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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 91 (2005), No. 1

  • Learn from the Past and Aim for a New Stage

    pp. 1-1

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  • History of Iron and Steel Making Technology in Japan

    pp. 2-10

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    Iron making from iron sand in Chugoku district began soon after the introduction of iron ore smelting by the low shaft box-type furnace in the middle of the sixth century and it rapidly spread all over the country, but Chugoku district continued to be the center of its progress. The process consistently developed throughout the ancient and the medieval times towards more elevated furnace temperature by means of increased furnace volume, improved underground facilities for moisture elimination and increased blowing capacity of bellows. The development resulted in the birth of Tatara as the finally-evolved box-furnace on the one hand and in the change of the chief product of smelting from lumpy mixture of metal with slag or a large metal block involving some slag to molten pig iron (Zuku) on th other hand. The priority production of Zuku led to the invention of the two-stage refining process for its conversion into wrought iron (Ohkaji) in the 17th century. Zuku-making by Tatara and refining by Ohkaji formed Japanese indirect wrought iron making system.
    Metal block (Kera), which was formed in Zuku making from a sort of iron sand hard to fuse (Masa) compared with another sort of iron sand (Akome), proved to contain about 50% parts of steel high in carbon content, which, naturally, were taken out by hammering after the rough crushing by falling-weight methd.
    Because of economical disadvantages mainly due to inefficiency of iron sand smelting, Japanese indirect iron making system could not survive after 1923 in spite of several successes in developing new iron making process of blast furnace-type. However Tatara is preserved as a technical heritage and is still operated several times a year for direct steel making through Kera.
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    Readers Who Read This Article Also Read

    1. Some Considerations of Decarbonizing Process at the "Ohkajiba" Furnace Tetsu-to-Hagané Vol.91(2005), No.1
    2. Development of Management of Tatara Iron Making at Oku-Izumo in Edo Era Tetsu-to-Hagané Vol.91(2005), No.1
    3. Behavior of Dioxins in the Sintering Process of Iron Ores Tetsu-to-Hagané Vol.87(2001), No.5
  • The History of Ironware in Japan Revealed by the AMS-carbon 14 Age Method

    pp. 11-15

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    This paper focuses on the influence what the AMS-carbon 14 age method attains to the history of the iron in the Japanese Islands.
    The research team in National Museum of Japanese History makes a clear that the Yayoi period began in 10 Cen. cal BC. However, there was a problem in this.
    It is iron. If the Yayoi period has started in the 10th Cen. BC, it means that the ironware in Japanese Islands had spread early rather than it spreads in China.
    The research team reexamined the ironware excavated from Magarita site in the Fukuoka Pref. considered to be the oldest ironware in Japan. Consequently, the excavation situation was indefinite and it turned out that we cannot specify the time to belong.
    Furthermore, 36 ironwares in the initial and early Yayoi were also already found by that time cannot be specified except for two points. Therefore, it turned out that Japanese ironware appeared in the 3rd century of B.C. What does this mean?
    Although it had been thought that the beginning of agriculture in Japan and the appearance of ironware were simultaneous, it turned out that agriculture has appeared early about in 700 years. Therefore, it became clear that agriculture of Japan started at the Stone Age.
  • Effect of Oxygen Potential on Cohesion of Pulverized Iron Oxide under a Reducing Atmosphere

    pp. 16-22

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    The effect of the oxygen potential on cohesion was examined by using the pulverized ore of iron sand, hematite ore, and magnetite ore. The sample was kept under atmosphere by which the oxygen potential and the temperature were kept constant during the fixed time, and the state of cohesion was examined. The temperature was an interval of 50°C of 11731423K, and the holding time was done in 15 min until 60 min.
    It has been understood to cohere easily in the oxygen potential in the stability area of the wüstite in each pulverized ore. Order of the tendency of cohesion was as follows; iron sand > hematite ore > magnetite ore. SiO2 and TiO2 of the mineral composition in iron sand are greatly related to cohesion. The surface of the ore particle melted, and the fusion of the ore particle each other was confirmed.
  • The Action of Titanous Oxide as Flux

    pp. 23-27

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    The most important mechanism in the Japanese pre-modern ironmaking method involves the action of titanous oxide as a flux on the viscosity of slag. In this paper slag excavated at historic sites was analyzed. It was concluded that the neutral or basic action of titanous oxide was a useful substitute for wustite in the slag. This paper clearly explains the mechanism involved.
  • Physical Chemistry of Iron Oxide Based Slags Containing Titanium Oxide

    pp. 28-32

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    Physical chemistry of TiO2-containing FeO-based slag should be valuable to understand the iron and steelmaking processes using iron sand. In the present work, the activity of each component was estimated for FetO-SiO22-TiO2-MOx (MOx=CaO, MgO, AlO1.5) melts by using regular solution model. The empirical equation to estimate the reduction rate of the same melts by CO gas was derived from the experimental data. The methodology of the estimation of thermodynamic and kinetic properties of TiO2-containing FeO-based slag was established.
  • Phase Diagram of Fe2SiO4-TiO2 System

    pp. 33-38

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    In order to discuss Tatara smelting process, a phase diagram of quasi binary system of fayalite-titania is studied by using of differential thermal analysis procedure (DTA).
    It is revealed that the system has eutectic and peritectic points which are located in area of comparatively low TiO2 content and comparatively low temperature.
  • Some Considerations of Decarbonizing Process at the "Ohkajiba" Furnace

    pp. 39-46

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    "Ohkajiba", which is the Tatara steelmaking process in Edo and Meiji eras, early modern times, corresponds to the recent steelmaking shop process including blooming mill process of the integrated iron and steel works. Those processes include the decarbonizing process of pig iron, Zuku and Bugera, the removal process of inclusions, mainly oxides, the homogenizing process and manufacturing process of products such as "Hocho-tetsu and Waritetsu", mild steel.
    Considering the thermal technology in early modern times, it was supposed not to be able to melt low carbon steel such as the Hocho-tetsu though pig iron was probably able to melt due to its low melting point. It means decarbonizing process at the "Ohkajiba" should basically be half-melt reaction or solid reaction. In spite that the rate of decarbonizing process under this half-melt reaction or solid reaction supposed to be extremely slow based on the general modern metallurgical reaction kinetics, decarbonizing rate at the "Ohkajiba" was very fast based on the some descriptions about the operation at the"Ohkajiba". That rate is equal to that in large size open-hearth furnaces, though it is slower than that of large size basic oxygen furnaces. Those facts are amazing for modern metallurgists.
    In this report, supposed operations with decarbonizing process in the "Ohkajiba", information from a modern blacksmith of Japanese swords and the simulation results were proposed and some considerations from the point of view of modern metallurgy were discussed through those results.
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    Readers Who Read This Article Also Read

    1. History of Iron and Steel Making Technology in Japan Tetsu-to-Hagané Vol.91(2005), No.1
    2. The History of Ironware in Japan Revealed by the AMS-carbon 14 Age Method Tetsu-to-Hagané Vol.91(2005), No.1
    3. Classification of the Iron-making Processes for Excavated Slag by the Evaluation of Chemical Composition Tetsu-to-Hagané Vol.91(2005), No.1
  • Classification of the Iron-making Processes for Excavated Slag by the Evaluation of Chemical Composition

    pp. 47-54

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    The results of chemical compositions for excavated slag were drawn as figures of the relation between T.Fe and TiO2, and the relation between T.Fe and SC (slag component defined as SC=SiO2+Al2O3+CaO+MgO). The excavated slag can be classified to 6 regions of ironmaking process and forging process as follows; 1. Smelting slag of iron-sand process, 2. Refining slag of iron-sand process, 3. Forging slag, 4. Slag adhered to refractory clay, 5. Smelting slag of iron-ore process, and 6. Semi-reduced iron-sand.
    The extrapolated and specified points of analyzed data as described in Fig. 2 were referred to the phase diagram for FeO-SiO2-TiO2 system. Resultant classification of excavated slag for the iron-making processes assisted by phase diagram was obtained as shown in Table 4.
    Accordingly, it may be concluded that at most high content of TiO2 or at lower content of TiO2 in the raw material of iron-sand, the smelting process of generated liquid-slag would be happened under nearly same conditions as smelting temperature (about 1250°C) and slag component (about SC=30% constant).
  • Distinguishable Procedure for Ancient Iron-making Slag by Using Major Elements

    pp. 55-61

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    To identify the process of iron production, some indicators are proposed by using the chemical components of excavated slag. Especially, the ratio of Ti/Fe and V/Fe are useful for this purpose. All indicators, however, are not always appropriate for the distinguishable procedure between bowl-shaped slag and other slag. It is not yet fundamentally explained that major elements of iron-making slag caused from any materials.
    In this article, ten major elements which are constituent of iron-making slag as Silicon (Si), Iron (Fe), Aluminium (Al), Titanium (Ti), Manganese (Mn), Magnesium (Mg), Calcium (Ca), Sodium (Na), Potassium (K) and Phosphorus (P) are considered by using the released analytical data. Every element has been normalized against Si, and the correlation diagrams are plotted. The correlation diagram with Si can be distinguished as 3 groups.
    ( 1 ) Elements Al, Ca, Na, K and P have positive correlation with Si.
    ( 2 ) Elements Ti, Mn, and Mg do not correlate with Si.
    ( 3 ) Fe has negative correlation with Si.
    Elements of group (1) as Ca, Na, K and P increase the content in any slag during the smelting, refining and forging processes. Thus, it is obvious that these four elements can not be utilized for the distinguishable procedure of ancient iron-making slag.
    On the other hand, elements of group (2) as Ti, Mn and Mg are appropriate to be indicators for the distinguishable procedure of two types slag between forging slag (sometimes in refining process) and other slag (normally in smelting process). On the basis of concentration of the 3 elements, it is indicated that bowl-shaped slag is formed in forging (sometimes in refining), and other slag is done in smelting.
    As the result of this study, the ratio of element as Mn/Ti, Mn/Si, Mg/Ti and Mg/Si are suggested to be useful as indicators for the distinguishable procedure between bowl-shaped slag and other slag.
  • Analysis of Temperature Distribution in Modified Tatara Furnace

    pp. 62-67

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    From influence of temperature being big in an iron manufacture principle during the operation in modified tatra steelmaking furnace method, the temperature of inside of whole in modified tatra steelmaking furnace was measured, and the non-equilibrium reaction temperature was examined. I did condition setting of simulation afterwards and made temperature distribution by ANSYS by analysis of temperature distribution in a furnace. The carbon content of "Kera" was around 1.5 mass%. I could grasp temperature distribution in modified tatra steelmaking furnace as a result of having done a temperature distribution simulation in a furnace and was able to confirm a generation part of "Kera", shape again.
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    Readers Who Read This Article Also Read

    1. Effect of the Size for Small Tatara Steelmaking Furnace Tetsu-to-Hagané Vol.91(2005), No.1
    2. Development of Management of Tatara Iron Making at Oku-Izumo in Edo Era Tetsu-to-Hagané Vol.91(2005), No.1
    3. Role of "Kobune" in Underground Construction of Tatara Furnace Tetsu-to-Hagané Vol.87(2001), No.10
  • Effect of the Size for Small Tatara Steelmaking Furnace

    pp. 68-74

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    The steelmaking operations using a small "Tatara" furnace have been performed to investigate the effects of furnace size on the characteristics of "Kera" (steel bloom). The height and the cross-sectional area of the furnace are varied. The weight of Kera increases with increasing the furnace height due to the increased average temperature at upper tuyere, and the carbon concentration of Kera shows a linear relationship with the temperature. It is important for Tatara steelmaking operation to arrange the furnace size with which iron sand is reduced and carburized at temperatures around 1350°C without being blown out. From this viewpoint, the appropriate furnace size is discussed.
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    Readers Who Read This Article Also Read

    1. Analysis of Temperature Distribution in Modified Tatara Furnace Tetsu-to-Hagané Vol.91(2005), No.1
    2. Development of Management of Tatara Iron Making at Oku-Izumo in Edo Era Tetsu-to-Hagané Vol.91(2005), No.1
    3. Role of "Kobune" in Underground Construction of Tatara Furnace Tetsu-to-Hagané Vol.87(2001), No.10
  • Analysis of the Products of Ancient and Medieval Low Shaft Furnaces in Japan

    pp. 75-82

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    Archaeologists have classified the ancient and medieval shaft furnace into three types; "rectangular box", "self-standing" and "partly-undergrounded". Although the shaft wall lost its original shape, they have tried to pick up the brick pieces and reconstruct the wall. The heights of the restored shaft are reported to be ranging from about 50 to 70 cm. The author supposes that such a low shaft furnace could not have been able to smelt iron sand in liquid state.
    Under the optical microscope, graphite carbon, ledeburite and primary-crystallized cementite were observed in the inner part of metal-rich relics and identified to be the remaining structure of pig iron before decarbonization. Fair amounts of Cu, P, Ni and/or Co were contained in the excavated pig iron sample. These elements are estimated to originate in the raw magnetite ore. Analytical results of the samples taken from the three types furnace ruins have not shown any distinguishable relationship among the main slag components.
    It was considered that most of the ancient and medieval furnaces were operated for steelmaking of pig iron.
  • Influence of the Loading Ratio (Ironsand/Charcoal) on Productivity and Quality of the Products by Tatara Ironmaking Process

    pp. 83-90

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    The Japanese traditional steel making method which manufactures steel "Kera" or pig iron "Zuku" from iron sand and charcoal is so called "Tatara" steel making process. The influence of the loading ratio of iron sand to charcoal on the "Tatara" steel making was investigated. In the case of the loading ratio is equal to 1, high carbon steel "Kera" was produced at the high yield accompanied with viscous slag "Noro". In the meantime, in the case of the loading ratio is equal to 1.5, the carbon content of the produced steel "Kera" was low at the low yield accompanied with a lot of low viscous slag "Noro". In the case of low loading ratio, so called "light charge", iron sand was well deoxidized and carbonized in the furnace and became to high carbon steel "Kera" at the high efficiently. In that case, the slag "Noro" became to viscous one because of the reduction of FeO content.
    On the contrary, in the case of high loading ratio, so called "heavy charge", the deoxidization of iron sand was insufficient and most of iron sand was discharged as a slag "Noro" to the outside of the furnace. As the result, produced steel "Kera" yield lowered. During the "heavy charge" operation, the composition of the slag "Noro" became FeO-rich, and then the fluidity of the slag "Noro" increased. It was clarified that the controlling of the loading ratio was an important factor which affected both to the quality and productivity of steel "Kera" and the fluidity of slag "Noro" on "Tatara" steel making process.
  • Investigation of Oxide Film Grown over Japanese Nail Used at Bicchu-kokubun-ji Temple

    pp. 91-96

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    The ancient iron specimens are known to be highly corrosion resistant compared with the nowadays blast furnace iron. In the case of Japanese nail prepared by "Kaji", the surface is covered by the oxide film which has grown at the forging.
    In this work, to make how Japanese nail keeps high corrosion resistance clear, the structure characterization of the oxide film grown over the nail used at Bicchu-kokubun-ji temple by electron diffraction method was attempted. The blast furnace iron was also similarly examined for comparison.
    The main results obtained as follows:
    (1) Japanese nail contained in quantity of non-metallic inclusion, mainly wustite (FeO) and silicate, was covered by dense and minute poly-crystal oxide film which the thickness was about 4 pm,
    (2) The crystal unit size of the FeO was about 10nm,
    (3) While the FeO grown on the blast furnace iron was mono-crystal and the crystal unit size was about 3 pm.
  • The Investigation of Establishing Time of Zuku-Oshi and Kera-Oshi with Data of Iron Image of Buddha Making Age and Old Document "Kokon-Kajibiko"

    pp. 97-102

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    "Tatara" is a traditional box-type furnace in Japan and had produced iron from iron sand and charcol. In this Tatara there were two techniques which were called Zuku-Oshi and Kera-Oshi. Zuku means pig-iron and Kera means steel. The Tatara started in the latter half of six century and is continuing up to today. I am interested in when did the two techniques establish. So I tried to investigate the question with data of iron (pig-iron) image of Buddha making age and old document which is called "Kokon-Kajibiko". It is concluded that Zuku-Oshi has established regularly in Kamakura period (1192-1333). In Kera-Oshi case is the latter half of Muromachi period (1392-1573).
  • Metallurgical Research on Japanese Swords-Focusing on Swords for Practical Use-

    pp. 103-107

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    Following research into methods for making practical use of Japanese swords, the following points were noted;
    (1) Upon examination of the forging face, it was found that the microstructure, hardness, and residual stress differed.
    (2) In order to discover more about clad forging, a pre-heat treatment of the full annealing process was necessary.
    (3) Especially in the core steel, non-metallic inclusion was noted in the area of the sharp side of sword.
    (4) Upon examination of sample A, B, and C, all were found to contain pure material; the sample C however had high amount of Ti, Ca and V.
    (5) Ordinary a core hardness of Hv 200 is obtained by addig 0.1% C while quenching, however, an edge hardness of Hv 700800 can be easily obtained by the addition of 0.50.6% carbon.
    (6) Compared to other research materials, sample C had a low residual stress after compressive stress; however, sample C showed signs of past tempering and grinding that may account for the low residual stress. It is assumed not to be an error in measurement.
    (7) Upon examination of the microstructure, the central portion of the sword showed overheating in low carbon steel ferrite. Follow-up research on old and new sword should include the traditional Japanese sword virtues of strength, cutting ability, and flexibility.
  • Alloy Steel Manufacture at Naval Arsenal of Meiji Period and Tatara Ironproduct

    pp. 108-115

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    The traditional steel manufacturing (Tatara) of Japan which developed in the early modern times fell into the decline in the Meiji Period. On the other hand, because it is being made by reducing iron sand with charcoal, the amount of phosphorus and sulfur of Tatara iron is low. Therefore it was adopted as a raw material of the alloy steel at Naval Arsenal of the Meiji latter period. The purpose of the main subject is to explain that process.
    The quality which the navy demanded was limited to the speck of the low phosphorus. Then, the navy never tried to admit the cost which corresponded with that quality. The makers of Tatara iron had efforts to cope with a naval requirement. But, they had to give up their Tatara business suddenly. That was because naval warship manufacture stopped observing Washington disarmament treaty. They advanced all together to charcoal industry after that.
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    Readers Who Read This Article Also Read

    1. Analysis of C + O = CO Reaction in Modified Tatara Steelmaking Furnace by Chemical Affinities Tetsu-to-Hagané Vol.87(2001), No.7
    2. Steelmaking Mechanisms for a Modified Tatara Furnace Tetsu-to-Hagané Vol.84(1998), No.10
    3. TATARA…An Introduction to Traditional Steel Making Process of Japan Tetsu-to-Hagané Vol.52(1966), No.12
  • Iron Prices in Ancient Japan and the International Comparison

    pp. 116-121

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    Nothing tells us more eloquently on the level of a technology than the cost or the quantity. If we know the prices of some metals at any period in any location, we can discuss the technical level to a certain degree only from the information. From the above idea this author is carrying out a compilation of worldwide historical metal prices and so on. In this report this author deliberates on iron prices in ancient Japan and makes an attempt to compare the prices internationally with ancient China or medieval Europe. The results are summarized as follows. (1) The ratios of iron prices for rice prices in ancient Japan are concentrated in 6 to 8 (2) The values are slightly higher than in ancient China (the ratios of iron price for rice prices are about 5), but there is no significant difference. (3) As to ancient Europe there is no appropriate document but from the 14th England case (the ratio of iron price for wheal price is 4.8) there would not be much difference. (4) The ratio of iron price for rice price is gradually decreasing worldwide and reaches 2 in 17th or 18th century.
  • Development of Management of Tatara Iron Making at Oku-Izumo in Edo Era

    pp. 122-126

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    Iron making by Tatara at Oku-Izumo developed from reopening in 1638 after prohibition of operation to becoming the center of iron production in Japan in the end of Edo era. The history of its management was studied from the stand point of countermeasure to environmental and economic problems, and quality of the product, in order to get the hints for the future iron and steel making.
    (1) Managers of tatara at Oku-Izumo held concurrently the manager of agriculture, forest and stock farming. As the results of the all-round management, social system of circulation was established, under cooperation with the administration.
    (2) The change of Tatara operation from 4 to 3 d in the first half of 19th century was trial and error for economical production system, and fixing of 3 d operation was interpreted as the flexible production system.
    (3) Superiority of Kera produced by Tatara process as the material for production of sword by forging was originated in un-uniformity. This suggests that conception surpassing the optimum of partial process is valid for cost down of quality assurance and the creation added value of the product in modern iron and steel making.
    x

    Readers Who Read This Article Also Read

    1. Effect of the Size for Small Tatara Steelmaking Furnace Tetsu-to-Hagané Vol.91(2005), No.1
    2. Analysis of Temperature Distribution in Modified Tatara Furnace Tetsu-to-Hagané Vol.91(2005), No.1
    3. History of Iron and Steel Making Technology in Japan Tetsu-to-Hagané Vol.91(2005), No.1
  • Life Cycle Assessment for Assessing Open Cycle Recycling of Materials

    pp. 127-134

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    Life Cycle Assessment (LCA) is a useful tool to evaluate environmental impacts associated with products during their life cycle. However, it has been recognized that LCA has a limitation in assessing open cycle recycling of materials because of inevitable subjective judgments in setting system boundary. According with the enforcement of recycling laws, there has been a rapid increase in recycling ratio of materials at the end-of-life of products in Japan. So, materials' life cycle is getting more complicated, which makes it difficult to quantify the environmental impacts of materials used in a product in an appropriate way. This paper reviews this limitation of conventional LCA and suggests a new methodology for assessing open cycle recycling of materials. The new tool is called "Strategic Integrated LCA Technology for sustainable society, SILT", in which LCA is integrated with population balance model and pinch technology. This tool deals with dynamic aspects of recycling materials and has macro point of view. One can assess the maximum recyclable ratio of the scrap materials and total environmental impacts caused by the material production in asociety in each year. In addition, reduction potential of environmental impacts by theintroduction of new technology, such as DfE, can be quantified by this tool.
  • Recycling of Steel Cans and LCA Study

    pp. 135-140

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    Steel cans are characterized by high strength to withstand internal pressures and low environmental load because of their high suitability for recycling. The annual consumption of steel cans is 910, 000 tons, with a recycling ratio of 87.5% (2003). This recycling ratio is high compared to containers of other materials, which is also at the highest level, internationally. Moreover, if the further recycling of cans, other than standard scraps, being made after incineration is taken into consideration, the recycling ratio rises more than 90%. This report attempts to give a detailed description of the actual state and characteristic features of steel-can recycling.
    As a result of the LCA (life cycle assessment) of steel cans, based on the fact of "steel products being used cyclically in steel products, " it has been proved that steel cans are environment-friendly containers with low CO2 emissions and energy consumption during life cycle.
    If people associated with steel continue to advocate the above characteristics of steel cans vigorously and widely for the benefit of general consumers, even higher consumption and recycling ratios can be expected.
  • Origin of Steel Scrap Generated in Japan

    pp. 141-146

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    The origins and characters of steel scrap were quantitatively estimated by using officially published statistic data combined with unpublished data which were available only within individual industries. The estimation procedures include (1) tabulating the amounts of steel products in the past 45 years, (2) classifying steel scrap into individual origins, and then (3) revealing the characters of the scrap. As results, the origins of the scrap generated in 2000 were made clear based on the whole material flow ; for example, 75% in the total amount of steel scrap was produced by basic oxygen converter in the past and 45% of the obsolete scrap was generated from cold-rolled coil.
  • Relationship between Scrap Mixing and Steel Products for Electric Furnace

    pp. 147-149

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    In this study, sources of steel scraps for electric furnace steel products were investigated as fundamental data for studies aiming at improvement of recycling of steel.
    The amounts of steel scraps generated in 2001 were divided into heavy scrap processed by guillotine (58.7%), shredded scrap (7.2%), pressed scrap (3.4%), koudarai scrap (6.9%), shindachi scrap (17.6%) and others (6.2%). Then, the mixing ratios of various kinds of steel scrap and pig iron for raw materials of electric furnace (EF) were estimated. It was found that the mixing ratio of the steel scraps was dependent on steel products, and hence different in three groups ; family EF companies of blast furnace (BF) steel makers, mild steel EF makers and special steel EF makers. For example, the BF family companies produced mild steel (21.6%) and special steels (78.4%) by employing the mixing of 42.2% inhouse scrap, 15.3% heavy scrap, 19.8% shindachi scrap, 7.4% koudarai scrap and 1.3% pig iron for the raw material.
  • Iron and Steel Scrap Flow Analysis in Japan

    pp. 150-153

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    An effective utilization of scraps has been required for a establishing a sound material-cycle society. In order to understand the supply and demand system of the scrap at the present time, it is necessary to know the detail and precise scrap flow. For this purpose, the present study aims a material flow analysis for the iron and steel scraps. Since the iron and steel are the most typical base-materials for the society, it has been believed that we have enough amount of statistical information on their scrap markets. It is found by the present study, however, that the domestic circulation figure for iron and steel scrap was hard to be drawn due to mainly the discrepancy of the definition of each scrap category between the supplier and the user. Such discrepancy results in the following three major problems; (1) discontinuity of the scrap flow, (2) mismatching of the categories of supplied and used scraps, and (3) the lack of the data about un-collective scrap.
  • Estimation of the Amount of Iron and Steel Industrial-scraps Using I/O Table

    pp. 154-158

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    The Japan Ferrous Raw Materials Association has already established two methods for the estimation of amounts of iron and steel industria scraps. In this study, the third method using the I/O table and the unit prices of scrap was proposed, and a database of iron and steel industrial-scraps was constructed according to this method. Since the I/O table is reliable and detail data source authorized by the government, it is possible to do precise evaluation for the amounts of iron and steel industrial-scrap in each category. The total amount of iron and steel industrial-scrap generated in 1995 was evaluated as 8316×103 t.
  • Development of Methodology for Analyzing the Average Number of Times of Use and the Average Residence Time of Iron Element in Society by Applying Markov Chain Model

    pp. 159-166

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    The life cycle of steel begins in the mining of iron-ore from the earth. Steels are produced in steel works and used in various products. Some of the steels are recycled at the end-of-life of the products and used as a resource for the production of steel products in electric furnace, while the other steels are used just one time in products and go into landfill. As the recycle ratios of steel from used products increase, the average number of times of use and residence time of Iron element that comes into society as iron are and goes out from the society as landfill will increase. So these values indicate "sustainability of material use" in a society. In this work, a methodology was developed for analyzing the average number of times of use and residence time of Iron element in a society by applying Markov chain model. It was calculated that the average number of times of use and residence time of Iron element in a society based on the material flow of steels in Japan in 2000 are 2.67 and 62.9 years, respectively. Both of these values are significantly dependent on the recycle ratio of steels from civil & building facilities and automobiles. It was indicated that the average number of times of use and residence time of Iron element in a society would increase up to 3.17 and 75.8 if the recycle ratio of steels from civil and building facilities increase from 50 to 60%.
  • The Steel Scrap Statistics in Japan

    pp. 167-170

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    [in Japanese]
  • Development of a Dynamic Model for Assessing Environmental Impact Associated with Cyclic Use of Steel

    pp. 171-178

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    Steels are produced in large quantities and being recycled at high rate in Japan. However, recycling of steel scraps would lead to the enhancement of contamination of undesirable tramp metals in steel scraps. So, the limitation of recycling of the steel scarps would be expected in the near future. This may increase in the production of virgin steels and environmental impacts associated with total steel production in Japan. The authors have developed a dynamic model to assess the maximum recyclable ratio of steel scraps and the total environmental impacts caused by the steel production in Japan. The model is based on population balance model (PBM), material pinch technology in corporate with LCA. The amount of steel scraps generated in Japan and their concentration of tramp metal during 1990-2030 were estimated by PBM. The maximum recyclable ratio of steel scraps in each year was calculated by material pinch technology, in which assessed were optimal balance between the amount and quality of steel scraps and those of steel products. The total CO2 emissions caused by steel production in Japan during 1990-2030 were estimated by LCA.
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    1. Estimation of Quality Change in Domestic Steel Production Affected by Steel Scrap Exports Tetsu-to-Hagané Vol.92(2006), No.6
  • Assessing Environmental Impact Associated with Cyclic Use of Steels-Indirect Reduction Potential of Environmental Impacts by the Introduction of Easy Disassemble Design for Automobiles

    pp. 179-183

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    Promotion of recycling may cause the increase in concentration of undesirable tramp elements in steel scraps. In the future, some of the steel scraps may be unusable due to the high concentration of tramp element. So, the introduction of new technologies, such as easy disassembly design, that enhances the separation of tramp elements from steel scraps at the end-of-life of products could increase the maximum recyclable ratio of steel scraps. This could indirectly lead to the reduction of environmental impacts caused by crude steel production.
    In this study, the indirect reduction potential of CO2 emissions by the introduction of easy disassembly design for automobiles was analyzed. The dynamic model that has been developed by the authors in the previous paper was used for assessing the reduction potential of CO2 emissions. It was found that the reduction potential of CO2 emissions by the introduction of easy disassembly design for automobiles in 2010 were up to 0.62 t-CO2 and 0.98 t-CO2 per automobile, depending on scenario. There was little reduction potential of CO2 if the concentration of tramp element (Cu) in automobile scraps was more than 0.5 wt%.
  • Life Cycle Inventory and Cost Analysis of Waste Plastics Utilization in the Steel Industry

    pp. 184-191

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    Environmental impact and cost of waste plastics utilization in the steel industry as feedstock materials for blast and electric furnaces were evaluated using scenario-based life cycle assessment technique. These processes were compared with conventional processes including liquefaction and incineration with electric power generation. Since existent process inventory data do not include an input flow of plastic materials and cannot be used for the analysis of scenarios varying plastics flow rate, new process inventory models, which have an input flow of plastics and have other input/output flows depending on the flow rate of plastics, were developed.
    A case study of the utilization of the industrial waste plastics from Aichi district was performed using our life cycle model. Total emission of carbon dioxide and total energy consumption were used as environmental indices and costs of transportation, investments and utilities were estimated as well. We found that every process is effective from the view point of the reduction of carbon dioxide emission and energy consumption. Especially, the blast furnace has large potential to reduce carbon dioxide emission. The transportation does not have significant contribution to environmental impacts and total cost. As a result, waste plastics utilization in the steel industry is an effective technology to reduce environmental impacts.
  • Environmental and Economic Analysis of Recycling System Using Gasification Plant for Flame Retardance Waste Plastics from Used Home Appliances and Automobile Shredder Residue

    pp. 192-198

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    Recycling of waste plastics from household appliances and automobile shredder residue (ASR) is a major concern in Japan along with the enforcement of recycling law. Chemical recycling technology for waste plastics (including flame retardance plastics) has been developed by Japanese industries. In this work, life cycle inventory analysis and project finance method were applied to analyze CO2 emissions and economic feasibility of this technology and compared with those of conventional technologies. It was found that chemicals (Br) recovery in conjunction with energy recovery by this recycling technology could lead to significant reduction of CO2 emissions compared with those from conventional incineration. It was found that economic feasibility of this technology is strongly dependent on disposal cost of waste plastics and cost of electricity.
  • Material Flow of Fluorine in Steel and Chemical Industries

    pp. 199-205

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    It is very important to know material flows of various substances for better understanding of the environmental impacts of the substances. The material flow of fluorine in the industrial use and the influence of the environmental regulation were investigated from a total point of view for trying to control the fluorine waste in environment. The waste water-Discharge standards of fluorine based on the law on water pollution prevention was reinforced from 15 mg/l to 8 mg/l in 2001.
    Almost 100% of fluorine was imported and 90% of it was fluorspar. Main users of fluorine in Japan were the steel industry and the chemical industry and over 90% of fluorine was consumed in both industries during the period investigated in this study.
    The amount of fluorine use in Japan decreased totally after reinforcement of waste water-Discharge standards due to the decrease of the steel industry use. Because most fluorine finally changes to slags as a by-product and they are target of reinforcement. On the other hand, fluoride compounds produced in the chemical industry are valuable products. Only the production of Chlorofluorocarbons was stopped to prevent a destruction of ozone layer. The drain management techniques of waste water containing fluorine were also discussed and a simple concept for the recycling of fluorine was proposed.
  • High Oxidation-resistance Coating for Steel by Using Aluminum and Titanium Powders

    pp. 206-211

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    A coating method for steel using a mixture of Al and Ti powders has been developed. Pure iron and a carbon steel (JIS-S45C) were successfully coated by the new method, where the coated layer consisted of iron aluminide: Al2TiFe, FeAl, etc. The thickness and chemical compositions of the layer were influenced by heating history and mixing weight ratio of Al and Ti powder. The coated specimen showed neither cracking nor peeling after cyclic heating test between 293 and 973K in air, revealing high oxidation resisitance.
  • Surface Modification of Carbon Steel and Tool Steel by Auminizing with Powder Liquid Coating and Plasma Nitriding

    pp. 212-216

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    Powder liquid coating is applied as an aluminization technique for carbon steel (JIS S45C), and subsequent plasma nitriding for tool steel (SKD61). In this process, Fe2Al5 forms initially on S45C, and the intermetallic compound decomposes into α-Fe during heat treatment at 1273 K, excluding C atoms from the aluminized layer (α-Fe) to the substrate (γ-Fe). Aluminized layer of α-Fe including vanadium carbide particles is formed on SKD61 by heating at 1303 K, and the substrate transforms into martensite during N2 gas flow cooling after heat treatment. By plasma nitriding of aluminized SKD61, hardness of HV1200-1600 is achieved at previously aluminized layer, exhibiting no detectable aluminium nitride but Fe3N, Fe4N, and highly strained α-Fe matrix in its surface XRD. Although the hardening mechanism of the modified layer is not clarified, it is suggested from XRD that the hardness is attributed to precipitation hardening by nitrides (ε-Fe3N, γ'-Fe4N) as well as solid solution hardening by Al.
  • Improvement in the Oxidation of TiAl by Molten Salt Boronizing

    pp. 217-223

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    The high temperature oxidation resistance of high specific strength intermetallic compound TiAl was improved by boronizing using chrolide and boride molten salt. The molten salt process has some remarkable characteristics as follows; 1) very simple process, 2) the atomosphere doesn't effect on the chemical reaction in the liquid, 3) specimen is fully dipped into the treatment liquid. TiB2 and Al3Ti layers were produced on the surface of TiAl by this process. The dense and protective Al2O3 phase was observed on the Al3Ti layer. The boronized TiAl was investigated in continuous and cyclic oxidation test at 1173K and 1123K. The mass gain due to oxidation of TiAl decreased by boronizing, where no pealing was observed during oxidation test.
  • Mixing Time of Cylindrical Bath Agitated by Swirl Motion of Gas-liquid Two-phase Jet and Sludge Treatment Using Ozone

    pp. 224-229

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    Sludge treatment using a gas-liquid two-phase swirling jet and ozone was proposed. The swirl motion of a gas-liquid two-phase jet appeared in a cylindrical bath under certain injecting conditions, and the bath was strongly agitated in the presence of the swirl motion. The swirling jet brought a very excellent effect on the ozone reaction with sludge. The intensity of agitation was quantitatively evaluated by means of mixing time. An empirical equation was derived for the mixing time. Sludge was decomposed by this method and, as a result, BUD5 and SS in the sludge were significantly decreased.
  • Effect of Off-centered Nozzle Position on Swirling Liquid Jet in a Cylindrical Bath

    pp. 230-235

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    Investigation was carried out on a swirl motion of a cylindrical bath agitated by a bottom blown liquid jet. The nozzle was placed at an off-centered position. Particular attention was paid to the boundary of the region in which the swirl motion appears, the period of the swirl motion, the transient period from the start of water injection to the occurrence of the swirl motion, and the transient period from the stoppage of water injection to the annihilation of the swirl motion. The nozzle positon affected only the occurrence region of the swirl motion. Empirical equations proposed for a centered nozzle were applicable to the other quantities for the off-centered nozzle.
  • Swirl Motion of Bubbling Jet in Highly Viscous Liquid Contained in a Cylindrical Vessel

    pp. 236-240

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    Investigation was made on an effect of the kinematic viscosity of a liquid on a swirl motion of the liquid in a cylindrical vessel. The swirl motion appeared when the liquid was agitated by bottom gas injection. Water and silicone oil were used as the working fluids. Particular attention was paid to the period, Ts, amplitude, A, starting time, Ts, s, damping time, Ts, d of the swirl motion. The preferable occurrence condition of the swirl motion was also determined. The occurrence region was expressed in terms of the aspect ratio and gas flow rate. It became narrow as the kinematic viscosity of liquid increased. An empirical equation was newly proposed for the amplitude, A. Empirical equations proposed previously for the remaining parameters, Ts, Ts, s Ts, d were applicable under the present experimental conditions.
  • Discussion on the Occurrence of Swirl Motion of Bubbling Jet in Highly Viscous Bath

    pp. 241-243

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