T. O. 1-1A-9
TABLE 2-14.
GENERAL FILLER ROD DIA, TIP SIZE, GAS PRESSURE TO METAL THICKNESS
SELECTION CHART
METAL
FILLER RCD
WELDING TIP
REF PRES-
OXY/ACETYLENE
THICKNESS
DIA
SIZE TIP
ORIFICE
SURE APPROX
USED CU FT PER
SIZE
OXY/ACETYLENE
HOUR APPROX
3.25 -0.62
1/16
1
0.037
1
4 - 4.5
0.062-0.125
1/16- -1/8
2
0.042
2
4.5 - 5.0
0.125-0.1875
1/8
3
0.055
3
7 - 8
0.1875-0.3125
3/16
4
0.063
4
10- 12
0.3125- 7/16 in
3/16
5
0.076
5
18 - 19
7/16 - 1/2 in
1/4
6
0.086
6
20 - 23
1/2 - 3/4 in
1/4
7
0.098
7
34
3/4 - 1 in
1/4
8
0.1065
8
48
Over In
1/4
9
0.116
9
56
Over In
1/4
10
0. 140
10
95
Over In
1/4 - 5/16
11
0.147
10
100
Heavy Duty
1/4 - 5/16
12
0.149
10
100
2-130. For best results when welding the low carbon steel, a netural flame is used, and for medium and high carbon
steel (above 0.30%carbon),a slight excess of acetylene (carburizing) flame is recommended. The tip and rod diameter
for welding, etc., should also be selected according to amount of heat required and thickness of metal involved. For
general data on tip sizes, gas pressures etc., see Table 2-14. For general data on rod type/grade selection see Table 2-
15.
NOTE
Table 2-14 also generally applies to gas welding of all alloys, i.e., aluminum, stainless, except tips
used for stainless and aluminum are selected 1-2 sizes smaller.
2-131. SHIELDED METAL ARC WELDING OF CARBON STEEL
2-132. The weldability of carbon steel by the metal arc process will depend on the carbon content of base metal, as
previously stated. Generally "Hydrogen free" coated electrodes are recommended to help prevent (hydrogen
embrittlement) cracking in toe and root areas. The medium carbon grade (0.30-0.50% carbon) are usually preheated at
3000 500°F to minimize cracking brittleness, and stress relieved after welding by heating to 1100 1200°F. The high
carbon grades are not usually recommended for welding because of the adverse effect that welding has on mechanical
properties. However, where welding is required, parts should be postheated at approximately 400°F and normalized after
welding at 1350°1450SF (except where worn surfaces are being built up, then preheat and postheating can be omitted in
most cases).
2-133. Electrodes should be carefully selected to obtain a moderate, dense and tough weld deposit. Another
consideration in selecting the electrode is absorption of carbon from the base metal into the weld deposit, which
decreases the ductility of the joint (For additional information see specification MIL-W-8611 and Table 2-15.
2-134. Joints separation (general) for butt welding by the shielded metal arc method should be from 0-1/32 inch for thin
material to about 1/8-3/16 inch for 3/81/2 inch thickness material. Multi-layer welds with standard V/U joint are used,
unless otherwise specified, when material exceeds thickness of 3/16 inch and weld can only be applied to one side, such
as for welding tubing/pipe. Each layer/pass should not exceed 1/8 inch thickness, and finishing bead (width) should
extend to 1/16 inch minimum (beyond level) on to the base metal on each side. Finish welds shall not be undercut, have
depressions below surface of the base metal, or have blow holes. Precautions should be taken to assure starting the arc
in the weld area. For joint designs see MIL-STD-22A and Figure 2-2 which shows some of the standard joints.
2-80
