Sequential Casting Research Articles

Mathematical Modeling of Iron and Steel Making Processes. Optimum Magnetic Flux Density in Quality Control of Casts with Level DC Magnetic Field in Continuous Casting Mold.

Application of level DC magnetic field (LMF) in continuous casting mold decreases the mixing length at the ladle change region in sequential casting of different steel grades and improves the inclusion quality of cast slabs. Until now control condition for the mixing of steel compositions which depends on the fluid flow of molten steel has only been clarified. However, control condition for the inclusion whose behavior is not always the same as the behavior of the molten steel flow has not been clarified yet. In this study, continuous casting experiment and numerical analysis were conducted to derive the control index for inclusion and to estimate the optimum condition for improvement of inclusion quality in cast slabs with LMF. The followings are results: Optimum magnetic flux density exists to control the inclusion quality in cast slabs with LMF. Inclusion behavior is explained by the balance between the penetration of inclusion controlled by magnetic field and the floatation of inclusion. This optimum magnetic flux density can be characterized by the interaction parameter, which is expressed by the ratio of inertial force caused by pouring flow to magnetic braking force (Lorentz's force) caused by magnetic field.

製鋼 ＣＣタンディッシュ熱間リサイクル技術の改善

In recent years, the diversification in steel grades and smaller lot in weight is strongly desired among customers. Those results in the decrease of sequential casting ratio, and the refractory cost of tundish raises. To solve this problem, tundish recycle operation in hot condition was developed in Chita Plant, Daido Steel Co. Moreover several improvements are applied to TDR operation to extend TD life. They are summarized as follows: (1) The immersion nozzle quick exchange operation and the slide valve quick exchange operation have been developed in order to avoid the problem of refractory life such as immersion nozzle and slide valve. (2) The improvement of stopper tip refractory makes it possible to decrease the failure in not only stopping molten steel at the end of cast but also the break of stopper tip at the beginning of cast. As the result, we succeeded in the extension of the TDR operation and the TD refractory cost is decreased to 40% of that without TDR operation.

Influence of Roll Bending on Center Segregation in Continuously Cast Slabs.

The influence of roll bending on center segregation in continuously cast slabs was studied by conducting the test in which roll bending was controlled during casting. The behavior of roll bending and center segregation in sequential casting were also investigated. As a result, it was clarified that (1) variations in center segregation in the casting direction are attributable to roll bending and center segregation deteriorates with increasing roll bending, (2) the amount of roll bending increases up to 1.7 mm during casting, as a result of which variations in center segregation in the casting direction are increased and segregation deteriorates with increasing number of cast heats in sequential casting, and (3) the use of divided rolls in the final stae of solidification is effective in decreasing roll bending and keeping center segregation at lower level. Of all mechanical factors, roll bending was estimated to be the largest factor for deterioration of center segregation in the case of casting employing one-piece rolls of conventional type.