Research On Metal Flow Law Of Ultra-heavy Plate During Variable Gauge Rolling Process

As one of the important steel products,the ultra-heavy plate is widely used in various aspects of national economic construction,such as architecture,bridges and military.The continuous casting heavy slab has many problems,such as the internal organization loose,grain coarsening and segregation,insufficient compression ratio during conventional hot rolling,poor strain permeability in the thickness direction,uneven deformation,load restriction on the rolling equipment and so on.This paper gives the idea to use the variable gauge rolling technology to produce ultra-heavy plate in order to overcome the bite limit of continuous casting heavy slab and reduce the impact of head impact torque peak on rolling equipment.Furthermore,this technology also can improve the deformation permeability of the rolling stock by increase the single pass reduction in order to promote the deformation to the core of the rolling plate and improve the core performance and quality of the ultra-heavy plate products.Based on the basic theory of variable gauge rolling,a three-dimensional variable gauge rolling model was built by DEFORM finite element software.The effects of different rolling process parameters on the deformation stress-strain distribution,metal flow law and rolling load of rolling plate were obtained by numerical simulation.The main research contents are as follows:(1)The similarities and differences between conventional rolling and variable gauge rolling are analyzed based on the traditional rolling theory.The parameter equations such as the bite angle,neutral angle,contact arc length and forward slip formula of variable gauge rolling are derived.(2)The functional characteristics and solving steps of DEFORM finite element software are introduced,three-dimensional model of conventional rolling?variable gauge rolling and wedge rolling were established.The influence of three rolling processes on the core strain of rolling plate were analyzed.The results show that the variable gauge rolling is beneficial to the metal deformation to the core of the rolling stock.(3)With finite element software,the linear and arc-type curve types of variable gauge rolling process were simulated.The influence of the different curve type on the metal flow and the rolling load of the ultra-heavy plate were analyzed.The result shows when the pass reduction is larger at the first pass of the rolling of straight line thickness curve,and the first pass reduction of the arc-shaped thickness variation curve is smaller and then the core strain of the rolled piece is larger when the two passes are completed.The rolling force and rolling torque are positively correlated with the rolling reduction.(4)The variable gauge rolling process of ultra-heavy plate with three kinds of velocity schedule,such as rectangular schedule,triangular schedule and trapezoidal schedule,were simulated.The effects of different velocity schedule on the metal flow and rolling load of the ultra-heavy plate were analyzed.The result shows that when the horizontal speed is 1.4m/s?1.6m/s for all three velocity schedules,the strain of the core metal is larger and the deformation is easy to penetrate into the core.The rolling force and rolling torque are positively correlated with rolling speed and the rolling reduction.(5)The industrial experiments of conventional rolling and variable gauge rolling were completed on the plate mill.The effects of the two rolling processes on the microstructure and mechanical properties of the ultra-heavy plate were analyzed.The experimental result shows that comparing with conventional rolling process,the variable gauge rolling can increase the core deformation of plate,improve the deformation permeability and the intrinsic quality of the ultra-heavy plate.