Cu-Si Titanium Sheet Composition for Weldable Strength and Formability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
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 increases in the Heat Affected Zone (HAZ) during welding.
Innovation Solution
The titanium sheet is optimized with specific chemical compositions and microstructures, including predetermined amounts of Cu, Si, Cr, Mn, O, Fe, N, C, and H, with controlled crystal grain sizes and intermetallic compounds to achieve a balance of strength and formability, with a 0.2% proof stress of 215 MPa or more and fracture elongation of 42% or more, while minimizing strength decrease in the HAZ region during 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 (O: 0.03-0.08 mass%, Fe: 0.01-0.05 mass%, Cu: 0.1-0.5 mass%, Si: 0.05-0.2 mass%) and microstructure parameters (average crystal grain size: 15-30 μm) to achieve high strength without increasing thickness, thereby maintaining the light-weight advantage while resolving the strength-thickness contradiction
Solution Approach 2:
The patent creates a composite microstructure consisting of α phase and precipitated intermetallic compounds (Cu-rich and Si-rich phases) within the titanium matrix. This composite structure provides both high strength through precipitation hardening and maintains the base titanium's low density, resolving the contradiction between strength and weight
2Productivity
If the sheet is thinned to improve heat exchange efficiency, then heat exchange efficiency improves, but formability and pressure resistance deteriorate
Solution Approach 1:
The patent changes the material parameters by optimizing chemical composition (adding Cu and Si as alloying elements) and controlling microstructure (average grain size 15-30 μm with precipitated intermetallic compounds), enabling thin sheets to maintain high formability and pressure resistance while achieving improved heat exchange efficiency
Solution Approach 2:
The patent introduces local quality variations through precipitated intermetallic compounds distributed within the α phase matrix, creating localized strengthening zones that enhance overall mechanical properties of the thin sheet without compromising its formability
3Strength
If alloy elements are added to achieve high strength, then strength increases, but formability decreases
Solution Approach 1:
The patent optimizes the parameters of alloy element concentrations (O: 0.03-0.08 mass%, Fe: 0.01-0.05 mass%, Cu: 0.1-0.5 mass%, Si: 0.05-0.2 mass%) to achieve the right balance where sufficient strength is obtained through controlled alloying without excessive deterioration of formability, unlike conventional high-alloy compositions
4Strength
If the crystal grain size is reduced to improve strength, then strength increases, but the complexity of manufacturing control increases
Solution Approach 1:
The patent sets the average crystal grain size parameter within the range of 15-30 μm, which is coarser than conventional fine-grained titanium (typically 5-15 μm). This parameter change reduces the complexity of manufacturing control while still achieving high strength through the combined effects of grain boundary strengthening and precipitation hardening from intermetallic compounds
5Ease of manufacture
If welding is performed to join components, then assembly is achieved, but strength decreases in the Heat Affected Zone due to grain size increase
Solution Approach 1:
The patent incorporates Cu and Si alloying elements before welding that will form precipitated intermetallic compounds in advance. These pre-formed strengthening phases provide a cushioning effect during welding, maintaining strength in the HAZ despite grain growth, because the precipitation hardening mechanism remains effective even with coarser grains
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
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).