Papers by Keyword: Temper Rolling

Abstract: The current trend in temper rolling is to make a small reduction to steel strip in order to achieve higher strength with good formability and toughness. In addition, very high strength steels can be cold rolled twice with very small reductions. This causes problems in setup values for cold rolling. Rolling models are usually overestimating roll flattening in the case of small reductions.In temper rolling thickness reduction is small (0.5 – 3%) and the elastic deformation of the work roll should be taken into account [3]. However, standard circular arc roll gap models (e.g. Bland Ford Ellis combined with Hitchcock model) fail to predict the roll flattening and thus the rolling force [4]. In this work, finite element method has been used to define a simplified model for work roll flattening and contact length. Model describes the effect of reduction, strength of steel strip and roll radius.

Abstract: The present work investigates texture evolution stages in vacuum-degassed non-oriented electrical steels. The main idea behind the improvement of soft magnetic properties relies on deformation induced grain growth phenomena and heat transport phenomena promoting the preferable formation of columnar grains with so called cube crystallographic orientation {100}<0vw>. In order to achieve the desired orientation with appropriate microstructure state from magnetic properties point of view, we have used an adjusted temper rolling process at elevated temperature and subsequent dynamical annealing in laboratory conditions.

Abstract: Examination of the SIBM mechanism based on the dislocation substructure at the interior of the Goss oriented grain was carried out by changing the grain size prior to the temper rolling. The following results were obtained. 1) SIBM significantly increased Goss orientation during the eminent grain growth with the initial grain sizes from 18 to 55μm. 2) When the initial grain sizes were large, i.e. 37μm and 55μm, the rolling with the reduction beneath the critical value could not promote SIBM, even the normal grain growth could also be hindered. Consequently a proposal was made that the nucleation of the recovery appeared among substructure domains containing sluggish strain. There exists an adequate size of the domain which varies with the change both of the rolling reduction and the initial grain size.

Abstract: Semi-processed nonoriented electrical steels are very attractive products whose magnetic properties are significantly improved through annealing treatment in customers plant. The improvement is due to strong Goss texture formation by strain induced boundary migration (SIBM). In order to the effect of temper rolling reduction on the strengthening of Goss texture, temper rolling reduction was changed in the range of 2% to 8%. The annealing times was changed from 10 minutes to 180 minutes. A mechanism of grain growth during SIBM is suggested from our experimental data. In the specimen temper-rolled by 2%, relatively strong {111}<112> texture develops, whereas in the specimens temper-rolled by 4% through 8%, strong Goss texture develops as a result of SIBM during final annealing. It can be found from observed EBSD data that the Goss grains have the lowest stored energy in all temper-rolled specimens, which is confirmed by average image quality value in EBSD measurements. However, for the Goss grains to grow preferentially, stored energy difference between Goss grains and their neighboring grains may have to be higher than a certain critical value.

Abstract: During temper rolling, the reduction is small, the length of contact arc is short, and the elastic deformation of work roll is large. Roll shape is not circular arc, the assumption of circular roll shape is no longer applicable. In this paper, quintic B-spline function is used in interpolation operations with normal pressure distribution so that roll shape can be solved by Gaussian integration. And a rolling model based on non- circular contact arc for cold strip temper rolling is established. The calculated results show good agreement with the actual value. The model can meet manufacturing requirement of the field and receives better control effect of elongation.

Abstract: A set of new mathematical models have been developed to calculate the temper rolling force of 2050 strip temper rolling mill. Based on the fact of small plastic deformation and elastic deformation occurring on the entry and exit of the deformation zone, new stress boundary conditions are described. The inhomogeneous distribution of internal stress in thickness direction is taken into account in the models, instead of uniform internal stress and assumption of plane strain traditionally. The new mathematical models have been applied into the temper rolling of 2050 hot rolling mills with good results. Comparison of calculated values and testing values for nine typical products has been given. The result shows that the calculated value of rolling force of temper mill is accurate.

Abstract: This paper focuses on the analysis of the microstructure and of the texture through the sheet thickness after temper rolling of very thin ferritic steels. The study uses EBSD and X-Ray diffraction. Comparison is made between an interstitial-free (IF) steel and of some industrial low carbon ferritic steels used after ageing. The experimental results are discussed with respect to the anisotropy of the mechanical behaviour after temper rolling during simple shear tests.

Abstract: In temper rolling thickness reduction is small (0,5 – 2%) and the elastic deformation of the work roll should be taken into account. During finishing rolling, classical cold rolling theories fail to predict the roll flattening and thus the rolling force. Numerous different mathematical models have been developed for temper rolling process. However, often the non-circular theories are computationally expensive and the range of usability is questionable. In this study, elasto- plastic finite element analysis, laboratory rolling tests and inverse computing from skin pass mill process data has been carried out. The aim is to find the roll shape, contact length and the rolling force to create a simplified model for controlling of temper rolling. In addition, the ability of different skin pass rolling theories has been compared with measured process values.

Abstract: In order to elucidate the predominance of Goss grains after SIBM in electrical steel sheets, Goss, D-Cube and {111}<112> grains after temper rolling of 5 and 9% reduction were observed by TEM. In 5% strain the amount of dislocations in Goss grains was the smallest of the three orientations. In 9% strain dislocations in Goss grains were distributed more heterogeneously than the other two types of grains. It is considered that {111}<112> grains have large amounts of dislocations owing to high Taylor factors and the differences of microstructures between Goss and D-Cube grains are due to orientation stabilities. Goss grains are speculated to be easy to recover and therefore they are predominant after SIBM.

Abstract: The evolution of the microstructure, macrotexture, microtexture and mesotexture has been studied during the annealing at 760°C after temper rolling (9% thickness reduction) of a non-oriented electrical steel sheet containing 2 wt. % Si. Results showed that the coarse grained microstructure, obtained on annealing, is produced through a recrystallization mechanism that advances from the surface to the interior of the sheet. However, starting of this process is delayed due to the presence of Si. The majority of experiments carried out in this work have been repeated for a low-carbon steel (C = 0.0385; Mn = 0.18%) containing only 0.03% Si and the results obtained were practically identical to those observed in the steel containing 2% Si. The main difference observed between both steels was that the process of formation of the exaggeratedly large grains was slower in the steel containing 2% Si.