Zn-Ni Alloy Coated Pipe Threaded Connection Anti-Galling
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Solution Overview
Problem
Threaded connections for oil country tubular goods face challenges with galling resistance, anti-misalignment properties, torque management, and corrosion resistance, particularly when subjected to repetitive use and varying temperatures, leading to reduced adhesiveness and increased shouldering torque.
Innovation Solution
A threaded connection featuring a Zn-Ni alloy plating layer, a phosphating layer, and a solid lubricant coating, stacked in that order, which enhances anti-misalignment properties, corrosion resistance, and adhesiveness, while maintaining appropriate torque levels and preventing scaling-off of the lubricant coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compound grease containing heavy metals is used to improve galling resistance, then galling resistance is improved, but environmental harm increases
Solution Approach 1:
The invention extracts and removes the harmful heavy metal components (Pb, Zn, Cu) from the compound grease formulation while retaining the essential lubricating and galling-resistant properties through alternative organic-based additives and formulations
Solution Approach 2:
The invention changes the chemical composition parameters of the grease by replacing heavy metal compounds with organic additives, altering the chemical structure while maintaining the functional properties of galling resistance and lubrication
2Productivity
If repetitive fastening and loosening is performed, then inspection and reuse are enabled, but galling occurs due to strong friction on thread portions and unthreaded metal contact portions
Solution Approach 1:
The invention applies a specialized grease formulation in advance before fastening operations begin, creating a protective film on the thread portions and unthreaded metal contact portions that prevents galling during subsequent repetitive fastening and loosening cycles
Solution Approach 2:
The invention introduces grease as an intermediary substance between the metal surfaces, reducing direct metal-to-metal contact and friction on the thread portions and unthreaded metal contact portions during fastening and loosening operations
3Adaptability or versatility
If misalignment occurs during fastening, then assembly flexibility is improved, but shouldering torque increases and galling resistance deteriorates
Solution Approach 1:
The invention modifies the physical and chemical parameters of the grease to enhance its film strength and load-carrying capacity, enabling it to maintain effective lubrication and galling resistance even when misalignment occurs 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
The solution provides excellent anti-misalignment properties, corrosion resistance, and high adhesiveness of the solid lubricant coating, reducing galling and shouldering torque, and maintaining lubricity even under temperature fluctuations.
Implementation Method 1
an alloy plating layer consisting of a Zn-Ni alloy
Implementation Method 2
a phosphating layer
Implementation Method 3
a solid lubricant coating
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An objective of the present invention is to provide a threaded connection for pipe or tube having an excellent anti-misalignment property and an appropriate shouldering torque, and further having excellent corrosion resistance and an excellent adhesiveness of a solid lubricant coating, and to provide a method of producing the threaded connection for pipe or tube. The threaded connection for pipe or tube according to the present embodiment includes a pin (13) and a box (14). The pin (13) and the box (14) have contact surfaces including thread portions (15) and (20) and unthreaded metal contact portions. The threaded connection for pipe or tube comprises an alloy plating layer (21) consisting of a Zn-Ni alloy on the contact surface of at least one of the pin (13) and the box (14), a phosphating layer (22), and a solid lubricant coating (23). These are stacked in an order of the alloy plating layer (21), phosphating layer (22), and the solid lubricant coating (23), from a contact surface side.