ny that hair-line seams do not in any way affect the
endurance of a crankshaft in service, provided they are parallel to
the grain of the steel and do not occur on a fillet. Of the 20,000
Liberty engines produced, fully 50 per cent of the crankshafts
used contain hair-line seams but not at the locations mentioned.
There has never been a failure of a Liberty crankshaft which could
in any way be traced to hair-line seams.

It was found that hair-line seams occur generally on high
nickel-chromium steels. One of the main reasons why the comparatively
mild analysis nickel-chromium steel was used was due to the very
few hair-line seams present in it. It was also determined that
the hair lines will in general be found near the surface of the
forgings. For that reason, as much finish as possible was allowed
for machining. A number of tests have been made on forging bars
to determine the depths at which hair-line seams are found, and
many cases came up in which hair-line seams were found 3/8 in.
from the surface of the bar. This means that in case a crankshaft
does not show hair-line seams on the ground surface this is no
indication that it is free from such a defect.

One important peculiarity of nickel-chromium steel was brought
out from the results obtained on impact tests. This peculiarity
is known as "blue brittleness." Just what the effect of this is
on the service of a finished part depends entirely upon the design
of the particular part in question. There have been no failures of
any nickel-chromium steel parts in the automotive industry which
could in any way be traced to this phenomena.

Whether or not nickel-chromium-steel forgings will show "blue
brittleness" depends entirely upon the temperature at which they
are tempered and their rate of cooling from this temperature. The
danger range for tempering nickel-chromium steels is between a
temperature of from 400 to 1,100 deg.F. From the data so far gathered
on this phenomena, it is necessary that the nickel-chromium steel
to show "blue brittleness" be made by the acid process. There has
never come to my attention a single instance in which basic open
hearth steel has shown this phenomena. Just why the acid open hearth
steel should be sensitive to "blue brittleness" is not known.

All that is necessary to eliminate the presence of "blue brittleness"
is to quench all nickel-chromium-steel forgings in water from their
tempering temperature. The last 20,000 Liberty cr