Control Method for Steel Strip Roughness in Two-stand Temper Mill Rolling

How to control surface roughness of steel strip in a narrow range for a long time has become an important question because surface roughness would significantly influence the appearance of the products. However, there are few effective solutions to solve the problem currently. In this paper, considering both asperities of work roll pressing in and squeezing the steel strip, two asperity contact models including squeezing model and pressing in model in a two-stand temper mill rolling are established by using finite element method（FEM）. The simulation investigates the influences of multiple process parameters, such as work roll surface roughness, roll radius and roll force on the surface roughness of steel strip. The simulation results indicate that work rolls surface roughness and roll force play important roles in the products; furthermore, the effect of roll force in the first stand is opposite to the second. According to the analysis, a control method for steel strip surface roughness in a narrow range for a long time is proposed, which applies higher work roll roughness in the first stand and lower roll roughness in the second to make the steel strip roughness in a required narrow range. In the later stage of the production, decreasing the roll force in the first stand and increasing the roll force in the second stand guarantee the steel strip roughness relatively stable in a long time. The following experimental measurements on the surface topography and roughness of the steel strips during the whole process are also conducted. The results validate the simulation conclusions and prove the effect of the control method. The application of the proposed method in the steel strip production shows excellent performance including long service life of work roll and high finished product rate.

Nonlinear Finite Element Analysis of Thin Strip Temper Rolling Process

To reveal the basic deformation mechanisms under the conditions of high friction, small reduction, and long contact length in thin strip temper rolling process, an elastoplastic finite element analysis of plane strain upsetting was made based on the FEM software Marc. The results indicated that a near flat ＇zero reduction＇ region was present in the center of the contact arc. The simulation results about the effect of rolling parameters on the central flat region showed that any change of increasing the rolling force could result in or enlarge the central flat region in the deformation zone. Stress distribution results illustrated that the metal was in triaxial compression state. Although the maximum and minimum principal stresses were all much larger than the yield stress of the strip, the equivalent stress became lower than that, and no further plastic strain, even a small elastic spring-back occurred in the central flat region. That was the problem of ‘hydrostatic pressure＇ in thin strip temper rolling.

Effect of Temper Rolling on Tensile Properties of Low-Si Al-Killed Sheet Steel

The tensile properties of steel after temper rolling are affected by the reduction; low-Si Al-killed sheet steel was taken to study the effect of temper rolling on the tensile properties. The results indicate that the yield strength first decreases with the increase of reduction,and then increases. The relationship between the yield strength and the reduction can be expressed using quadratic function. The tensile strength increases with the increase of the reduction,while the total elongation decreases with the increase of the reduction,and the relationship between them and the reduction can be expressed using power function. Under the same condition,the results also indicate that the yield strength and tensile strength of steels across the rolling direction are all larger than those along the rolling direction; there is no obvious distinction between the total elongation along the rolling direction and that across the rolling direction.

Generation mechanism of quarter buckle in hot-rolled temper rolling

To reveal the generation mechanism of the quarter buckle in the process of hot-rolled temper rolling,the elastic–plastic finite element method is used to calculate the deformation of the roll and the strip during the temper rolling.The change of the cross section of the strip and the distribution of the longitudinal stress are analysed under different bending forces to obtain the boundary conditions of the quarter buckle.The generation of the quarter buckle is further analysed from the bending and contact flattening of the roll system and the elastic recovery of the strip after rolling.We found that the quarter buckle is closely related to the high-order distribution of the contact flattening between the work roll and the strip and is less affected by the bending deformation of the roll and the contact flattening between the rolls.Finally,a new work roll contour of the locally variable crown is proposed to change the distribution of contact flattening between the work roll and the strip.It is verified through theoretical calculations and industrial applications that the new contour can effectively improve the quarter buckle.

Numerical simulation of air purging conditions during steel sheet temper rolling process

The application of the lubricant in the temper rolling process of tinplate manufacturing improves the mechanical properties and surface quality of the steel sheet.The removal of the residual lubricant deserves and has rarely been studied via numerical simulation.A simplified model of a single stand temper mill was established and was discretized into cells of block-structured grids.The criterion whether the lubricant could be removed was decided via multiphase simulation of a smaller model.Three parameters,the gap between the deflector and the rolls,the length of an additional baffle and the velocity of the purging air,were considered and scores of different working conditions were performed.The shapes of the steel sheet between the temper rolls and the bridle roll were also studied to screen out the conditions that the sheet could move steadily.