Titanium, despite what currently
is known, is not a metal and is the fourth most
abundant structural metal in the earth's crust
and is the ninth industrial metal used,
Currently is found in nature as oxide in Ilmenite,
black volcanic sands and Ruthile. Metallic titanium
is obtained by 3 different processes:
• transformation into
sponge;
• melting by VAR / EBM to obtain
ingots/ slab;
• then forged/rolled into specific
shape and sizes for further processes
such as plate; sheets, coils; bars, rings,
metallic titanium is a silvery,
ductile metal with density inferior to iron,
hardness superior to Al and corrosion resistance
nearly as good as platinum.
Titanium is presenting a combination of technological
features extremely favourable for a wide range
of industrial application:
• High Mechanical
resistance, related to a relatively low
density (4,51 Kg /dm3);
• high corrosion resistance in aggressive
environments;;
• high biocompatibility;
• high melting temperature (1668°);
• amagneticity;
• low modulus of elasticity, thermal
conductivity and coefficient of thermal
expansion
Titanium could have 2 different crystalline
form:
The first one, namely "Alfa"
, corresponding to an hex compact structure,
stable at low temperatures, the second one,
namely "Beta" has
a cubic structure and it is stable at high
temperature. In Pure titanium, the alfa phase,
is stable at all the temperature up to 882
C, where we assist at the trasformation into
the Beta phase. This temperature level (882C)
is also known as Beta –Transus and it
is constant to the melting point.
Titanium and its alloys are divided in 3
major categories acc. To the predominant assumed
by their structure at room temperature. Alfa
alloys , Beta alloys
e Alfa-Beta alloys.
Last are mostly a compromise between the Alfa
and the Beta alloys. Alpha alloys are non-heat
treatable and are generally very weldable.
They have low to medium strength, good notch
toughness, reasonably good ductility and possess
excellent mechanical properties at cryogenic
temperatures. The more highly alloyed alpha
and near-alpha alloys offer optimum high temperature
creep strength and oxidation resistance as
well.
Alpha-Beta alloys are heat
treatable and most are weldable. Their strength
levels are medium to high. Their hot-forming
qualities are good, but the high temperature
creep strength is not as good as in most alpha
alloys.
Beta or near-beta
alloys are readily heat treatable,
generally weldable, and capable of high strengths
and good creep resistance to intermediate
temperatures. Excellent formability can be
expected of the beta alloys in the solution
treated condition. Beta-type
alloys have good combinations of properties
in sheet, heavy sections, fasteners and spring
applications
Tipi
di titanio
Principali
applicazioni
Ti
Grade 1
Widely used for chemical
implants for its corrosion resistance,
most suitable for cold forming and for
deep drawing.
Ti
Grade 2
It is the most common grade,
widely used in the majority of application
for its mechanical properties and as well
for behaviour in forming.
Ti
Grade 3
For oxidising ambient and
as well for application at low temperature
Ti
Grade 4
The CP titanium with highest mechanical
properties, Commonly used for the production
of Anodising jigs, shows optimum corrosion
resistance and good mechanical properties
and elasticity
Ti
Grade 5
( 6Al-4V )
It is the most popular titanium alloy
when high mechanical properties are required
up to medium temperature (400° C).
Good forging properties and high ductility
in the annealed conditions.
Ti
Grade 7
( Ti Gr.2 e 0,2 Pd)
As grade 2, higher performance
with low pH and up to 425°C (constant
service) and up to 540 Degres for intermittent
service.
Alpha
Alpha-Beta
Beta
Alpha
alloys are non-heat treatable and are
generally very weldable. They have low
to medium strength, good notch toughness,
reasonably good
ductility and possess excellent mechanical
properties at cryogenic temperatures.
The more highly alloyed alpha and near-alpha
alloys offer optimum high temperature
creep strength and oxidation resistance
as well.
Alpha-Beta
alloys are heat treatable and most are
weldable. Their strength levels are medium
to high. Their hot-forming
qualities are good, but the high temperature
creep strength is not as good as in most
alpha alloys.
Beta or near-beta alloys are readily
heat treatable, generally weldable, and
capable of high strengths and good creep
resistance to intermediate temperatures.
Excellent formability can be expected
of the beta alloys in the solution
treated condition. Beta-type alloys have
good combinations of properties in sheet,
heavy
sections, fasteners and spring applications
