Study On Process And Key Technology Of Two-roll Straightening

With rapid development of machinery industry and the national economy, especiallyin the automotive and aviation industries, the increasingly high demand of steel productsis put forward, especially in higher requirements for the quality and accuracy ofbar.Straightening is a very important and critical process in the manufacture andproduction of bars. Two-roll straightener attracts more and more attention due to itssimpler structure, higher straightening precision and lower cost than multi-rollstraightener. But the design of two-roll straightener and roll shape is far behind theproduction requirements. There is no clear guidance in the actual production process. Thekey technology of roll shape is mastered by foreign manufactures, and replacing roll canonly rely on expensive imports, which greatly increases the cost of domestic production.Developing the new two-roll straightener with independent intellectual property rightscan significantly reduce production costs and improve straightening quality. Thereforethere is far-reaching significance of developing two-roll theory and technology for thedevelopment of domestic steel industry.Firstly, referring to actual production, the finite element model(FEM) of two-rollstraightening is built through ABAQUS. The contact area between bar and rolls andguides in straightening is analyzed. Curves of straightening force and supporting forceversus time are given. The stress-strain state is analyzed in different moments ofstraightening. The straightness of bar is obtained by analyzing the central nodecoordinates distribution. By comparison with actual production, the analysis results are inline with the actual situation, so there is reference value of this FEM.Secondly, as reasonable process parameters are not easy to determine and wear ofrolls and guides is severe during straightening. Based on above FEM, variations ofstraightening force, supporting force of guides, degree of plastic deformation, residualstress and the maximum deflection of bar after straightening are analyzed in differentprocess parameters. Reasonable parameter values are presented by comprehensiveconsideration. The new parameter values can satisfy the straightness, as well as lowerenergy consumption and reduce wear of rolls and guides. Thirdly, the study of roll shape is started from elastic-plastic bending theory of bar,then the relationship between various curvature is analyzed. The change law of residualcurvature in straightening is given, and the single-arc roll is presented that it can alsostraightens bar through theoretical analysis. The rolls designed by existing design methodare found that they cannot satisfy straightness and the reason is pointed out. Throughanalyzing the plastic deformation and straightness after straightening, the bendingcurvature is adjusted constantly and the responding straightening is simulated by FEM atthe same time until straightness of bar meet the requirement. The roll shape designed bynew method is contrast with the real roll and the shapes are basically identical. Theprocess of design will provide reference for the subsequent design of concave roll shape.Finally, with improvement requirements for the bar quality, residual stress hasbegun to attract attention of customers. In this paper, the residual stress is tested byblind-hole method and the result of simulation is contrasted with the test.In short, the FEM of two-roll straightening is built by reference to the actualconditions. The process parameter values are modified by analyzing various factors indifferent values of parameter. The energy consumption is lowered and wear is reduced byusing proposed process parameter values. The roll designed by new method is consistentwith the actual roll, so the problem of rolls relying on import is solved, and the cost ofchanging rolls is greatly reduced.