Abstract: Traditional cold extrusion process of internal thread is only fit for processing low-intensity and high plasticity metals such as non-ferrous metals and low-carbon steel. But the internal thread of the key parts such as airplane and high speed train is processed with high-strength steel. During cold extruding high-strength steel internal thread, the effects of lubricant, workpiece bottom hole diameter, extrusion speed and extrusion times on wear and fracture of the tap and manufacturing quality of the internal thread are great. The process of cold extrusion of Q460 high-strength steel internal thread is studied through experiments. The effects of lubricant, workpiece bottom hole diameter, extrusion speed and extrusion times on extrusion torque and extrusion temperature is analyzed. And the ideal internal thread is obtained through optimizing technological parameters. It provides a new basis for improving the surface quality and the fatigue property of internal thread. The test results show that Q460 high-strength steel internal thread is better formed by cold extrusion through one-step forming technology. The fluidic thin film lubricant whose viscosity number is between 10 and 12 is selected. The best range of workpiece bottom hole diameter is between 21.20 mm and 21.30 mm. And the generally selected extrusion speed is between 30 and 60 mm•min–1.

Key words: Extrusion, Internal thread, Quality, Temperature, Torque