A study to predict the creation of surface defects on material and suppress them in caliber rolling process

초록

Finite element analysis coupled with a shear fracture model was carried out to predict the creation of surface defects on a material (AISI 4140 steel) and to reduce the surface defects in the caliber (or groove) rolling process, one of steel manufacturing processes. It was assumed that shear fracture owing to shear band localization in the material leads to onset of surface defects of the material during groove rolling. The shear fracture model used to simulate the crashworthiness of aluminum extrusions was applied to the groove rolling after the relation between shear stress ratio and equivalent plastic strain at fracture was modified. To validate the effectiveness of the proposed approach, a roll groove in an actual rod mill (SEAH BESTEEL Inc at Kunsan in Korea) was redesigned and field test was conducted as well. Results revealed that the surface defects on the material during groove rolling could be predicted by checking the number of elements that satisfied the shear fracture criterion. When the newly designed groove was used, finite element simulation of the 6-pass rolling sequence showed that the total number of the damaged elements was reduced from 796 to 629 by 21.0 %. Field test results showed that the total number of products that the surface defects was generated on the surface decreased from 405 to 259 by 36.0 % when the newly designed groove was used.

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