Welding Technology for Grooved Drill Pipe Wear-Resistant Zones

With the decreasing shallow oil reserves, ultra-deep wells, highly deviated wells, and extended reach wells have gradually replaced traditional shallow and short-reach wells, becoming the main direction of current oil drilling. Meanwhile, offshore oil drilling platforms are also widely used. This shift has led to a significant increase in drilling cycles, and the lateral force exerted on the casing by the grooved drill pipe continues to increase, making the wear problem between the drill pipe and casing pipe increasingly prominent.

Grooved drill pipe joints are key components in drilling operations. With the continuous development of drilling technology, higher requirements are placed on their wear resistance. Therefore, how to effectively improve the wear resistance of joints, extend their service life, and improve drilling efficiency has become an urgent engineering problem to be solved.

Overview of Grooved Drill Pipe Joint Wear-Resistant Zones:

Grooved drill pipe joints not only endure severe wear downhole but also face erosion wear, resulting in a rapid wear rate. To improve wear resistance, welding or spray welding processes are typically used to clad a ring-shaped wear-resistant band, approximately 30–50 mm wide and 2–3 mm thick, around the joint circumference; this is known as a "grooved drill pipe joint wear-resistant band." This wear-resistant band exhibits superior wear resistance compared to the substrate and reduces wear on the casing, thus playing a crucial role in addressing drill pipe and casing wear problems.

Welding and spray welding, as important processes in modern materials processing and manufacturing, are widely used to improve joint service life and reduce manufacturing costs. Currently, various alloy powders and flux-cored welding wires have been developed, enabling the wear-resistant band to possess both excellent wear and corrosion resistance. Simultaneously, the resulting high-hardness wear-resistant alloy weld overlay can also be used for the repair and manufacture of wear-resistant parts in other industrial fields.

The following is a brief introduction to commonly used surfacing techniques and their hardness characteristics for wear-resistant bands on grooved drill pipe joints:

1. Open Arc Surfacing with Flux-Cored Wire:

Open arc surfacing technology has the following advantages:

Simple equipment and convenient operation; No preheating required before welding, no heat treatment required after welding, high welding efficiency, and energy saving; Equipped with a dust extraction system, resulting in less welding fumes and a superior working environment; Low weld dilution rate, resulting in good corrosion and wear resistance.

This process is suitable for field repairs in drilling, coal mining, and mining machinery. Grooved drill pipe joints often use single-layer surfacing, with strict requirements on weld dimensions. For example, YD-100 flux-cored wire produces good weld formation and minimal spatter during welding, and its single-layer surfacing weld has a uniform Rockwell hardness of approximately HRC60.

2. Plasma Spraying with Alloy Wire:

Most oilfields in China use plasma spraying to prepare wear-resistant bands for grooved drill pipe joints, achieving a hardness of approximately 55 HRC after spraying. When using D100 alloy welding wire, no preheating is required before welding, and no heat preservation is needed after welding. It also exhibits excellent repeatability. This process is low-cost and easy to operate. Experiments and applications show that compared to ordinary steel joints, this wear-resistant band can reduce casing wear by 86%; compared to tungsten carbide-treated joints, casing wear is reduced by 76%. In highly deviated wells, due to the reduced friction coefficient, drill string rotation resistance is significantly reduced, torque is increased by 30%, and fuel consumption is saved by 10%. Under open-hole drilling conditions, it can more effectively protect drill pipe joints and slow down wear.

D100 material also supports repeated welding on worn wear-resistant bands. Experiments have shown that the re-welded wear-resistant bands did not exhibit spalling or peeling, showed uniform wear, and demonstrated good repeatability.

3. Oxy-acetylene flame spraying technology:

Oxy-acetylene flame spraying technology features simple equipment, flexible operation, and low cost. When using nickel-based self-fluxing alloy powder for spray welding, the following process points must be noted, otherwise porosity or edge cracks are likely to occur:

The workpiece needs to be preheated, and the welding powder must be kept dry;
The substrate surface should have appropriate roughness to enhance bonding strength, but rougher is not necessarily better;
Operators must be proficient in spray welding techniques.

Meeting the above process requirements can effectively reduce porosity and micro-cracks, extending the joint's service life.

4. Machining of the wear-resistant band after overlay/spray welding:

The hardness of the grooved drill pipe joint after overlay or spray welding typically reaches HRC50 or higher, belonging to high-hardness, difficult-to-machine materials. Currently, the tools suitable for such materials mainly include carbide tools, ceramic tools, and non-metallic bonded cubic boron nitride tools (such as BN-S20 grade).

Carbide tools: Hardness approximately HRC71–76, suitable for machining materials below HRC45. When used for wear-resistant bands with higher hardness, the tool wears quickly, the machining effect is unsatisfactory, and the economic benefits are low.

Ceramic cutting tools: Hardness reaches HRC95–100, but are brittle and have poor impact resistance. Suitable for machining conditions with hardness below HRC55 and small feed rates.

Cubic boron nitride cutting tools, grade BN-S20: These tools are specifically designed for the wear-resistant zones of grooved drill pipes. They maintain high hardness while improving toughness, combining wear resistance and impact resistance. They support large depths of cut and large allowance cutting, and do not chip when machining high-hardness (HRC45 and above) wear-resistant zones. They effectively improve machining efficiency and reduce costs, making them suitable for mass production.

Conclusion:

With the advancement of drilling technology and the deepening of exploration and development, higher requirements are placed on drill string performance. The application of welding and spray welding technologies has strongly promoted the development of the drilling industry; however, the resulting high-hardness, difficult-to-machine layers have once constrained machining efficiency and cost control. With continuous innovation in tool materials and new processes, such as the application of high-performance cubic boron nitride tools, the machining level of grooved drill pipes has been significantly improved, providing strong support for the industry's sustainable development.

Read more: API 5DP Drill Pipe Specification or Drill Pipe Connection Method