Lubricant Coating Composition for Galling-Resistant Pipe Threads
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Solution Overview
Problem
Threaded connections for oil country tubular goods face challenges with galling resistance and over-torque performance, particularly when metal seal portions and shoulder portions experience friction, leading to potential plastic deformation and reduced fastening torque adjustability.
Innovation Solution
A lubricant coating layer composition containing Cr2O3, a metal soap, a wax, and a basic metal salt of an aromatic organic acid is applied to the contact surfaces of threaded connections, enhancing galling resistance and over-torque performance by reducing friction and increasing yield torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy metal-containing compound greases are used to improve galling resistance, then galling resistance is improved, but environmental harm increases due to heavy metal contamination
Solution Approach 1:
The invention extracts and removes heavy metal components (Pb, Zn, Cu) from the lubricant composition while retaining the essential lubricating function through alternative organic-based additives and formulation, thereby eliminating environmental harm while maintaining galling resistance
Solution Approach 2:
The invention changes the chemical composition parameters of the lubricant by substituting heavy metal compounds with organic-based lubricating additives and optimized base oil formulations, achieving the same protective function without harmful heavy metals
2Reliability
If fastening torque is increased to ensure sufficient seal interfacial pressure, then gas tightness is improved, but plastic deformation of metal occurs leading to reduced fastening torque adjustability
Solution Approach 1:
The invention applies lubricant coating before fastening operations to reduce friction coefficients in advance, allowing sufficient seal pressure to be achieved at lower torque values, thereby preventing plastic deformation while maintaining gas tightness and preserving torque adjustability
Solution Approach 2:
The invention changes the friction parameter through lubricant application, which modifies the torque-pressure relationship, enabling sufficient sealing pressure at reduced torque levels and maintaining fastening torque adjustability
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 composition significantly improves galling resistance and over-torque performance, allowing for repeated fastening without galling and easy adjustment of fastening torque, with Cr2O3 content between 1-20% and other components within specific ranges for optimal results.
Implementation Method 1
The threaded portions and unthreaded metal contact portions of the pin and box repeatedly experience strong friction during fastening and loosening of the pipes. If these portions are not sufficiently resistant to friction, galling (unrepairable seizure) will occur during repeated fastening and loosening.
Data Source
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AI summary
This invention provides a composition, and a threaded connection for pipes or tubes (1) that includes a lubricant coating layer (21) formed from the composition. The composition according to the present embodiment is a composition for forming a lubricant coating layer (21) on a threaded connection for pipes or tubes (1), and contains Cr2O3, a metal soap, a wax and a basic metal salt of an aromatic organic acid. The threaded connection for pipes or tubes (1) according to the present embodiment includes a pin (5) and a box (8). The pin (5) and the box (8) each include a contact surface including a threaded portion (4), (7) and an unthreaded metal contact portion. The threaded connection for pipes or tubes (1) includes, as an outermost layer, a lubricant coating layer (21) formed from the aforementioned composition on at least one of the contact surfaces of the pin (5) and the box (8).