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A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A R C H 2 0 1 5
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METALLURGY LANE
Metallurgy Lane, authored by ASM life member Charles R. Simcoe, is a yearlong series dedicated to the early history of the U.S. metals
and materials industries along with key milestones and developments.
TITANIUM: A METAL FOR THE AEROSPACE AGE — PART I
THE ONLY PROCESS AVAILABLE FOR PRODUCING TITANIUMWAS PATENTED BY WILLIAM J. KROLL IN 1940,
MARKING THE DAWN OF A NEWMETALS INDUSTRY.
T
itanium is found in many popular
consumer items, such as jewel-
ry, watches, golf clubs, eyeglass
frames, bicycle and auto engine parts,
and handguns. More recently, it has
been used in the biomedical field in the
form of knee and hip joints. Titanium’s
most spectacular use may be for the ar-
chitectural covering of the Guggenheim
Museum in Bilbao, Spain, designed by
Frank Gehry. However, these consum-
er uses were not anticipated in the late
1940s and 1950s when the metal was
William J. Kroll, inventor of the titanium
sponge production process. Courtesy of
Oregon State University.
The GuggenheimMuseumBilbao,
designed by architect Frank Gehry, is
made of titanium, glass, and limestone.
Courtesy of Wikimedia Commons.
promising to military units on the cut-
ting edge of developing jet engines, su-
personic aircraft, missiles, and lighter
weight trucks, tanks, landing craft, and
other hardware for both the Cold War
and Korean War.
The only problem was the lack of
a process and an industry for titanium
production. In May 1940, a middle-aged
research engineer emigrated from Lux-
embourg to the U.S. with a patented
method for making titanium. Dr. William
J. Kroll’s novel process would soon be-
come the basis for the titanium industry.
WILLIAM J. KROLL
William J. Kroll was born in 1889 in
Esch, Luxembourg. He earned a Doctor
of Engineering degree inmetallurgy from
theRoyal Institute of Technology inChar-
lottenburg, Germany, in 1917. After sev-
eral years of employment in Germany,
Austria, and Hungary, Kroll established
his own research laboratory in a home
he purchased in his native Luxembourg
where he conducted groundbreaking re-
search in metallurgy and electrochemis-
try. Kroll received some financial help for
his titanium research from the German
firm of Siemens & Halske AG. When the
company lost interest in supporting his
work, he obtained control of the foreign
patent rights and invested his own funds
to continue development in his private
laboratory. By 1938, he had produced 50
pounds of metal.
The very first published report on
Kroll’s process was a paper he present-
ed at the 1940 meeting of The Electro-
chemical Society. That same year, he
was issued U.S. Patent 2,205,854 for
Hip joint prosthetic made of titanium
alloy, center. Courtesy of Wellcome
Images, operated by Wellcome Trust, UK,
wellcomeimages.org.
primarily considered a promising struc-
tural material for defense applications.
Titanium was discovered in 1790
by William Gregor, an English clergy-
man and amateur chemist. It was re-
discovered in 1795 by Austrian chemist
Martin Heinrich Klaproth while study-
ing the mineral rutile. It was Klaproth
who named this new metal after the Ti-
tans, deities with tremendous strength
in Greek mythology.
Titanium is element 22 on the pe-
riodic table. Its density is 4.5 grams/
cm
3
, midway between aluminum at
2.7 and iron at 7.86. Its melting point is
1812°C (3294°F), compared with 1535°C
(2795°F) for iron. Its lowdensity and high
melting point compared with iron indi-
cate a metal with impressive structural
qualities. Corrosion resistance further
expanded titanium’s potential applica-
tions. It seemed to be the ideal answer
to the need for a strong, lightweight, and
corrosion-resistant metal for numerous
structural designs. In the late 1940s and
early 1950s, these advantages looked