Manufacturing Process and Advantages of Friction Welded Drill Pipes

Introduction to Friction Welded Drill Pipes:

Friction welding of drill pipes is the most core and advanced process in modern drill pipemanufacturing. It refers to connecting the drill pipe body and drill pipe tool joint into a single unit using friction welding, a solid-state welding technology.

Comparison with Traditional Methods: Previously, threaded connections or flash butt welding were used, but these methods have shortcomings in strength, reliability, and production efficiency.

Friction Welding Principle: The heat generated by the relative rotational friction of the workpiece contact surfaces brings the material to a thermoplastic state, and then metallurgical bonding is achieved under axial upsetting pressure. The entire process takes place below the melting point of the base material, belonging to solid-state welding.

Manufacturing Process of Friction Welded Drill Pipes:

1. Rotary Friction Stage: The tool joint (or pipe body) is clamped and rotated at high speed, simultaneously contacting the fixed pipe body end face and applying initial pressure. The heat generated by friction rapidly brings the metal at the contact surface to a thermoplastic state.

2. Upsetting and Forging Stage: Once the required temperature is reached, rotation immediately stops, and a much larger axial upsetting pressure than in the friction stage is applied. This pressure extrudes the softened metal layer (forming "flash") and achieves a strong metallurgical bond between the pure hot metal and the entire interface. This stage is similar to "forging," refining the grain and improving performance.

3. Post-Weld Treatment: After welding, the external flash needs to be removed, and the welded area is heat-treated to relieve stress and homogenize the microstructure. Finally, high-precision threads are machined on the tool joint.

Four Core Advantages of Friction Welded Drill Pipes:

1. Extremely High Weld Strength: This is its greatest advantage. Friction welding produces a forged structure in the weld seam, whose strength, toughness, and fatigue resistance can reach or even exceed the properties of the drill pipe base material itself. The joint is no longer a weak point.

2. Stable and Reliable Welding Quality: The process is precisely controlled by a computer (speed, pressure, time, displacement), resulting in stable parameters, consistent weld quality, and virtually no defects such as porosity and slag inclusions found in traditional fusion welding.

3. High Efficiency and Economy: Short welding time (usually measured in seconds), high degree of automation, suitable for mass production, reducing the manufacturing cost per drill pipe.

4. Wide Material Applicability: It can weld different metal materials (such as welding high-strength alloy steel tool joints to the pipe body), and the requirements for pipe end face machining are relatively low.

Features of Friction Welded Drill Rods:

1) Achieves optimal combination of drill rods; the rod body and joint can be made of different materials, improving heat treatment optimization performance. This is not possible with other types of drill rods.

2) The joint has high mechanical properties and wear resistance. It has a longer service life than other types of drill rods.

3) Lightweight and flexible.

4) The internal drilling fluid channel of the drill rod can be designed. The design of the inner hole channel of the threaded probe can fully consider reducing hydraulic loss during passage, especially reducing losses caused by the threaded joint, thus improving the working efficiency of the drilling fluid system.

5) With the improvement of welding equipment, welding processes and technologies, and heat treatment technology, the connection strength of friction welded drill rods is now higher than the strength of the base material itself. After further upsetting and thickening, the weld strength of the weld is even higher than the strength of its base material.

6) After upsetting the rod body of the friction welded drill rod, overall quenching and tempering heat treatment is performed, which greatly improves its bending resistance and flexibility.

Read more:  Casing Pipe vs. Drill Pipe or Drill Pipe Structure and Common Specifications