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ANP PROJECT PROGRESS REPORT
the shrinkage data described herein should be
determined by conducting another test prior to
attempting fabrication of a pump with a complex
volute.
Since the shrinkage at position 3 was less than
expected, it was not possible to use the spacers,
as machined, to prevent further shrinkage during
annealing. The pump casing was annealed at
185OOF for 4 hr in order to determine the necessity
for this operation. The additional shrinkage of
0.002 to 0.004 in. observed indicates that the role
of residual stresses is significant. Properly
machined spacers should be used to prevent further
shrinkage during annealing, as was accomplished
in the previous investigation.'
Brazing Studies
Tests have also been performed to study the
feasibility of a brazed NaK (PK-2) pump volute.
The component parts for the test are shown in
Fig. 3.4.4. The bottom volute is shown with eight
0.187-in.-diaI 1-in.-long lnconel shear pins inserted
into 0.197-in.dia holes drilled to a depth
of ?$ in. These pins were intended to provide
approximately 5 in.2 of shear area to supplement
the 18 in.2 of area that constitutes the faying
surfaces of the upper and lower volutes in the
brazed assembly. The top volute is shown with
0.200-in.-ID tubes welded over the shear pin holes
to act as reservoirs for the Coast Metals No. 52
brazing alloy. The alloy was applied in the form
of 3.16-in.-dia slugs, which ranged from 3.8 to
4 in. in length and were fabricated by casting
in graphite molds. Several of these slugs are
shown in the center of Fig. 3.4.4. A total of
30.8 g of Coast Metals No. 52 alloy was used.
This amount was calculated to supply approximately
0.19 in? of alloy, of which 0.048 in.3
would fill the space between the shear pins and
the shear pin holes and approximately 0.054 in.
3
would comprise a 0.0003-in.-thick brazing alloy
layer between the faying surfaces of the volutes.
It was expected that a surplus of brazing alloy
would be desirable to ensure complete brazing.
The excess alloy was to remain in the reservoirs.
A 0.003-in. separation between the parts of the
volutes was achieved by using 0.003-in.dia nickel
wire as a spacer.
Micrometer measurements were made before and
after brazing at the positions described in Fig.
3.4.5. The assembly was braze$ at 1050°C in
dry hydrogen. The heating and cooling rate of
the brazing cycle was approximately 35O0C/hr,
178
and a hold time of 3 hr at 1050°C was used. A
photograph of the completed assembly is shown
in Fig. 3.4.6. As may be seen, excess brazing
alloy flowed out of the capillary and down the
side of the casing. A similar condition was
evident on the inside of the volute; there wps a
fillet of brazing alloy thinly distributed around
the bottom volute.
The failure of the reservoirs to retain the excess
brazing alloy is attributed to the relatively large
clearance between the lnconel shear pins and the
shear pin holes. It is expected that a clearance
of 0.001 to 0.002 in., coupled with a supplementary
capillary on the periphery of the casing, which
could be removed later, would remedy this dif-
ficulty.
The braze joint was subjected to dye-penetrant
and radiographic inspections and was considered
to be sound. The degree of correlation between
the radiographic interpretation and the joint sound-
ness should be determined by metallographic
exam i no t i on.
The results of the micrometer measurements are
summarized in Table 3.4.2. As may be noted,
most of the dimensional changes found are within
the limit of error of the measurements. As was
expected, the data indicate that the brazed con-
struction affords a high degree of dimensional
control and should be given consideration as a
fabrication method.
TABLE 3.4.2. RESULTS OF MICROMETER
MEASUREMENTS BEFORE AND AFTER BRAZING
OF NaK (PK-2) PUMP VOLUTE
Position
Dimensions* (in.)
As Assembled After Brazing Change
A-1 3.815 3.813 -0.002
2 3.818 3.817 -0.001
3 0.629 0.628 -0.001
B-1 3.817 3.817 0
2 3.816 3.816 0
3 0.629 0.627 -0.002
c- 1 3.81 9 3.820 +0.001
2 3.81 8 3.81 8 0
3 0.629 0.628 -0.001
D-1 3.818 3.817 -0.001
2 3.816 3.815 -0.001
3 0.629 0.628 -0.001
*Estimated accuracy of measurement *0.001 in.
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