2009 Volume 95 Issue 11 Pages 801-806
Straightening process of steel tubes is the final process in tube making processes and it has a very important role for straightening in the longitudinal direction and improving roundness and thickness distribution of the cross section. To satisfy the demand for the higher tolerance of steel tubes, optimization of the working conditions in this process has been a serious problem. However, there are few studies on the straightening process of tubes because of the complexity of 3-D deformation behavior. In this research, effects of roll inclination and crushing on the roundness of a tube are examined by FE analysis of rounding of the cross section with a single straightening machine. When the crushing is large, spiral redundant plastic deformation occurs in the tube and the roundness of tube becomes bad. When the crushing is very small, elastic strain which occupies almost of the deformation is recovered. Since the roundness is improved by bending and unbending the cross section repeatedly, it is clarified that the number of cycles of the spiral deformation is an effective parameter. Therefore, we define the contacting ratio between the rolls and the tube and improvement of the roundness can be estimated by this ratio. When the contacting ratio is larger than 80%, the roundness becomes good.
