著者

Takehiko TOH Hideaki YAMAMURA Hiroyuki KONDOH Masamitsu WAKOH Eiichi TAKEUCHI

出版者

一般社団法人 日本鉄鋼協会

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.45, no.7, pp.984-990, 2005 (Released:2006-01-27)

参考文献数

14

被引用文献数

4 8 4

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Fusion of metals in a cold crucible is known as a clean melting method without contamination by refractory. For this reason, it is commonly applied to the fusion of high melting point metals or reactive materials. As the usage of the clean melting function, this technique is also applied to the cleanliness assessment method as an advanced technique of electron beam melting method.In this paper, oxide inclusions behavior in a cold crucible levitation melting of steel is discussed through fundamental experiments and numerical simulations in order to clarify the inclusions behavior during the fusion. Experiments showed a rapid removal of oxides from the bulk molten metal to the sample surface without remarkable change in shape and size distribution of contained oxides. Numerical analyses revealed the dominant factors of this phenomenon, and explained the reason why the size distribution of oxides does not change during the fusion.

著者

Walter NICODEMI Carlo MAPELLI Roberto VENTURINI Riccardo RIVA

出版者

一般社団法人 日本鉄鋼協会

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.45, no.9, pp.1358-1367, 2005 (Released:2006-01-27)

参考文献数

16

被引用文献数

6 8 6

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This study aims at casting new light about the knowledge of the metallurgical techniques developed by the Etruscan and the Romans during their political and cultural interactions in Central Italy. The analysis of two weapons found at the Etruscan sites of Vetulonia and Chiusi have pointed out some new information about the production process performed. The optical microscopy analysis has allowed to identify the sequence of the microstructural constituents present in the two ancient weapons. SEM-EDS has permitted to identify the chemical composition of the non metallic inclusion and to estimate the average temperature of the reduction process. The analysis of the metal matrix performed by a coupled argon plasma spectrometer permitted to measure the average chemical compositions of the studied alloys. SEM-EBSD analysis has allowed to identify the crystallographic textures present within the different zones of the sword blades and this has indicated the realization of a forming process that gave interesting mechanical properties to the metal products. The results obtained by the Etruscans artisans were of very high standard quality and their production system had been certainly assimilated by the Romans who found in them a strategic factor to increase their power.

著者

Gregory Poole Nagy El-kaddah

出版者

一般社団法人 日本鉄鋼協会

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.54, no.2, pp.321-327, 2014-02-15 (Released:2014-03-11)

参考文献数

34

被引用文献数

2 12

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This paper examines the role of induction coil design on stirring of molten metal in electromagnetic (EM) solidification processes. A model is presented to describe the EM, heat transfer, and fluid flow phenomena in these processes. It is based on a dual-zone description of the mushy region, and accounts for damping of turbulence by the solidified crystallites. The electromagnetic field equations were solved using the mutual inductance technique, while the temperature and turbulent flow fields were calculated using the control volume method. Calculations were performed for solidification of an Al–Cu alloy placed in a stationary magnetic field generated by an induction coil. The effect of coil design on the flow structure was investigated for three different coil positions. It was found that changing the coil position significantly alters the flow pattern from four recirculating loops when the coil is above the midsection of the melt to two loops, typical of a travelling magnetic field, when the coil is at the base of the melt. This significantly modifies the rate of solidification across the ingot, as well as the temperature gradient, in the mushy region. The decay of the velocity and turbulent fields in the mushy region was found to be exponential, with the maximum rate of decay at the solidification front. These results indicate that through changes in coil design, it is possible to control the flow characteristics and solidification behavior in the molten metal.

著者

Tomohiro Takaki

出版者

一般社団法人 日本鉄鋼協会

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.54, no.2, pp.437-444, 2014-02-15 (Released:2014-03-11)

参考文献数

200

被引用文献数

18 162 32

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The phase-field method has recently emerged as the most powerful computational tool for simulating complicated dendrite growth. However, these simulations are still limited to two-dimensional or small three-dimensional spaces; therefore, to realistic and practical dendritic structures, it is crucial to develop a large-scale phase-field simulation technique. This review discusses the phase-field modeling and simulations of dendrite growth from the fundamental model to cutting-edge very-large-scale simulations. First, phase-field models for the dendrite growth of pure materials and binary alloys and their histories are summarized. Then, models and studies of interface anisotropy, polycrystalline solidification, and solidification with convection, which are very important in dendritic solidification, are reviewed. Finally, by introducing very-large-scale phase-field simulations performed recently using a graphics processing unit supercomputer, the power, potential and importance of the very-large-scale phase-field simulation are emphasized.

著者

Huseyin Aydin Elhachmi Essadiqi In-Ho Jung Stephen Yue

出版者

一般社団法人 日本鉄鋼協会

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.53, no.10, pp.1871-1880, 2013-10-15 (Released:2013-10-30)

参考文献数

22

被引用文献数

1 5

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In the present work, the effects of intercritical annealing parameters on the microstructure and cold rollability (deformation rate and ratio) of “3rd Generation Advanced High Strength Steels (AHSS)” were studied. Hence, this paper discusses the formation of microstructures with different volume fractions of ferrite, martensite, bainite and retained austenite (RA). Two novel microstructures have been created, based on two levels of manganese (Mn): (i) ferrite plus martensite nucleated in austenite microstructure (FMNA structures), using Mn levels of 5 to 7 wt% and (ii) ferrite plus retained austenite duplex structure (FADP steels) for a Mn level of 10 wt%. In general, the ductility is a function of the amount of retained austenite and the strength is highly dependent on the martensite level.

著者

Yoshimasa Funakawa Tsuyoshi Shiozaki Kunikazu Tomita Tetsuo Yamamoto Eiji Maeda

出版者

一般社団法人 日本鉄鋼協会

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.44, no.11, pp.1945-1951, 2004-11-15 (Released:2007-05-31)

参考文献数

24

被引用文献数

132 444

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A ferritic steel precipitation-strengthened by nanometer-sized carbides was developed to obtain a high strength hot-rolled sheet steel having tensile strength of 780 MPa grade with excellent stretch flange formability. Manganese in a content of 1.5% and molybdenum in a content of 0.2% were added to 0.04% carbon Ti-bearing steel in order to lower austenite-ferrite transformation temperature for fine carbides and to retard generating of pearlite and large cementites, respectively. Tensile strength of hot-rolled sheet steel increased with titanium content and it was achieved to 800 MPa in a 0.09% Ti steel. Microstructure of the 0.09%Ti steel was ferrite without pearlite and large cementites. Fine carbides of 3 nm in diameter were observed in rows in the ferrite matrix of the 0.09% Ti steel with transmission electron microscope. The characteristic arrangement of the nanometer-sized carbides indicates that the carbides were formed at austenite-ferrite interfaces during transformation. By energy dispersive X-ray spectroscopy, the carbides were found to contain molybdenum in the same atomic concentration as titanium. Crystal structure of the nanometer-sized carbides was determined to be NaCl-type by X-ray diffractometry. The calculated amount of precipitation-strengthening by the carbides was approximately 300 MPa. This is two or three times higher than that of conventional Ti-bearing high strength hot-rolled sheet steels.Based on the results obtained in the laboratory investigation, mill trial was carried out. The developed hot-rolled high strength sheet steel exhibited excellent stretch flange formability.

著者

Noriyuki Tsuchida Taiji Kawahata Eiichiro Ishimaru Akihiko Takahashi Hiroshi Suzuki Takahisa Shobu

出版者

一般社団法人 日本鉄鋼協会

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.53, no.7, pp.1260-1267, 2013 (Released:2013-08-20)

参考文献数

27

被引用文献数

3 26

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To investigate the tensile deformation behavior of a lean duplex stainless steel (S32101) from the viewpoints of plastic deformability among phases or grains, we performed static tensile tests, in situ neutron diffraction, and white x-ray diffraction experiments at room temperature. In the static tensile tests, the S32101 steel displayed a larger uniform elongation and a better tensile strength–uniform elongation balance than a commercial SUS329J4L duplex stainless steel. A larger uniform elongation of S32101 is associated with the macroscopic work hardening behavior that a work hardening rate higher than the flow stress can maintain up until high true strains. From the experimental results of synchrotron radiation white x-ray diffraction experiments, the hard phase of S32101 was changed from the ferrite (α) phase to austenite (γ) one during tensile deformation. This led to a larger stress partitioning between the phases at the latter stage of deformation. From the experimental results of in situ neutron diffraction, it was found that the stress partitioning of the γ phase in the S32101 was the largest among the present results. Therefore, the larger work hardening rate of S32101 can be explained by the large stress partitioning of the γ phase, that between γ and α phases and γ volume fraction.

著者

Nirsanametla Yadaiah Swarup Bag

出版者

一般社団法人 日本鉄鋼協会

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.52, no.11, pp.2069-2075, 2012 (Released:2012-11-15)

参考文献数

40

被引用文献数

5 39

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Double-ellipsoidal volumetric heat with Gaussian distribution of heat intensity is one of the most popular heat source model used in fusion welding process simulations. However, the major difficulty of this kind of heat source model is to define the parameters before start of simulation. It is common practice to define the heat source parameters from experimental measurement of weld dimensions for a particular welding condition that meet the demand of two parameters i.e. weld width and penetration. Till date, the definition of front and rear length of double ellipsoidal is to-some-extent arbitrary in linear welding. A sensitivity analysis shows that this ratio has significant effect on weld dimensions as well as thermal distortion and residual stress of final weld joint. This problem has been addressed in present work where the optimum value of the ratio of front and rear length of double ellipsoidal heat source model is designed within the kernel of an integrated optimization algorithm. The ratio is assumed as function of weld velocity and a suitable functional form is designed over a range of welding current and velocity. The proposed trend of ratio along with optimum values demonstrate fair agreement of experimentally measured weld dimensions for linear gas tungsten arc (GTA) welding process. 3D finite element model of thermal and mechanical analysis is developed and assuming elasto-plastic response of material. Temperature dependent material properties along with latent heat of melting and solidification are incorporated in numerical simulation.