Dynamics of rolling of welded joints
Keywords:CONTINUOUS ROLLING, WELDED JOINTS, INTERSTAND TENSION, SPEED, LEAD, STRIP THICKNESS
The results of studies of transients and loads in the inter-cage spaces during continuous cold rolling of strips with welded joints are presented.
A mathematical model developed earlier and adapted to a 5-stand mill and a computer program for filling a continuous group of stands with a strip recorded in absolute values of variables are applied. Two types of perturbations acting from the side of the seam are considered: its thickening by 0.1-0.2 mm up to 20 mm long and the excess of deformation resistance by 10 + 20% compared to abutting strips. When a thickened seam enters cdet No. 1, a short-term decrease (weakening) of the back tension occurs to 0.6 of the initial value between stands No. 1 and 2. The action of the seam in the following stands is significantly weakened due to the transformation of its shape. A more dynamic case occurs when the deformation resistance of the weld metal is exceeded: jerks of the front and rear tension are formed up to 1.5-2.2 steady-state values, their dependence on the rolling speed increases. In both cases, imprints of vertical cage vibrations remain on the seam, and the seam becomes multi-thickness. Thinning (“pinch”) of the strip by 0.07 mm is observed immediately after the seam, which contributes to an undesirable concentration of longitudinal stresses.
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