Plotting of tension curves of 3-roller tension unit

Applying elastic-plastic bending theory,a corresponding math model for calculating the tension produced by 3-roller tension unit was established.A brief calculating equation was given and the tension curves were plotted.The relationship between the screw-down principle to steel strip thickness,steel character and tension was discussed.The plotted diagram of tension curves is very accurate compared with the practical applied curves of the tension unit imported from Japan.According to the research results,parabola can be used to describe the relation of the tension to the strip thickness approximately and the tension is proportional to the yield stress of steel strip,i.e.the thicker the strip thickness,the greater the influence of the crew-down on the tension.When the screw down is 60 mm,the change of the screw-down will give rather strong influence upon the tension of various thickness of strips.When the thickness of strip is ≥7 mm,the crew-down cannot be increased without giving a full consideration.For thin strip,the crew-down should be increased to make sure sufficient coiling tension produced by the tension unit.This research conclusion may be greatly helpful to the design of tension unit and the determination of the operating mode.