Experimental and Simulation Study on the Effect of Reduction Pretreatment on the Void Healing of Heavy Plate

Zhen Ning,Wei Yu,Qingwu Cai,Hongqiang Liu,Xue Li

doi:10.3390/met12030400

Zhen Ning, Wei Yu + Show 3 more

Open Access

https://doi.org/10.3390/met12030400

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Abstract

In addition to eliminating voids in a billet, the reduction pretreatment (RP) process can refine the austenite structure after reheating and can deform the residual voids, which affect the void healing behavior during insulation before rolling, and then can affect the final quality of the steel plate. In this study, the effect of the RP process on the evolution of voids in billets and steel plates was investigated by experimental and numerical simulation. RP and non-RP billets were reheated and rolled into 60 mm-thick steel plates, respectively, and the evolutionary behavior of voids within the plates was analyzed using ultrasonic flaw detection methods. Finite element method (FEM) and phase-field method (PFM) were used to investigate the mechanism behind improving the quality of steel plates under the RP process. The simulation results show that, in addition to directly closing the voids through plastic deformation, the RP process can promote the diffusive healing behavior during insulation before rolling by refining the reheated austenite organization and by increasing the curvature of the void surface. Due to the reduction in voids inside the steel plate, the impact energy of the RP steel plate is higher.

Highlights

Compared with isothermal deformation, when there is a temperature gradient between the workpiece’s surface and center, it is easier to eliminate the voids in the workpiece center [5,9,10]
The temperature gradient causes a difference in the deformation resistance between the surface and the core of the workpiece and leads to greater plastic deformation in the billet center
B it can be seen that there are some voids with a large size and a near-circular shape in Plate A and only some small voids in Plate B. This indicates that, in the case of the same total deformation, the reduction pretreatment (RP) process can effectively reduce the number of voids in the steel plate and can improve the quality of the steel plate

Summary

Introduction

Due to volume shrinkage that occurs during the solidification process, voids in a billet are inevitable. The common feature between these technologies is the use of the temperature gradient generated by solidification waste heat to produce a relatively large equivalent strain in the billet center, to eliminate void-type defects in the billet, to break the coarse as-cast structure, and to have a positive effect on improving the quality of the billet. For these processes, researchers have carried out much follow-up research.

RP Process

Rolling Process

Finite Element Method (FEM) Simulation for the RP Process

Results and Discussion