There are four grades of unalloyed titanium (commercially pure titanium): Grade 1, Grade 2, Grade 3, and Grade 4. The metallographic structure of all grades at room temperature is α phase (HCP). When the temperature is at about 885°C [1625°F], it transform to a beta phase structure (BCC). The α transus temperature and β transus temperature differ slightly for each grade due to the differentiated amount of interstitial alloying elements. The typical transus temperatures are listed in below table.

Titanium	Typical β Transus Temp.		Typical α Transus Temp.
Designation	°C	°F	°C	°F
Grade 1	888	1630	880	1620
Grade 2	913	1675	890	1635
Grade 3	920	1685	900	1650
Grade 4	950	1740	905	1660

*Below α transus temperature, the alloy is all-alpha phase; above β transus temperature, the alloy is all-beta phase; between the temperatures, both alpha and beta are present.
*Depending on level of interstitial impurities (C,H,O,Fe,N), an uncertainty of about ±15°C [±25°F] shall be considered.