Evaluation of Weld Joint Quality in Drill Pipe Based on Heat Input Variation in Bending and Microstructure Test

Drill pipes are critical components in oil, gas, and geothermal drilling operations, serving as conduits for circulating drilling fluids from the surface to the borehole while simultaneously transmitting mechanical loads. Due to severe operating conditions, including high pressure, cyclic loading, and corrosive environments, the integrity of welded joints in drill pipes must be ensured through appropriate welding methods and quality evaluation. This study investigates the effects of heat input v