The purpose of
pipe end sizing is to reduce the ellipticity of steel pipe to ensure that the steel pipe after machining the dimensional accuracy, mainly for oil casing. After the end of the diameter of the casing, the end of the car when the black leather buckle (leaving the leakage surface of the thread) a small number, can improve the finished product rate.
Pipe end sizing is a cold deformation process, the commonly used sizing method has a punch diameter and punch diameter + diameter ring compression two. The effect of reducing the ellipticity of the pipe when the punch is enlarged depends to a large extent on the uniformity of the wall thickness of the pipe. On the uneven thickness of the hot rolling pipe, such as the cycle of rolling mill rolling pipe (see the cycle of rolling mill rolling mill), the punch after the expansion of the pipe surface quality deterioration. Therefore, in order to eliminate the influence of uneven wall thickness and reduce the ellipticity of steel pipe, should adopt the punch diameter + sizing ring compression method. As the cold diameter, the tube end not only produce elastic deformation but also a small amount of plastic deformation. After the sizing, there may be different degrees of residual stress in the transition zone with diameter and non-expanding diameter, and the internal and external surface scratches caused by the punch and the sizing ring may occur, resulting in slight stress corrosion. Therefore, try to improve the dimensional accuracy of hot-rolled steel pipe, to avoid the use of pipe diameter method.
