Study of the Formation Mechanism of A-Segregation Based on Microstructural Morphology

Carbon Macrosegregation Pattern in 30Cr15Mo1N Ingot: Impact of Pouring Rate

“…Notably, the region with the largest SR is not at the center but at approximately a quarter radius from the center, which indicates the occurrence of A-segregation within the ingot. [12,27] This is because the growth of equiaxed grains partially restricts the solute-enriched liquid steel from moving toward the center. At approximately the quarter radius region, the CET is completed and the number of equiaxed grains increases, as shown in Figure 1.…”

“…Therefore, the carbon macrosegregation is the most pronounced at approximately the quarter radius position of the ingot. [12,27] The segregation ratio at the center line of the ingot is shown in Figure 7b. Taking 0.28 kg s À1 as an example, it can be found that the SR at the top of the ingot is greater than 1, which is positive segregation; and the SR at the bottom of the ingot is less than 1, which is negative segregation.…”

“…Taking 0.28 kg s À1 as an example, it can be found that the SR at the top of the ingot is greater than 1, which is positive segregation; and the SR at the bottom of the ingot is less than 1, which is negative segregation. [12,27] To explain this result, the temperature, fraction solid and flow of molten steel at 0.28 kg s À1 were investigated as shown in Figure 8. During the pouring process, the newly entering molten steel flows downward due to gravity.…”

“…This affects the quality of the ingots and may even render them unusable. [ 12 ] Moreover, macrosegregation is difficult to eliminate through subsequent heat treatment. [ 13 ] Therefore, reasonable control of casting process parameters to improve the degree of macrosegregation is extremely important for the successful preparation of high quality 30Cr15Mo1N steel ingot.…”

Multiphase Solidification Modeling of Solidification Structure Evolution and Macrosegregation of Round Bloom Continuous Casting Process with Mold Electromagnetic Stirring and Final Electromagnetic Stirring

“…[10][11][12][13][14][15] Although significant progress has been made in developing the mixture model, the effect the solidification structure on the macrosegregation cannot be elucidated till now, because the mixture model lacks the capability of considering the solidification structure evolution and solute distribution between the dendrite trunk and interdendritic liquid. CA, as a stochastic method for micro/macrostructure simulation, has been widely used to directly predict the solidification evolution in continuously cast steel, [16][17][18][19][20] and some successful works for macrosegregation simulation in small size castings with CA method has been reported, [21][22][23][24] but it still faces a great challenge of directly coupling solute diffusion, fluid flow, and grain growth during the continuous casting process of steel, because of huge computation burden. Compared with the continuum method and CA method, the representative volume element (RVE) is introduced into the volume-averaged method to avoid directly predicting the solidification microstructure evolution, and the typical solidification features, such as microstructure evolution, interdendritic solute diffusion, interphase heat transfer, interphase mass transfer, fluid flow, etc., are all included in the RVE.…”