2014 Volume 100 Issue 12 Pages 1535-1541
If surface defects on hot rolled wire rod subsequently remained, it might become the origin of cracks in the forging process. Therefore, the surface quality for hot rolled wire rod is strongly required. In order to avoid surface defects, it is important to establish methods for predicting the positions and the criteria of the defects as a function of rolling conditions.
In the previous paper, we assumed a defect to be a kind of plastic buckling and we introduced a new parameter indicative thereof. We also indicated that a hard surface layer promoted the occurrence of surface defects.
For this paper, we rolled a lead alloy with copper plating and a lead alloy without plating and compared their surface shapes after rolling. As a result, it was verified that “surface defects are caused by plastic buckling and defects are promoted by hardening the surface.” In addition, we quantified the effects of various rolling conditions on the occurrence of surface defects using the parameter above.
The friction coefficient affects the depth and position of surface defects. The larger the friction coefficient, the greater the depth of the defect and the further to the side the position of the defect moves.
Rolling tension also affects surface defects. Back tension has a greater affect than front tension. With compression tension, the depth of defects increases and the position moves to the free face.