The density of titanium and titanium alloy is only 4.51g/cm3, which is smaller than that of steel and only half the weight of steel, but its strength is similar to that of ordinary carbon steel.
Titanium belongs to thermodynamically unstable metals and is very active.
Titanium metal can form a natural oxide film (titanium dioxide) with air.
This layer of stable, strong adhesion and good protective oxide film determines the corrosion resistance of titanium.
Therefore, titanium has excellent corrosion resistance, followed by light texture, high tensile strength and good mechanical properties.
It is another excellent feature of titanium alloy.
Classification of titanium alloys:
Titanium alloys can be divided into corrosion-resistant titanium alloy, structural titanium alloy, heat-resistant titanium alloy gold and low-temperature titanium alloy according to their uses.
At room temperature, titanium alloys have three kinds of matrix structures, and titanium alloys can be divided into the following three types: α alloys,（ α+β) alloys and β alloy.
1.α titanium alloy
It is a single-phase alloy composed of α-phase solid solution.
Both at normal temperature and at higher practical application temperature is α phase.
It has stable structure, higher wear resistance than pure titanium and strong oxidation resistance.
2.β titanium alloy
It is a single-phase alloy composed of β-phase solid solution.
It has high strength without heat treatment.
After quenching and aging, the alloy is further strengthened, and the strength can reach 1372 ～ 1666 MPa at room temperature.
3.α+β titanium alloy
It is a two-phase alloy with good comprehensive properties, good structural stability, good toughness, plasticity and high-temperature deformation properties.
It can be well processed by hot pressing, and can be quenched and aged to strengthen the alloy.
Difference between titanium and stainless steel
1. It can be distinguished by color.
Titanium is a little dark, showing a cool color. I think it’s cool. Titanium is darker than steel.
Steel is white and pale.
The two colors are quite distinct.
2. It can also be distinguished by chemical methods, that is, soaking with nitric acid.
Titanium does not react, and stainless steel will react strongly once it is put down.
The distinction between pure titanium and titanium alloy is difficult to see from the appearance.
3. Titanium can make gray black marks on ceramic tiles, but stainless steel cannot make marks.
4. Titanium has good corrosion resistance: under 550 ℃, titanium alloy is easy to form dense oxide film, so it is not easy to be further oxidized.
It has high loss resistance to gas, sea water, steam and some acid, alkali and soft media.
5. Titanium has good thermal strength: the melting point of titanium alloy is 1660 ℃, which is higher than that of iron and has higher thermal strength.
It can work under 550 ℃ and has better toughness at low temperature.
6. Titanium processing is difficult: welding, electroplating and cold stretching are very difficult.
Welding and electroplating must be carried out in vacuum or under the condition of being filled with inert gas (vacuum ion plating)
How to distinguish titanium from stainless steel?
1. Composition is different:
(1) Titanium alloy is an alloy composed of titanium and other elements.
There are two kinds of homogeneous and heterogeneous crystals of titanium: titanium α with dense hexagonal structure below 882 ℃ and titanium β with body centered cubic structure above 882 ℃.
(2) Stainless steel refers to the steel resistant to weak corrosive media such as air, steam and water and chemical corrosive media such as acid, alkali and salt, also known as stainless and acid resistant steel.
In practical application, the steel resistant to weak corrosion medium is often called stainless steel, while the steel resistant to chemical medium is called acid resistant steel.
2. Different performance:
(1) Titanium is a new type of metal. The performance of titanium is related to the content of carbon, nitrogen, hydrogen, oxygen and other impurities.
The purity of titanium iodide is less than 0.1%, but its strength is low and its plasticity is high.
(2) Stainless steel:
Corrosion resistance: most stainless steel products require good corrosion resistance;
Polishing performance: in today’s society, stainless steel products are generally polished during production.
Only a few products, such as water heaters and water dispenser liners, do not need polishing.
3. Different functions:
(1) Titanium alloy is mainly used for making compressor parts of aircraft engines, followed by structural parts of rockets, missiles and high-speed aircraft.
(2) 304 stainless steel is widely used in curtain walls, side walls, roofs and other building applications, but in the highly corrosive industrial or marine atmosphere, 316 stainless steel is used.