Continuous casting of flat products today is a mature technique for production of steel semis with an as‐cast thickness of 200 mm. At present, the thin slab casting is developed to the extent of casting and in‐line rolling of strips with a thickness of 1–2 mm. Up to now, it is reported that 27 thin slab production lines are under construction or in operation. The strip‐casting technique is the next generation of production lines for steel to be developed for production of flat products. There are 2 main directions in the development of strip casting. The 1st is the twin roll casting technique, which so far has concentrated its efforts on production of stainless steel strips. The 2nd is the single‐belt casting technique (DSC – Direct Strip Casting) which is aiming for high production volumes of flat products with the necessary hot reduction possibility to receive good material properties.The development of strip casting at MEFOS started in the late 80s with the joint efforts of a Nordic group of steel companies. The aim of the project was to built up know‐how in the field of strip casting by the erection and operation of a strip caster at MEFOS. After a 1‐year prestudy, the single‐belt casting technique was chosen. The German machine‐building company, Mannesmann Demag Metallurgy, and the Nordic consortium had complementary interests, and in 1991, a co‐operation agreement was signed in the field of strip casting. At MEFOS, the emphasis is focused on the industrial application of casting 870 mm wide strips, while the focus of the development at Technical University of Clausthal (TUC) is devoted to casting and in‐line rolling. Based on the potential of the process and the promising results obtained in the research facilities, the industrial partners are now in the position to decide on building a demonstration caster in a steel plant.
When Inexa planned to increase charge weights, it was important to increase productivity of the caster in order to meet the requirements from the primary furnaces. With the existing caster and for certain grades difficulties arise to meet quality standards at increased casting speed. To counteract this problem soft reduction technique was planned to be developed. A solidification model of the Inexa bloom caster was developed using the software package TEMPSIMU to aid in the design of a soft reduction unit. Additionally, a 3‐dimensional solidification model of the crater end position and shape during transient casting conditions was developed using the software THERMAL TRACKING. Shell thickness measurements using the wedge method were conducted for calibration of these models. A soft reduction unit was built and installed in one strand of the Inexa bloom caster. Soft reduction trials were carried out on the caster. The result from the trials indicated that it is possible to improve or maintain the centre quality of the blooms at increased casting speed with the installed soft reduction unit.
Ultrasonic-induced cavitation studies were conducted in lead-bismuth alloy at 500 and 1500 F, in mercury at 70 and 500 F, and in water at 70 F for a wide variety of materials, including refractory alloys, steels, brasses, copper, nickel, and plastics. Correlations of the cavitation damage with applicable mechanical and fluid properties were carried out. Some conclusions are: 1. Damage rates in mercury were 3 to 20 times greater than in water, depending upon the material. Hence, clearly no correlating equation which considers only the mechanical properties of the material can apply for both fluids. 2. There is no single material mechanical property which can be used to correlate the damage, even if coupling parameters to account for fluid property changes are included in the correlation. 3. In general, the best correlations include energy-type mechanical properties, strength-type properties, and fluid coupling parameters. 4. No relatively simple single correlating equation applies well to all the data. This may indicate the insufficiency of the statistically determined mechanical and fluid properties for the correlation of cavitation damage which is known to be a highly transient process.
Utilizing an ultrasonic vibratory cavitation facility, the onset of cavitation was observed in liquid sodium for different liquid sodium temperatures and at various sinusoidal pressure field frequencies. It was observed that the pressure oscillation required to initiate cavitation decreases linearly as the temperature of the sodium is increased from 500 to 1500 deg F. For frequencies below 20 kHz the cavitation threshold pressure amplitude is essentially independent of frequency. For frequencies above 20 kHz the cavitation threshold begins to increase sharply. Using the onset of cavitation data and the saturation temperature-pressure data for liquid sodium, the superheat required to produce nucleate boiling in liquid sodium was calculated. As the saturation temperature of liquid sodium is increased the calculated superheat decreases. For frequencies below 20 kHz the calculated sodium superheat requirements, which are independent of frequency, are in good agreement with steady-state sodium superheat data reported in the literature.
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