Oil-Well Pipe Thread Surfaces Balancing Galling Resistance and Torque
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Solution Overview
Problem
Oil-well metal pipes face challenges in achieving both high yield torque and excellent galling resistance, particularly when subjected to high rotational torque during directional drilling or horizontal drilling, where plastic deformation can occur, compromising gastightness performance.
Innovation Solution
An oil-well metal pipe design featuring a plating layer on one contact surface, a solid lubricant layer on the plating layer, and a semi-solid or liquid anti-rust coating on a roughened second contact surface with an arithmetic average roughness of 0.5 to 10.0 μm, enhancing galling resistance and yield torque through increased friction and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid lubricant coating is applied to improve galling resistance, then galling resistance is improved, but yield torque decreases due to reduced friction
Solution Approach 1:
The patent applies different surface treatments to different contact surfaces: one contact surface receives a solid lubricant coating for galling resistance, while the other contact surface is left rough (Ra: 0.5 to 10.0 μm) to maintain high friction and yield torque. This local differentiation resolves the contradiction by optimizing each surface for its specific function.
Solution Approach 2:
The patent creates a composite surface structure combining a solid lubricant coating layer on one surface with a rough metal surface on the other, achieving both low friction (for galling resistance) and high friction (for yield torque) in the same threaded connection system.
2Reliability
If heavy metal-containing compound greases are used to improve galling resistance, then galling resistance is improved, but environmental harm increases
Solution Approach 1:
The patent replaces heavy metal-containing compound greases with a solid lubricant coating that is environmentally friendly. The solid lubricant coating serves as a durable, non-contaminating alternative that eliminates the need for hazardous materials while maintaining galling resistance.
Solution Approach 2:
The patent changes the physical state from liquid/grease to solid coating, and changes the material composition from heavy metal-containing to environmentally friendly substances, thereby eliminating environmental harm while preserving lubrication function.
3Strength
If the second contact surface is roughened to increase yield torque, then yield torque is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a relatively wide roughness range (Ra: 0.5 to 10.0 μm) for the second contact surface, which balances the need for high yield torque with practical manufacturability. This parameter optimization allows standard machining processes to achieve the required performance without excessive precision requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design effectively achieves high yield torque and excellent galling resistance, preventing plastic deformation and maintaining gastightness even under high rotational torque conditions.
Implementation Method 1
a solid lubricant layer is formed on the plating layer
Implementation Method 2
an arithmetic average roughness Ra of a second contact surface is within a range of 0.5 to 10.0 μm
Data Source
AI summary
This invention provides an oil-well metal pipe which is capable of achieving both high yield torque and excellent galling resistance in a compatible manner. An oil-well metal pipe of the present disclosure includes a pipe main body. The pipe main body includes a pin that is formed at the first end portion, and a box that is formed at the second end portion. A plating layer is formed on a first contact surface, which is one of a pin contact surface of the pin and a box contact surface of the box, and a solid lubricant layer is formed on the plating layer. An arithmetic average roughness Ra of a second contact surface, which is the other of the pin contact surface and the box contact surface, is 0.5 to 10.0 μm, and a semi-solid or liquid anti-rust coating is formed on the second contact surface.