The contact angles between three non-metallic inclusion-type oxide substrates, viz. Al2O3, MgO, and MgO·Al2O3, and molten Fe and molten Fe-based stainless steel (Fe-Cr-Ni alloy) were measured using ...the sessile drop method in Ar atmosphere at 1873 K. The contact angles between molten Fe and oxide substrates ranged between 111° and 117°, while that between molten Fe-Cr-Ni alloy and substrates ranged between 103° and 105°. The angles between the alloy and each of the substrates were smaller than the corresponding values for Fe, which was attributed to the superior wettability of molten Fe-Cr-Ni alloy on the substrates. The wettability of the molten materials is related to the interfacial tension between the molten metals and each substrate. Thus, the interfacial tension between the molten metals and the non-metallic substrates was quantitatively evaluated using Young’s equation and the measured contact angles; the interfacial tension for molten Fe ranged from 1.862 to 2.781 N·m−1, while that for molten Fe-Cr-Ni alloy ranged from 1.513 to 2.286 N·m−1. Owing to the higher reactivity between molten Fe-Cr-Ni alloy and the substrates, the interfacial tension and energy between them were lower than those between molten Fe and the substrates.
The contact angles between three non-metallic inclusion-type oxide substrates, viz. Al2O3, MgO, and MgO·Al2O3, and molten Fe and molten Fe-based stainless steel (Fe-Cr-Ni alloy) were measured using ...the sessile drop method in Ar atmosphere at 1873 K. The contact angles between molten Fe and oxide substrates ranged between 111° and 117°, while that between molten Fe-Cr-Ni alloy and substrates ranged between 103° and 105°. The angles between the alloy and each of the substrates were smaller than the corresponding values for Fe, which was attributed to the superior wettability of molten Fe-Cr-Ni alloy on the substrates. The wettability of the molten materials is related to the interfacial tension between the molten metals and each substrate. Thus, the interfacial tension between the molten metals and the non-metallic substrates was quantitatively evaluated using Young’s equation and the measured contact angles; the interfacial tension for molten Fe ranged from 1.862 to 2.781 N·m−1, while that for molten Fe-Cr-Ni alloy ranged from 1.513 to 2.286 N·m−1. Owing to the higher reactivity between molten Fe-Cr-Ni alloy and the substrates, the interfacial tension and energy between them were lower than those between molten Fe and the substrates.
In the current study, the solidification structure, non-metallic inclusions and hot ductility of continuously cast high manganese TWIP steel slab have been investigated and the inclusion formation ...behavior have been revealed by FactSage (CRCT-ThermFact Inc., Montréal, Canada). The area ratio of equiaxed grain zone of the TWIP steel slab is 0.18. Two main types of inclusions in the TWIP steel slab are single AlN particle and AlN+MnS aggregates. It is found that MgAl2O4 and AlN particles can precipitate in the initial solidification stage, which can act as heterogeneous nuclei of other inclusions. In the high temperature tension test, the reduction of area (RA) of the TWIP steel slab samples are higher than 40 pct in the temperature range from 873 K to 1473 K (600°C to 1200°C). Brittle fractures are observed in the fracture surface of the TWIP steel slab samples with dimples. Contents of manganese, carbon, sulfur and phosphorus, strain rate, and dynamic recrystallization (DRX) are factors influencing the hot ductility of TWIP steel slab.
Experiments were carried out to investigate the deformation and fracture of non-metallic inclusions in steel at different temperatures. The deformation of inclusions at high temperature could be ...characterized by viscosity. Meanwhile, the apparent deformation of inclusions at high temperature was also related to the difference of viscosity between inclusions and the steel matrix. Lower inclusion viscosity leads to better deformability when the viscosity of inclusions was smaller than that of steel matrix, otherwise, the inclusion deformation would be limited. The Young's modulus of inclusions could be used to characterize the deformation of inclusions at low temperature. Generally, the deformation of inclusions at low temperature increased with the decrease of Young's modulus. The intrinsic reason for the different characterization parameters of inclusion deformation at different temperatures was supposed to be the brittle to ductile transition phenomenon of inclusions in the process of temperature change. The work provided new ways to control the deformation of inclusions, for instance, by adjusting the temperature and strain rate during the processing of steel.
This paper qualitatively explains the differences in the cathodoluminescence (CL) colors of alumina (Al2O3) inclusions in steels and presents a method of distinguishing MgAl2O4 spinel inclusions from ...other inclusions using CL imaging. It was found that the presence of chromium (Cr) and titanium (Ti) in Al2O3 inclusions increases CL intensity in the red region, while elements that increase oxygen vacancies such as magnesium relatively increase CL intensity in the blue region. We could distinguish MgAl2O4 spinel inclusions, which produce green luminescence, from Al2O3 inclusions by capturing CL images. We were also able to identify MgAl2O4 spinel in an agglomerated inclusion consisting of MgAl2O4 spinel, Al2O3, and MgO from its CL image. Capturing CL images whose wavelength is less than 600nm simplifies the identification of Al2O3 and MgAl2O4 spinel inclusions because all the Al2O3 and MgAl2O4 spinel inclusions produced blue and green luminescence, respectively. The present study suggests that CL image capture is a rapid identification method for inclusions in steels, especially MgAl2O4 spinel and Al2O3 inclusions, because it takes less than 30s to obtain CL images.
Display omitted
•Differences in the CL colors of alumina inclusions in steels are explained.•Cr and Ti in Al2O3 inclusions increase CL intensity in red region.•Elements increasing oxygen vacancies in Al2O3 increase CL intensity in blue region.•Method to distinguish MgAl2O4 spinel inclusions from other inclusions is presented.
An improvement of automatic ultrasonic testing through a double probe technique along the longitudinal bar axis used in a round bar, with a diameter of several millimeters, is proposed. Non-metallic ...inclusions of several tens of micrometers in the cross-sectional length can be detected using this novel technique, whereas the detectability in a conventional normal beam technique is limited to 100–150 µm. The main advantages of this technique are an increased working sensitivity owing to a decreased surface echo width and the use of a shear wave with a shorter wavelength as compared with a conventional normal beam technique. As another advantage of this technique, malfunctions caused by air bubbles in the coupling medium can be eliminated. Further, the beam paths of the surface echo and the bottom echo are discussed herein using the propagation time difference between both echoes in Appendix.
Steel is a critical material in our societies and will remain an important one for a long time into the future. In the last two decades, the world steel industry has gone through drastic changes and ...this is predicted to continue in the future. The Asian countries (e.g. China, India) have been dominant in the production of steel creating global over-capacity, while the steel industry in the developed countries have made tremendous efforts to reinforce its global leadership in process technology and product development, and remain sustainable and competitive. The global steel industry is also facing various grand challenges in strict environmental regulation, new energy and materials sources, and ever-increasing customer requirements for high quality steel products, which has been addressed accordingly by the global iron and steel community.
This Special Issue, “Ironmaking and Steelmaking”, released by the journal Metals, published 33 high quality articles from the international iron and steel community, covering the state-of-the-art of the ironmaking and steelmaking processes. This includes fundamental understanding, experimental investigation, pilot plant trials, industrial applications and big data utilization in the improvement and optimization of existing processes, and research and development in transformative technologies. It is hoped that the creation of this special issue as a scientific platform will help drive the iron and steel community to build a sustainable steel industry.
Determining non-metallic inclusions (NMIs) are essential to engineer ultra-high-strength steel as they play decisive role on performance and critical to probe via conventional techniques. Herein, ...advanced Synchrotron X-ray absorption coupled with photoemission electron microscopy and first-principles calculations are employed to provide the structure, local bonding structure and electronic properties of several NMI model systems and their interaction mechanism within and the steel matrix. B K-, N K-, Ca L2,3- and Ti L2,3-edge spectra show that the additional B prefers to result in h-BN exhibiting strong interaction with Ca2+. Such Ca2+-based phases also stabilize through TiN, revealing the irregular coordination of Ca2+. Observed intriguing no interaction between TiN and BN is further supported with the first-principles calculations, wherein unfavorable combination of TiN and h-BN and stabilization of bigger sized Ca2+-based inclusions have been found. These observations can help to optimize the interaction mechanism among various inclusions as well as steel matrix.
Display omitted
In this article, the industrial experiments of calcium treatment on the modification of inclusions in NM500 wear-resistant steel were carried out. There are four types of inclusions, which are Type A ...of Al2O3 based inclusions, Type C of inclusions containing CaO without S, Type S of inclusions containing S, and Type M of MnS. Three types of CaO·MgO·Al
2
O
3
inclusions after calcium treatment are embedded MgO·Al
2
O
3
+ CaO·Al
2
O
3
, wrapped MgO·Al
2
O
3
+ CaO·Al
2
O
3
and combined CaO·MgO·Al
2
O
3
+ MgO. There are four types of CaO·MgO·Al2O3·CaS inclusions of multilayer MgO·Al
2
O
3
+ CaO·MgO·Al
2
O
3
+ CaS, embedded MgO·Al
2
O
3
+ CaO·Al
2
O
3
+ CaS, wrapped CaO·MgO·Al
2
O
3
+ CaS and composite MgO·Al
2
O
3
+ CaO·Al
2
O
3
+ CaS·CaO·Al
2
O
3
in the steel after calcium treatment.
PDF
