Oil Well Steel Pipe Collapse Strength via Composition Control
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Solution Overview
Problem
Existing electric resistance welded steel pipes for oil wells require further improvement in collapse strength, which can be achieved through heat treatment after pipe making, but existing methods do not effectively enhance both strength and toughness simultaneously.
Innovation Solution
Adjusting the chemical composition of the steel pipe to specific ranges, including carbon, silicon, manganese, phosphorus, sulfur, niobium, titanium, aluminum, nitrogen, copper, nickel, chromium, molybdenum, vanadium, and boron, and applying heat treatment to optimize the 0.2% proof stress to tensile strength ratio and 2% flow stress to tensile strength ratio, while minimizing residual stress and enhancing weld crack sensitivity and positron lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat treatment is applied after pipe making to improve collapse strength, then collapse strength is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by controlling chemical composition and processing parameters during pipe manufacturing to pre-establish the microstructure and mechanical properties needed for high collapse strength, reducing or eliminating the need for subsequent heat treatment operations
Solution Approach 2:
The patent employs parameter changes by optimizing chemical composition (C: 0.23-0.45%, Si: 0.02-0.60%, Mn: 1.50-3.00%, etc.) and processing parameters (tensile strength: 780-1100 MPa, elongation: 10-20%, yield ratio: 0.80-0.98) to achieve the desired collapse strength without requiring additional heat treatment steps
2Strength
If chemical composition is adjusted to specific ranges to improve strength and toughness, then both strength and toughness are enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for chemical composition (C: 0.23-0.45%, Si: 0.02-0.60%, Mn: 1.50-3.00%, P: ≤0.030%, S: ≤0.030%, Nb: 0.010-0.100%, Ti: 0.010-0.050%, Al: 0.010-0.100%, N: ≤0.0100%) and mechanical properties (tensile strength: 780-1100 MPa, elongation: 10-20%, yield ratio: 0.80-0.98) to achieve both high strength and toughness while maintaining manufacturability
Solution Approach 2:
The patent utilizes composite material principles by combining multiple alloying elements (C, Si, Mn, Nb, Ti, Al, and optional Cu, Ni, Cr, Mo, V, B) in specific proportions to create a synergistic effect that enhances both strength and toughness properties simultaneously
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 significantly enhances the collapse strength of the steel pipes by achieving a collapse strength ratio of 1.10 or more, improving tensile strength to 780 MPa or more, and maintaining adequate toughness, thereby increasing design flexibility and reducing material costs.
Implementation Method 1
performing heat treatment at low temperature to increase the yield strength utilizing the Cottrell effect
Implementation Method 2
performing heat treatment at low temperature to increase the yield strength utilizing the Cottrell effect
Implementation Method 3
performing heat treatment at high temperature to remove residual stress
Data Source
AI summary
An electric resistance welded steel pipe for an oil well includes in terms of mass %: 0.02 to 0.14% of C, 0.05 to 0.50% of Si, 1.0 to 2.1% of Mn, 0.020% or less of P, 0.010% or less of S, 0.010 to 0.100% of Nb, 0.010 to 0.050% of Ti, 0.010 to 0.100% of Al, and 0.0100% or less of N. Contents of Cu, Ni, Cr, Mo, V, and B are 0 to 0.50%, 0 to 1.00%, 0 to 0.50%, 0 to 0.30%, 0 to 0.10%, and 0 to 0.0030%, respectively. Remainder consisting of Fe and unavoidable impurities. In a case that a full thickness specimen is subjected to a pipe axis direction tensile test, a tensile strength is 780 MPa or more, 0.2% proof stress/tensile strength is 0.80 or more, and 2% flow stress/tensile strength is from 0.85 to 0.98.