Titanium Sheet Composition for Strength, Formability, and Welded HAZ Stability
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Solution Overview
Problem
Current titanium sheets face challenges in achieving a balance between high strength and sufficient formability, particularly in applications like plate heat exchangers, where thinning for improved heat exchange efficiency compromises formability and pressure resistance, and maintaining strength after welding is difficult due to grain size changes in the Heat Affected Zone (HAZ) region.
Innovation Solution
A titanium sheet with specific chemical compositions and microstructural characteristics, including Cu, Cr, Si, and controlled oxygen content, is developed to achieve a balance of strength and formability, with a microstructure comprising predominantly α phase, minimal β phase, and intermetallic compounds, and a crystal grain size range that maintains strength and ductility, even after welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the sheet thickness is increased to improve strength, then the strength increases, but the light-weight feature of titanium is compromised
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (Cu: 0.03-1.5 mass%, Si: 0.01-0.5 mass%, Mn: 0.01-0.5 mass%, Cr: 0.01-0.4 mass%, O: 0.03-0.1 mass%) and microstructural parameters (average crystal grain size 10-50 μm, α phase area fraction 90-99%) to achieve high strength without increasing thickness. The specific compositional ranges and microstructural controls enable strength enhancement through alloying and grain boundary strengthening mechanisms.
Solution Approach 2:
The patent creates a composite microstructure consisting of multiple phases (α phase as matrix, β phase, and intermetallic compounds) with controlled distribution and proportions. This composite microstructure, achieved through specific alloy composition and heat treatment, provides enhanced strength through phase interaction and precipitation hardening while maintaining the base titanium's lightweight特性.
2Productivity
If the sheet is thinned to improve heat exchange efficiency, then the heat exchange efficiency improves, but the formability and pressure resistance deteriorate
Solution Approach 1:
The patent utilizes parameter changes by optimizing the alloy composition parameters (particularly Cu and Si content) and microstructural parameters (crystal grain size and phase distribution) to achieve a microstructure that provides both high formability and sufficient strength. The controlled α phase predominance with fine grain size enables excellent formability, while the precipitation-hardened intermetallic compounds provide the necessary strength for thin-walled applications.
3Ease of operation
If the crystal grain size is increased to improve formability, then the formability improves, but the strength decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the crystal grain size parameter within the optimal range of 10-50 μm and adjusting the alloy composition parameters to achieve a balance between formability and strength. The specific grain size range provides sufficient ductility for forming operations, while the alloying elements and phase distribution compensate for strength reduction through solid solution strengthening and precipitation hardening.
Solution Approach 2:
The patent creates a composite microstructure with multiple phases (α, β, and intermetallic compounds) distributed throughout the matrix. This composite structure provides formability through the ductile α phase while the dispersed intermetallic compounds and β phase provide strength through precipitation hardening and phase boundary strengthening, resolving the trade-off between grain size, formability, and strength.
4Ease of operation
If the O content and Fe content are reduced to maintain formability, then the formability is maintained, but the strength is insufficient
Solution Approach 1:
The patent applies parameter changes by shifting the strengthening mechanism from oxygen-dependent solid solution strengthening to alloying-element-dependent precipitation hardening. By controlling Cu (0.03-1.5 mass%), Si (0.01-0.5 mass%), Mn (0.01-0.5 mass%), and Cr (0.01-0.4 mass%) within specific ranges, the patent achieves strength enhancement through intermetallic compound precipitation while maintaining low O (0.03-0.1 mass%) and Fe content for excellent formability.
Solution Approach 2:
The patent creates a composite microstructure where intermetallic compounds (formed from Cu, Si, Mn, Cr alloying elements) are precipitated within the α phase matrix. This composite structure provides strength through precipitation hardening mechanisms, replacing the traditional oxygen-based strengthening approach and enabling high strength with low oxygen content, thus maintaining both formability and strength.
5Strength
If alloy elements are added to achieve high strength, then the strength increases, but the formability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the alloy element content within optimal ranges (Cu: 0.03-1.5 mass%, Si: 0.01-0.5 mass%, Mn: 0.01-0.5 mass%, Cr: 0.01-0.4 mass%) and adjusting the microstructural parameters (grain size: 10-50 μm, α phase area fraction: 90-99%). This balanced control ensures that alloying provides sufficient strength through precipitation hardening without excessive alloy content that would harm formability.
Solution Approach 2:
The patent creates a composite microstructure where moderate amounts of alloy elements form dispersed intermetallic compounds within a continuous α phase matrix. This composite structure provides strength through precipitation hardening while the dominant ductile α phase (90-99% area fraction) maintains excellent formability, resolving the trade-off between alloying-induced strength and formability.
Data Source
AI summary
A titanium sheet including the following chemical components in mass %: Cu: 0.70 to 1.50%, Cr: 0 to 0.40%, Mn: 0 to 0.50%, Si: 0.10 to 0.30%, O: 0 to 0.10%, Fe: 0 to 0.06%, N: 0 to 0.03%, C: 0 to 0.08%, H: 0 to 0.013%, elements except the above and Ti: 0 to 0.1% each, with a total amount of the elements being 0.3% or less, and the balance: Ti, wherein A value defined by Formula (1) is 1.15 to 2.5 mass %, and the titanium sheet having a metal microstructure in which an area fraction of an α phase is 95% or more, an area fraction of a β phase is 5% or less, and an area fraction of an intermetallic compound is 1% or less, wherein an average crystal grain size D (μm) of the α phase is 20 to 70 μm and satisfies Formula (2).