Duplex Stainless Steel Seamless Pipe With Balanced Axial Yield Strength
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Solution Overview
Problem
Existing duplex stainless steel seamless pipes used in oil and gas wells face challenges in achieving high axial tensile yield strength and corrosion resistance while maintaining a small difference between axial tensile and compressive yield strengths, as current methods often compromise on corrosion resistance or strength due to the Bauschinger effect during cold rolling processes.
Innovation Solution
Incorporating specific amounts of Ti, Al, V, and Nb to form fine nitrides that control the solid solution nitrogen, thereby maintaining corrosion resistance and improving strength without consuming Cr and Mo, and using a combination of cold rolling and heat treatment techniques to manage the Bauschinger effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Cr and Mo are added to improve corrosion resistance, then corrosion resistance is improved, but strength may be compromised due to the Bauschinger effect
Solution Approach 1:
The invention introduces Ti, Al, V, and Nb as intermediary elements that form fine nitrides to provide strength enhancement. These intermediary elements take over the strength-providing function, allowing Cr and Mo to focus on corrosion resistance without being consumed in strength-forming reactions
Solution Approach 2:
The invention changes the compositional parameters by limiting C to 0.005-0.08% and N to 0.150-0.400%, while adding specific amounts of Ti, Al, V, and Nb. This parameter optimization ensures that corrosion-resistant elements Cr and Mo are not consumed in nitride formation, maintaining both corrosion resistance and strength
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 proposed solution achieves high corrosion resistance and strength with a minimal difference between axial tensile and compressive yield strengths, allowing for more flexible pipe design and improved performance under compressive stress, particularly in deep well applications.
Implementation Method 1
Incorporating specific amounts of Ti, Al, V, and Nb to form fine nitrides that control the solid solution nitrogen
Implementation Method 2
pipes to be used as oil country tubular goods are processed to improve axial tensile yield strength by dislocation strengthening using various cold rolling techniques
Implementation Method 3
using a combination of cold rolling and heat treatment techniques to manage the Bauschinger effect
Data Source
AI summary
Provided herein is a duplex stainless steel seamless pipe and a method for manufacturing the same. The duplex stainless steel seamless pipe has a composition comprising, in mass %, C: 0.005 to 0.08%, Si: 0.01 to 1.0%, Mn: 0.01 to 10.0%, Cr: 20 to 35%, Ni: 1 to 15%, Mo: 0.5 to 6.0%, N: 0.150 to less than 0.400%, and one, two or more selected from Ti: 0.0001 to 0.3%, Al: 0.0001 to 0.3%, V: 0.005 to 1.5%, Nb: 0.005 to less than 1.5%, and the balance being Fe and incidental impurities. The duplex stainless steel seamless pipe contains N, Ti, Al, V, and Nb so as to satisfy the following formula (1). The duplex stainless steel seamless pipe has an axial tensile yield strength of 757 MPa or more, and a ratio of 0.85 to 1.15 as a fraction of axial compressive yield strength to axial tensile yield strength.0.150>N−(1.58Ti+2.70Al+1.58V+1.44Nb) (1),wherein N, Ti, Al, V, and Nb represent the content of each element in mass %.