saving strategy is developed to obtain strong but tough low‐alloyed steels. A medium‐carbon steel (42CrMo) is used for demonstration. Warm deformation (tempforming) is applied to the hot‐rolled and air‐cooled 42CrMo steel. After tempforming, the microstructure consists of nano‐sized carbides and highly textured ultrafine grains. The tensile strength of the tempformed steels can reach 1.2 GPa, while the impact toughness is higher than 100 J even at temperatures as low as −80 °C, which are one order of magnitude higher than the counterpart steel after tempering. The present work sheds light on the design and fabrication of high‐performance engineering steels with an excellent combination of strength and toughness.

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High‐Strength and High‐Ductility Nanostructured and Amorphous Metallic Materials

2014

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The development of materials with dual properties of high strength and high ductility has been a constant challenge since the foundation of the materials science discipline. The rapid progress of nanotechnology in recent decades has further brought this challenge to a new era. This Research News highlights a few newly developed strategies to optimize advanced nanomaterials and metallic glasses with exceptional dual mechanical properties of high strength and high ductility. A general concept of strain non-localization is presented to describe the role of multiscale (i.e., macroscale, microscale, nanoscale, and atomic scale) heterogeneities in the ductility enhancement of materials reputed to be intrinsically brittle, such as nanostructured metallic materials and bulk metallic glasses. These nanomaterials clearly form a new group of materials that display an extraordinary relationship between yield strength and the uniform elongation with the same chemical composition. Several other examples of nanomaterials such as those reinforced by nanoprecipitates will also be described.

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Influence of Warm Tempforming on Microstructure and Mechanical Properties in an Ultrahigh-Strength Medium-Carbon Low-Alloy Steel

Cited by 52 publications

References 61 publications

Influence of Carbon Content on Toughening in Ultrafine Elongated Grain Structure Steels

Influence of Carbon Content on Toughening in Ultrafine Elongated Grain Structure Steels

Strengthen and Toughen the Low‐Alloyed Steel by Direct Tempforming

High‐Strength and High‐Ductility Nanostructured and Amorphous Metallic Materials

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