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22H Forging - S tamping - Heat 'Beating
FIG. 6—Brinell test for hardness.
be impracticable the piece is drilled on its side and
drillings taken to represent the portion midway between
the outside and center of the part. In some
cases this procedure would destroy a costly part and
wherever this occasions the sampling is done to approach
this method as closely as possible and still not
destroy the component. Surface drillings in all cases
are discarded.
The chemical analysis is one of great importance
when testing steel for axle parts, for it is by this
method that the material can be placed in its proper
category; as it is the chemical composition that regulates
the heat treatment and partially determines what
the resultant mechanical properties are to be.
July, 1925
This method of inspection is of unestimable value
when testing for objectionable impurities, or whether
the carbon content is too high or too low, whether the
manganese content is outside of the specified range
and whether or not a straight carbon steel had been
substituted for an alloy, all of which should be determined
before converting the material into the finished
product.
The proportion of impurities permitted depends to
a considerable degree upon the conditions to which
the part or material is subjected, and not only is the
quantity of importance, but likewise its distribution.
This being especially true of the elements phosphorus
and sulphur.
FIG. 7—Shore test for hardness.
Sulphur prints made on material to show the distribution
of this element, and specimens which have
been etched with "Steads" reagent to show phosphorus
banding have often proved invaluable.
Mechanical Tests.
Just as important as the chemical analysis is mechanical
testing. Various parts have different func-
FIG. 8 (left)—Structure of a badly overheated forging (etched). FIG. 9 (center)—Same as Fig. 8, but unetched.
FIG. 10 (right)—Forging of .35 carbon steel, showing large crystals caused by overheating.