Study On The Machinability Of High-grade High-Cr Alloy Steel Oil Country Tubular Goods Buttress Thread

With the development of oil-gas exploration, geological conditions are becoming more and more complicated. Oil country tubular goods(OCTG) are facing even more critical conditions, hence higher requirement is proposed. As high-Cr alloy steel, BG95-13Cr has comparatively good synthetic performance, which makes it suitable to work as buttress thread under the condition of high temperature, high pressure and corrosive environment. Turning of buttress thread is a high-load-machining method, which places high requirement on the whole system including machine, tool and clamp, especially on the tool. Based on the cutting characteristics of buttress thread and the condition of laboratory, we studied the machinability of buttress thread by cutting experiment and finite element method. All the results will provide constructive suggestion for the production of OCTG. Accordingly, the following works has been done during this research.(1) According to the cutting principle and characteristics of screw machining, the cutting mechanism of buttress thread were studied in preparation for cutting experiment arrangement afterward and technique improvement.(2) Based on the cutting characteristics of buttress thread, the cutting experiments were performed following three steps. The cutting mechanism of high-Cr alloy steel buttress thread is studied on the aspects of cutting force, chip morphology, tool wear and surface quality.(3) Finite element method was used for the simulation on the cutting process of buttress thread. It would validate of the experimental results in terms of theory and uncover the cutting mechanism of buttress thread machining. Moreover, the machining conditions during production of buttress thread were simulated and directive suggestions were advanced.