Correct conditions for heat treatment of butt welded oil drilling pipes

Abstract

1. Our investigation of the effect of the parameters of induction heating at phase transformation temperatures on the structure, impact strength, and hardness of the weld seams allowed us to construct a diagram of the optimum conditions. This diagram makes it possible to select the normalization temperature for different rates of induction heating according to the wall thickness of the pipe. 2. High frequency induction heating under optimum conditions results in complete phase transformations and diffusion processes, and this improves the structure and properties of the seam metal. 3. The application of optimum normalization conditions decreases the hardness and increases the impact strength of drilling pipes used in geological survey work by 100% and that of oil drilling pipes by 25–30%, the ultimate strength remaining the same. 4. The new technique of heat treating the weld seam—normalization with high frequency induction heating—is more effective than normalization by the old technique: intermediate frequency induction heating (50 Hz) while clamped in the butt welding machine. The new technique improves the quality of the pipes, increases the productivity 30%, and decreases the manufacturing cost by 25%.