FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 4. Metal Structure, Welding, and Brazing | 5. Welding and Brazing | 4-77. Preparation for Welding
AC 43.13-1B CHG 1
9/27/01
factors, the selection may vary with each spe
cific application. Metals having refractory sur
face oxide films (i.e., magnesium alloys and
aluminum and its alloys), are generally welded
with alternating current (AC), while direct cur
rent (DC) is used for carbon, low alloy, non-
corrodible, and heat-resisting steels. General
recommendations covering current and polar
ity are shown in table 4-12.
(b) Oxyacetylene gas equipment is suitable
for welding most metals. It is not, however,
the best method to use on such materials as
stainless steel, magnesium, and aluminum al
loys; because of base metal oxidization, dis
tortion, and loss of ductility.
NOTE: If oxyacetylene is used for
welding stainless steel or aluminum, all
flux must be removed, as it may cause
corrosion.
b. Clean parts to be welded with a wire
brush or other suitable method prior to weld
ing. Do not use a brush of dissimilar metal,
such as brass or bronze on steel. The small
deposit left by a brass or bronze brush will
materially weaken the weld, and may cause
cracking or subsequent failure of the weld. If
the members are metallized, the surface metal
may be removed by careful sandblasting fol
lowed by a light buffing with emery cloth.
4-78. INSPECTION OF A COMPLETED
WELD. Visually inspect the completed weld
for the following:
(a) The weld has a smooth seam and uniform
thickness. Visual inspection shall be made of
the completed weld to check for undercut
and/or smooth blending of the weld contour
into the base metal.
4-76. ACCURATELY IDENTIFY THE
TYPE OF MATERIAL TO BE RE
PAIRED. If positive identification of the
material is not possible, contact the aircraft
manufacturer or subject the item to a metallur
gical laboratory analysis. Before any welding
is attempted, carefully consider the weldability
of the alloy, since all alloys are not readily
weldable. The following steels are readily
weldable; plain carbon (of the 1000 series),
nickel steel (of the Society of Automotive En
gineers (SAE) 2300 series), chrome-nickel al
loys (of the SAE 3100 series), chrome-
molybdenum steels (of the SAE 4100 series),
and low nickel-chrome-molybdenum steel (of
the SAE 8600 series).
4-77. PREPARATION FOR WELDING.
(b) The weld is tapered smoothly into the
base metal.
(c) No oxide has formed on the base metal
more than 1/2 inch from the weld.
(d) There are no signs of blowholes, poros
ity, or projecting globules. Many military
specifications, as well as American Society of
Testing Materials (ASTM) codes, specify ac
ceptable limits of porosity and other types of
defects that are acceptable.
(e) The base metal shows no signs of pitting,
burning, cracking, or distortion.
(f) The depth of penetration insures fusion of
base metal and filler rod.
a. Hold elements to be welded in a welding
jig or fixture which is sufficiently rigid to pre
vent misalignment due to expansion and con
traction of the heated material and which
positively and accurately positions the
pieces to be welded.
(g) The welding scale is removed. The
welding scale can be removed using a wire
brush or by sandblasting. Remove any
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