Research On Rolling Theory And Experiment For Longitudinally Variable Gauge Cold Rolling

One of the major issues that the steel industry will face in the12th Five Year period is to improve the quality and property of steel products and to realize the reduction for both steel production and steel application. The production of materials saving products, for example, Tailor Rolled Blanks (TRB) and Longitudinal Profile plates (LP plate) using Variable Gauge Rolling (VGR) technology is a useful method to realize the reduction of steel application. VGR technology has been used abroad right now; however, the research on it has not been thorough in China. This paper was based on theoretical research and the process of VGR cold rolling was studied. The main research results are as follows:(1) The characteristic of longitudinally VGR was analyzed. Fundamental equations of longitudinally VGR, differential equation of force equilibrium and horizontal speed equation in deformation areas, were built in this paper. These two fundamental equations are the cores of rolling theory for VGR. They play an important role in guiding the practice of VGR.(2) Differential equations of force equilibrium for both upwards rolling and downwards rolling were solved referring to the idea that A.и.Ц,eлнков used to solve the Karman differential equations of force equilibrium for common rolling. The unit rolling pressure distribution function for VGR was got.(3) Unit rolling pressure distribution function calculation application was developed. Combining with Origin7.0, the application was used to study the influence of some parameters on the unit rolling pressure distribution function for VGR by means of graphical method. In the same initial conditions, the peak of unit rolling pressure distribution curve increased with the increase of the friction coefficient and rolling reduction. It also increased with the increase of transition region shape factor during upwards rolling but decreased during downwards rolling.(4) Cold rolling deformation resistance of the high strength low alloy steel CR340was tested in the way of rolling and drawing experiment. The relationship between strength of materials and engineering strain was got so that cold rolling deformation resistance model was built by means of regression analysis. (5) Rolling force of upwards rolling and downwards rolling in a certain condition was calculated. The relationship between rolling force and nominal exit gauge was linear; If nominal exit gauge was same, the deformation areas and rolling force of downwards rolling were bigger than that of upwards rolling, however, the neutral angle was smaller.(6) Reliability of theoretical calculation was proved by means of rolling experiment. The reason for the difference between calculated value and actual value were analyzed. Gap setting method considering the mill spring and the elastic flattening of rolls was the reason of that difference in thick region rolling. A.и.Цeликов model has overestimated the friction peak and that caused the difference during the thin region rolling.(7) The sudden change of rolling force at the end of downwards rolling and the beginning of upwards rolling was discovered. The shift to rolling process, change of deformation areas and transformation of vertical motion state of rolls has caused this phenomenon.The base theory of longitudinally VGR built in this paper and the experiment analysis results serve as a basis for the application of VGR. They also set a basis to the setting of VGR parameters calculation.