Chapter 8 Manual Welding Techniques
129
Forgings
Forging refers to pressing a shaped die into
hot metal under high pressure. The metal is heated
to a plastic state before it is forged so it will take on
the shape of the die that is pressed into it. Forgings
are made from billets, bars, round stock, or square
stock. Forgings can be identifi ed by the remnants of
the fl ashing usually extending around the center of
the part. Since the forging operation is done while the
part is hot, a scale forms on the surface, similar to the
scale on hot-rolled steel.
Steel Classifi cations
Steels are manufactured to specifi cations devel-
oped by various organizations, including ASTM
International. One grouping of steels under this clas-
sifi cation is ASTM A335. The assigned designation
identifi es the material as high-ferritic steel alloy pipe
for high-temperature applications. Other steel specifi -
cations include SAE International’s Aerospace Mate-
rial Specifi cations (AMS), the American Iron and
Steel Institute (AISI) classifi cations, and corporation
specifi cations.
Filler Metals
Filler metals used to join carbon steels, low-alloy
steels, and tool steels must be selected to produce the
desired mechanical properties of the weldment after
any required welding or heat treatment. Carbon and
low-alloy steel fi ller metals are selected from specifi -
cations, such as AWS A5.18, AWS A5.28, MIL-E-23765,
MIL-S-6758, and AMS6370.
When selecting a steel fi ller metal, the welder
should consider the basic type of steel to be welded
and the possibility of excessive porosity within the
completed weld. Figure 8-1 lists three classifi cations
of fi ller metal, each with a 70,000 psi tensile strength
that can be used to weld porosity-prone material.
Figure 8-2 lists several types of fi ller metals that can be
used to weld HSLA (high-strength, low-alloy) steels.
Chromium-molybdenum steels (chrome-moly
steels) are a class of extremely strong and hard steels.
If the chrome-moly weldment is to be hardened after
being welded, one of the following fi ller metals should
be used:
• 1-1/4% chrome—1/2% moly fi ller metal
• 2-1/4% chrome—1% moly fi ller metal
• 4%–6% chrome (AISI 502)
If the chrome-moly steel weldment will not be
hardened after welding, the following stainless steel
fi ller metals can be used:
• 25% Cr—20% Ni stainless steel fi ller metal
• 25% Cr—12% Ni stainless steel fi ller metal
Do not use stainless steel fi ller metals for welds
in service over 1000°F (538°C). Welds subjected to
temperatures above 1000°F (538°C) will have carbon
migration from the steel to the stainless steel, which
can cause weld failure.
When selecting fi ller metals for tool steels, refer
to the fi ller metal manufacturer for the recommended
type. These fi ller metals have been specially devel-
oped for specifi c applications and are not made to
precisely conform to specifi cations issued by organi-
zations such as ASTM or AISI.
Filler Metal Quality
Steel fi ller metals are supplied by the manufac-
turer with a bright fi nish, oiled fi nish, or copper fl ash
fi nish. Since these materials are susceptible to rusting,
store them in a dry, heated area until they are needed.
Always clean the fi ller metal with acetone or alcohol
just before use. Return all unused material to the
storage area.
Solid Wires for Carbon
Steela
Per AWS A5.18
Classification Composition
C Mn Si Ti Zr Al
ER70S-2 0.07 0.90– 0.40– 0.05– 0.02– 0.05–
1.40 0.70 0.15 0.12 0.15
ER70S-3 0.06– 0.90– 0.45– – – –
0.15 1.40 0.70
ER70S-5 0.07– 0.90– 0.30– – – 0.50–
0.19 1.40 0.60 0.90
a
P, 0.025; S, 0.035; Cu 0.50.
Figure 8-1. The letters E and R in the classifi cation code
identify these fi ller metals as solid electrode wires that can
be used in the GTAW process. The letter E indicates the
wire is designed to carry current for the GMAW process.
Some electrode wires can also be used (without current)
as fi ller metal for the GTAW process. If the electrode wire
can also be used for GTAW, the letter E is followed by the
letter R (which stands for “rod”).