The drill collar, located at the bottom of the drill string, is a key component of the lower drill string assembly. Its primary characteristics are its thick wall thickness (typically 38-53 mm, equivalent to 4-6 times the drill pipe wall thickness), resulting in high resistance and rigidity.Material and Structure:The mainstream material is AISI4145H chromium-molybdenum alloy steel, which achieves a Brinell hardness of 285-341 after heat treatment.Drill collars are categorized...