A BRIEF HISTORY of STAINLESS BLADE STEEL

   by Bernard Levine (c)1989,1998

Updated from "KNIFE LORE" #13, NATIONAL KNIFE MAGAZINE, AUGUST 1989

  The story of stainless steel spanned a century of research 
into the alloy potential of chromium, plus a further three 
decades in the perfection of heat treatment. The invention of 
stainless steel required the ability to see beyond the 
obvious, indeed to defy the clear conclusions of scientific 
research. 

  By 1819, Faraday and Stodardt in Britain had formulated the 
first alloy of iron and chromium, and had demonstrated that 
adding chromium increased iron's resistance to corrosion. 
Then, in France, Berthier combined Faraday's ferrochrome with 
carbon steel to form the first chromium steel. A few blades 
were forged from this alloy. They had superior cutting 
ability but did not resist corrosion from strong acids, or 
even from sea water. Much later their chromium content was 
found to be less than 3%. 

  In New York in 1865, Julius Baur patented a chromium alloy 
steel, and promoted its enhanced toughness for safes and jail 
bars. Custom knifemakers in San Francisco (Will & Finck) 
forged slicer blades from it (at $100 to $350 each), but 
these turned black and pitted with use. This alloy's chromium 
content was around 5-7%, and at those levels chromium, in the 
presence of carbon and the absence of nickel, acts as a 
catalyst that encourages iron to oxidize. This phenomenon was 
demonstrated by English metallurgist Robert Hadfield (the 
inventor of manganese steel) in 1892, and the search for 
chromium based stainless steel very nearly ended. 

  There matters stood until 1914. Then two men, unknown to 
each other, returned to Faraday's original finding. Both 
noted that the effects of increased chromium content did not 
appear to be linear. Both wondered what would happen if a lot 
more chromium were added. 

  Harry Brearley was in the industry, research metallurgist 
at the Firth steel works in Sheffield. Elwood Haynes of 
Kokomo, Indiana, was the consummate amateur scientist, a 
schoolteacher with a modest metallurgy lab in his basement -- 
amateur or not, Haynes had founded America's first automobile 
manufacturer two decades earlier, and had already invented 
and commercialized the "Stellite" brand alloys of cobalt and 
tungsten. 

  Both men observed that when they pushed the chromium 
content of a carbon alloy steel up past about 11%, again 
while excluding nickel, they produced an alloy that resisted 
corrosion from all but the strongest reagents, and which 
could be hardened and tempered much like plain high-carbon 
steel (chromium-nickel stainless steels are even more 
corrosion resistant, but they cannot be hardened). 

  Both men applied for patents, and that was when they 
learned of each other. Both recalled the generations-long 
litigation over the sewing machine and telephone patents. 
Rather than fight, and likely die bankrupt, they pooled their 
applications (Brearley did go to court, to fight his 
employer's claim to his share, but they settled to the 
enrichment of both). 

  Development was stalled by World War I, as chromium was 
essential to machinery parts, while Haynes Stellite could be 
used where corrosion resistance was vital -- high-speed 
cutters for cast iron, searchlight reflectors, and certain 
surgical instruments. After the war Brearley and Haynes 
created a brilliantly simple licensing scheme. The thousands 
of fabricators who wanted to use stainless steel each 
received a free license, its only requirement being that the 
licensee report his sources of supply. Steel makers -- fewer 
than 100 in the world -- paid for their licenses, but merely 
with a modest per-ton royalty. Only one steel firm tried to 
evade, and the others helped pay for the litigation that 
punished it. 

                          *     *     *


SEQUEL

  In the generation after 1919, stainless steel knives came 
to dominate the consumer kitchen and table cutlery market, 
but the quality of mass-produced blades rarely matched that 
attainable in the laboratory. The problem was "retained 
austenite." Austenite is the soft form of carbon steel. In 
the batch heat-treating of stainless blades, varying amounts 
of austenite would fail to be transformed into hard 
"martensite." This problem so tarnished the reputation of 
stainless steel blades that many consumers are still 
skeptical of them today -- even though this problem was 
solved in the early 1950s. 

  This part of the story is hazy, but evidently the solution 
was discovered by Emerson Case, president of Robeson Cutlery 
Co. in Rochester, New York. I believe he got the idea from a 
careful reading of the new 1951 edition of the "Republic 
Enduro Stainless Steels" handbook, in particular the 
seemingly unrelated chapter, "Effect of Sub-Atmospheric 
Temperatures on the Properties of Stainless Steel." The 
chapter describes the effects on variously treated stainless 
steels of using and abusing them in extreme cold -- the 
stratosphere, polar regions in winter, and harsh industrial 
environments such as "refrigeration of frozen foods, 
petroleum dewaxing, [and] synthetic rubber manufacture..."  

  Two sets of data in this chapter likely pointed Case in the 
right direction. The first is on page 159: "The quenched and 
tempered hardenable chromium types show a more gradual change 
from ductile to brittle behavior, and can retain some degree 
of ductile characteristics to the neighborhood of -75 degrees 
F." In other words, if you want stainless blade steel to stay 
soft, do not chill it below -75 degrees F. 

  The second set of data is depicted in the graph on page 
169. It plots the effect of temperature on the impact 
resistance of conventionally hardened and tempered 440-C 
blade steel. Unlike the charts for all the other stainless 
steel types, such as the nickel-based 300 series, which are 
more or less S-shaped, reflecting significant reactions to 
low temperatures, this one is a nearly straight horizontal 
line throughout the range of testing, from -200 to +200 
degrees F. In other words, chilling stainless blade steel 
below -75 degrees, even down to -200 degrees, does not harm 
it. 

  Put these two sets of data together and what do you get? 
What Emerson Case got was the Robeson "Frozen Heat" process: 
"Knife blades are loosely piled in trays, and are heat 
treated in an oven to a temperature... [slightly] above the 
temperature normally used... The blades are then bathed in 
quenching oil at about 140 degrees F. and left there long 
enough to cool to bath temperature. The blades are [then] 
cleaned and clamped tightly together to prevent warping, and 
then [are] placed in the freezing chamber [where they are] 
exposed to temperatures of -100 degrees F. for about 45 
minutes. After that they are heat treated to relieve the 
usual stresses..., cooled gradually to room temperature, and 
tempered by reheating again." 

  Variations of this process are today used on all but the 
cheapest of stainless steel knife blades. And unlike other 
"early" stainless blades, 45-year old Robeson "Frozen Heat" 
blades are equal in quality to the best knives made today. 

                           *    *    *

Bernard Levine is the author of "Levine's Guide to Knives and 
Their Values, 4th Edition," and writes for "Knife World" and 
"Blade" magazines. 

Bernard Levine
PO Box 2404
Eugene OR 97402-0124      541-484-0294    brlevine@ix.netcom.com

http://www.knife-expert.com/