Processing practice of Baosteel drill pipes

摘要

Drill pipe products are the most critical service requirement,the highest performance requirement and the highest quality reliability OCTG products.Through the continuous research on steelmaking,upset, heart treatment,straightening and friction welding,Baosteel improves the key technical parameters which affect the quality of drill pipe,such as material purity,Miu of internal upset transition area,toughness and straightness.Baosteel drill pipe products have met the demanding requirement of drilling operations.By BRP dephosphorization and LF desulfurization,the P,S content of Baosteel drill pipe is very low.The S content of S-135 drill pipe can be controlled in less than 10ppm.Baosteel designs a new closed-loop control system of upset end induction heating system.The system use temperature measurement inside the oven and closed-loop control.The temperature accuracy of the system can be guaranteed within the±15℃to get a stable upset quality.The upsetting process of the drill pipe is optimized by using patented technology and made the Miu from 100 mm to 140 mm.This make a substantial increase in fatigue life of the drill pipe.To improve the impact toughness of the drill pipe body,the drill pipe body material is changed from Cr-Ni-Mo system to Cr-Mo-V system and the heat treatment is changed from oil quenching to water quenching.To improve the impact toughness of the tool joint,the tool joint furnace is upgraded to improve heating capacity.To improve the impact toughness of the weld zone,a new fuzzy control system of weld zone heat treatment is developed.The temperature accuracy of the system can be guaranteed within the±5℃to get a stable heat treatment quality.A new drill pipe straightness automatic detection devices and self-learning method of straightening are developed to achieve automated straightening.A welding process with high speed,single-stage pressure and high forging force is applied to inertia friction welding.A welding process with low speed,three-stage pressure and low forging force is applied to continous friction welding.