Failure of Tungsten Carbide Rolls from a Wire and Rod Mill

Abstract

The paper presents the failure analysis of tungsten carbide rolls for the Wire and Rod Mill (WRM) and establishes the failure reasons and the corrective and preventive actions taken to improve roll performance. A sharp continuous increase in failure rate and decrease in average time between failure (ATBF) was observed during 2001 to 2004. The increase in premature failure of these rolls (16 rolls in 2003 and 38 rolls in 2004) raised the cost of operations. Due to unscheduled stoppage of the mill after roll failures, the unplanned mill delays also increased, causing production losses. The analysis revealed significant increase in premature failure of rolls in the finishing stands 19, 22, 23, and 24 and prefinishing stand 14. The primary causes of such failures were faulty roll cooling and roll mounting and accumulation of cobbles. Implementation of modified cooling headers, a calibrated gage to monitor hydraulic pressure during roll mounting, and eddy current inspection resulted in decreasing the trend in roll failure and increasing the trend in ATBF.