Macrosegregation Quality Criteria and Mechanical Soft Reduction for Central Quality Problems in Continuous Casting of Steel

Abstract

In order to study the central quality of continuously cast tool steel slabs, the simple model has been developed to simulate the macrosegregation quality criteria. The model calculates different quality criteria such as average macro-segregation level criterion "ASL", its fluctuation level "FSL" and its segregation quality number "SQN". These criteria are calculated based on the previous measurements of carbon and sulfur concentrations distributions in final region of spray zones and centerline area of lower and upper slab sides. The effect of mechanical soft reduction Technique "MSR" on the slab centerline quality is examined and analyzed. The model results show that MSR affects the quality of centerline areas significantly by different ways based on the casting speed. The experimental and theoretical results clarify that the qualities of different slab sides are different for all collected samples. The model results show also that the accuracy of the macro-segregation quality criteria increases quantitatively with increasing the number of analyzed segregated elements. Therefore, the macrosegregation quality criteria and their distributions can be considered as the most simple and vital tool to evaluate the various slab qualities. Finally, the mechanism of centerline segregation formation with mechanical soft reduction is discussed in this study.

Coordinating optimisation of F-EMS and soft reduction during bloom continuous casting process for special steel

“…Moreover, Figure 4 gives the local topography of shrinkage cavity shown in Figure 1 using SEM analyses. It is seen that there are many columnar crystals present inside of the cavity, which means that the current parameters of soft reduction listed in Table 3 cannot sufficiently compensate the volume contraction at the final solidification stage [18,19]. Based on the discussions above, it can be concluded that the technique parameters of F-EMS and soft reduction have not met the critical conditions.…”

Industrial Application of Mechanical Reduction on Continuous Casting of Bearing Steel Bloom

“…The internal quality of the bearing steel bloom has great influence on its reliability and service life due to the inheritance of the defects from the bloom, such as shrinkage porosity, center segregation, and V-shaped segregation to the subsequent rolling product. Generally, homogenization of the chemical composition by means of electromagnetic stirring (EMS), pulsed magneto-oscillation (PMO), low superheat casting, low secondary cooling intensity, etc., is the most well-known approach to minimize the center segregation [1][2][3][4][5][6]. This approach aims to produce large ratio of equiaxed grains during solidification and normally is an effective way to reduce center segregation.…”

Electromagnetic Effects on Solidification Defect Formation in Continuous Steel Casting

“…However, it is difficult to respond instantaneously because most process parameters are difficult to control during operation. Mold taper, 11,12 spray cooling, 13,14 and soft reduction systems 15,16 are often set before starting casting and focus on steady-state solidification. Corrective action, such as responding to alarms from online breakout detection systems, for example, typically involve suddenly slowing the casting speed, which can lead to quality problems due to the transient conditions.…”