Process management for stretch-reducing tube rolling mills

摘要

For many decades, Mannesmann Demag has been furthering the technical development of sizing and stretch-reducing mills [1,2]. The many technical innovations have ensured Mannesmann Demag has a very strong market position, reflected in the safes of 117 stretch-reducing mills since 1950 alone. During the stretch-reducing process, a shell or mother tube is continuously formed in a large number of roil stands arranged in-line, Figure 1. As the shell passes through the stands, its outside diameter is gradually reduced in a pre-determined pass sequence. At the same time, the shell undergoes a defined change in wall thickness as a result of variable settings of the stand roll speeds which exert wall thickness infiuencing tensile stresses on the shell. The desired wall thickness of the shell is thus achieved relatively simply; namely without an internal tool, simply by inducing longitudinal stresses in the rolling stock. The magnitude of these longitudinal tensile stresses is controlled by con-trolling speed of the stand drive motors. This technique allows a wide range of finished tube sizes to be produced from only one shell size at a very high output rate.