WHAT IS A METAL?
A metal is a chemical element that is a good conductor of electricity and heat and forms cations
and ionic bonds with non-metals. In chemistry, a metal is an element, compound, or alloy
characterized by high electrical conductivity. In a metal, atoms readily lose electrons to form
positive ions. Those ions are surrounded by delocalized electrons, which are responsible for the
conductivity.
WHAT ARE THE MAIN METALLIC PROPERTIES?
Hardness
Hardness refers to the ability of a metal to resist abrasion, penetration, cutting action, or permanent
distortion. Structural parts are often formed from metals in their soft state and then heat treated to
harden them so that the finished shape will be retained. Hardness and strength are closely associated
properties of all metals.
Malleability
A metal that can be hammered, rolled, or pressed into various shapes without cracking or breaking. It is
said to be malleable. This property is necessary in sheet metal that is to be worked into curved shapes
such as cowlings, fairings, and wing tips. Copper is one example of a malleable metal.
Ductility
Ductility is the property of a metal that permits it to be permanently drawn, bent, or twisted into various
shapes without breaking. This property is essential for metals used in making wires and tubes. Ductile
metals are greatly preferred for aircraft use because of their ease of forming and resistance to failure
under shock loads. For this reason, aluminum alloys are used for cowl rings, fuselage and wing skin, and
formed or extruded parts, such as ribs, spars, and bulkheads. Chrome-molybdenum steel is also easily
formed into desired shapes. Ductility is similar to malleability.
Conductivity
Conductivity is the property that enables a metal to carry heat or electricity. The heat conductivity of a
metal is especially important in welding, because it governs the amount of heat that will be required for
proper fusion. Conductivity of the metal, to a certain extent, determines the type of jig to be used to
control expansion and contraction. In aircraft, electrical conductivity must also be considered in
conjunction with bonding, which is used to eliminate radio interference. Metals vary in their capacity to
conduct heat. Copper, for instance, has a relatively high rate of heat conductivity and is a good electrical
conductor.
METALS CLASSIFICATION
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IRON PRODUCTION
The modern production of iron involves heating iron ore with coke and limestone in
a blast furnace, where temperatures range from 392°F (200°C) at the top of the
furnace to 3,632°F (2,000°C) at the bottom. Some blast furnaces are as tall as 15story buildings and can produce 2,400 tons of iron per day.
Inside a blast furnace, a number of chemical reactions occur. One of these is the
reaction between coke (nearly pure carbon) with oxygen to form carbon monoxide.
This carbon monoxide then reacts with iron ore to form pure iron and carbon
dioxide. Limestone is added to the reaction mixture to remove impurities in the iron
ore. The product of this reaction, known as slag, consists primarily of calcium
silicate. The iron formed at the bottom of a blast furnace exists in a molten form
known as pig iron. The slag is also molten but less dense than the iron.
Efforts to use pig iron for commercial and industrial applications were not very
successful. The material is brittle. There are several methods to convert pig iron
into stronger forms of iron like cast iron and wrought iron. More importantly, when
additional elements, such as manganese and chromium, are added to the converter,
a new product—stainless steel—is formed.
Vocabulary:
Raw material: materia prima
Range: rango
Iron ore: mineral de hierro
coke: coque, tipo de carbón.
limestone: piedra caliza
blast furnace: horno vertical
top: upper part of something
bottom: is the opposite of top.
occur: happen
nearly: casi
slag: escoria
pig iron: molten iron, fundición de
hierro.
brittle: property of a material to
break easily.
manganese: manganese
chromium: cromo
steel: acero
tough/toughness:
(tenacidad)
mechanical property. A tough material
can resist hitting.
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FERROUS METALS
NAME
ALLOY OF IRON AND….
Mild steel
Up to 0,6% of Carbon Tough (tenaz)
(C)
It rusts easily.
Up to 1,6% C
Tough (tenaz =
(acero templado)
Carbon steel
(acero al carbono)
PROPERTIES
USES
Common in
workshops.
Cutting tools
resistente a los golpes)
Stainless steel
Nickel and chromium
Cast iron
Up to 6% of C
Resistant to rust.
Home,
Tough.
knives
Strong but brittle Engines
(fundición)
(quebradizo)
NON FERROUS METALS
NAME
COLOUR
ALUMINIUM
Whitish grey
COPPER (cobre)
Redish brown
SILVER (plata)
Whitish grey
LEAD (plomo)
Bluish grey
TIN (estaño)
Bluish grey
NON FERROUS ALLOYS
NAME
ALLOY OF …
BRASS (latón)
Copper+Zinc
BRONZE (bronce) Copper+Tin
PROPERTIES
USES
Light, soft, ductile,
malleable, easy to
work
corrosion resistant,
ductile, malleable
Ductil,
malleable,
resists corrosion
Heavy, ductile,
malleable.
Soft, it does not rust
PROPERTIES
USES
Hard, easy to machine.
Soft, resists corrosion, easy
to polish.
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buildings,
TOOLS USED TO WORK WITH METALS:
TO MEASURE AND DRAW:
TO CUT:
TO HOLD:
TO HOLE:
TO FILE:
TO JOIN:
TO FINISH:
A:
B:
C:
D:
E:
F:
G:
H:
I:
J:
K:
L:
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