May_AMP_Digital

41 / 70

ADVANCED MATERIALS & PROCESSES • MAY 2014 41
4-6% chromium (manganese was no longer used),
and 10-20% tungsten.
Mathews was granted a patent in 1905 for the ad-
dition of vanadium to high-speed steel. With the ad-
dition of about 1% vanadium to the 18% tungsten, 4%
chromium, and 0.60-0.80% carbon steel, the first
truly universal high-speed steel was born. By 1905,
the “18-4-1 high-speed steel” was in commercial pro-
duction and would remain the major tool steel for
metal machining during the next 35 to 40 years.
Metallurgical research moves forward
One of the first research studies on high-speed
steels was by H.C. Carpenter of England, who believed
that the high-temperature phase (austenite) was the
source of red hardness. He was led into this error due
to the large amount of austenite he found in samples
after cooling from the hardening temperatures.
Another British metallurgical research study un-
dertaken by C.A. Edwards and H. Kikkawa provided
the first comprehensive understanding of the major
metallurgical phenomena in high-speed steel. They
concluded that chromium imparts the self-hardening,
and that the extremely high hardening temperature was
needed to dissolve the tungsten. Maximum resistance
to tempering can only be ob-
tained by getting the tungsten
into solution. They also con-
cluded that careful tempering
studies with hardness measure-
ments could provide valuable
information on the relative
merits of cutting tools.
Shortly after Edgar Bain’s
early work using x-rays to de-
termine the crystal structure of
austenite (fcc), ferrite (bcc), and
martensite (bcc), he and Zay
Jeffries, while working at the
GE Lamp Division, published
their famous paper in Iron Age
in 1923 on the “Cause of Red
Hardness of High Speed Steel.”
This paper is considered
a classic in the field of metals
technology, not because it
changed industrial practices, but because it combined
the latest research tool (x-ray diffraction) with the
most recent theory of hardening—slip interfer-
ence by precipitated particles. This paper showed,
as concluded earlier by Edwards and Kikkawa,
that the high hardening temperatures are needed
to dissolve the particles of tungsten-containing
carbide in the austenite. Bain and Jeffries then
concluded that the softening of hardened steel
during tempering, which occurs in ordinary steel
at low temperatures (300° to 900°F), is caused by
grain growth and carbide particle growth beyond
the critical size. They reasoned that the greater
stability of the tungsten carbide forces its forma-
tion at 1000° to 1200°F, where it increased the
hardness to a peak called “secondary hardening.”
It is only at these temperatures that the larger
tungsten atoms can move within the iron space
lattice to form the alloy carbides. Later studies
would confirm the thrust of their theories, al-
though the details of alloy carbide formation
would be more complex in detail.
The following year, 1924, Edgar Bain moved from
General Electric Co. to Atlas Steel Co. in Dunkirk,
N.Y., where he worked with one of America’s most
interesting and prolific metallurgists, Marcus A.
Grossmann. The publications of Bain and Gross-
mann in 1924 included high-carbon, chromium
steels, chromium in high-speed steel, and their major
work, “On the Nature of High Speed Steel,” which
they published in Great Britain in the Journal of The
Iron and Steel Institute. This paper was a compilation
of the arts on the manufacturing and metallurgy of
high-speed steel. In some ways, it appears to be a
combination of Grossmann’s practical knowledge
with the metallurgy and theory reported earlier by
Bain and Jeffries. Grossmann and Bain expanded this
effort in their collaboration in 1931 with the publica-
tion of a textbook entitled “High Speed Steel.”
For more
information:
Charles R. Simcoe
can be reached at
.
For more metallurgical
history,
visit
.
Edgar Bain, a
research
metallurgist who
worked with Marcus
Grossman to publish
research studies
and a book on high-
speed tool steels.
Courtesy of Library
of Congress/U.S.
public domain.
Variation of hardness with tempering temperature for four typical tool steels. Cour-
tesy of Wrought Tool Steels, Properties and Selection: Irons, Steels, and High-Per-
formance Alloys, Vol 1, ASM Handbook, ASM International, 1990.
Zay Jeffries (pictured)
published on the theory
of red hardness in high-
speed tool steels with
Edgar Bain and served as
ASM president in 1929.
Courtesy of ASM
International.