Concerning the 3-roll skew rolling process of round billets, a 3-D thermo-mechanical coupled simulation is performed with the aid of commercial FE code MSC.SuperForm. The influence of the feed angle and inlet cone angle of the roll on the strain and damage filed are investigated. It is found that the distribution pattern of the equivalent plastic strain in the longitudinal section of the billet presents U-shape, and that the feed angle and inlet cone angle of the roll make difference in the gradient of deformation intensity in radial direction of round billet. The ring-shaped distribution of the damage field in transverse cross section of the billet indicates a high tendency for the ring-shaped inner crack to occur, instead of the center crack appearing in 2-roll skew rolling of round billet. The results show that the critical parameters to control the ring-shaped crack during the 3-roll skew rolling process are the feed angle and inlet surface cone angle of the roll. It should be avoided to use too large feed angles so as to reduce the tendency of annular inner crack in the actual rolling of high-alloy steels with poor hot workability.
A three-dimensional thermo-mechanical coupled model of hot leveling and cooling processes of the steel plate has been conducted with MSC.Superform software. Four kinds of initial temperature distribution patterns have been determined according to literature. The effects of hot leveling and cooling processes on the transversal and longitudinal residual stresses of the steel plate have been analyzed. The results show that the initial temperature distribution patterns have significant influence on the residual stress of the plate. The more uniform temperature distribution patterns along the width of the plate, the smaller residual stress and also the smaller stress fluctuations. The cooling process has greater effect on the residual stress compared with the hot leveling process. The bigger the temperature gradient along the width of steel plate, the larger the residual stress and its fluctuation is. Through the FEM study, the value and direction of transversal and longitudinal residual stresses can be confirmed quantitatively at various positions along the width and length of plate, which can provide guidance to actual measurement of residual stress.
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.
With the aid of commercial finite element analysis software MSC. Superform, the high pressure boiler steel tube continuous rolling process with 6-stand semi-floating mandrel is simulated, and the distribution characteristic of transverse wall thickness is analyzed. It indicates that it presents “M” shape that the distribution of transverse wall thickness of hollow tube along one-fourth groove periphery. Transverse wall thicknesses have low values at the top, the bottom and sidewall 45 degree or so of groove, and they have high values at the sidewall 23 degree and 67 degree or so of groove. Then the improved measure is put forward on the basis of analyzing the causes responsible for transverse wall thickness. By the comparison of the simulation results, they have been improved obviously that transverse wall thickness precision and real roundness of rolled hollow tube using the improved measure.
A 3-D thermal-mechanical model was built to simulate the hot rolling process of medium plate, with the aid of nonlinear commercial FE code MSC.SuperForm on a company's actual process parameters. The hot rolling process of single-pass which slab thickness is 180mm was simulated, and the influence of pass reduction on metal flow, stress-strain field, contact stress and rolling force were researched. The study revealed that pass reduction should be at least 20% by increase depress in pass in addition to rolling efficiency. As that, rolling efficiency be increased, roll contact stress be brought down, and its service life be prolonged. And metal plastic strain enhanced, metal flow increased, but its strain field non-uniformly distributed, metal flow and plastic deformation would be strengthen by increase pass reduction, and the lateral broadening in the head is bigger than that in the tail.
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