Many strip materials are coiled after rolling process. The stresses are imposed on the material wound on the automatically controlled collapse mandrel under the coiling tension. The coiling process can be described by...Many strip materials are coiled after rolling process. The stresses are imposed on the material wound on the automatically controlled collapse mandrel under the coiling tension. The coiling process can be described by three typical cases: winding without automatic adjustment, winding with automatic adjustment and after mandrel removal. A new model of equations for predicting the stresses during the strip coiling process is built by consideration of the three cases respectively. By solving the equations of different typical cases, the radial stresses and tangential stress of the layers of coil can be calculated. Also, the coiling parameters, such as strip thickness, coiling tension and necking critical pressure, affecting the coil performance are investigated. It is believed that the present model can be used for design and control of the automatically controlled collapse mandrel.展开更多
The present work aimed to investigate the effect of coiling process conditions on microstructure development in a low-Si content TRIP （transformation-induced plasticity）-assisted steel after thermomechanical process...The present work aimed to investigate the effect of coiling process conditions on microstructure development in a low-Si content TRIP （transformation-induced plasticity）-assisted steel after thermomechanical processing. In this framework, compression samples which were deformed above Tnr and then intercritically annealed were held isothermally for different durations at temperatures below bainite transformation start temperature. Microstructure of samples were characterized by optical and electron microscopy, XRD （X-ray diffraction） and M6ssbauer spectroscopy. The results indicated that due to low-silicon content of the present steel, the incomplete bainite reaction phenomena was not observed and, hence, the maximum carbon enrichment of residual austenite was achieved in the samples which held for short durations. It was also shown that the maximum carbon enrichment and volume fraction of residual austenite were achieved at intermediate bainite hold temperature of 450 ℃ as the result of competing phenomena, such as microstructural refinement, dislocation density, carbide precipitation and growth.展开更多
During the thin strip coiling process, it is necessary to use a sleeve with a mandrel to prevent excessive deformation of the strip. Stress distribution in the sleeve and in the strip is an important factor that deter...During the thin strip coiling process, it is necessary to use a sleeve with a mandrel to prevent excessive deformation of the strip. Stress distribution in the sleeve and in the strip is an important factor that determines the quality of the coil. However, owing to the accumulation of high pressure, it is difficult to determine the stress distribution through experimentation. Thus, stress analysis of the strip coiling process was conducted. Finite element analysis was used to investigate the effects of the weight of the strip and the mandrel on the stress distribution and stress concentration near the starting point of the coil. The radial stress was predicted for a coil with a stacked thickness of 384 mm, which corresponds to a strip length of 1486 m, using the stress analysis model developed in a preceding research. A method was presented to reduce the weight and radial stress of a strip coil. It was found that the deformation of the sleeve can be reduced by decreasing the gap between the mandrel segments. The thickness of the sleeve can be reduced from 120 to 106 mm using the stress analysis results. Furthermore, coiling tension can be reduced by 44% compared to the existing value considering the interlayer slip of the strip coil.展开更多
文摘Many strip materials are coiled after rolling process. The stresses are imposed on the material wound on the automatically controlled collapse mandrel under the coiling tension. The coiling process can be described by three typical cases: winding without automatic adjustment, winding with automatic adjustment and after mandrel removal. A new model of equations for predicting the stresses during the strip coiling process is built by consideration of the three cases respectively. By solving the equations of different typical cases, the radial stresses and tangential stress of the layers of coil can be calculated. Also, the coiling parameters, such as strip thickness, coiling tension and necking critical pressure, affecting the coil performance are investigated. It is believed that the present model can be used for design and control of the automatically controlled collapse mandrel.
文摘The present work aimed to investigate the effect of coiling process conditions on microstructure development in a low-Si content TRIP （transformation-induced plasticity）-assisted steel after thermomechanical processing. In this framework, compression samples which were deformed above Tnr and then intercritically annealed were held isothermally for different durations at temperatures below bainite transformation start temperature. Microstructure of samples were characterized by optical and electron microscopy, XRD （X-ray diffraction） and M6ssbauer spectroscopy. The results indicated that due to low-silicon content of the present steel, the incomplete bainite reaction phenomena was not observed and, hence, the maximum carbon enrichment of residual austenite was achieved in the samples which held for short durations. It was also shown that the maximum carbon enrichment and volume fraction of residual austenite were achieved at intermediate bainite hold temperature of 450 ℃ as the result of competing phenomena, such as microstructural refinement, dislocation density, carbide precipitation and growth.
文摘During the thin strip coiling process, it is necessary to use a sleeve with a mandrel to prevent excessive deformation of the strip. Stress distribution in the sleeve and in the strip is an important factor that determines the quality of the coil. However, owing to the accumulation of high pressure, it is difficult to determine the stress distribution through experimentation. Thus, stress analysis of the strip coiling process was conducted. Finite element analysis was used to investigate the effects of the weight of the strip and the mandrel on the stress distribution and stress concentration near the starting point of the coil. The radial stress was predicted for a coil with a stacked thickness of 384 mm, which corresponds to a strip length of 1486 m, using the stress analysis model developed in a preceding research. A method was presented to reduce the weight and radial stress of a strip coil. It was found that the deformation of the sleeve can be reduced by decreasing the gap between the mandrel segments. The thickness of the sleeve can be reduced from 120 to 106 mm using the stress analysis results. Furthermore, coiling tension can be reduced by 44% compared to the existing value considering the interlayer slip of the strip coil.
