In standard YB/T169-2000

it is defined that the percentage of sorbite in structure of high carbon steel is measured based on the difference structure between bright and dark under optical microscope. In order to analyze the structure corresponding to each bright and dark region under optical microscope t the different region in sample of lead bath annealed Φ0. 9 mm 82A high carbon steel wire with tensile strength 1 296 MPa is marked by microhardness tester and observed by optical and scanning electron microscope

and the reason to occur the bright and dark region is analyzed by different etching method. The results confirm that the bright region and the similar pearlite lamella structure are all sorbite structure. Partial deep-etching leads to false appearance of lamella

and the occurred bright region and similar pearlite are related to the sorbite block which is perpendicular to drawing direction.