No abstract

With the aid of commercial FE code MSC.SuperForm, the structural steel tube continuous rolling process of a typical hollow tube specification 152.5×12.5mm is simulated based on Bao Steel 152.5 main pass sequence of 140mm 8-stand mandrel mill, and the distribution characteristics of stress/strain, outline lateral spread, temperature changes of workpiece in continuous rolling process and distribution of stress/strain, friction of workpiece in deformation zone are analyzed. Analysis results indicate that deformation of workpiece along the width of the groove, especially at the top and the bottom of the groove is highly inhomogeneous due to the unequal draught and the longitudinal stress of special position (the top and the bottom of the groove) of workpiece is always an alternate state, in a tensile-compressive-tensile manner, and has a distinct rule. In the first stand, outline dimension of workpiece gradually increases during reducing process and early stage of wall thickness reduction, but it gradually decreases during middle-late stage of wall thickness reduction and tends towards stability at last. It is inhomogeneous that distribution of unit compressive stress and longitudinal strain of workpiece in deformation zone, and contact stress and total equivalent plastic strain are maximal in inner surface of workpiece contacting with mandrel. Temperature difference between the outer and the inner surfaces of workpiece is obvious.

No abstract

In continuous tube rolling process, it has an obvious influence on the stability of rolling process, tools wear and the quality of rolled hollow tube that configuration of roll rotational speed per stand. In this paper, various roll working diameters per stand are determined by velocity integral method (VIT) and FEM respectively, and two roll rotational speed schedules are obtained correspondingly based on 133 main pass sequence of 89mm 6-stand semi-floating mandrel mill. With the aid of commercial FE code MSC.SuperForm, the high pressure boiler steel tube continuous rolling process of a typical hollow tube specification 133.0×5.2mm are simulated, and force parameters, transverse wall thickness precision, outline dimension and real roundness of rolled hollow tube and clearance between the mandrel and rolled hollow tube are analyzed and compared on the condition of two different roll rotational speed schedules, which provides scientific basis for configuring reasonable roll rotational speed per stand in pass design and optimization. Analysis results indicate that roll working diameter obtained per stand is smaller and roll rotational speed configured is higher correspondingly using FEM compared to VIT. Using FEM, there exist front and back tensions between stands and maximal rolling force, rolling moment and mandrel axial force decrease 10% or so in continuous tube rolling process, and outline dimension and real roundness of rolled hollow tube is better. However, transverse wall thickness of rolled hollow tube at the bottom of groove is pulled thin slightly, and clearance between the mandrel and rolled hollow tube is less than normal.