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ANP PROJECT QUARTERLY PROGRESS REPORT
Pig. 12.2. Two-Pass Chasacteristcs of Cone-Arc Welds. (a) Tube Plush with
plate. (b) Tube recessed 0.022 inch. Etched with aqua regia. 194X.
joint. As the arc distance increases,
more of the arc beam impinges upon the
header sheet, and the drastic heating
of the tube wall is minimized.
Resistance Welding. Since it is
desirable to determine the feasibility
of electrical -resistance spot welding
of stainless steel clad fuel elements
to both themselves and to stainless
steel sheet, an investigation is
being made in which the welding vari-
ables are precisely controlled. The
goal of the preliminary experiments
in this program was merely the produc-
tion of sound, high-strength welds
under conditions that do not materially
harm the core structure of the fuel
elements, Welds were made at several
values of electrode force to obtain
the optimum value, which was considered
to be the minimum force that would
consistently result in crack-free,
nonporous, weld nuggets. By using
this optimum electrode force and a
re asonabl e we1 d time, experiment a1
welds were then made over a wide
162
range of welding current. Examination
of metallographic sections of these
welds will enable the determination
of the permissible range of current
over which good welds can be made and
also allow the selection of the most
satisfactory value of welding current.
Any major defects resulting from
welding can also be investigated by
me t a1 1 o gr aphi c s ec ti on i rig.
A photomicrograph of a sound, high-
strength, spot weld made in 0.030-in.
fuel elements containing cores of 50%
UO, and 50% Fe is shown in Fig. 12.3a.
The electrode force used was 800 lb,
the weld time was 5 cycles, and the
welding current was 6300 amp. The
dark etching areas in t,he cores are
thought to result from the partial
melting of the iron portions of the
core metal. The lower l i m i t of the
permissible current range is exhibited
in Fig. 12.3b. The welding conditions
in this case are identical to those
used in Fig. 12.3a except that the
welding current was reduced to 5800