Two-Stage Taper Threaded Joint for Pipe Fatigue and Galling
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Solution Overview
Problem
Existing threaded joints for steel pipes face challenges in uniformly applying shot peening to complex thread parts, leading to potential galling and inadequate sealing performance, while also requiring improved anti-fatigue resistance in harsh drilling environments.
Innovation Solution
A threaded joint design featuring a two-stage taper male thread part with varying taper ratios for different regions, ensuring greater taper ratios for the first region compared to the second region, which exceeds the taper ratio of the female thread part, enhancing anti-fatigue and galling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If shot peening is performed on specific portions of the thread parts to improve anti-fatigue performance, then the fatigue strength becomes high, but the surface roughness increases and galling may occur
Solution Approach 1:
The patent applies shot peening selectively to specific portions of the thread parts (male and female threads) rather than uniformly across all surfaces. This localized treatment improves fatigue strength at critical stress points while maintaining smoother surfaces in other areas to prevent galling during the fastening process.
2Strength
If shot peening is performed uniformly on all thread parts to maximize anti-fatigue performance, then the fatigue strength becomes very high, but galling occurs during fastening due to increased surface roughness
Solution Approach 1:
The patent implements selective shot peening on specific portions of the thread parts, applying the surface treatment only where fatigue resistance is most critical while leaving other areas untreated to maintain low surface roughness and prevent galling during assembly.
3Strength
If the taper ratio of the male thread part is increased to improve anti-fatigue performance, then the fatigue strength becomes high, but the sealing performance may deteriorate
Solution Approach 1:
The patent optimizes the taper ratio parameter of the male thread part to achieve a balance between anti-fatigue performance and sealing performance. By carefully selecting the taper ratio within a specific range, the patent ensures sufficient fatigue strength while maintaining adequate sealing capability.
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 significantly improves anti-fatigue performance and secures galling resistance by optimizing the taper ratios of the male thread part, while maintaining effective sealing and reducing the likelihood of galling during fastening.
Implementation Method 1
The taper ratio of the first region is greater than the taper ratio of the second region. The taper ratio of the first region is greater than the taper ratio of the taper female thread part. The taper ratio of the second region is greater than the taper ratio of the taper female thread part.
Data Source
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AI summary
A threaded joint for steel pipes capable of improving the anti-fatigue performance while securing the galling resistance is provided. The threaded joint includes a pin and a box. The pin includes a taper male thread part (11), and the box includes a taper female thread part (21) to be engaged with the taper male thread part (11). The male thread part (11) is divided into a first region (15) on the free end side of the pin, and a second region (16) on the tubular side of the pin along a tube axis (CL) direction. The taper ratio (Tp1) of the first region (15) is greater than the taper ratio (Tp2) of the second region (16). The taper ratio (Tp1) of the first region (15) is greater than the taper ratio (Tb) of the female thread part (21). The taper ratio (Tp2) of the second region (16) is equal to or greater than the taper ratio (Tb) of the female thread part (21).