Abstract
Thermal simulation equipment (TSE) was recently developed to simulate the solidification process in the industrial continuous casting of slab. The grain growth, solid-liquid interface movement, and columnar-to-equiaxed transition (CET) in the continuous casting process can be reproduced using this equipment. The current study is focused on the effects of different cooling rates and superheat conditions on the grain growth in the solidification process of chromium-saving ferritic stainless steel (B425). The temperature distribution and microstructure evolution are simulated by a Cellular Automaton-Finite Element (CAFE) model. The experimental results demonstrate that the temperature gradient and the grain growth rate of the sample can be effectively controlled by the equipment. It is observed from optical micrographs of the microstructure that the average equiaxed grain ratio increases when the superheat temperature decreases. The average equiaxed grain ratio is approximately 26% and 42% under superheat conditions of 40 °C and 30 °C, respectively, and no apparent columnar grain generation in the samples occurs under superheat conditions of 10 °C and 20 °C, as the result of a large thermal resistance at the copper-sample interface and low superheat inside the sample. A lower cooling rate results in a higher equiaxed crystal ratio in the sample. As the cooling rate decreases, the equiaxed crystal ratio becomes 14%, 23%, and 42%. Comparing the simulation results with the experimental observations, a reasonable qualitative agreement is achieved for the chilled layer thickness, grain morphology, and CET in the sample. Thus, the CAFE model in the current study can accurately predict the grain growth under different superheating and cooling rate conditions.
Highlights
High temperature, opacity and difficult control are the characteristics of metal solidification processes
Zhai [11] has designed a Thermal Simulation Equipment (TSE), which is based on characteristics similar to that of the heat transfer and grain growth characteristics in a continuous casting slab
The results indicate that the columnar by experimental and numerical simulations
Summary
Opacity and difficult control are the characteristics of metal solidification processes. Over the last several decades, metallurgical technicians have used a considerable amount of labor and financial resources to obtain technological information during the solidification of a continuous casting strand They have designed several modeling experimental types of equipment (such as a scaled-down continuous caster) to study the continuous casting process in lower solidus temperature alloys instead of steel [9,10]. Zhai [11] has designed a Thermal Simulation Equipment (TSE), which is based on characteristics similar to that of the heat transfer and grain growth characteristics in a continuous casting slab. Compared with industrial and modeling experiments, this thermal simulation method has more advantages, such as simple operation, changeable cooling condition and low cost This equipment can be used to optimize the cooling conditions and technology parameters in the continuous casting process to improve the quality of the product. The nucleation and growth parameters of a CA model were validated by the TSE results; the CA model can accurately describe the grain growth process in the continuous casting of slab
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