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History and Latest Trends in Converter Practice for Steelmaking in Japan

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History and Latest Trends in Converter Practice for Steelmaking in Japan Mineral Processing and Extractive Metallurgy Transactions of the Institutions of Mining and Metallurgy ISSN: 2572-6641 (Print) 2572-665X (Online) Journal homepage: http://www.tandfonline.com/loi/ympm21 History and latest trends in converter practice for steelmaking in Japan Shin-ya Kitamura, Ken-ichiro Naito & Goro Okuyama To cite this article: Shin-ya Kitamura, Ken-ichiro Naito & Goro Okuyama (2018): History and latest trends in converter practice for steelmaking in Japan, Mineral Processing and Extractive Metallurgy, DOI: 10.1080/25726641.2018.1504661 To link to this article: https://doi.org/10.1080/25726641.2018.1504661 Published online: 01 Aug 2018. Submit your article to this journal Article views: 9 View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ympm21 MINERAL PROCESSING AND EXTRACTIVE METALLURGY https://doi.org/10.1080/25726641.2018.1504661 History and latest trends in converter practice for steelmaking in Japan Shin-ya Kitamuraa, Ken-ichiro Naitob and Goro Okuyamac aInstitute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan; bKashima R&D Labs., Nippon Steel & Sumitomo Metal Corporation, Kashima, Japan; cSteelmaking Technology Department, JFE Steel Corporation, Tokyo, Japan ABSTRACT ARTICLE HISTORY In this paper, the history and latest trends in the converter-based steelmaking process in Japan Received 4 July 2018 were summarised. After World War II, Japanese steel companies introduced the LD converter, Accepted 22 July 2018 and various original technologies have been developed to increase productivity, reduce the KEYWORDS production cost, and improve the quality of steel. About 20 years after the introduction, the Word; steelmaking; necessity of the additional stirring was recognised and various types of top-and-bottom- converter; history; Japan; hot blowing converters were developed. By using this process, hot-metal dephosphorisation and metal dephosphorisation; smelting reduction were developed. In addition, fundamental research related to the smelting reduction; converter technology is shown. Japanese steelmaking technology has been developed by thermodynamics; kinetics the collaboration of university and industry. In industry, each company has an R&D centre where the applied and practical research is conducted. The research in academia is concentrated on the fundamentals. Recently, ISIJ organised the research projects on ‘multi- phase slag refining’ and ‘enhancement of lime dissolution’. Introduction History of converter technology in Japan Japan is the second largest producer of steel in the Introduction of LD converter world after China, producing approximately 100 The history of the steelmaking process in Japan has million tons every year. Because of the high price of already been reviewed by Emi in Steel Research Inter- electricity, the production ratio by converter process national in 2014 (Emi 2014). In addition, in Japanese, reaches 75% or more. During World War II, the Japa- the history of the LD converter (oxygen top-blown nese steel industry was destroyed completely, and the converter) was published by the Iron and Steel Institute annual production in 1946 was only 557 thousand of Japan (ISIJ) in 1980 (ISIJ 1980). In this section, the tons. However, in 1956, steel production reached 10 background to introduce the LD converter after million tons, and in 1973, it exceeded 100 million World War II is briefly introduced. tons. To support this rapid growth, the introduction Japanese steelworks had been destroyed by bom- of the LD converter (top-blown converter) played an bardment from warships during World War II. In important role. For the reconstruction of steel industry, 1946, the annual production was decreased to 557 kt Japanese steel companies noticed this process, which from 7,650 kt in 1943, and only four open-hearth fur- had just begun to operate in 1952 in Austria. After naces (OH) were operated. For the recovery of the severe competition and arbitration by the government, Japanese economy, the reconstruction of the steel the first LD converter in Japan was built in 1957. Var- industry was a priority. In 1953, the crude steel pro- ious research and developments were achieved to duction had recovered to the pre-war level and many increase productivity, reduce the production cost, and OHs were built. However, as the domestic supply of improve the quality of steel. After the growing stage scrap was limited and import from the US was of steel production, the annual production became restricted, steelmaking by OH was insufficient to satisfy almost constant for the past 40 years. However, the the increasing demand of the domestic market. performance of steel products are improving every The LD converter was developed by Vöest and day. The development of the technology to produce Alpine, and began to operate in 1952 at Linz and Dona- high-grade steel, which cannot be imitated easily, is witz steelmaking shops in Austria. Among the several the essential strategy of the modern Japanese steel integrated steelmaking companies in Japan, Yawata industry. For this purpose, the innovation of converter Iron & Steel and Nippon Kokan (NK) had interest in process still plays an important role. In this paper, the this just-born technology. By coordination of the history and latest trends in converter practices for steel- MITI (Ministry of International Trade and Industry), making in Japan are summarised. CONTACT Shin-ya Kitamura [email protected] Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan © 2018 Institute of Materials, Minerals and Mining and The AusIMM Published by Taylor & Francis on behalf of the Institute and The AusIMM 2 S.-Y. KITAMURA ET AL. NK bought the exclusive license in 1956, and Yawata refractory at the bottom of the furnace and a decrease and the other companies received sub-licenses. In in the iron yield by the generation of spitting (scatter- 1957, the first LD converter began operation in Yawata, ing of fine metal droplets from the furnace) or slopping followed by NK in 1958. This technology met the needs (blown-out of slag from the furnace). To solve this pro- of the Japanese steel industry, i.e. low scrap consump- blem, a top lance with multiple holes was developed tion, low-phosphorus-containing iron ore, high energy and installed in the industrial furnace in 1962 (Morita efficiency, and high productivity. The introduction of et al. 1964). Figure 2 shows the number and inclination the LD converter was accelerated in many companies angle of the nozzle in the lance installed for various by the financial support of MITI, and the production sizes of converters (ISIJ 1979, p. 468). By the appli- ratio by LD converter exceeded that by OH in 1965; cation of a lance with 3 holes, the skull formation of the last OH operation was ended in 1977. During this the converter mouth was decreased and the iron yield period, the ‘LD committee’ was launched in 1958 by was improved (Hayashi et al. 1965). the steelmaking companies to exchange their oper- In the steelmaking process, by decarburisation, ational results. This society played an important role high-temperature CO gas with fine dust is formed in accelerating the technological development of the from the furnace, and treatment of the off-gas is LD converter. The change in the ratio of crude steel necessary. In the small-scale converter, CO gas was produced by LD converter is shown in Figure 1 (ISIJ fully combusted by air. However, as the capacity of 1980, p. 84), compared with that in other countries. the converter increased, the off-gas volume increased The Japanese steelmaking companies led the world to and the investment cost of the gas-treatment system spread the technology of LD converter. In addition, became high. To overcome these problems, a process the LD converter contributed greatly to the rapid growth of steel production, which led to the rapid growth of Japanese economy. Development of original technologies for LD converter To increase productivity and expand the application of the LD converter for various grades of steel, several innovative technologies were developed. The capacity of the first LD converter was 50 t. The rapid increase in the demand of steel production required higher productivity, which caused an increase in the size of the converter, and in 1970 the maximum capacity reached 300t (ISIJ 1980, p. 155). In the LD converter, high-purity oxygen is blown from a Laval nozzle in the top-blown lance. With the increase in Figure 2. The number and the inclination angle of the nozzle capacity, the flow rate of oxygen from the nozzle also in the lance installed for various sizes of converters by ISIJ increased, which caused severe damage to the (1979), redrawn with permission. Figure 1. The change in the ratio of crude steel produced by LD converter by ISIJ (1980), redrawn with permission. MINERAL PROCESSING AND EXTRACTIVE METALLURGY 3 to recover the CO gas without combustion was devel- oped. From pilot plant trials, a basic design to supress the explosion was established, named ‘OG system: Oxygen-converter gas-recovery system’ (Ikeda et al. 1962). The first plant was installed to the 130-t LD con- verter in 1962. In this process, the recovery ratio of energy was about 60% from waste-gas recovery, and it increased to about 70% when part of the sensible heat was recovered in the form of steam using a boiler (Yamaguchi et al. 1978). In addition, Emi pointed out the following technol- ogies that supported the development of the LD con- verter in Japan. (1) The sub-lance system, in which Figure 3. Various types of combined blowing converter, shown the temperature is measured by thermocouple and car- in the relation between bottom gas blowing rate and perfect bon content is determined using liquidus temperature mixing time by Nagai et al. (1982), used with permission.
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