Cementite

Bhadeshia, H. K. D. H.

doi:10.1080/09506608.2018.1560984

Cited by 110 publications

(57 citation statements)

References 188 publications

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“…Therefore, in the low-temperature region, the most stable clusters in the melt are formed on the basis of cementite Fe 3 C, which has a melting point of 1923 K [30]. Iron in cementite can be replaced by Mn or other transition metals [31].…”

Section: Resultsmentioning

confidence: 99%

Thermophysical Properties of Pipe Steel in the Liquid State

Цепелев

Starodubtsev

Tsepeleva

2021

Metals

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The temperature dependences of the kinematic viscosity and surface tension of liquid pipe steel with different modes of melt preparation were investigated. A transition zone was found on the temperature dependences of the thermophysical properties, which separates the regions with different activation energies of viscous flow and surface tension. At the heating stage in the transition zone, the thermal decomposition of clusters based on cementite Fe3C occurs. As a result of the decomposition, free carbon atoms appear which tend to give a uniform distribution in liquid iron with increasing temperature. At a low content of alloying elements and impurities, a high-temperature melt should have a large-scale cluster structure, which provides a more uniform distribution of chemical elements. The melt after vacuum degassing has a narrow transition zone near 1920 K, in contrast to the wide transition zone of the melt without vacuum degassing. The wider transition zone is shifted to high-temperature and this shift is associated with the thermal decomposition of carbides and oxides. Studies have shown that heating liquid pipe steel above the temperature of the liquid–liquid structural transition makes it possible to obtain a more homogeneous structure with a more uniform distribution of alloying and impurity elements in the melt. The sharp drop in surface tension at temperatures above 1920 K in the melt without vacuum degassing is associated with the diffusion of free S and O atoms, which are released after thermal decomposition of sulfides and oxides.

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Section: Resultsmentioning

confidence: 99%

Thermophysical Properties of Pipe Steel in the Liquid State

Цепелев

Starodubtsev

Tsepeleva

2021

Metals

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“…Upper limit of the shape anisotropy ( K d ) estimated from the dependence

, which is valid for non-interacting particles having an oblate spheroidal shape (b >> a) [ 46 , 48 ] and lower limit calculated for prolate nanoparticles

[ 47 ]. Density for cementite: 7.6 g/cm 3 [ 49 , 50 ] . In parentheses, K d values are given for weighted average density: 6.5 g/cm 3 ; in this case 5.3 g/cm 3 for Fe 2 O 3 , ~4.0 g/cm 3 for ferrihydrates [ 51 ], 7.9 g/cm 3 for Fe, and 7.6 g/cm 3 for Fe 3 C. Contributions of these iron phases were taken from the Mössbauer spectra at 85K ( Table S1 ).…”

Section: Figurementioning

confidence: 99%

Effect of Grinding and the Mill Type on Magnetic Properties of Carboxylated Multiwall Carbon Nanotubes

et al. 2021

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The influence of the grinding process on the magnetic properties of as prepared and functionalized multiwall carbon nanotubes (MWCNTs) is presented. We have observed that 3 h mechanical grinding at 400 rpm in contrast to functionalization does not remove the iron contamination from MWCNTs. However, it changes the Fe chemical states. The magnetic properties of iron nanoparticles (Fe-NPs) embedded in the carbon matrix of MWCNTs have been analyzed in detail. We have proven that single-domain non-interacting Fe(C,O)-NPs enriched in the Fe3C phase (~10 nm) enclosed inside these nanotubes are responsible for their magnetic properties. Mechanical grinding revealed a unique impact of -COOH groups (compared to -COONH4 groups) on the magnetism of functionalized MWCNTs. In MWCNT-COOH ground in a steel mill, the contribution of the Fe2O3 and α-Fe phases increased while the content of the magnetically harder Fe3C phase decreased. This resulted in a 2-fold coercivity (Hc) decrease and saturation magnetization (MS) increase. A 2-fold remanence (Mr) decrease in MWCNT-COOH ground in an agate mill is related to the modified Fe(C,O)-NP magnetization dynamics. Comparison of the magnetostatic exchange and effective anisotropy length estimated for Fe(C,O)-NPs allows concluding that the anisotropy energy barrier is higher than the magnetostatic energy barrier. The enhanced contribution of surface anisotropy to the effective anisotropy constant and the unique effect of the -COOH groups on the magnetic properties of MWCNTs are discussed. The procedure for grinding carboxylated MWCNTs with embedded iron nanoparticles using a steel mill has a potential application for producing Fe-C nanocomposites with desired magnetic properties.

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“…Meteoric irons, known as Fe–Ni alloys with various nickel contents from a minimum of 5 up to 60 mass%, can be classified into several types exhibiting different microstructural features based on their overall nickel content 1 . The main phases of meteoric iron are kamacite with a body-centred cubic (BCC) structure, taenite with a face-centred cubic (FCC) structure, and cohenite with an orthorhombic structure, which correspond to α-ferrite, γ-austenite, and Fe 3 C cementite in artificial steel, respectively 2 – 6 . The unique microstructure of meteoric iron is formed by the nucleation and growth of kamacite from taenite during the slow cooling of the parent body 1 , with the cooling period for a 1 K temperature decrease estimated as a few hundred to thousands of years 1 .…”

Section: Introductionmentioning

confidence: 99%

Excellent mechanical properties of taenite in meteoric iron

Ueki

Mine

Takashima

2021

Sci Rep

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Meteoric iron is the metal that humans first obtained and used in the earliest stage of metal culture. Advances in metallographic analysis techniques have revealed that meteoric iron largely comprises kamacite, taenite, and cohenite, which correspond to ferrite, austenite, and cementite in artificial steel, respectively. Although the mechanical properties of meteoric irons were measured previously to understand their origin and history, the genuine mechanical properties of meteoric iron remain unknown because of its complex microstructure and the pre-existing cracks in cohenite. Using micro-tensile tests to analyse the single-crystalline constituents of the Canyon Diablo meteorite, herein, we show that the taenite matrix exhibits excellent balance between yield strength and ductility superior to that of the kamacite matrix. We found that taenite is rich in nitrogen despite containing a large amount of nickel, which decreases the nitrogen solubility, suggesting that solid-solution strengthening via nitrogen is highly effective for the Fe–Ni system. Our findings not only provide insights for developing advanced high-strength steel but also help understand the mysterious relationship between nitrogen and nickel contents in steel. Like ancient peoples believed that meteoric iron was a gift from the heavens, the findings herein imply that this thought continues even now.

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Cementite

Cited by 110 publications

References 188 publications

Thermophysical Properties of Pipe Steel in the Liquid State

Thermophysical Properties of Pipe Steel in the Liquid State

Effect of Grinding and the Mill Type on Magnetic Properties of Carboxylated Multiwall Carbon Nanotubes

Excellent mechanical properties of taenite in meteoric iron

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