Titanium and its features
In addition to be the fourth metal for its great abundance, titanium is the ninth element in order of industrial usage. It is preceded – obviously – by aluminum, iron and magnesium.
With atomic weight of 47,88 it is light and robust: its features combine high resistance, tenacity, rigidity, low density and a good resistance to corrosion.
Its low density (about 60% of iron density) can be strengthened through alloy elements and deformation processes. It is non-magnetic and it has a good characteristic of thermal exchange. Its coefficient of thermal dilation is a little bit lower than that of the steels and it is less than half of that of aluminum. Further useful trait is the high melting point of 3135° F (1725 ° C), about 400° C higher than that of the steel and about 2000 ° F higher than that of aluminum.
Titanium can be passivated, and it resists to the attacks of acids and base better than the stainless steel. The excellent resistance to corrosion and biocompatibility, combined with mechanical resistance, make it suitable for the chemical and petrochemical, sea environment and biomedical applications.
Regarding the electrical conductivity, the titanium’s one is 3,1% of the coppers one. So, titanium is not a good electrical conductor and it offers a high electrical resistance.
For a more complete vision, here you can find a table with the summarized titanium properties:
| Main titanium’s features | |
| Specific weight | 4.5 g/cm3 |
| Density | 4500 Kg/m3 |
| Melting temperature | 1680 °C |
| Thermical conductivity | 17 W/m°C |
| Linear thermal expansion coefficient (20-100 °C) | 8.9*10-6 /°C |
| Electrical conductivity | 3% IACS (copper 100%) |
From pure titanium to the alloys
The commercially pure titanium can be classified in 4 grades, that are essentially different for:
- resistance;
- usability.
In a nutshell, when the grade raises, the first increases and the second decreases.
The titanium alloys are divided into:
- Commercially pure titanium (CO): It’s the grouping that contains the highest proportion of titanium. Typical features are the high tendency to corrosion and mechanical features of medium-low value.
- α alloys: they present good weldability and maintenance of the mechanical characteristics also at high operating temperature, thanks to the generally high content of aluminum. The usage in components particularly solicited is impeded by the fact that these cannot be submitted to any thermal treatment.
- b alloys: they guarantee the best mechanical features. These have very restricted or null weldability, these are used in the constructions of bolts and springs and in strongly solicited parts.
- α+b alloys: in the group there are the most used alloys with elevated mechanical characteristics and largely used in the production of airplane’s components.
The titanium alloys, that are rather numerous, are classified in grades.
In the traditional manufacture, as also in the 3D printing, the following types of alloys are especially used:
- the Ti6Al4V (grade 5)
- the Ti6Al4V ELI (grade 23).
Among all titanium alloys, the grade 5 is the most used: engine parts, structural parts of airplane and automotive, fastening aerospace elements, and sport equipment of high quality.
The Ti 6Al4V ELI, or simply the grade 23, is the purer version of grade 5. Thanks to its biocompatibility, to its good resistance to stress and to the low module, it can be used in dental and health care sector.
Hot and cold forging of titanium
Hot or cold forged, titanium consents to create special processing of excellent quality.
In particular, the hot process guarantees significant advantages such as:
- Increase of resistance: the longitudinal continuity, even in the critical transit area between head and stem, is kept unchanged. The raw material can be shaped, by avoiding the cuts typical of the traditional turning works. The phenomenon of detachment between head and stem decreases and it is frequent in the wrought that are submitted to excessive stress. The absence of cut fibers increases the resistance.
- Saving of raw material; optimization of costs. Swarf are not created during the process: the raw material is not wasted and the price of the product decreases.
Advantages and disadvantages of titanium usage
Advantages:
- low specific weight
- Hardness
- Resistance to corrosion
- low thermal conductivity
- Radiolucency
- Biochemical inert
- Biotolerance
- Not toxicity
- Absence of taste
- Resistance to chewing
Disadvantages:
- Not enough precise melting
- Formation of a layer of oxide on the surfaces
- Detachments of ceramic covering
- Inner porosities
- Surface porosity that allow higher accumulations of plaque than the traditional alloys.
The brief overview of information about a such promising metal (for booming sectors like health care, for example) like titanium, shows how all the above mentioned disadvantages can appear essentially just in case of melting, and so these are totally avoided by the hot forging with appropriate furnace or press, alongside an expert consultant that can address the choice of the proper machine, and suggest the working modalities and of course guarantee an impeccable customer service that avoids criticalities and tensions at the moment of operativity starting.