ORNL-1771 - Oak Ridge National Laboratory

Creep and stress-rupture testing have, in the
post, been performed primarily on uniaxially stressed
specimens. Tests of this type are continuing, but
the interest is now centered on tube-burst tests in
which a tube that is closed at one end is stressed
with on internal gas pressure. The stress pattern
introduced into the specimen in this test more
nearly approaches the stress pattern that will be
found in ANP-type reactors. The ratio of the tun-
gential stress to the longitudinal stress is quite
important in the ductility of the metal being tested,
ond therefore equipment in which the longitudinal
and the tangential stresses can be varied has been
constructed. A theoretical analysis of a stressed
cylindrical pressure vessel has been made with
which o check on the experimental results can be
obtained. Also, to determine the effect of tan-
gential and compressive stresses on the corrosion
rate of metal in contact with fused salts, on op-
paratus for loading a sheet specimen in bending
was designed and constructed; tests are now being
made.
In the investigation of high-thermal-conductivity
materials for fins for sodium-to-air radiators, stress-
rupture and creep tests were made on copper fins
with various types of cladding at stress levels be-
tween 500 and 2000 psi at 1500°F. The tests have
shown that for a 1000-hr exposure in air, stresses
greater than 500 psi and less than 1000 psi ore
tolerable; that is, in this stress range there is no
indication of brittleness in the core or oxidation of
the core due to cladding failure. Thermal conduc-
tivity measurements of a 6% AI-94% Cu aluminum
bronze were made in the temperature range 212 to
1562OF.
Tests of brazing olloys have shown that in braz-
ing high-conductivity fin materials to lnconel tubing
there are four alloys that can be used: low-melting-
point Nicrobraz (LMNB), Coast Metals alloy 52,
electroless nickel, and an Ni-P-Cr alloy. From the
over-all considerations of melting point, oxidation
resistance, dilution of fin and tube wall, formation
of low-melting eutectics, and flowability, it was
found that Coast Metals alloy 52 was the best
alloy for the construction of radiators with high-
conductivity fin s.
7. METALLURGY
W. D. Maniy
Metallurgy Division
PERIOD ,ENDING SEPTEMBER 10, 1954
A sodium-to-air rodiator with 6 in. of type-430
stainless-steel-clad copper high-conductivity fins
was fabricated by using a combination heliarc
welding and brazing procedure. The tube-to-fin
sections were assembled and brozed with Coast
Metals alloy 52. The tube-to-header joints were
made by using the semiautomatic welding equipment
and then back-brazing. The header sections were
closed by manual heliarc welding.
In the construction of a 100-kw gas-fired liquid-
metal-heater system, packed-rod nozzle assemblies
were needed as the inlets for air and gas. These
devices were made by brazing 1 G-in.-dia stainless
steel rods in a tight assembly with a ductile,
oxidation-resistant alloy of 82% Au--l8% Ni.
Work has started on the formation of duplex tubing
in an attempt to prepare alloy composites that have
good corrosion resistance on the inner surface and
oxidation resistance on the outer surface. Com-
posites of copper and type 310 stainless steel,
lnconel and type 310 stainless steel, Inconel and
Hastelloy B, and Hastelloy 5 and type 310 stainless
steel have been prepared. Tubing produced from
stainless-steel-clad molybdenum and columbium and
from several special Inconel-type alloys was fabri-
cated into thermal convection loops for fluoride
corrosion testing. Several new alloys were produced
for the corrosion tests with liquid lead.
Attempts are being made to find new alloys in
the nickel-molybdenum system that wi It have better
high-temperature strength and fluoride corrosion
resistance than lnconel has. Hastelloy B satisfies
these requirements, but it has poor fabrication
properties and oxidation resistance, and it loses
its ductility in the temperature range of interest for
appl i cation in high-temperature c ircu fating-fuel re-
actors. Investigations are under way in an effort
to find a suitable melting and heating treatment that
will increase the ductility of Hastelloy B in the
temperature range of interest.
Investigations of methods for producing boron
carbide shield pieces of the required density and
shape indicate that the pieces should be molded
with nonmetallic bonding material by cold pressing
followed by sintering. The bonding materials being
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