Titanium Multilayer Surface Film for Corrosion and Yield Loss
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Solution Overview
Problem
Conventional methods for producing titanium materials fail to achieve homogeneous, corrosion-resistant, and lubricious surfaces due to the formation of titanium carbide and nitride compounds, leading to yield loss and surface degradation, and existing surface treatment methods do not adequately control the formation of these compounds.
Innovation Solution
A titanium material with a multilayer surface film structure, comprising a surface layer of titanium oxide with a hardness of 5 GPa to 20 GPa and an inner layer containing titanium carbide or nitride, achieved through hot rolling, cold rolling, annealing in a combustion gas atmosphere, acid washing, and electrolytic pickling in acidic or neutral aqueous solutions with controlled electrical potential and current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional annealing and pickling is used to remove oxidized scale, then corrosion resistance is improved, but yield loss increases due to dissolution of bare metal
Solution Approach 1:
The invention extracts and removes only the harmful oxidized scale layer from the titanium material surface through controlled acid washing, while preserving the underlying bare metal. This selective removal approach eliminates the need to dissolve healthy metal to achieve corrosion resistance, thereby reducing yield loss while maintaining protective oxide film formation capability
Solution Approach 2:
The invention creates a non-uniform surface condition through controlled oxidation, where a thin protective oxide film is formed only in specific locations or to a controlled thickness, rather than allowing thick uniform scale formation. This local quality control allows corrosion resistance without excessive material loss
2Loss of substance
If bright annealing is used to preserve rolled gloss and avoid oxidized scale, then yield loss is reduced, but titanium carbide and nitride formation degrades surface characteristics
Solution Approach 1:
The invention performs preliminary removal of carbon and nitrogen contaminants from the titanium surface before the annealing process. By eliminating these harmful elements in advance, the subsequent annealing can proceed without forming titanium carbide or nitride compounds, thus preserving surface characteristics while maintaining the benefits of bright annealing
Solution Approach 2:
The invention rapidly processes through the annealing stage by controlling the atmosphere and parameters to minimize the time window during which carbon and nitrogen could react with titanium. This rushed-through approach prevents carbide and nitride formation while achieving the desired oxide film and surface finish
3Reliability
If thick oxidized scale is formed during heating, then corrosion resistance is improved, but acid washing removes excessive metal and increases yield loss
Solution Approach 1:
The invention changes the oxidation parameters by controlling the heating atmosphere composition, temperature, and exposure time to form only a thin protective oxide film rather than thick scale. This parameter control ensures sufficient corrosion resistance while minimizing the amount of oxide that would subsequently be removed during acid washing, reducing yield loss
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 titanium materials with excellent surface lubricity and corrosion resistance, reducing yield loss and enhancing the adhesion of coatings or plating films, while maintaining the aesthetic appearance and corrosion resistance of titanium.
Implementation Method 1
Since titanium has high activity and high affinity to oxygen compared to other commonly-used metals, a titanium material usually has a layer mostly formed of titanium oxide with a thickness of several nm to several tens of nm on the surface. The surface film of oxide is mainly formed during annealing in production
Implementation Method 2
a method for producing a titanium material including a surface film having a surface layer formed of titanium oxide, comprising the successive steps of: hot rolling pure titanium or titanium alloy to form a plate, repeatedly subjecting the plate to cold rolling, annealing in a combustion gas atmosphere and acid washing to make a secondary half-finished product, cold rolling and annealing the secondary half-finished product to form a titanium material including a surface layer containing at least one of titanium carbide and titanium nitride; and then electrolytically pickling the titanium material by anode electrolysis or alternating electrolysis in acidic aqueous solution or neutral aqueous solution containing an oxidizing reagent
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3~4
AI summary
Disclosed are a titanium material having excellent surface characteristics and a method for readily producing a titanium material having excellent surface characteristics. More specifically, provided is a titanium material including a surface film having a multilayer structure provided with at least two layers, namely a surface layer and an inner layer in contact with the inner side of the surface layer, wherein the surface layer is formed of titanium oxide with a hardness of 5 GPa to 20 GPa, and the inner layer contains at least one of titanium carbide and titanium nitride.