Study On Heat Treatment Process Of 26CrMnMo Steel Drill Pipe

The drill pipe consists of two parts,the drill pipe body and the drill pipe joint,which are connected together by inertia friction welding.Its main function is to transmit torque and transport drilling fluid.The stress conditions of the drill pipe under the hole are very complicated,and are mainly subject to axial tensile / compressive stress and shear stress,so the comprehensive performance requirements are high.API Spec 5DP "Drill Pipe Specification" clearly proposes that G105 steel grade and S135 steel grade drill pipe are high-strength drill pipes.26 Cr Mn Mo low-alloy steel is selected as the material of the drill pipe body,and the performance requirements of G105 steel grade can be met after the quenching and tempering treatment.Therefore,it is necessary to research and optimize the quenching and tempering treatment process of 26 Cr Mn Mo steel drill pipe body and welding seam for the overall improvement of the stability of performance.In this project,the heat treatment process of 26 Cr Mn Mo steel quenching and tempering and friction butt welding structure was studied.The changes of the structure and mechanical properties of 26 Cr Mn Mo steel and friction welding under different quenching and tempering processes were analyzed.The quenching temperature,tempering temperature and tempering insulation were studied.The influence of time on strength,plasticity and impact performance,and the methods of SEM,XRD and EBSD were used to analyze the impact fracture morphology,composition phase and grain orientation of friction welding structure.According to the characteristics of natural gas stepping heat treatment furnace an d medium frequency induction heating heat treatment equipment,the specif ic parameters of the production process of 26 Cr Mn Mo steel drill pipe heat treatment process were formulated to improve the performance stability of mass production drill pipes.The results show that the quenching and tempering process of 26 Cr Mn Mo steel drill pipe body is quenching heating temperature 920 ℃,quenching and holding time 30 min,tempering heating temperature 595 ℃,and tempering holding time 50 min.After adopting the above thermal process,the yield strength of 26 Cr Mn Mo steel drill pipe body is 845 MPa,tensile strength 919 MPa,elongation 21.1%,impact absorption work 96 J,and microstructure is uniform tempered sorbite.Welding medium frequency induction heating quenching heating temperature 890 ℃,holding time 90 s,tempering heating temperature 625 ℃,tempering holding time 360 s.After adopting the above heat treatment process,the weld strength of 26 Cr Mn Mo steel drill pipe is 840 MPa,the tensile strength is 935 MPa,the elongation is 17%,the impact absorption work is 105 J,and the tempered sorbite is completely transformed.Under the influence of the structure of the natural gas stepping heat treatment furnace and the induction heating coil,the heating temperature deviation of the tube body in the quenching and tempering treatment should be controlled between(10～15)℃,and that of the weld bead in the quenching and tempering treatment should be controlled between(5～10)℃.During mass production,non-destructive testing is performed on areas such as the rough end of the pipe body,the transition zone,the weld seam,and the heat-affected zone by means of A-type pulsed ultrasonic and fluorescent magnetic particle detection methods,which facilitates timely detection of near surface and internal cracks and adjusts the heat treatment process To meet the mechanical performance requirements of the API Spec 5DP " Specification for Drill Pipe ".