Defects, causes and prevention controls in the continuous bronze/steel bimetal strip sintering process

Plain bearings are among the most important components which determine the reliability and life of combustion engines. While bearing failures are well known, little consideration has been given to strip that is used to manufacture bearings, though defects in other sintered products are well understood. Bimetal strip defects can under certain circumstances lead to bearing failures in the field. Sintered bronze/steel bimetal strip production is a continuous process, in which the properties of the lining as well as the adhesion between the two dissimilar materials, bronze and steel, are developed during the sintering, compaction rolling, and resintering processes. This paper presents the results obtained by examining different defects in 1250 km of sintered bronze/steel bimetal strip, which was manufactured over three years in an industrial bearing manufacturing facility. The most frequently found defects are porosity, delamination, coarse bronze grains and coarse or non-homogenously distributed lead pools. Strip defects were examined and documented using micrographic analysis and photographs. Fault tree analysis (FTA) was performed to determine the root cause of the defects and prevention controls are discussed.