In the past, the calculation of the internal stress in the coiling process of color steel coil was based on the calculation of the steel coil as an elastic thick wall cylinder or an elastic combined cylinder. In fact, the thickness of color steel coil
is generally large, and color steel coil has obvious non-circular characteristics along the circumference. If color steel coil is treated according to circular curve, the calculation error will be large.
Therefore, in the process of coiling, with the increase of the thickness of the strip, the non-circular characteristics of the strip inside the coil are more obvious along the circumferential direction. However, the closed cylinder model used in the past
not only deviates from the actual state of the strip, but also can not accurately predict the interlayer slip. Based on the equipment and process characteristics of hot rolling coiling process, a set of internal stress distribution model of steel coil
suitable for hot rolling color steel coiling is proposed by adopting spiral opening cylinder model, considering the nonuniformity of stress and deformation along circumferential direction during coiling process and the feature of incomplete contact between
coil head coil and drum, and corresponding judgment conditions of interlayer slip are given The corresponding prediction software of internal stress and interlayer slip of steel coil is developed and applied to production practice.
In the process
of coiling, with the increase of coil diameter, the radial pressure of a certain layer of color steel coil increases; for the inner layer of color steel coil, that is, the increase of the head is particularly large, which will increase the probability
of adhesion between layers; but for the coil unloading, the radial pressure decreases from inside to outside layer by layer; for the circumferential stress law is different, The minimum value usually occurs in a certain layer inside the coil, the hoop
stress at the head of the coil decreases with the increase of its pressure, and some layers in the middle of the coil decrease to the maximum. If the initial coiling tension is large, negative value may appear.
For the soft and thin color steel
coil, when the tension of color steel coil is less than the initial set value and there is no hoop, the radial stress inside the coil is too small, which is easy to cause the slip between layers and cause the collapse of the coil; although the large tension
can be used to avoid the collapse of the coil, for the head of color steel coil, the coiling tension is too large, which causes the tangential compressive stress of the first few coils to be too large, When the steel coil is disturbed by impact during
lifting or placing, it often produces heart-shaped defects;
In view of the current hard core coiling technology with cone control, when the coil is removed from the drum, the inner layer of the coil shrinks inward, and when the decline slope of
the tension taper curve is too large, the core pulling is likely to be caused by too large tensile stress at the core.