Zn-Ni Coated Pipe Threads Without Blasting for Low Torque
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Solution Overview
Problem
Threaded connections for pipes in oil country tubular goods face challenges with galling resistance and shouldering torque, particularly when repeated fastening and loosening occur, and existing solutions require blasting treatments that can be cumbersome and environmentally impactful.
Innovation Solution
A threaded connection featuring a Zn-Ni alloy plated layer with 10-16% Ni, formed through electrolytic plating without blasting, combined with a solid lubricant coating, which enhances galling resistance and maintains low shouldering torque even with repeated use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blasting treatment is performed to improve galling resistance, then galling resistance is enhanced, but the manufacturing process becomes more complex and environmentally impactful
Solution Approach 1:
The invention changes the surface roughness parameter of the plated layer by controlling plating conditions (current density, plating solution composition, temperature) to achieve Ra1 > Ra2 without blasting. This parameter change allows the plated layer itself to provide the roughness needed for galling resistance, eliminating the need for separate blasting treatment and reducing manufacturing complexity
Solution Approach 2:
The invention extracts and eliminates the blasting treatment step from the manufacturing process by incorporating the roughness-providing function directly into the electrolytic plating process. The plated layer is designed to inherently provide the necessary surface roughness through controlled deposition parameters, removing the harmful and complex blasting operation
2Reliability
If compound grease containing heavy metal is used to improve galling resistance, then galling resistance is enhanced, but environmental harm increases
Solution Approach 1:
The invention replaces the harmful compound grease (containing Pb, Zn, Cu) with a solid lubricant coating that is environmentally friendly. The solid lubricant coating, applied over the roughened plated layer, provides the necessary lubrication and galling resistance without introducing heavy metals into the environment, making it a safer, more sustainable solution
Solution Approach 2:
The invention introduces a solid lubricant coating as an intermediary layer between the roughened plated layer and the contacting surfaces. This solid lubricant acts as a mediator that provides lubrication and protects against galling without the environmental harm associated with heavy metal-containing compound greases
3Manufacturing precision
If electrolytic plating is performed to form a smooth coating, then surface smoothness is improved, but galling resistance decreases
Solution Approach 1:
The invention changes the electrolytic plating parameters (current density, plating solution composition, temperature, plating time) to control the deposition process and achieve a plated layer with controlled roughness (Ra1 > Ra2). By optimizing these parameters, the plated layer provides both protection and the necessary surface roughness for galling resistance, unlike conventional smooth plating
Solution Approach 2:
The invention creates a composite surface structure consisting of a roughened plated layer (providing mechanical interlocking and roughness) combined with a solid lubricant coating (providing lubrication). This composite structure achieves both the roughness needed for galling resistance and the lubrication needed for low friction, resolving the contradiction between smoothness and galling resistance
4Adaptability or versatility
If repeated fastening and loosening occur, then the threaded connection undergoes wear, but shouldering torque increases and galling occurs
Solution Approach 1:
The invention performs preliminary surface treatment by forming a roughened plated layer and applying a solid lubricant coating before the threaded connection is put into service. This preliminary preparation ensures that the contact surfaces have the necessary roughness for mechanical interlocking and are pre-lubricated, reducing friction and shouldering torque during repeated fastening and loosening operations
Solution Approach 2:
The invention changes the surface properties of the contact surfaces by controlling the plated layer roughness (Ra1 > Ra2) and applying solid lubricant. These parameter changes ensure that the surfaces maintain low friction and shouldering torque even after repeated fastening and loosening, improving the connection's adaptability to repeated use
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 galling resistance comparable to blasting-treated connections without the need for blasting, while maintaining low shouldering torque and ensuring the durability of the threaded connection during repeated fastening and loosening processes.
Implementation Method 1
a Zn—Ni alloy plated layer which is formed in an electrolytic plating treatment on the contact surface
Implementation Method 2
a solid lubricant coating that is formed on the Zn—Ni alloy plated layer
Data Source
AI summary
A threaded connection for pipe includes a pin and a box. The threaded connection for pipe includes a Zn—Ni alloy plated layer and a solid lubricant coating. The Zn—Ni alloy plated layer is formed on a contact surface of at least one of the pin and the box and contains 10 to 16 mass % of Ni. The solid lubricant coating is formed on the Zn—Ni alloy plated layer. The contact surface on which the Zn—Ni alloy plated layer is formed is ground. Now define arithmetic average roughness of the surface of the Zn—Ni alloy plated layer as Ra1, and arithmetic average roughness of the contact surface as Ra2. Ra1 ranges from 0.1 to 3.2 μm. Ra1 is more than Ra2.