Three roller unit has work cut sheets racks and finishing stands, of which metal deformation is mainly done on the rack at work. This results in a uniform lateral flow of metal. Meanwhile tube before entering and leaving the hole after hole, by the influence of the tension between the rack, the outer surface of the radial stress and tensile stress state present. Zhang reduction process first determines the number of racks and wall thickness factor, on this basis, the tension distribution for each rack, reducing rates of distribution and roll pass design. Each rack roll pass hole geometry is characterized by the roll surface relative to the rotation plane of the axis of symmetry, it can take a half and steel roll surface corresponding to the study. By a transverse wall thickness distribution of the accumulated value can be seen in the third frame lateral wall dramatic changes in the hole wall a slight increase at the wall phenomenon.
Less time sheets without internal steel mandrel, in turn pass through the rack, steel pipe for continuous processing, the reduced diameter while achieving less wall. Zhang reduction unit rolls are mostly oval hole by hole shape, pass reducing the amount of rack space and other factors, likely formed inside the pipe within the hexagonal defects. Present on the surface when the tube sheets less heat conduction, convection and radiation three types of boundary conditions, since the convection heat loss generated by a smaller proportion, the deformable body as rolling, roll regarded as a rigid body, the roll speed of the rack According to the actual speed setpoint without artificially given tension. Imposed on the rolling speed becomes zero, and then rolling friction in the roll into the turn, driven up the rack until the rack from the last one rolled out. Reasonable process design allows the unit after a series of tube pass after rolling, to achieve the total transverse metal flow gradually become more uniform, thereby reducing the production of qualified steel.
Was measured after reducing pipe geometry (diameter and wall thickness), after cooling down from rolling on the interception of a finished steel as a sample, face grinding treatment, using a scanner directly to the steel sectional view of the input to the computers, measured once, get pipe wall thickness at different points in cross-section value, the corresponding analog completed finite element mesh tube wall thickness was also measured roll passes are basically non-hole-type, according to the plastically deformable body mechanics shows determines the stress state of the metal flow. First slip region is formed axial tensile stress, compressive stress after the slip region is formed, resulting in uneven metal longitudinal flow, further affecting the metal lateral flow. Since the first frame reducing the amount of small, small changes in lateral wall, the second frame and the third frame lateral wall are reduced at the end roller, roll joints increases. Roll grooved structure as the roller rolling surface of each point of different diameters, the roll contact points on the pipe surface is not the same line speed.