8th International Symposium on High Temperature Metallurgical Processing: Ironmaking and Steelmaking
Sponsored by: TMS Extraction and Processing Division, TMS: Pyrometallurgy Committee
Program Organizers: Jiann-Yang Hwang, Michigan Technological University; Tao Jiang, Central South University; Mark Kennedy, Proval Partners SA; Onuralp Yücel, ITU; P. Chris Pistorius, Carnegie Mellon University; Varadarajan Seshadri, Universidade Federal de Minas Gerais; Baojun Zhao, The University of Queensland; Dean Gregurek, RHI AG; Ender Keskinkilic, Atilim University
Wednesday 2:00 PM
March 1, 2017
Location: San Diego Convention Ctr
Session Chair: Dean Gregurek, RHI AG; Guanghui Li, Central South University
2:00 PM Introductory Comments
Evolution of Oxide and Sulfide Inclusions in the Ladle Furnace during Calcium Injection: Seyed Yousef Tabatabaei Majd1; Kenneth Coley1; Gordon Irons1; Stanley Sun2; 1McMaster University; 2ArcelorMittal Dofasco
Clogging of casting nozzles by solid alumina inclusions is a common problem during continuous casting of aluminum killed steel. Calcium treatment is usually employed to modify the alumina inclusions to liquid or partially liquid calcium aluminates. However, injected calcium can also react with the dissolved sulfur to form calcium sulfide. In the present work, a model has been developed by considering (a) dissolution rate of calcium from the bubbles to the steel melt as well as (b) calcium transfer to the inclusions and (c) diffusion within the calcium aluminate product layer. Furthermore, the competition of sulfide inclusions with alumina for calcium is taken into account. The results from the model show good agreement with industrial data for calcium pick up by inclusions in the melt.
Formation Mechanisms of Inclusions in Spring Steels: Sha Lv1; Zongze Huang2; Zan Yao2; Xiaodong Ma1; Geoff Wang1; Zhouhua Jiang3; Jin Zou1; Baojun Zhao1; 1The University of Queensland; 2Baosteel; 3Northeastern University
55SiCr is one of the important spring steels widely used in automobile manufacturing. The presence of micro inclusions in the steel can significantly inﬂuence a number of spring properties such as fatigue strength. It is important to understand the mechanisms of the inclusion formation so that size and proportion of the inclusions can be controlled. Inclusions in Si-killed 55SiCr spring steel have been analysed by scanning electronic microscopy and electron probe X-Ray microanalysis. The chemistry of the inclusions observed in 55SiCr steels can be represented by the SiO2-Al2O3-CaO-MgO system. It was found that the compositions of the inclusions cover a wide composition range which indicates that these inclusions were formed from different reactions. The possible mechanisms of the inclusion formation are discussed. It would be possible to use these fundamental properties to characterize and manage the inclusions in the spring steels deoxidised by Si.
Investigation on Coal Combustion Behaviors under the Oxygen Blast Furnace: Zhenfeng Zhou1; Yuanyuan Zhang1; Guang Wang1; Jingsong Wang1; Qingguo Xue1; 1University of Science and Technology Beijing
The oxygen blast furnace was a new technology of ironmaking, and the oxygen and CO2-stripped blast furnace top gas were blown into the blast furnace replacing the conventional hot air. The oxygen blast furnace could reduce the consumption of coke and emission of carbon dioxide. In this paper, a three-dimensional numerical model was developed to simulate the lance-blowpipe-tuyere-raceway region of a blast furnace, and the flow and combustion behaviors of coal particles were investigated based on an oxygen blast furnace. Compared with the traditional blast furnace, the combustion characteristic in the raceway of the oxygen blast furnace was different. In addition to the combustion of coal and coke, the combustion of large amount of reducing gas was included. The coal combustion of different oxygen content (70%、80%、90%、100%) and coal ratio were investigated.
Inclusion Control with Ca Treatment to Improve Castability of a Low Carbon Al Killed Steel: Stanley Sun1; Steve Waterfall1; Norbert Strobl1; Dongsheng Liao1; Don Holdridge1; 1ArcelorMittal Hamilton
High melting point inclusions, such as spinel, Al2O3 and Al2O3 rich calcium-aluminates, have strong tendency to agglomerate on tundish stopper rod and SEN during steel casting process and eventually to cause SEN clogging. Ca treatment by Ca wire injection during steel refining at LM is commonly used to modify those inclusions to low melting point inclusions. However, too much Ca injection (Ca over-treated) could cause operational issue (slide gate plate erosion), as well as increase Ca cost. Therefore, it is desirable to control an appropriate amount of Ca to avoid either under- or over-treatment. Based on inclusion analysis with ASPEX system, Al2O3 and Al2O3 rich calcium-aluminates were identified as major contribution to SEN clogging at ArcelorMittal Dofasco EAF steelmaking stream. A Ca treatment index was developed to evaluate effectiveness and to improve the inclusion modification. The improved inclusion control has reduced SEN clogging and improved steel quality.
3:25 PM Break
High Temperature Mineralization Mechanism of Granules during Iron Ore Sintering Process: Wei Lv1; Xiaohui Fan1; Min Gan1; Xuling Chen1; Zhiyun Ji1; Yang Zhou1; Guojing Wang1; Qiang Li1; 1Central South University
Mineralization during sintering is a process to make part of the raw material melt after serial complex chemical reactions at high temperature. However, high temperature mineralization behavior of the adhesion layer and nucleus particles in the granules during the sintering process has been studied. Research findings reveal that solid-phase reactions between iron ores and fluxes in adhesion layer occurred first, of which the product would induct the generation of the initial liquid phase. By the assimilation of the initial liquid phase, fluxes which served as nucleus particles in granules, such as limestone and dolomite, could dissolve in the liquid phase and extend its amount as increasing temperature, whereas iron ore nuclear particles remained as unfused ores for their insufficient mineralization. Therefore, the mineralization proceeding for sintering was achieved: the iron ores in fine fraction(-0.5mm) reacted with all fractions of fluxes to form the melt zone, while the coarse iron ores(+0.5mm) acted as unfused ores, which formed the final sinters together with the melt zone.
Investigation of High Chromium Steel on the Different Salt-bath Heat Treatment Conditions: Cheng-Yi Chen1; Fei-Yi Hung1; Truan-Sheng Lui1; Li-Hui Chen1; 1National Cheng Kung University
This research used the austempering heat treatment on the SS440 thin plate specimen with a type of double-loop and obtained the mixed phases which is bainite and carbide. The different salt-bath temperature was controled to obtain the content of the each phase. We used different austempering heat treatments to obtain a matrix containing bainite, retained austenite, martensite and the M7C3 phase to investigate the relationships between the resulting microstructure and tensile mechanical properties. Then we investigated the relationships between the resulting microstructure and tensile mechanical properties.
Reduction Behaviors of Sinter Made from Magnetite Concentrates in Reducing Process Simulated COREX Shaft Furnace: Benjing Shi1; Deqing Zhu1; Jian Pan1; Xuxiao Xue1; 1Central South University
COREX smelting reduction process which is freed of metallurgical coke provides a sustainable developing way for ironmaking industry. However, the shortage and high cost of pellets limit its development in China. Meanwhile, iron ore sinter has a great output in China. This work studied the reduction behaviors of sinter made from magnetite concentrates during the reducing process of COREX shaft furnace and compared the RI and RDI of sinter with BF process. The results showed that the reduction degree of sinter increased obviously during the temperature zone from 600℃ to 850℃, while the reduction degradation presented rapidly aggravate in the temperature zone from 450℃ to 550℃ in COREX shaft furnace. Sinter got higher RI than BF process but also got higher RDI in reduction temperature range from 450℃ to 600℃, which means sinter would have heavier disintegration in COREX shaft furnace.