|
Chemical Analysis
|
Carbon |
.80 - 1.2 % |
Manganese
S-70 -
S-110
S-170
S-230 and
Larger - All
Grit |
.35 - 1.2 %
.50 - 1.2 %
.60 - 1.2 % |
|
Silicon |
.4 % minimum |
|
Sulfur |
0.05 %
maximum |
|
Phosphorous |
0.05 %
maximum |
|
|
General Appearance
The cast steel shot
shall be as nearly
spherical as
commercially possible
and no more than 20% of
the shot particles shall
have objectionable
defects. |
| |
Voids for Shot
No more than 10% of the
cast steel shot
particles shall contain
voids as determined at
10X magnification. A
void must be greater
than 10% of the area of
the abrasive particle to
be considered harmful. |
|
Microstructure
The Microstructure of
cast steel shot and grit
shall be uniform
Martensite, tempered to
a degree consistent
with the hardness
range, with fine well
distributed carbides, if
any. |
|
Shrinkage
No more than 10% of the
cast steel shot
particles shall contain
shrinkage as determined
at 10X magnification.
Shrinkage is an internal
cavity with irregular
dendritic surface, whose
area is larger than 40%
of the particle area. |
|
Hardness
Shot
Ninety percent of random
hardness check performed
on a representative
sample shall fall within
the range of 402-558
Knoop hardness number
(40-51 HRC)
Grit
Ninety percent of
random hardness check
performed on a
representative sample
shall fall within the
following ranges:
 S
hardness range of
402-558 Knoop (40-51 HRC)
M
hardness range of
495-650 Knoop (47-56 HRC)
L hardness range 612-754 Knoop (54-61 HRC)
H
hardness of 732 Knoop
minimum (60 HRC).
The hardness may be
determined by any of the
various methods
applicable to small
sections such as Micro
Hardness Tester with a
Knoop indenter, at loads
determined to provide a
reliable conversion to
Rockwell C. |
|
Cracks
No more than 15% of cast
steel shot and 40% of
the cast steel grit
particles shall have
cracks as determined at
10X magnification. A
crack is a linear
discontinuity whose
length is greater than 3
times its width and
radial in direction. |
| |
Particle Shape of
Shot
When examined at 10X
magnification, no more
than 5% of the shot
particles will have a
length that is excess of
twice the cross section. |
|
Density
The density of cast
steel shall be not less
than 7.3 gm/cc grit and
7 gm/cc for shot. |
|
Mechanical Tests
Several designs of shot
testing machines are
available commercially
for application to
routine procedures. See
SAE J445 for methods of
checking uniformity of
shipments of shot or
grit to determine
relative fatigue life
and energy transfer of
different types of shot
or grit. |
