National Institute of Standards and Technology における超伝導研究及び生活

Steel slag in China: Treatment, recycling, and management.

Advancement of semiconductor devices requires the realization of an ultrathin diffusion barrier layer between Cu interconnect and insulating layers. The present work investigated the possibility of the self-forming barrier layer in Cu–Mn alloy thin films deposited directly on SiO2. After annealing at 450 °C for 30 min, a Mn containing amorphous oxide layer of 3–4 nm in thickness was formed uniformly at the interface. Residual Mn atoms were removed to form a surface oxide layer, leading to a drastic resistivity decrease of the film. No interdiffusion was detected between Cu and SiO2 within the detection limit of x-ray energy dispersive spectroscopy.

Self-forming diffusion barrier layer in Cu–Mn alloy metallization

On the influence of active element content on the thermal conductivity and thermal expansion of Cu-X (X = Cr, B) diamond composites

The latest publications regarding the development of technology to control inclusion compositions focusing on MgO·Al2O3 spinel inclusions were summarized in this review article. The problems caused by spinel inclusions, which affect practice as well as products were shown. The formation mechanism of MgO·Al2O3 spinel inclusions is secondly explained thermodynamically from the view points of chemistries of molten steels and slag compositions. Furthermore, crystallization behaviour of spinel was introduced. Countermeasures conducted in practices and laboratories were shown along with some problems still left that should be solved in the future.

https://www.jstage.jst.go.jp/article/isijinternational/50/10/50_10_1333/_pdf

Control of MgO·Al2O3 Spinel Inclusions in Stainless Steels

The nonmetallic spinel inclusion, MgOzAl2O3, has a high melting point and produces an undeformed C-type inclusion in steel products. Therefore, it is very harmful in the production of high grade wire, spring, and bearing steels. Thus, it is necessary to develop a methodology by which we can predict the occurrence of such defects. The thermodynamics of the formation of spinel nonmetallic inclusions during co-deoxidation with aluminum and magnesium is discussed in the present work. Previous literature thermodynamic values for strong deoxidizers such as aluminum, magnesium, and calcium are not in good agreement with the observed results and measurements. This discrepancy between predicted and measured results is due to an incomplete expression of the activities of dissolved oxygen and deoxidizers in current literature. Namely, only first-order interaction parameters are available despite the very strong interactions among the dissolved elements. In the present work, the deoxidation equilibrium with magnesium in liquid iron was studied in order to evaluate the activities of oxygen and dissolved magnesium and, include in the thermodynamic description, the firstand second-order interaction parameters, including the cross-product terms. A dolomite crucible was used to enhance the magnesium content in liquid iron in the present experiment on thermodynamics of spinel formation with reference to the study on desulfurization with a dolomite crucible undertaken by Ototani et al.[1] The assessment of aluminum-oxygen equilibrium in liquid iron reported by other investigators was also reviewed to develop values for the second-order interaction parameters. Finally, thermodynamic data on calcium deoxidation equilibrium were obtained. The iron sample was melted by a high frequency induction furnace. Iron of about 90 grams was charged into a crucible. The added weight of a deoxidizer such as magnesium and calcium was 1 mass pct of the weight of iron. The experimental procedure is briefly shown as follows. After the iron melted under a gas flow of a mixture of Ar-50 vol pct H2, hydrogen was impinged onto the melt surface to reduce dissolved oxygen content until it was less

Thermodynamics on the Formation of Spinel Nonmetallic Inclusion in Liquid Steel

Spinel (MgO.Al 2 O 3 ) is known as one of the most harmful non-metallic inclusions in steel. However, the technology to avoid spinel formation has not yet been established due to lack of thermodynamic information on the spinel itself. In the present work, the free energies of formation of MgO and MgO.Al 2 O 3 , and the activities of the constituents in spinel solid solution have been directly measured by the chemical equilibrium technique. The free energies of formation of MgO and MgO.Al 2 O 3 determined in the present work are expressed by the following equation: Mg(l)+1/2 O 2 (g)=MgO(s) ΔG°f,MgO=-669 350+135.0T (J/mol) Al 2 O 3 (s)+MgO(s)=MgO.Al 2 O 3 (s) ΔG°f,MgO.Al2O 3 =-20 790-15.7T (J/mol) The activity of stoichiometric MgO.Al 2 O 3 exhibits negative deviation from ideality in the spinel solid solution. Phase stability diagram of spinel formation in liquid steel was assessed as a function of aluminum, magnesium and oxygen contents in iron at 1 873 K. The predicted phase boundaries of MgO.Al 2 O 3 , MgO and Al 2 O 3 agreed well with previous observations by one of the present authors.

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Activities of the constituents in spinel solid solution and free energies of formation of MgO, MgO.Al2O3

https://www.jstage.jst.go.jp/article/tetsutohagane1955/83/12/83_12_773/_pdf

Assessment of Al Deoxidation Equilibrium in Liquid Iron

Heat transfer in continuous casting mold is important to decide the surface quality of the cast slab of middle carbon steel. Many researchers have recently studied the mechanism of reducing the heat transfer between the mold and the solidified shell, and some of them have pointed out that the interfacial thermal resistance between the mold and surface of solidified mold flux has caused decreasing heat transfer. In the present study, the surface roughness of solidified mold fluxes used for low carbon and middle carbon steel casting, Na2O-CaO-SiO2 and Li2O-CaO-SiO2 slag systems, was measured by a confocal scanning laser microscope combined with an infrared image furnace. It was found that the surface roughness was in the range of approximately 10-30 μm when the crystalline phase precipitated. Furthermore, the faster the cooling rate, the smoother the surface roughness of the solidified mold flux became. In the contrast, the surface roughness of the slag, of which critical cooling rate is faster, increased. The surface roughness of the mold flux for middle carbon steel casting became rougher than that for low carbon steel casting. As a result, the surface roughness was related to normalized cooling rate, which is the ratio of actual experimental cooling rate to critical cooling rate. The experimental data of surface roughness were fairly in agreement with calculated values on the assumption of one dimensional heat transfer in the continuous casting mold.

https://www.jstage.jst.go.jp/article/isijinternational1989/39/11/39_11_1150/_pdf

Mitsutaka Hino

Papers

Thermodynamics on the Formation of Spinel Nonmetallic Inclusion in Liquid Steel

Activities of the constituents in spinel solid solution and free energies of formation of MgO, MgO.Al2O3

Assessment of Al Deoxidation Equilibrium in Liquid Iron

Surface Roughness of Solidified Mold Flux in Continuous Casting Process

Thermodynamics on the Formation of Non-metallic Inclusion of Spinel (MgO·Al2O3) in Liquid Steel