Dual Phase Stainless Steel Pipe Yield Strength Anisotropy
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Solution Overview
Problem
Dual phase stainless steel pipes used in oil wells face challenges in maintaining balanced yield strength across different stress directions due to varying environmental stress distributions, with existing manufacturing methods not sufficiently reducing the difference between compressive and tensile yield strengths.
Innovation Solution
A dual phase stainless steel pipe with specific yield strength ratios in both axis and circumferential directions, manufactured through cold working followed by straightening and low temperature heat treatment between 350°C to 450°C, to reduce anisotropy and enhance durability under diverse stress conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cold working is performed to increase compressive yield strength in the pipe axis direction, then compressive yield strength increases, but the difference between compressive and tensile yield strength is not sufficiently reduced
Solution Approach 1:
The patent applies low temperature heat treatment at 200-450°C to change the physical state of the steel pipe after cold working. This heat treatment parameter change causes dislocation reorientation, which reduces the difference between compressive and tensile yield strengths while maintaining high compressive yield strength, thereby achieving balanced yield strength across different stress directions
Solution Approach 2:
The patent replaces purely mechanical cold working with a combination of mechanical cold working and thermal processing. The low temperature heat treatment substitutes for additional mechanical processing by using thermal energy to reorient dislocations, achieving better yield strength balance without requiring complex mechanical operations
2Strength
If manufacturing methods focus on increasing compressive yield strength, then compressive yield strength improves, but the pipe may not be usable with respect to stress applied from directions other than pipe axis direction
Solution Approach 1:
By introducing low temperature heat treatment as a parameter change after cold working, the patent achieves dislocation reorientation that simultaneously improves compressive yield strength and reduces anisotropy. This enables the pipe to maintain high strength in the pipe axis direction while also achieving better performance under stresses from other directions, thereby increasing adaptability to various stress distributions
Solution Approach 2:
The low temperature heat treatment process serves multiple functions: it maintains the high compressive yield strength achieved through cold working, reduces the difference between compressive and tensile yield strengths, and improves the pipe's performance under circumferential and diagonal stresses. This multi-functional approach makes the pipe universally applicable to various stress conditions in oil well environments
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 achieves reduced anisotropy in yield strength, enabling the pipe to withstand various stress distributions effectively, thus ensuring durable performance in oil well applications.
Implementation Method 1
a dislocation which is introduced into the steel by cold working is reoriented by the heat treatment
Implementation Method 2
a heat treatment is performed at 200° C. to 450° C. with respect to the steel pipe which is subjected to cold working
Data Source
AI summary
A dual phase stainless steel pipe includes tensile yield strength YSLT of 689.1 MPa to 1000.5 MPa in a pipe axis direction of the dual phase stainless steel pipe, in which the tensile yield strength YSLT, a compressive yield strength YSLC in the pipe axis direction, a tensile yield strength YSCT in a pipe circumferential direction of the dual phase stainless steel pipe, and a compressive yield strength YSCC in the pipe circumferential direction satisfy all Expressions (1) to (4),0.90≤YSLC/YSLT≤1.11 (1)0.90≤YSCC/YSCT≤1.11 (2)0.90≤YSCC/YSLT≤1.11 (3)0.90≤YSCT/YSLT≤1.11 (4).