Pure Titanium Sheet Stamping Formability Balance
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Solution Overview
Problem
Current titanium sheets fail to achieve a balance between sufficient strength and stamping formability, particularly for applications like plate heat exchangers, where higher strength and formability are required to enhance heat exchange effectiveness and pressure tightness, without compromising material properties.
Innovation Solution
A pure titanium sheet with a 0.2% yield strength of 215 MPa or more, featuring a hexagonal crystal structure with specific average grain sizes and Schmidt factors, optimized through controlled cold rolling and annealing processes to enhance twin deformation and crystal orientation, ensuring a balance between strength and formability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the strength of pure titanium is increased to meet the requirements for heat exchanger pressure tightness, then the strength improves, but the stamping formability deteriorates
Solution Approach 1:
The invention changes the microstructural parameters of pure titanium by controlling grain size (25-75 μm) and crystal orientation (Schmidt factor 0.055-0.084), which fundamentally alters the deformation mechanism from dislocation slip to twin deformation, simultaneously achieving high strength (≥215 MPa) and excellent stamping formability
Solution Approach 2:
The invention creates local quality differences within the titanium sheet by controlling the distribution and orientation of grains and twins, where the specific crystallographic orientation (high Schmidt factor) promotes twin deformation in stamping directions while maintaining overall high strength properties
2Ease of manufacture
If JIS Grade 1 pure titanium is used to achieve good stamping formability, then the stamping formability improves, but the strength becomes insufficient for high pressure tightness requirements
Solution Approach 1:
The invention transforms the deformation mechanism parameter from dislocation slip (dominant in soft Grade 1 titanium) to twin deformation (dominant in the invention's optimized structure), enabling Grade 2 strength levels (≥215 MPa) to achieve formability comparable to or exceeding Grade 1 titanium
3Ease of manufacture
If conventional techniques for improving stamping formability are applied to pure titanium with strength corresponding to JIS Grade 2, then the formability does not improve sufficiently, because these techniques are designed for softer titanium grades
Solution Approach 1:
The invention identifies and controls the critical parameters of grain size (25-75 μm) and Schmidt factor (0.055-0.084) that govern twin deformation behavior, creating a quantitative framework that reliably achieves excellent formability in Grade 2 titanium, unlike conventional qualitative approaches designed for softer grades
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 optimized titanium sheet exhibits excellent stamping formability and high strength, making it suitable for complex shapes in heat exchangers and chemical plants, while maintaining the required strength and formability levels.
Implementation Method 1
optimized through controlled cold rolling and annealing processes to enhance twin deformation and crystal orientation
Implementation Method 2
enhance twin deformation and crystal orientation
Data Source
AI summary
Disclosed is a pure titanium sheet having a strength corresponding to JIS Grade 2 level (215 MPa in terms of 0.2% yield strength) or more and having satisfactory stamping formability. The pure titanium sheet includes titanium and inevitable impurities, has a 0.2% yield strength of 215 MPa or more, has an average grain size d of its structure of 25 μm or more and 75 μm or less, and has a hexagonal crystal structure, in which respective grains in the hexagonal crystal structure have an average of Schmidt factors (SF) of (11-22) twins with a rolling direction as axes, and the average Schmidt factor (SF) and the average grain size d satisfy following Expression (1):0.055≦[SF/√d]≦0.084 (1).