METAL PROPERTIES, CHAR, USES, AND CODES - OD1643 - LESSON 1/TASK 1
1,400 and 1,700 Fahrenheit for about 150 hours in boxes containing
hematite ore or iron scale.
This heating causes a portion of the
combined carbon to change into the free or uncombined state.
The
free carbon separates out in a different manner from carbon in gray
cast iron. It is called temper carbon, and it exists in the form of
small, somewhat rounded particles, which give malleable iron castings
the ability to bend before breaking and to withstand shock loads
better than gray cast iron. The castings have properties like those
of pure iron; namely, high strength, ductility, toughness, and
ability to resist shock.
Malleable cast iron can be brazed.
Any
welded part should be annealed after welding.
(3) Steel. Modern steel was first produced in the United States
in 1860.
Today, steels are produced in several different types of
furnaces, as mentioned in paragraph 3b(4), page 9. The raw materials
used to produce steel include pig iron, iron ore, limestone, and
scrap metal.
A form of iron, steel contains less carbon than cast
iron but considerably more than wrought iron. Carbon content is from
0.03 to 1.7 percent.
Basic carbon steels are alloyed with other
elements, such as chromium and nickel, to increase certain physical
properties of the metal.
(a) Uses.
Steel is used to make such items as nails, rivets,
gears, structural steel, axles, desks, vehicle body parts, and tools.
(b) Capabilities. Steel can be machined, welded, and forged to
a varying degree depending on the type of steel.
(c) Limitations.
Highly
alloyed
steels
are
difficult
to
fabricate.
(d) Low-Carbon Steels.
These steels are soft and ductile and
can be rolled, punched, sheared, and worked when either hot or cold.
They are easily machined and can be readily welded by all methods.
They do not harden to any appreciable amount when quenching from a
high temperature.
(e) M e d i u m - C a r b o n S t e e l s .
T h e s e s t e e l s m a y b e h e a t-
treated after fabrication and used for general machining and
forging of parts that require surface hardness and strength.
T h e y a r e m a n u f a c t u r e d i n b a r f o r m a n d i n t h e c o l d- r o l l e d o r
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