Finite Element Analysis of Dynamic Recrystallization of Casting Slabs during Hot-Core Heavy Reduction Rolling Process

Haijun Li,Zhaodong Wang,Tianxiang Li,Meina Gong,Guodong Wang

doi:10.3390/met10020181

Haijun Li, Zhaodong Wang + Show 3 more

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https://doi.org/10.3390/met10020181

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Abstract

Hot-core heavy reduction rolling (HHR2) is an innovative technology, where a two-high rolling mill is installed after the solidification end of a strand, which can significantly eliminate the core defects of the slab. The mill exhibits a heavy reduction ratio, which promotes the dynamic recrystallization (DRX) of the slab. This study aims to optimize the parameters of the HHR2 process considering the effect of DRX on microstructure homogeneity. The secondary development of commercial software DEFORM-3D is conducted to calculate the deformation and DRX behavior of HHR2 for different reduction ratios. The parameters of DRX volume fraction and DRX grain size are compared, and finer DRX grains are obtained when the greater reduction ratios are conducted in HHR2. Then, corresponding to the deformation conditions in the HHR2, the thermal–mechanical simulations are conducted on the Gleeble3800 to obtain the average grain sizes before and after this process. When the reduction amount increases from 20 mm to 50 mm, the difference of average grain size between the core and the surface reduces by 52%. In other words, appropriately enhancing the reduction ratio is helpful to reduce the average austenite grain and promote the microstructure uniformity of the slab. These results provide some valuable information on the design of deformation parameters for HHR2.

Highlights

As the raw material of hot-rolled steel, the quality of continuous casting slab has an essential influence on the quality of final products
Owing to an insufficient reduction ratio, these defects cannot be effectively eliminated in the subsequent rolling processes; heavy plates manufactured from slabs are always subjected to the deterioration of soundness and mechanical properties
As described above, owing to the mill, a large reduction is observed near the strand where the slab is wholly solidified during the HHR2 process

Summary

Introduction

As the raw material of hot-rolled steel, the quality of continuous casting slab has an essential influence on the quality of final products. The internal defects of continuous casting slab include center segregation, porosity, and shrinkage cavity. As reported by Thome and Karste [9], the SR should be conducted without creating internal cracks This technique generally allows a small reduction amount (a total reduction amount: 4–7 mm) to avoid the formation of internal cracks [10]. In this case, for blooms or slabs with larger sections, the amount of SR maybe not be sufficient to overcome the resistance of the thicker shell; the inner qualities could not be efficiently improved

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