Fluorite is added to steelmaking slag to improve fluidity and desulfurization reaction. Leaching of fluorine to soil, however, is regulated by notification of environmental ministry and is the tasks to be settlement in slag recycle. It is necessary to know a quantity of fluorine in slag correctly in order to solve above problem. Therefore, rapid analysis method of accurate fluorine quantity in slag is developed. This analysis method is extracts fluorine from slag by pyrohydrolysis, and to measure the fluorine with ion chromatograph. Addition of tungsten trioxide as reaction accelerator and heated at 1100 ℃ for over ten minutes as the pyrohydrolysis condition which completely extracted fluorine is adopted in this method. Quantity of fluorine analysis method has developed and shows good accuracy and compatible with good efficiency. It is revealed from the fact that this analysis method could analyze a quantity of fluorine with twenty samples automatically and the accuracy was about 2 % relative standard deviation.
Products made with magnesium alloy rolled sheets, such as cases of personal computers and so on, are recently increased by the advantage of the light weight. On the other hand, Ca addition into magnesium is also focused by a lot of researchers from the metallurgical point of view. The purpose of this study is to make clear the effect of casting conditions and Ca addition on the slab qualities of magnesium alloy. The results are follows. 1. By using of water cooled mold, the cooling rate at the center of the slab is about 5 times higher than that with non-water cooled mold. The high cooling rate reduces β phases (Mg17Al12), refines the grain size and enhances the hot workability. 2. The using of immersion nozzle and moving mold reduce the splash of the molten metal and improve the slab surface qualities. 3. Low casting rate reduces the porosity defects inside slabs. 4. Ca addition to magnesium alloy creates Al-Ca inter-metallic precipitates in place of β phases. Moreover, it makes the hot workability worse remarkably.
High nitrogen stainless steels have got a lot of attention recently because of its high material performance. In Europe, high nitrogen steels are produced through PESR (Pressurized Electro Slag Remelting) process. Silicon or chromium concentration is increase because silicon nitride or chromium nitride are used as nitriding agent in this process. Gaseous nitriding during melting by pressurized induction furnace is a favorable method to avoid this problem. Clarifying the nitrogen dissolution rate in the steel melt and formation condition of pore in ingots is important for operation. However, behavior of nitrogen dissolution into molten steel and formation of pore during solidification under pressurized atmosphere have not been cleared in larger scale furnace. Therefore, authors have investigated it by the use of 500 kg pressurized induction furnace. The results are follows: (1) Nitrogen dissolution rate of the 500 kg furnace was slower than that of 50 kg furnace. It is thought that this comes from the difference of surface detention time of steel melt. (2) Nitrogen concentration is able to predict with using appropriate thermodynamic parameters. (3) Nitrogen limit is proportional to square root of nitrogen pressure. Pore formation condition is same for the both size ingots and sample that directly took from melt before casting.
Since physico-chemical properties of liquid iron alloys and molten slag affects various phenomena in steelmaking process, the information on those properties is indispensable to control and design new technical processes. We sometimes, however, come across a situation of lacking those information, and we have to estimate the properties from some fundamental physical quantities. This paper describes some procedures to predict the surface tension and the viscosity of liquid iron alloys and molten slag. In addition, some useful literatures will be given on the prediction of the properties.
The steel making section in Chita plant, Daido Steel Co., Ltd. has many facilities, five electric arc furnaces, many kinds of refining devices, and two continuous casting machines, No.1CC, and No.2CC, and produce approximately 140 k tons a month crude steel which covers more than 90 % of that of Daido Steel. Forever, the ladle transportation delay due to the lack of the number of ladle crane and ladle transportation line cause the amount of CC production which is less than that of their ability to decrease. New ladle crane in CC shop, and new ladle transportation line from refining yard to CC shop have been introduced in order to solve the problems in Oct. 2004, and Jan. 2006. The effects of these works are the following. 1) Both No.1CC and No.2CC productivity increased (+18 ton/hr) because of the reduce of process time from the end of LF to CC start. 2) Power consumption of EAF and LF reduced because of decreasing of the molten steel temperature after refining. 3) CC tundish refractory life increased because of decreasing of continuous casting time and molten steel temperature in tundish.
Daido steel has developed a new caster, which features are semi-continuous, large cross section and vertical type. It was built in July 2004, and named "PHC"(Promising Hybrid Caster). The PHC has characteristics and advantages of both continuous caster and ingot casting process. And the process has the following quality results of the PHC bloom. -1) By applying extremely low speed casting technology, the internal quality of PHC bloom has improved. Its quality level is equivalent to that of the conventional bloom. -2) Variable width mould mechanism has been developed and introduced to PHC. The mechanism has made it possible to cast tapered bloom and greatly improved the internal quality of high carbon grades. -3) Punching press was introduced to prevent the oxidizing of cut section of the PHC bloom during cutting or reheating. The process is very effective to improve the quality of center part of PHC bloom and the rejection ratio because oxidizing of cut section is zero. -4) Shrinkage of the top part of PHC bloom has greatly improved by Top-heater. A s a result, crop loss of top part of Top-heated bloom has reduced by 80 % compared to that of as cast bloom.
As social concern in environmental issues had been rising, Kyoto protocol on preventing global warming came into force on February 16, 2005. In the protocol, Japan was required to cut the greenhouse gasses by 6 % compared to the year of 1990 during the five-year period of 2008-12. Placing the environmental issues as one of the most important issues through our business activities from a cooperate social responsibility standpoint, we recognize that reducing CO2 emissions is our high priority task which should be achieved as early as possible. Pursuant to Voluntary Action Program for Environmental Protection by Steelmakers presented by the Japanese Iron and Steel Federation, we have been promoting various environmental activities to reduce CO2 emission by 10 % compared to the year of 1990. In the steelmaking shop of our main plant, Chita plant, electricity accounts for large percentage of energy consumption followed by fuels such as heavy oil and kerosene. As in the fig.1, fuel cost for ladle preheater is 49.3 % of total fuel cost in Chita steelmaking shop. Being the key factor of reducing the whole fuel cost, yet its fuel consumption had not been greatly improved. Thanks to the introduction of regenerative burner on April 2005 and its optimization of combustion, fuel consumption of ladle preheater was improved. Outline of the improvements are described here.
As a furnace crucible refractory of Vacuum Induction Melting (VIM) furnaces, the precasting sleeve which had not been applied for the furnace having over 3 tons capacity has been applied for 3, 6, and 9 tons VIMs in Shibukawa plant, Daido Steel Co., Ltd. in order to increase its productivity. Daido had succeeded to increase lifetime of the precasting sleeve by couples of improvements, the composition of the material particle and the chemical composition, for example. On the other hand, the detection system of molten metal leak into the furnace refractory has been equipped for general VIM as the refractory lifetime judgment system to protect the induction coil and the insulator material. However the same system had been equipped for VIMs in Shibukawa plant for long time, it had a problem in detection accuracy and this was one of the major factors of inpede to increase the furnace refractory lifetime. A new detection system was installed in August 2004 in order to resolve this problem. However, there was also some difference between the system detection and actual value of the length of molten metal leak at the refractory replacement. Results of analyzing the factor that caused the differences and evaluation of the accuracy of the new system were reported in this paper.
As the treatment process of sewage sludge, we had already developed a new technology, carbonization, taking place of conventional prcesses such as compost, incineration and melting. Daido's carbonizing process produces a carbonized sludge adequate to utilization as a standby of soil or chacoal by the character of chemical contents, porous saface, and grain size etc. In recent years, the electric power industry was obliged to use a fixed quantity of new energy including biomass fuel by the enforcement of renewable portfolio standard. Carbonized sludge has also high calorific value and the field of electric power industry has a large potential of using carbonized sludge as biomass fuel. So we researched the additional application of utilizing it for biomass fuel and we introduce the results herewith.
The electronic toll collection (ETC) and the dedicated short range communication (DSRC) in intelligent transport systems (ITS) are realized. To improve electromagnetic environment of ITS beacon antenna, a wave absorbing pavement material consists of a carbon fiber has been developed. However, the oblique incidence characteristic of the pavement material that has been developed for the ETC is not enough to use for ETC and DSRC. Therefore, this research group is developing the wave absorbing pavement that mixed with DSM (Daido Special Recycling Process for Dust and Slag Melting) slag into asphalt. On the other hand, there was a base concrete layer under two asphalt layers. To design the wave absorbing pavement, we calculated with consideration of the impedance of the base concrete layer. In this paper, the relative complex permeability and permittivity of the pavement material were measured by the free space methods and the waveguide method. And the impedance of the base concrete layer was measured by the free space method. Then, the wave absorbing pavement of the oblique incidence characteristic was designed using the obtained material constants.