Research On Deformation Behavior Of Thick Plate Rolling With Inter-Pass Cooling Process

With the development of social economy and the improvement of productivity,the demand for plates in marine ship,aerospace,transportation,energy and major equipment is increasing,and the thickness specification and quality performance of plates are getting higher and higher requirements.Due to the slab has internal defects such as looseness,shrinkage cavity and segregation on the casting process,the quality of the final product is seriously affected.Therefore,eliminating the internal defects is an urgent problem to be solved in the current thick plate production.However,in the conventional hot rolling,the thick plate has a issue of inhomogeneous deformation and small compression radio.It results in the problem that the internal defects cannot be closed.The rolling with inter-pass cooling process can be used to rapidly cool the plate before rolling to form a temperature gradient field with a core temperature higher than the surface temperature.It improves deformation permeability and solves the problem of insufficient internal deformation to improve product quality.It is based on the national thirteenth five-year science and technology support project(2016YFB0300600).In this paper,the deformation behavior of rolling is studied by the rolling with inter-pass cooling process.The main works and achievements are as follows:(1)Because of the limitation of solving the velocity and strain distribution during rolling with inter-pass cooling process by the plain cross-section assumption,three different crosssection assumptions were proposed in combination with the variation law of rolling velocity on rolling deformation zone.It improved the traditional velocity model and developed a rolling velocity model which is more consistent with the velocity of rolling deformation zone.The metal flow model which can predict the shape of the plate head on the rolling with inter-pass cooling process was derived by the improved velocity model.(2)The traditional rolling force model was improved by the parabolic rolling velocity model.Because of the large error in the calculation of rolling force on rolling with inter-pass cooling process by the conventional rolling force model,a rolling force model basing on the rolling with inter-pass cooling process was established by dividing the thickness temperature range and using a weight factor.It realized the prediction of rolling force on the rolling with inter-pass cooling process.(3)Because of the issue that the defects of thick plates cannot be eliminated due to insufficient internal deformation,the rolling processes basing on different temperature gradient were mainly researched.It was analyzed that water cooling coefficient,reduction rate,plate thickness and rolling pass how to effect the plastic strain state and the metal flow.The rolling conditions for improving the internal deformation rate were explored,which provided a theoretical basis for the rolling with inter-pass cooling process strategy in practical application.(4)Through comparing of the conventional rolling process and the rolling with inter-pass cooling process,it was analyzed that different reduction rates how to effect the thickness deformation rate,lateral spread and head flow.The experimental results showed that the rolling with inter-pass cooling process is beneficial to improve the deformation of the internal in comparison to the conventional rolling.The experimental results also verified the accuracy of simulation results,which has guiding role for process control with the mathematic model.