Study on the inheritance relationship between billet and rail surface defects

In the test, artificial defects were made in the rolling slip area and rolling stable area on the surface of the casting slab without over standard defects. Normal heating, rolling and straightening processes were adopted, and samples were taken and polished at the corresponding artificial defects of the rail according to the rolling elongation coefficient. Nondestructive testing equipment such as eddy current flaw detector was used to analyze the defect morphology and to evaluate the relationship between the surface defects of the casting slab and the rail. At the same time, the evolution law of slab defects is deduced, and the inheritance relationship between slab and rail surface defects is fitted by analyzing the morphology and distribution of rail defects. The defects on rail are successfully traced back to the slab by using this inheritance relationship. The correspondence of defect tracing morphology is as high as 90%, and the defect tracing positioning error is ±2‰. It can help technicians quickly and accurately locate the defect positions on the slab, predict the defect morphology and initiation area on the slab, select suitable strategies in time to eliminate defects, and effectively improve the yield of rails.