It is also used in parts such as ball bearings, shafts,
and forming into plates, billets, bars, or structural
and valve stems that are subject to high pressure and
shapes.
high temperature.
Plain steels that have small additions of sulfur
Vanadium. --Vanadium is added in small
(and sometimes phosphorous) are called free-cutting
quantities to steel to increase tensile strength,
s t e e l s . These steels have good machining
toughness, and wear resistance. It is most often
characteristics and are used in applications similar to
combined with chromium. It is used for crankshafts,
carbon steels. The addition of sulfur and phosphorous
limits their ability to be formed hot. We will now
axles, piston rods, springs, and other parts where high
discuss a few of the plain carbon steels.
strength and fatigue resistance are required. Greater
amounts of vanadium are added to high-speed steel
Low-carbon steel.--Low-carbon steel (0.05 to
cutting tools to prevent tempering of their cutting
0.30 percent carbon), usually called mild steel, can be
edges during high temperatures.
easily cut and bent and does not have great tensile
strength. Steels with less than 0.15 percent carbon are
Nickel. --Nickel is added to steel to increase
usually more difficult to machine than those with a
corrosion resistance, strength, toughness, and wear
higher carbon content.
resistance. Nickel is used in small amounts in the
steel used to armor plate a ship because it resists
Medium-carbon steel.--Medium-carbon steel
cracking when penetrated. Greater amounts of nickel
(0.30 to 0.60 percent carbon) is considerably stronger
are added to chromium to produce a metal that
than low-carbon steel. Heat-treated machinery parts
withstands severe working conditions. Crankshafts,
arc made of this steel.
rear axles, and other parts subject to repeated shock
are made from nickel chrome steel.
High-carbon steel.--High-carbon steel (0.60 to
1.50 percent carbon) is used for many machine parts,
Molybdenum.--Molybdenum is added to steel to
handtools, and cutting tools and is usually called
increase toughness, hardenability, shock resistance,
carbon tool steel. Do not use cutting tools of
and resistance to softening at high temperatures.
high-carbon steel when the cutting temperature will
Molybdenum steel is used for transmission gears,
exceed 400F.
heavy-duty shafts, and springs. Carbon molybdenum
(CMo) and chrome molybdenum (CrMo) are two
ALLOY STEELS.--The steels discussed so far
alloy steels with molybdenum added that are widely
are true alloys of iron and carbon. When other
used in high-temperature piping systems in Navy
elements are added to iron during the refining
ships. Relatively large amounts of molybdenum are
process, the resulting metal is called alloy steel.
used in some of the cutting tools used in the machine
There are many types, classes, and grades of alloy
shop.
steel.
Tungsten.--Tungsten is used primarily in
Alloy steels usually contain several different
high-speed steel or cemented-carbide cutting tools. It
alloying elements, and each contributes a different
gives the cutting tools their hard, wear-resistant and
characteristic to the metal. Alloying elements can
heat-resistant characteristics. Tungsten can be
change the machinability, hardenability, weldability,
air-hardened. It allows tools to be hardened without
corrosion resistance, and surface appearance of the
using oil or water to cool the tool after heating.
metal. If you know how each of the alloying elements
affects a metal, you'll more readily select the best
Nonferrous Metals
metal for a given application. In the following
paragraphs, we'll discuss a few of the more common
Copper, nickel, lead, zinc, tin, and aluminum are
alloy steels and the effects of certain alloying
included among the nonferrous metals. These metals
elements upon the mechanical properties of steel.
and their alloys are used in large amounts in the
Chromium. --Chromium is added to steel to
construction and maintenance of Navy ships.
increase hardenability, corrosion resistance,
toughness, and wear resistance. The most common
COPPER ALLOYS.--Copper has a variety of
uses of chromium are in corrosion-resistant steel
uses. You will see it aboard ship in the form of wire,
rod, bar, sheet, plate, and pipe. As a conductor of both
(commonly called stainless steel) and high-speed
heat and electricity, copper ranks next to silver and
cutting tools. Stainless steel is often used to
has a high resistance to saltwater corrosion.
manufacture parts that are used in acids and salt water.
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