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Gas Tungsten Arc Welding Handbook
Base Materials (Steel)
Many types and grades of steel are included in
the steel family. These materials are typically magnetic
and melt at approximately 2500°F (1371°C).
Carbon Steels
Carbon steels are identifi ed as a group that
contains the following materials:
• Carbon—1.70% maximum
• Manganese—1.65% maximum
• Silicon—0.60%
Carbon steels are further classifi ed as low, mild,
medium, and high carbon:
• Low-carbon steel—less than 20% carbon
• Medium-carbon steel—0.20%–0.50% carbon
• High-carbon steel—over 50% carbon
Low-Alloy Steels
Low-alloy steels contain varying amounts of
carbon and a variety of alloying elements. These
elements include chromium, molybdenum, nickel,
vanadium, and manganese. These elements increase
the strength and toughness of the material and, in
some cases, increase resistance to corrosion.
Heat-Treated Materials
Heat-treated steels are used for many different
applications. Heat treating is a process in which the
material is heated and cooled to specifi c temperatures
for specifi c amounts of time. A material is heat treated
to obtain desirable qualities or to reduce undesir-
able qualities. Many materials and alloys, including
aluminum, copper, titanium, nickel, and chromium-
molybdenum, can be heat treated to make the material
perform in different ways. Heat treating of a material
is most commonly done as part of the manufacturing
process.
Quenching is the process of rapidly cooling a mate-
rial to obtain certain material properties that increase
the material’s toughness. The quenching process
changes the crystalline structure of the material.
Tempering is a heat treatment that can improve
the mechanical properties of a material. Tempering
involves heating the metal to a certain temperature
below the material’s melting temperature for a certain
length of time. This process allows trapped carbon to
produce a different crystalline structure. The material
is then cooled at a controlled rate to a low temperature.
The temperature and the duration of the tempering
process determine which mechanical properties will
be enhanced.
Annealing is a heat treatment that involves
heating the material to a temperature that rearranges
the crystalline structure and reduces internal stress
of the material, making the material softer and more
ductile. Annealing is typically done to improve the
cold working properties of a material.
Tool Steels
Tool steels are steels with a combination of high
carbon and alloy content. Tool steels are used for
making dies, cutting bits, and many other types of
tools. Dies and other tools are formed from annealed
tool steel. Later in the manufacturing process, after
the tools are formed, the metal is treated to harden or
temper the metal as needed.
The various types of tool steel include W1, W2,
SI, S5, S7, 01, 06, A2, A4, and D2. Also included are
H11, H12, H13, and M1, M2, M10. The numbers for the
various tool steels identify the various compositions.
The letters usually indicate the type of quenching
required to achieve full mechanical values.
Forms and Shapes of Steel
Steel is supplied in many forms and shapes for
welding. Some of the more common shapes are hot-
rolled steel, cold-rolled steel, castings, and forgings.
Hot-Rolled Steel
Hot-rolled steel includes plate and structural
forms which are allowed to cool in air after rolling.
After cooling, the oxide fi lm on the surface is light
blue in color.
Cold-Rolled Steel
This material is fi nal-rolled to the required
dimensions in the cold condition and does not have
an oxide fi lm on the surface. A light coating of oil is
placed on the material to prevent rusting.
Castings
Casting refers to pouring molten metal into a
mold that has the desired shape. The metal is kept in
the mold until it solidifi es, at which point the mold is
removed. The cast metal inside has the same shape as
the inside of the mold. Castings are usually made in a
sand mold and have a rough surface. New castings are
sandblasted, leaving a dull silver surface.