K. Sorimachi

Bio: K. Sorimachi is an academic researcher from Kawasaki Steel Corporation. The author has contributed to research in topics: Continuous casting & Ductility. The author has an hindex of 1, co-authored 1 publications receiving 250 citations.

Crack formation in the continuous casting of steel

Abstract: This review examines the different types of internal and surface cracks that can form during the continuous casting of steel. For each crack type, the operating and metallurgical factors that are known to influence crack formation are assessed in the light of the high temperature mechanical properties of steel and a knowledge of the stresses generated in the solidifying shell. The importance of two zones of low ductility in steel is demonstrated by this approach. One zone exists above 1340°C and probably accounts for the formation of all internal cracks and surface longitudinal cracks. The other zone lies between 700 and 900°C and is related to the presence of soluble aluminum, niobium and vanadium. Transverse surface cracks in slabs can be related to the latter zone.

Aluminium nitride in steel

Abstract: Aluminium nitride (AlN) nucleates with difficulty in steel, unless precipitation is enhanced by thermal or mechanical treatments. This important characteristic determines the precipitation kinetics of AlN, and accounts for the wide variations in precipitate morphology achieved following different processing histories. The most significant effect of AlN in steel is on grain size control, which directly influences hardenability, hot ductility, texture development, and mechanical properties. In addition, the accompanying removal of nitrogen from solid solution affects the strain aging characteristics, weldability, mechanical properties, and creep performance. Aluminium nitride also exerts important second order effects through its influence on the precipitation of other alloy nitrides. The precipitation of AlN can cause embrittlement and cracking phenomena in castings, continuously cast products, ingots, and rolled or forged products, However, the basic mechanisms are well understood, and the occurre...

Hot-ductility behaviour of C–Mn–Nb–Al steels and its relationship to crack propagation during the straightening of continuously cast strand

Abstract: The influence of composition on the tendency for surface-crack propagation to occur on straightening of continuously cast strand of a commercial C–Mn–Nb–Al grade of steel has been examined and compared with the hot-ductility behaviour obtained from Gleeble tensile tests, using reduction of area as the measure for hot ductility. The tendency for surface-crack propagation was found to increase with Nb and soluble Al addition and to decrease with a rise in the P level. Hot ductility was also found to be affected in a similar manner by these elements. The results have been interpreted in terms of differences in the effectiveness of the NbCN precipitation in pinning the γ grain boundaries during deformation. From the close agreement between the hot-ductility behaviour as given by the Gleeble tests and the tendency for surface cracks to propagate during straightening of these steels at the exit from the continuous-casting machine, it has been concluded that the Gleeble test can be used with a fair degre...

The effect of melt composition on solidification cracking of steel, with particular reference to continuous casting

Abstract: An analysis is presented describing the microsegregation of phosphorus in steel, intended to be representative of the behavior of the tramp elements associated with solidification cracking (hot tearing). The expected effect of carbon content is incorporated into the model and the rationale may be extended to encompass other addition elements influencing the preferential freezing of ferritic or austenitic phases. The treatment employs partition coefficients and diffusivity data from the literature and is based on a new back-diffusion model. This approach allows the cracking susceptibility criterion suggested by Clyne and Davies to be applied and leads to predictions concerning the effect of carbon level which are in broad agreement with experimental data.

Mathematical modeling and optimization strategies (genetic algorithm and knowledge base) applied to the continuous casting of steel

Abstract: The control of quality in continuous casting products cannot be achieved without a knowledge base which incorporates parameters and variables of influence such as: equipment characteristics, steel, each component of the system and operational conditions. This work presents the development of a computational algorithm (software) applied to maximize the quality of steel billets produced by continuous casting. A mathematical model of solidification works integrated with a genetic search algorithm and a knowledge base of operational parameters. The optimization strategy selects a set of cooling conditions (mold and secondary cooling) and metallurgical criteria in order to attain highest product quality, which is related to a homogeneous thermal behavior during solidification. The results of simulations performed using the mathematical model are validated against both experimental and literature results and a good agreement is observed. Using the numerical model linked to a search method and the knowledge base, results can be produced for determining optimum settings of casting conditions, which are conducive to the best strand surface temperature profile and metallurgical length.

Initial Development of Thermal and Stress Fields in Continuously Cast Steel Billets

Abstract: A mathematical model has been developed to compute the thermomechanical state of the shell of continuously cast steels in a round billet casting mold. The model determines the temperature distributions, the stresses in and the gap between the casting mold and the solidifying strand. The effect of variations in steel carbon content and mold taper on the thermal, displacement, and stress fields are examined. Comparisons with available experimental observations verify the predictions of the model. The model demonstrates that the thermal shrinkage associated with the phase change from delta-ferrite to austenite in 0.1 Pct C steel accounts for the decreased heat transfer observed in that alloy, as well as its susceptibility to cracking.