Crystallographic Analysis of Lath Martensite in Ferrite-Martensite Dual Phase Steel Sheet Annealed after Cold-Rolling

Yoshida, Hiromi; Takagi, Shusaku; Sakai, Shota; Morito, Shigekazu; Ohba, Takayoshi

doi:10.2355/isijinternational.isijint-2014-641

Cited by 16 publications

(5 citation statements)

References 19 publications

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“…On the other hand, the pre-formed recrystallized texture was randomized by γ single-phase 2nd-annealing due to the full transformation to austenite [2,3]. The resultant weak γ-fiber, however, suggested the existence of some texture memory effects [4] in the transformed ferrite as well as the martensite phase adjacent to the transformed ferrite grains [5]. (The ODFs from the EBSD analysis were slightly different from those from the X-rays shown in Figure 3.…”

Section: Thermec 2016mentioning

confidence: 90%

Effects of α+γ Intercritical and γ Single-Phase Annealing on Texture Evolution in Cold-Rolled Dual-Phase Steel Sheets

Minami¹,

Kaneko²,

Okuda³

et al. 2016

MSF

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Dual-phase (DP) steel sheets composed of both soft ferritic and hard martensitic phases are typical advanced high strength steel sheets applicable to a variety of automobile parts. The crystallite texture of the steel sheet is one of the important factors that influence press formability. However, the texture of the martensite itself in DP steels has not been discussed since the texture was generally measured by the X-ray diffraction method, which does not distinguish the texture of martensite from that of ferrite. The objective of this study is to investigate the effects of intercritical and γ single-phase annealing on the texture evolution in DP steels by a newly-developed analysis method using Electron Back-Scatter Diffraction (EBSD) to obtain the texture of each phase separately. The chemical composition of the steel used was 0.1%C-1.2%Si-2.3%Mn-0.1%Ti (mass%). The 1st-annealing was carried out at 948K, which is below the Ac1 temperature, in order to finish recrystallization after hot and cold rolling so as to focus on the transformation texture evolution itself. The steels were subsequently annealed both at 1123K in the intercritical region and at 1223K in the γ single-phase region to obtain DP microstructures with approximately 40% volume fraction of martensite. The overall texture including martensite in the case of intercritical annealing was similar to the initial texture before annealing, while the texture became randomized in the case of γ single-phase annealing. Moreover, our unique EBSD analysis method clearly showed that the textures of the martensite themselves were close to those of ferrite under the two annealing conditions.

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Section: Thermec 2016mentioning

confidence: 90%

Effects of α+γ Intercritical and γ Single-Phase Annealing on Texture Evolution in Cold-Rolled Dual-Phase Steel Sheets

Minami¹,

Kaneko²,

Okuda³

et al. 2016

MSF

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“…32) Recent studies on martensite hardening are as follows: Ohlund et al 33) for grain defining, Hidaka et al 34) for carbon in solution, Man et al 35) and Tsuchiyama et al 36) for dislocation hardening, and Ping et al 37) for carbide precipitation. In addition, other studies from various angles, such as crystallography, 38) thermodynamics, 39) elasto-dynamics and mathematical simulations 40) have made significant progress with understanding of martensitic transformation and hardening over the decades. However, these studies do not perfectly clarify the scientific mechanisms of martensite hardening.…”

Section: Influence Of Natural Scientific Understanding Level About Physical Phenomena In Steelmentioning

confidence: 99%

Influence of Understanding of Physical Phenomena in Materials on Supply Chain Patterns of Steel Products

Nishio

Fujimura

2020

ISIJ Int.

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In this study, supply chain patterns of steel products are investigated from the viewpoints of quality assurance responsibility and understanding of physical phenomena in steel. This study focuses on the differences in supply chain patterns between steel nails for common use and valve springs for the automotive industry. In the supply chain of steel nails for common use, which takes a conventional pattern from raw materials to final products, the quality of each supplier's product is guaranteed just by the Japanese Industrial Standards (JIS), and no supplier takes quality assurance responsibilities beyond its business range. By contrast, in the supply chain of valve springs for automotive use, each supplier takes quality assurance responsibilities for the final product beyond its business range, and the suppliers cooperate with one another to fulfill stringent quality requirements by automotive manufacturers. Therefore, the supply chain pattern of valve springs is different from the conventional pattern of common use steel products like steel nails. It was also found that the supply chain pattern of valve springs can be caused by the insufficient understanding of physical phenomena in steel, martensitic transformation and hardening in this case. This study suggests that the conditions that determine the supply chain pattern of a steel product could be business practices for quality assurance, namely based on standard specifications or users' requirements, and the natural scientific understanding level about physical phenomena in steel. Although this study focuses on steel nails and valve springs, this finding is applicable to other steel products.

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“…8(b) are represented on the {001} and {011} pole figures. Because the crystal orientation relationship of the martensitic blocks and the adjacent ferrite had a common {011} pole, having a so-called close-packed plane parallel relationship, 12) it was assumed that they had a common Bain axis (B1). 13) The deviation of the common rotation axis between the martensitic blocks and the adjacent ferrite was small, being less than 3°.…”

Section: Effect Of Intercritical and γ Single-phase Annealing On Textmentioning

confidence: 99%

Effects of α+γ Intercritical and γ Single-Phase Annealing on Martensitic Texture Evolution in Dual-Phase Steel Sheets

Minami¹,

Okuda²,

Kaneko³

et al. 2018

ISIJ Int.

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Dual-phase (DP) steel sheets composed of soft ferrite and hard martensite phases are typical advanced high strength steel sheets applicable to a variety of automobile parts. The crystallite texture of steel sheets is an important factor which influences the press formability. However, the texture of the martensite itself in DP steel sheets has not been discussed, since the texture was generally measured by the X-ray diffraction method, which does not distinguish the texture of martensite from that of ferrite. The objective of this study is to investigate the texture evolution behavior of each compromising phase; especially the martensite phase, in DP steel sheets by a newly-developed analysis method using Electron Back-Scatter Diffraction (EBSD). The chemical composition of the steel used was 0.088%C-1.23%Si-2.29%Mn-0.093%Ti (mass%). The two sequent annealing was conducted, changing the second annealing temperature, both in the intercrtical region and in the γ single-phase region. The obtained DP microstructures were controlled to have the same volume fraction of martensite of approximately 40%. The overall texture including martensite after the intercritical annealing was similar to the texture before 2nd-annealing, while the texture after the γ single-phase annealing became weak. The new analysis technique using OIM clearly revealed that the discriminate textures from only martensite were close to, but slightly weaker than those of ferrite under the two annealing conditions.

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Crystallographic Analysis of Lath Martensite in Ferrite-Martensite Dual Phase Steel Sheet Annealed after Cold-Rolling

Cited by 16 publications

References 19 publications

Effects of α+γ Intercritical and γ Single-Phase Annealing on Texture Evolution in Cold-Rolled Dual-Phase Steel Sheets

Effects of α+γ Intercritical and γ Single-Phase Annealing on Texture Evolution in Cold-Rolled Dual-Phase Steel Sheets

Influence of Understanding of Physical Phenomena in Materials on Supply Chain Patterns of Steel Products

Effects of <i>α</i>+<i>γ</i> Intercritical and <i>γ</i> Single-Phase Annealing on Martensitic Texture Evolution in Dual-Phase Steel Sheets

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