Oil drill pipe is made by connecting the drill pipe joint and the rod body after they are manufactured separately. Although friction welding technology has been successfully applied to drill pipe welding, there are still some defects in the actual welding process, such as welding dislocation, flash on the outer wall, and coarse structure in the welding area. In view of the shortcomings in friction welding of drill pipe, the transition liquid phase diffusion welding connection of the drill pipe was carried out by diffusion welding (TLP) equipment under atmospheric conditions with Ar gas protection, and the joint with qualified structure and performance was obtained, which has certain significance for promoting the application of diffusion welding technology in the oil industry.
First, test materials
The test uses 127mmX10mm drill pipe body and drill pipe joint, the material is 35CrMo. The intermediate layer used is FeNi-CrSi-B iron-nickel based amorphous foil, the melting point is 1050~1100℃, and the thickness is 25μm.
Second, welding equipment
The special diffusion welding equipment for drill pipe is mainly composed of a medium frequency power supply and induction heater, clamp and hydraulic, cooling system, protection system, and control system. The induction heater is a single-turn upper and lower split, with a cooling water channel inside and a protective gas circuit outside. It integrates water, electricity, and gas, is easy to operate, and is convenient for the installation and removal of workpieces. The hydraulic system provides clamping force and top force to achieve the fixation and welding pressure of the workpiece. The control system adopts a PLC+PRC module and sets the process parameters through the touch screen to realize the human-machine interface dialogue. The cooling system consists of a water tank, a water pump, a heat sink, and a fan, and cools the fixture, induction heater, and hydraulic system through circulating water.
Third, the diffusion welding process
① Turning the drill rod joint and the rod end face, the average roughness is Ra6.3um.
② Turn on the induction heater, and lift the chuck on the C-frame and gantry. The drill rod joint is installed on the C-frame positioning seat. The travel switch controls the C-frame to run until the end face of the joint to be welded is located in the center of the induction heater. The drill rod body is loaded from the right side, and the rod body is clamped when the two welding end faces are in contact. Adjust the positioning seat on the C-frame for misalignment adjustment.
③Run the C-shaped frame to separate the two end faces to be welded, place the Fe-Ni-Cr-Si-B intermediate layer alloy foil with the same shape as the welding end face on the two end faces to be welded, push the C-shaped frame back to the top frame, and press the intermediate layer alloy foil.
④Close the induction heater, connect the optical fiber thermometer, turn on the cooling water and Ar protection, set the welding parameters and post-heat treatment parameters on the touch screen, and run the welding program through PLC + PRC. Drill pipe diffusion welding is carried out under the process parameters of heating temperature 1215℃, insulation time 4min, and pressure 9 MPa. Post-welding heating temperature 650℃, insulation 5min tempering,
⑤After the welding program is completed, turn on the induction heater, and lift the chuck on the C-shaped frame and the gantry. The drill pipe after welding is unloaded from the right side through the unloading mechanism, and the C-shaped frame returns to the left side, and the welding is completed.
Fourth, joint analysis
Tensile and bending tests are carried out on the post-welding sample. The drill pipe is welded by the transition liquid phase diffusion welding process, the joint deformation is small, there is no flash at the weld during friction welding, and the weld is beautiful. During the tensile test, the joint broke on the parent material. The strength of the diffusion welded joint was higher than that of the parent material. During the bending test, the joint was not broken after 180″ face and back bending. The joint had good plasticity.
Post time: Apr-08-2025