In practice, decarburization should
be evaluated on a plane transverse to the
hot working axis, as depth variation is
greater around the bar on the transverse
plane than at a specific constant position
along a longitudinal plane. Decarburization
depth can vary substantially around
the periphery of a bar, as shown in Fig. 1.
Qualitative measurements can be subjective
and biased. ฟรีเฟอร์ไรท์ depth
can also be erratic, even over a small surface
area, as shown in Fig. 2. Corners of
square or rectangular sections normally
exhibit greater decarburization depths
than planar surfaces. Sampling schemes
for large cross-sections are also illustrated
in ASTM E1077.