Steel Material Yield Strength and SSC Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing steel materials with yield strengths of 95 to 155 ksi grade often fail to stably achieve excellent sulfide stress cracking (SSC) resistance, despite previous technological advancements.
Innovation Solution
A steel material with a specific chemical composition and microstructure, including a range of elements such as C, Si, Mn, Cr, Mo, V, Ti, and alloy carbides, is developed to achieve both high yield strength and SSC resistance by controlling dislocation density and precipitate distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strength steel materials are used to enhance yield strength, then the strength is improved, but the sulfide stress cracking resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (C: 0.10-0.60%, Cr: 0.20-1.50%, Mo: 0.25-1.50%, V: 0.01-0.60%, Ti: 0.002-0.050%, B: 0.0001-0.0050%) and microstructural parameters (dislocation density, precipitate distribution and composition) to achieve both high yield strength (655-1172 MPa) and excellent SSC resistance simultaneously
Solution Approach 2:
The patent creates a composite microstructure consisting of multiple phases and precipitates including tempered martensite, MC-type carbides, M2C-type carbides, and fine precipitates with specific compositions. This composite structure provides both strength through precipitation hardening and SSC resistance through controlled micro morphology and distribution
2Strength
If conventional steel compositions are used to achieve high strength, then the yield strength is improved, but the stability of SSC resistance deteriorates
Solution Approach 1:
The patent establishes stable SSC resistance by defining specific ranges for multiple composition parameters and microstructural parameters. The controlled composition (particularly Cr: 0.20-1.50%, Mo: 0.25-1.50%, V: 0.01-0.60%) and microstructure (dislocation density, precipitate types and distributions) ensure consistent performance across different batches and service conditions
Solution Approach 2:
The patent applies local quality by creating different types of precipitates with specific compositions and distributions at different locations within the microstructure. MC-type carbides, M2C-type carbides, and fine precipitates are distributed strategically to provide localized strengthening and corrosion resistance, ensuring stable overall performance
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 steel material exhibits a yield strength range of 655 to 1172 MPa and superior SSC resistance, effectively addressing the stability issues of previous materials.
Implementation Method 1
the amount of precipitating carbides is within the range of 2 to 5 weight percent, and among the precipitating carbides the proportion of MC-type carbides is within the range of 8 to 40 weight percent
Implementation Method 2
A dislocation density ρ is not more than 3.5×10^15 m^-2. In a case where the yield strength is in a range from 655 to less than 758 MPa, the dislocation density ρ is less than 2.0×10^14 m^-2
Data Source
AI summary
A steel material having a yield strength in a range of 655 to 1172 MPa (95 to 155 ksi grade) and excellent SSC resistance is provided. The steel material according to the present disclosure has a chemical composition consisting of, in mass%, C: 0.10 to 0.60%, Si: 0.05 to 1.00%, Mn: 0.05 to 1.00%, P: 0.025% or less, S: 0.0100% or less, Al: 0.005 to 0.100%, Cr: 0.20 to 1.50%, Mo: 0.25 to 1.50%, V: 0.01 to 0.60%, Ti: 0.002 to 0.050%, B: 0.0001 to 0.0050%, N: 0.0020 to 0.0100%, and O: 0.0100% or less, with the balance being Fe and impurities. A dislocation density ρ is 3.5×1015 m-2 or less. Among fine precipitates, the numerical proportion of precipitates for which a ratio of the Mo content is not more than 50% is 15% or more. The yield strength is in a range of 655 to 1172 MPa.