How titanium is made – material, manufacture, making, history, used, processing, parts, components, composition

Background Titanium is known as a transition metal on the periodic table of elements denoted by the symbol Ti. It is a lightweight, silver-gray material with an atomic number of 22 and an atomic weight of 47.90. It has a density of 4510 kg/m 3 , which is somewhere between […]

Background

Titanium is known as a transition metal on the periodic table of elements
denoted by the symbol Ti. It is a lightweight, silver-gray material with
an atomic number of 22 and an atomic weight of 47.90. It has a density of
4510 kg/m

3

, which is somewhere between the densities of aluminum and stainless
steel. It has a melting point of roughly 3,032°F (1,667°C) and a
boiling point of 5,948°F (3,287 C). It behaves chemically similar to
zirconium and silicon. It has excellent corrosion resistance and a high
strength to weight ratio.

Titanium is the fourth most abundant metal making up about 0.62% of the
earth’s crust. Rarely found in its pure form, titanium typically
exists in minerals such as anatase, brookite, ilmenite, leucoxene,
perovskite, rutile, and sphene. While titanium is relatively abundant, it
continues to be expensive because it is difficult to isolate. The leading
producers of titanium concentrates include Australia, Canada, China,
India, Norway, South Africa, and Ukraine. In the United States, the
primary titanium producing states are Florida, Idaho, New Jersey, New
York, and Virginia.

Thousands of titanium alloys have been developed and these can be grouped
into four main categories. Their properties depend on their basic chemical
structure and the way they are manipulated during manufacture. Some
elements used for making alloys include aluminum, molybdenum, cobalt,
zirconium, tin, and vanadium. Alpha phase alloys have the lowest strength
but are formable and weldable. Alpha plus beta alloys have high strength.
Near alpha alloys have medium strength but have good creep resistance.
Beta phase alloys have the highest strength of any titanium alloys but
they also lack ductility.

The applications of titanium and its alloys are numerous. The aerospace
industry is the largest user of titanium products. It is useful for this
industry because of its high strength to weight ratio and high temperature
properties. It is typically used for airplane parts and fasteners. These
same properties make titanium useful for the production of gas turbine
engines. It is used for parts such as the compressor blades, casings,
engine cowlings, and heat shields.

Since titanium has good corrosion resistance, it is an important material
for the metal finishing industry. Here it is used for making heat
exchanger coils, jigs, and linings. Titanium’s resistance to
chlorine and acid makes it an important material in chemical processing.
It is used for the various pumps, valves, and heat exchangers on the
chemical production line. The oil refining industry employs titanium
materials for condenser tubes because of corrosion resistance. This
property also makes it useful for equipment used in the desalinization
process.

Titanium is used in the production of human implants because it has good
compatibility with the human body. One of the most notable recent uses of
titanium is in artificial hearts first implanted in a human in 2001. Other
uses of titanium are in hip replacements, pacemakers, defibrillators, and
elbow and hip joints.

Finally, titanium materials are used in the production of numerous
consumer products. It is used in the manufacture of such things as shoes,
jewelry, computers, sporting equipment, watches, and sculptures. As
titanium
dioxide, it is used as a white pigment in plastic, paper, and paint. It
is even used as a white food coloring and as a sunscreen in cosmetic
products.

History

Most historians credit William Gregor for the discovery of titanium. In
1791, he was working with menachanite (a mineral found in England) when he
recognized the new element and published his results. The element was
rediscovered a few years later in the ore rutile by M. H. Klaproth, a
German chemist. Klaproth named the element titanium after the mythological
giants, the Titans.

Both Gregor and Klaproth worked with titanium compounds. The first
significant isolation of nearly pure titanium was accomplished in 1875 by
Kirillov in Russia. Isolation of the pure metal was not demonstrated until
1910 when Matthew Hunter and his associates reacted titanium tetrachloride
with sodium in a heated steel bomb. This process produced individual
pieces of pure titanium. In the mid 1920s, a group of Dutch scientists
created small wires of pure titanium by conducting a dissociation reaction
on titanium tetraiodide.

These demonstrations prompted William Kroll to begin experimenting with
different methods for efficiently isolating titanium. These early
experiments led to the development of a process for isolating titanium by
reduction with magnesium in 1937. This process, now called the Kroll
process, is still the primary process for producing titanium. The first
products made from titanium were introduced around the 1940s and included
such things as wires, sheets, and rods.

While Kroll’s work demonstrated a method for titanium production on
a laboratory scale, it took nearly a decade more before it could be
adapted for large-scale production. This work was conducted by the United
States Bureau of Mines from 1938 to 1947 under the direction of R. S.
Dean. By 1947, they had made various modifications to Kroll’s
process and produced nearly 2 tons of titanium metal. In 1948, DuPont
opened the first large scale manufacturing operation.

This large scale manufacturing method allowed for the use of titanium as a
structural material. In the 1950s, it was used primarily by the aerospace
industry in the construction of aircraft. Since titanium was superior to
steel for many applications, the industry grew rapidly. By 1953, annual
production had reached 2 million lb (907,200 kg) and the primary customer
for titanium was the United States military. In 1958, demand for titanium
dropped off significantly because the military shifted its focus from
manned aircraft to missiles for which steel was more appropriate. Since
then, the titanium industry has had various cycles of high and low demand.
Numerous new applications and industries for titanium and its alloys have
been discovered over the years. Today, about 80% of titanium is used by
the aerospace industry and 20% by non-aerospace industries.

Raw Materials

Titanium is obtained from various ores that occur naturally on the earth.
The primary ores used for titanium production include ilmenite, leucoxene,
and rutile. Other notable sources include anatase, perovskite, and sphene.

Ilmenite and leucoxene are titaniferous ores. Ilmenite (FeTiO3) contains
approximately 53% titanium dioxide. Leucoxene has a similar composition
but has about 90% titanium dioxide. They are found associated with hard
rock deposits or in beaches and alluvial sands. Rutile is relatively pure
titanium dioxide (TiO2). Anatase is another form of crystalline titanium
dioxide and has just recently become a significant commercial source of
titanium. They are both found primarily in beach and sand deposits.

Perovskite (CaTiO3) and sphene (CaTi-SiO5) are calcium and titanium ores.
Neither of these materials are used in the commercial production of
titanium because of the difficulty in removing the calcium. In the future,
it is likely that perovskite may be used commercially because it contains
nearly 60% titanium dioxide and only has calcium as an impurity. Sphene
has silicon as a second impurity that makes it even more difficult to
isolate the titanium.

In addition to the ores, other compounds used in titanium production
include chlorine gas, carbon, and magnesium.

Titanium is used for a wide variety of items, such as bike frames,
hip implants, eyeglass frames, and earrings.

The Manufacturing

Process

Titanium is produced using the Kroll process. The steps involved include
extraction, purification, sponge production, alloy creation, and forming
and shaping. In the United States, many manufacturers specialize in
different phases of this production. For example, there are manufacturers
that just make the sponge, others that only melt and create the alloy, and
still others that produce the final products. Currently, no single
manufacturer completes all of these steps.


Extraction

  • 1 At the start of production, the manufacturer receives titanium
    concentrates from mines. While rutile can be used in its natural form,
    ilmenite is processed to remove the iron so that it contains at least
    85% titanium dioxide. These materials are put in a fluidized-bed reactor
    along with chlorine gas and carbon. The material is heated to
    1,652°F (900°C) and the subsequent chemical reaction results
    in the creation of impure titanium tetrachloride (TiCl4) and carbon
    monoxide. Impurities are a result of the fact that pure titanium dioxide
    is not used at the start. Therefore the various unwanted metal chlorides
    that are produced must be removed.


Purification

  • 2 The reacted metal is put into large distillation tanks and heated.
    During this step, the impurities are separated using fractional
    distillation and precipitation. This action removes metal chlorides
    including those of iron, vanadium, zirconium, silicon, and magnesium.


Production of the sponge

  • 3 Next, the purified titanium tetrachloride is transferred as a liquid
    to a stainless steel reactor vessel. Magnesium is then added and the
    container is heated to about 2,012°F (1,100°C). Argon is
    pumped into the container so that air will be removed and contamination
    with oxygen or nitrogen is prevented. The magnesium reacts with the
    chlorine producing liquid magnesium chloride. This leaves pure titanium
    solid since the melting point of titanium is higher than that of the
    reaction.
  • 4 The titanium solid is removed from the reactor by boring and then
    treated with water and hydrochloric acid to remove excess magnesium and
    magnesium chloride. The resulting solid is a porous metal called a
    sponge.


Alloy creation

  • 5 The pure titanium sponge can then be converted into a usable alloy via
    a consumable-electrode arc furnace. At this point, the sponge is mixed
    with the various alloy additions and scrap metal. The exact proportion
    of sponge to alloy material is formulated in a lab prior to production.
    This mass is then pressed into compacts and welded together, forming a
    sponge electrode.
  • 6 The sponge electrode is then placed in a vacuum arc furnace for
    melting. In this water-cooled, copper container, an electric arc is used
    to melt the sponge electrode to form an ingot. All of the air in the
    container is either removed (forming a vacuum) or the atmosphere is
    filled with argon to prevent contamination. Typically, the ingot is
    remelted one or two more times to produce a commercially acceptable
    ingot. In the United States, most ingots produced by this method weigh
    about 9,000 lb (4,082 kg) and are 30 in (76.2 cm) in diameter.
  • 7 After an ingot is made, it is removed from the furnace and inspected
    for defects. The surface can be conditioned as required for the
    customer. The ingot can then be shipped to a finished goods manufacturer
    where it can be milled and fabricated into various products.

Byproducts/Waste

During the production of pure titanium a significant amount of magnesium
chloride is produced. This material is recycled in a recycling cell
immediately after it is produced. The recycling cell first separates out
the magnesium metal then the chlorine gas is collected. Both of these
components are reused in the production of titanium.

The Future

Future advances in titanium manufacture are likely to be found in the area
of improved ingot production, the development of new alloys, the reduction
in production costs, and the application to new industries. Currently,
there is a need for larger ingots than can be produced by the available
furnaces. Research is ongoing to develop larger furnaces that can meet
these needs. Work is also being done on finding the optimal composition of
various titanium alloys. Ultimately, researchers hope that specialized
materials with controlled microstructures will be readily produced.
Finally, researchers have been investigating different methods for
titanium purification. Recently, scientists at Cambridge University
announced a method for producing pure titanium directly from titanium
dioxide. This could substantially reduce production costs and increase
availability.

Where to Learn More


Books

Othmer, K.

Encyclopedia of Chemical Technology.

New York: Marcel Dekker, 1998.


U.S. Department of the Interior U.S Geological Survey. Minerals
Yearbook Volume 1.

Washington, DC: U.S. Government Printing Office, 1998.


Periodicals

Freemantle, M. “Titanium Extracted Directly from TiO2.”

Chemical and Engineering News

(25 September 2000).

Eylon D. “Titanium for Energy and Industrial
Applications.”

Metallurgical Society AIME

(1987).


Other


WebElements Web Page.

December 2001. <

http://www.webelements.com

>.

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