Combination of In Situ Microscopy and Calorimetry to Study Austenite Decomposition in Inclusion Engineered Steels

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The quantitative analysis of inclusion and microstructure characteristics in the steels with TiN additions has been studied. The typical inclusion was detected to be a TiN + Mn‐Al‐Si‐Ti‐O + MnS phase. This identification was based on the measurements of scanning electron microscopy with energy‐dispersive X‐ray spectrometer (SEM‐EDS), electron probe microanalysis (EPMA), which equipped wavelength‐dispersive X‐ray spectroscopy (WDS), and equilibrium calculations by using the commercial software Thermo‐Calc. TiN was found to be the effective nucleation site for the formation of intragranular ferrite (IGF). Furthermore, the increased inclusion size led to the increased probability of IGF nucleation. In addition, this probability of IGF nucleation was slightly decreased with the increased sulfur content. This tendency could fit the tendency of the area fraction of IGF in the steels containing different sulfur contents.

Section: Introductionmentioning

confidence: 99%

Inclusion and Microstructure Characteristics in Steels with TiN Additions

Jönsson

Shibata

et al. 2015

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“…However, only the second peak could be observed in the Fe–0.4 mass% C alloy. In our previous study, the first peak is identified as the ferrite formation, and the second peak is identified as the pearlite formation. It is also noted that the second peak in the Fe–0.4 mass% C alloy increases sharply with the increase of the carbon content.…”

Section: Discussionmentioning

confidence: 96%

“…The DSC apparatus was used, as was reported by Nakajima et al, Zhang et al, and Mu et al During the sample preparation, the steel specimens were cut into small discs (4.1 mm in diameter and 1 mm in depth). Therefore, the disc shape sample was set into an alumina crucible (Ф 5.5 mm O.D.…”

Section: Methodsmentioning

confidence: 99%

“…The microstructure and inclusion characteristics in the steels were investigated by using electron backscatter diffraction (EBSD) and electron probe microanalysis (EPMA) . In addition, the continuous cooling formation (CCT) diagram for detecting the IGF, GBF, and pearlite formation was plotted based on the data from CLSM and differential scanning calorimetry (DSC) measurements …”

Section: Introductionmentioning

confidence: 99%

“…[7] In addition, the continuous cooling formation (CCT) diagram for detecting the IGF, GBF, and pearlite formation was plotted based on the data from CLSM and differential scanning calorimetry (DSC) measurements. [8] Besides the effect of the inclusion composition on the IGF formation, the element contents in the steels, such as sulfur and carbon, also affect the IGF formation. The effect of the sulfur content on the inclusion and microstructure characteristics has already been discussed in our previous study.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Carbon Content on the Potency of the Intragranular Ferrite Formation

Mao

Jönsson

et al. 2015

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The effect of the carbon content on the potency of the intragranular ferrite (IGF) formation for each inclusion size is investigated in the present work. The TiN inclusion was detected to be the effective nucleation site for the IGF formation in the Fe–0.2 mass% C alloy and the Fe–0.4 mass% C alloy. It is noted that the potency of the IGF formation for each inclusion size is decreased with the increase of carbon content. Moreover, the critical diameters of the TiN, TiO, and VN inclusions in the steels with different carbon contents are calculated based on the classical nucleation theory. The calculated critical diameter is also found to be decreased with the increase of carbon content. This is in agreement with the experiment results. Finally, the decrease of the potency of IGF formation for each inclusion size is due to a larger amount of pearlite formation in the steel containing a higher carbon content, which is detected by differential scanning calorimetry (DSC) measurements.

Combination of In Situ Confocal Microscopy and Calorimetry to Investigate Solidification of Super‐ and Hyper‐Duplex Stainless Steels

Wang

Sukenaga

Shibata

et al. 2023

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The solidification processes of super‐ and hyper‐duplex stainless steels (i.e., UNS S32750 and S 33 207) are investigated in situ by a high‐temperature confocal laser scanning microscope (HT‐CLSM) and differential scanning calorimetry (DSC). The variations of δ‐ferrite phase fraction during solidification are measured quantitatively. The results show that liquid L→δ‐ferrite transformation first occurs at a certain degree of supercooling during the solidification process of steel. UNS S3DSS 3207 with a higher Cr content can result in a higher nucleation temperature and faster growth of δ‐ferrite compared to those of UNS S332750 steel. Moreover, both the liquidus (TL) and solidus temperatures (TS) are increased with the increasing Cr content, while TL increases greater than TS. Electron microscopies are used to quantify the fraction and composition of each phase. Scheil equation is employed to predict the distribution behavior of the main alloying elements in the solidification process, and the predicted results are consistent with the experimental findings. This study aims to provide real‐time experimental insights into the solidification kinetics of state‐of‐the‐art high‐alloy‐grade duplex steels and benefits for controlling the casting process in the real production of stainless steels.