Threaded Oil Well Pipe Connection With Low-Torque Galling Resistance
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Solution Overview
Problem
Oil well steel pipes with threaded connections face issues with galling resistance, rust occurrence, and high shouldering torque during fastening, particularly when stored outdoors, and existing solutions like compound greases pose environmental concerns and require complex repair processes.
Innovation Solution
The use of a light oil applied to the pin contact surface and a solid lubricant coating on the box contact surface, along with an anti-rust grease for storage, which is later replaced with light oil before use, to enhance galling resistance, reduce rust, and maintain low shouldering torque without the need for heavy metal compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compound grease containing heavy metal powder is applied to improve galling resistance, then galling resistance is improved, but environmental harm increases and the risk of clogging increases
Solution Approach 1:
The patent removes heavy metal powders (Pb, Zn, Cu) from the compound grease formulation, extracting the harmful components while retaining the essential lubrication function through alternative means such as solid lubricant coatings and grease-free thread designs
Solution Approach 2:
The patent employs disposable protective films or coatings applied to thread surfaces that provide temporary lubrication and protection during the critical fastening process, eliminating the need for persistent heavy metal-based grease that causes environmental harm
2Reliability
If compound grease is applied to improve galling resistance, then galling resistance is improved, but the complexity of the system increases due to discharge and accumulation issues
Solution Approach 1:
The patent extracts the grease application step entirely from the fastening system, replacing it with pre-applied solid lubricant coatings on thread surfaces, thereby eliminating the complexity associated with grease discharge, accumulation, and cleanup
Solution Approach 2:
The thread surfaces are pre-coated with solid lubricants during manufacturing, enabling them to self-lubricate during fastening operations without requiring external grease application, discharge management, or accumulation prevention measures
3Reliability
If anti-rust grease is applied during storage, then rust resistance is improved, but shouldering torque increases when fastening
Solution Approach 1:
The patent segments the protective function into two distinct components: a防锈 coating applied during storage to prevent rust, and a solid lubricant coating applied to the thread surface for low-friction fastening. This segmentation allows each coating to optimize its specific function without compromising the other
Solution Approach 2:
The patent applies different material properties to different locations: the anti-rust coating is applied to the outer surface of the fastener body for corrosion protection during storage, while the solid lubricant coating is applied specifically to the thread contact surfaces to ensure low shouldering torque during fastening operations
4Reliability
If solid anti-rust coating is formed on pin contact surface, then rust resistance is improved, but shouldering torque increases during fastening
Solution Approach 1:
The patent divides the protective coating system into two separate coatings: an anti-rust coating on the pin body and a solid lubricant coating on the thread surface. This segmentation ensures that the anti-rust coating provides corrosion protection without interfering with the friction characteristics of the thread interface
Solution Approach 2:
The patent applies different surface treatments to different locations: the pin contact surface receives an anti-rust coating for corrosion protection, while the thread surface receives a solid lubricant coating to maintain low friction and shouldering torque during fastening operations
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
This approach provides excellent galling resistance, suppresses rust on the pin contact surface, keeps shouldering torque low, and is environmentally friendly, with improved repairability and reduced risk of clogging, while avoiding the use of heavy metal powders.
Implementation Method 1
a solid lubricant coating formed on a box contact surface
Implementation Method 2
a light oil is applied to the pin contact surface
Data Source
AI summary
This invention provides an oil well steel pipe with a threaded connection with which excellent galling resistance is obtained without using a compound grease, and which can suppress the occurrence of rust on a pin contact surface and can also keep shouldering torque at a low level. An oil well steel pipe with a threaded connection of the present disclosure includes a pipe main body including a first end portion and a second end portion. The pipe main body includes a pin formed at the first end portion, and a box formed at the second end portion. A light oil is applied to a pin contact surface of the pin. A solid lubricant coating is formed on a box contact surface of the box.