Characterizing the Inner Structure of Continuously Cast Sections by Using a Heat Transfer Model

Abstract

The inner structure of the continuously cast semis has a great importance from the point of view of further processing and application. The main reason for it is the very direct effect of the inner structure's features (i.e. porosity, macrosegregations, geometry of primary dendrites) on the technological characteristics features of the semis during further processing (i.e. crack sensitivity, formability, etc.). The paper deals with the possible ways of macrostructure determination on the basis of the results of mathematical modeling of continuous casting process. We paid special attention to the geometry of primary dendrites and to the columnar-equiaxed transition as a function of heat parameters of the casting process.

A Simple Model to Calculate Dendrite Growth Rate during Steel Continuous Casting Process

“…Due to the different cooling rates at different zones, the dendrite growth rate at the secondary cooling zone fluctuates a lot; however, the growth rate keeps in the range of 0.05-0.6 mm/s except that at the terminal solidification end, where a higher dendrite growth rate exists because of less heat released there. Many researchers 7,15,[21][22][23] reported the dendrite growth during continuous casting process ( Table 3) that agrees well with the current study. The orientation of the dendrite growth is illustrated in Fig.…”

Modeling on Dendrite Growth of Medium Carbon Steel during Continuous Casting

“…There exist some differences between Figure 3b and 3c because different casting conditions and different steel grades were used, such as casting speed as an important ingredient. In 19 the casting speed was 0.5 m/min, while in the current model the casting speed used was 1.0 m/min, which is a critical reason for the deviation in these two figures. Relatively, the consistent variation trends illustrate that the current calculations are reasonable.…”

“…So from that figure, the growth orientation is one branch of the casting speed direction. During solidification the dendrite tips are undercooled, so it can be supposed that the thermal gradient and cooling rate at liquid temperature should be determined 12. Assuming the slope of the isothermal surface of liquidus temperature is f (x, V c ) , where x is the distance downwards from the meniscus, which can be obtained by calculating the temperature field during solidification in continuous casting 8.…”

“…FiguresFigure33b and 3c show the validation of temperature gradient and cooling rate as a function of distance from the surface, respectively for the position of the liquidus temperature isotherm 19. There exist some differences between Figure 3b and 3c because different casting conditions and different steel grades were used, such as casting speed as an important ingredient.…”

“…Figure 6 shows the secondary dendrite arm spacing as a function of distance from the surface for different stability coefficients. The first validation uses the model that was based on the continuous casting process of a low carbon steel (0.16%C, 1.42%Mn) with 0.5 m/min casting speed and 45 K superheat 19. The second validation is based on a continuously cast near‐net shape (I‐beam) steel blank 20.…”