Pure Titanium Screw Stock With Uniform Hardness and Alloy-Level Strength
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Solution Overview
Problem
Existing medical screws made of pure titanium lack sufficient strength and uniform hardness, making them unsuitable for applications requiring minimal invasiveness, and conventional methods to enhance strength, such as bulk ultrafine grained processing, are complex and unreliable.
Innovation Solution
A base material for screws, particularly medical anchor screws, made of pure titanium with controlled orientation in the (1 0 -1 0) plane and specific hardness uniformity, produced through swaging without bulk ultrafine grained processing, ensuring consistent properties and high strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure titanium is used for medical screws, then corrosion resistance and biocompatibility are improved, but strength is insufficient
Solution Approach 1:
The invention changes the microstructural parameters of pure titanium by controlling crystal grain size (refining to ultrafine scale) and crystal orientation (promoting specific plane alignment). This allows pure titanium to achieve tensile strength comparable to Ti-6Al-4V alloy while maintaining its inherent corrosion resistance and biocompatibility
Solution Approach 2:
The invention creates a composite microstructure within pure titanium by combining ultrafine grain refinement with specific crystal orientation control. This internal composite structure enables the material to simultaneously exhibit high strength and excellent corrosion resistance, resolving the contradiction between these properties
2Strength
If swaging is used to improve strength of pure titanium, then tensile strength increases, but hardness becomes non-uniform and cracks may occur
Solution Approach 1:
The invention optimizes the swaging parameters by controlling the processing ratio (true strain ≥2) and implementing multi-pass swaging with intermediate annealing. This controlled parameter approach achieves uniform hardness distribution while preventing crack formation, unlike conventional single-pass swaging
Solution Approach 2:
The invention employs periodic action through multi-pass swaging with intermediate annealing treatments. This periodic cycling of deformation and recovery allows uniform plastic deformation throughout the material, ensuring homogeneous hardness while avoiding localized stress concentration that leads to cracking
3Strength
If bulk ultrafine grained processing is used to enhance strength, then mechanical properties improve, but process complexity increases and reliability decreases
Solution Approach 1:
The invention extracts and eliminates the need for complex bulk ultrafine grained processing by achieving ultrafine grain structure through controlled swaging and annealing. This simplifies the manufacturing process while still achieving the desired mechanical properties, directly addressing the contradiction between strength enhancement and process complexity
4Strength
If processing ratio is increased beyond 80%, then strength improves, but material becomes brittle and cracks occur
Solution Approach 1:
The invention uses periodic action through multi-pass swaging with intermediate annealing to distribute the total processing ratio (true strain ≥2) across multiple stages. This prevents excessive localized deformation that causes brittleness and cracking, while still achieving the required strength through cumulative plastic deformation
Solution Approach 2:
The invention applies preliminary annealing treatments before subsequent swaging passes to restore ductility. This preliminary action prevents the material from becoming too brittle during the overall processing sequence, allowing higher total processing ratios to be achieved without crack formation
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 method produces a pure titanium screw with comparable strength to titanium alloys, providing uniform hardness and torsional break torque, suitable for self-drilling applications with stable production and reliable management.
Implementation Method 1
swaging the pure titanium material to obtain the base material for the screw
Implementation Method 2
having 3 or more of a maximum specific intensity of an orientation in a (1 0 -1 0) plane in an axial direction
Data Source
Figure 1
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AI summary
The present invention provides a pure titanium screw or a base material for a pure titanium screw having sufficient strength comparable to that of titanium alloys. The present invention provides a substantially cylindrical pure titanium screw base material or screw, wherein the maximum value of the specific strength in the orientation of the (1 0 -1 0) plane in the axial direction of the substantially cylindrical shape is 3 or more, and the hardness of a center part and the hardness of an outer peripheral part in a substantially circular cross section orthogonal to the axial direction are approximately the same.