SUBJECT:SUBJECT:

LEARNING OUTCOMES:LEARNING OUTCOMES:Upon completion of the course, student will be able to

demonstrate the knowledge and understanding of:

• Properties and uses• Process• Basic metallurgy, metals and processes• Non-metallic materials• Materials under load• Vibration

ASSESSMENT: ASSESSMENT: Progress Tests 1 15% Progress Tests 2 15%Assignments 10%Final Examination 60%

• Explains in simple terms what influences the choice of material for a marine engineering component

• Describes in simple terms what is meant by the following mechanical properties: elasticity, brittleness, hardness, strength, toughness, ductility, malleability, plasticity and machinability

• Explains what is meant by low-; medium- and high-carbon steels• Compares the tensile strength, ductibility, and hardness of low-;

medium- and high carbon steels• States the uses of low-; medium- and high carbon steels • Describes the properties of cast iron and gives examples of its uses• Defines an alloy• States the uses of aluminum, copper, zinc, lead, tin, and antimony• States the component metals of brass, bronze and white metal• States the uses of the above alloys• Explains why the above alloys are suitable for the uses of the above

objectives

Types of Materials

Properties of a metal

Physical

Mechanical

Thermal

Chemical

Technological

Electrical

Mechanical Properties of a Metal

1. Elasticity defined as the property of a metal by virtue of which it is able to retain its original shape and size after removal of the load.

2. Brittleness defined as the property of a metal by virtue of which it will fracture without any appreciable deformation.

3. Hardness defined as the property of a metal by virtue of which it is able to resist abrasion, indentation and scratching by harder bodies.

4. Strength defined as the property of a metal by virtue of which it can withstand an external force or load without rupture.

Types of strengths: elastic, plastic, tensile, compressive, shear, bending and torsion

5. Toughness defined as the property of a metal by virtue of which it can absorb maximum energy before fracture takes place.

6. Ductility defined as the property of a metal by virtue of which it can be drawn into wires or elongated before rupture takes place.

7. Malleability defined as the property of a metal by virtue of which it can be deformed into thin sheets by rolling or hammering without rupture.

The following common metals have malleability in the decreasing order:

Gold, silver, aluminum, copper, tin, platinum, lead, zinc, iron and nickel

8. Plasticity defined as the property of a metal by virtue of which a permanent deformation take place whenever it is subjected to the action of external forces.

8. Plasticity defined as the property of a metal by virtue of which a permanent deformation take place whenever it is subjected to the action of external forces.

9. Machinability defined as the property of a metal by virtue of which indicates the case with which it can be cut or removed by cutting tools in various machining operations such as turning, drilling, boring, milling etc.

A vast range of metals exist and they fit in two categories, ‘ferrous’ and ‘non-ferrous’ metals. These metals can be used to build/manufacture an equally large range of items.

FERROUS METALS - Metals that contain iron

NON-FERROUS METALS - Metals that do not contain iron

NAME ALLOY OF PROPERTIES USES

Mild Steel Carbon 0.1 - 0.3%Iron 99.9 - 99.7%

Tough. High tensile strength. Can be case hardened. Rusts very easily.

Most common metal used in school workshops. Used in general metal products and engineering.

Carbon Steel Carbon 0.6 - 1.4%Iron 99.4 - 98.6%

Tough. Can be hardened and tempered.

Cutting tools such as drills.

Stainless steel Iron, nickel and chromium.

Tough, resistant to rust and stains. Cutlery, medical instruments.

Cast iron Carbon 2 - 6%Iron 98 - 94%

Strong but brittle. Compressive strength very high.

Castings, manhole covers, engines.

Wrought iron Almost 100% iron Fibrous, tough, ductile, resistant to rusting.

Ornamental gates and railings. Not

in much use today

SOME FERROUS METALS AND PROPERTIES

NAME COLOUR ALLOY OF; PROPERTIES USES

Aluminum

Light grey Aluminum 95%Copper 4%Manganese 1%

Ductile, soft, malleable, machines well. Very light.

Window frames, aircraft, kitchen ware.

Copper Reddish brown

Not an alloy Ductile, can be beaten into shape. Conducts electricity and heat.

Electrical wiring, tubing, kettles, bowls, pipes.

Brass Yellow Mixture of copper and zinc 65% - 35% most common ratio.

Hard. Casts and machines well. Surface tarnishes. Conducts electricity.

Parts for electrical fittings, ornaments.

Silver Whitish grey Mainly silver but alloyed with copper to give sterling silver.

Ductile, Malleable, solders, resists corrosion.

Jewellery, solder, ornaments.

Lead Bluish grey Not an alloy. Soft, heavy, ductile, loses its shape under pressure.

Solders, pipes, batteries, roofing.

SOME NON - FERROUS METALS AND PROPERTIES

If you use metals as part of a practical project a knowledge of the shape or ‘section’ of lengths of metals is important. The diagrams below show examples of solid lengths and also tubes. When you order metals you need to describe the section you want.

SECTIONS - SOLIDS AND TUBES

ROUND SECTION

HEXAGONAL SECTION

SQUARE SECTION

L-SECTION

ROUND TUBE

HEXAGONAL TUBE

SQUARE TUBE

L-SECTION TUBE

The American Iron and Steel Institute (AISI) defines carbon steel as follows:

Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, columbium [niobium], molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect;

Classification:

1. Low-carbon steel, also known as mild steel. It as less than 0.30 percent carbon and generally used for industrial products: bolts, nuts, sheet, plate, tubes and machine components.

2. Medium-carbon steel has 0.30 percent to 0.60 percent carbon. It is generally used in application requiring higher strength such as machinery, automotive and agricultural equipment parts, rail road equipment and parts for metalworking machinery.

3. High-carbon steel has more than 0.60 percent carbon. It is generally used for parts requring strength, hardness and wear resistance such as cutting tools, cable, springs and cutlery.

Iron is one of the three magnetic elements. Cast iron is very brittle but it has a greater resistance to corrosion than either pure iron or steel. Cast iron is used for manhole covers on roads and pavementsand as engine blocks for petrol and diesel engines.

Iron from the blast furnace contains about 5% carbonwhich comes from the coke in the furnace.It is cast into moulds called pigs and the iron is called cast iron or pig iron.

An alloy is a solid solution or homogeneous mixture of two or more elements, at least one of which is a metal, which itself has metallic properties. It usually has different properties from those of its component elements.

Alloys are used because they have specific properties or production characteristics that are more attractive than those of the pure, elemental metals. For example:

• some alloys possess high strength• others have low melting points• others are refractory with high melting temperatures• some are especially resistant to corrosion• and others have desirable magnetic, thermal, or electrical properties

These characteristics arise from both the internal and the electronic structure of the alloy. An alloy is usually harder than a pure metal and may have a much lower conductivity.

Aluminium is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al.

Aluminium is the most abundant metal and too reactive chemically to occur in nature as the free metal. Instead, it is found combined in over 270 different minerals. The chief source of aluminium is bauxite ore.

Aluminium is remarkable for its ability to resist corrosion and its low density. Structural components made from aluminium and its alloys are vital to the aerospace industry and very important in other areas of transportation and building.

Aluminium is the most widely used non-ferrous metal. Relatively pure aluminium is encountered only when corrosion resistance and/or workability is more important than strength or hardness.

A thin layer of aluminium can be deposited onto a flat surface by physical vapor deposition. When so deposited, a fresh, pure aluminium film serves as a good reflector (approximately 92%) of visible light and an excellent reflector (as much as 98%) of medium and far infrared.

Pure aluminium has a low tensile strength, but when combined with thermo-mechanical processing, aluminium alloys display a marked improvement in mechanical properties, especially when tempered.

Aluminium alloys form vital components of aircraft and rockets as a result of their high strength-to-weight ratio.

Aluminium readily forms alloys with many elements such as copper, zinc, magnesium, manganese and silicon.

Copper is a chemical element with the symbol Cu. It is a ductile metal with excellent electrical conductivity and is rather supple in its pure state and has a pinkish luster which is unusual for metals which are normally silvery white. It finds use as a heat conductor, an electrical conductor, as a building material, and as a constituent of various metal alloys.

Copper is also an important ingredient of many useful alloys—combinations of metals, melted together.

Brass is copper plus zinc. If it contains mostly copper, it is a golden yellow color; if it is mostly zinc, it is pale yellow or silvery. Brass is one of the most useful of all alloys; it can be cast or machined into everything from candle sticks to cheap, gold-imitating jewelry that turns your skin green.

Bronze is mainly copper plus tin

Uses of CopperCopper is vital for computers to work. Copper is used in building the integrated circuits, chips, and the printed circuit boards of the computer alone. Copper is becoming more and more popular to use in the layers of the build-up of a chip. IBM announced a plan to use copper in its computer chip rather than aluminum. Doing so would make the computer to be cheaper and would allow it to make faster calculations.

Copper is often used as a conductor of electricity. Almost all electrical devices rely on copper wiring because copper is inexpensive and highly conductive. The conductivity of copper is second only to silver. The reason why copper is a good conductor is because there are a lot of free electrons that can carry the flowing current efficiently. These free electrons do not remain permanently associated with the copper atoms, instead they form an electron ‘cloud’ around the outside of the atom and are free to move through the solid quickly.  

Copper is often used in currency. From 1909 to 1982, the American penny was 95% copper. The other 5% was either zinc or bronze depending on the year. The only exception was 1943. That year the penny had zinc-plated steel in it. Unfortunately, the steel was magnetic and kept getting stuck in vending machines. Also, the zinc corroded easily and was therefore often mistaken for a dime. In the early 1980’s copper increased in value. So in 1982, the United States switched the penny’s core to zinc and coated it with copper.

Zinc is a metallic chemical element with the symbol Zn. Commercially pure zinc is known as Special High Grade, often abbreviated SHG, and is 99.995% pure.

Zinc is relatively non-reactive in air or water. Consequently, it is applied in thin layers to iron and steel products that need to be protected from rusting. This process is called galvanizing in which the metal is dipped in molten zinc.

The second largest use of zinc is as an alloy and the remaining zinc consumption is for making paint, chemicals, agricultural applications, in the rubber industry, in TV screens, fluorescent lights and for dry cell batteries.

Zinc is also used as a main alloy for Brass. 

One of the biggest uses of zinc is in making protective coatings for steel. The development of the wide range of zinc coatings arose from two happy accidents of chemistry, the relatively slow and predictable rate of atmospheric corrosion of zinc compared with steel, and the relative positions of zinc and iron in the electrochemical series. Zinc will corrode preferentially to give cathodic protection to iron when both are in contact in an aqueous medium. This is used to good effect to protect immersed structures such as ships’ hulls, drilling rigs and pipelines. It also means that any bare areas in a zinc coating on steel, caused by damage or operations such as cutting or drilling, are still protected by the surrounding zinc.

Taken together, these two factors provide the basis of a unique corrosion protection system which uses some 4 million tonnes of zinc annually to protect around 100 million tonnes of steel. This represents almost half the total world consumption of zinc.

(Option)

Lead is a main group element with a symbol Pb. Lead is a soft, malleable poor metal, also considered to be one of the heavy metals.

Lead has a bluish white color when freshly cut, but tarnishes to a dull grayish color when it is exposed to air and is a shiny chrome silver when melted into a liquid.

Lead is used in building construction, lead-acid batteries, bullets and shot, weights, and is part of solder, pewter, and fusible alloys.

Tin is a chemical element with the symbol Sn. This silvery, malleable poor metal that is not easily oxidized in air and resists corrosion, is found in many alloys and is used to coat other metals to prevent corrosion.

Tin is obtained chiefly from the mineral cassiterite, where it occurs as an oxide. It can be alloyed with copper to make bronze. Pewter alloys contain from 85% up to 99% tin.

Antimony is a chemical element with the symbol Sb. A metalloid, antimony has four allotropic forms. The stable form of antimony is a blue-white metalloid. Yellow and black antimony are unstable non-metals.

Antimony is used in flame-proofing, paints, ceramics, enamels, a wide variety of alloys, electronics, and rubber.

Brass is a metal alloy of Copper and Zinc, with copper content ranging from 58% to 95%. In addition to Zinc, the major alloying element, small additions (less than 5%) of other alloying elements are added to modify the properties so that the resulting material is fit for a given purpose. Typical applications: are nuts, bolts, screw threads.

Important Properties of Brass:

• Excellent machinability

• Good strength (250 – 500 MPa)

• Corrosion resistance

• Conductivity

• Non sparking

• Attractive color

• Wear resistance

• Readily recycled

• Toughness

• No loss of properties at temperature up to 200OC

Bronze is any of a broad range of copper alloys, usually with tin as the main additive, but sometimes with other elements such as phosphorus, manganese, aluminum, or silicon.

The tin in bronze makes it more resistant to wear than unalloyed copper. Bronzes today are usually stronger and more resistant to corrosion than brass.

The variations in bronze composition significantly affect its characteristics: Wearability, machinability, corrosion-resistance and ductility for deep drawing are often considered.

Bronze parts are typically used for bearings, clips, electrical connectors and springs.

Commercial bronze, is 90-10, or 90% copper/10% tin. It is frequently the least expensive, most easily obtained grade of bronze.

Aluminium bronze is a copper-aluminium alloy that may contain iron, nickel, and/or silicon for greater strength. It is used for tools and, because it will not spark when struck, for parts to be used around flammable materials. Aluminium bronze is frequently used for aircraft and automobile engine parts.

Manganese bronze is actually a brass containing manganese. It is often used for ship propellers because it is strong and resists saltwater corrosion.

The white metals are any of several light-colored alloys used as a base for plated silverware, ornaments or novelties, as well as any of several lead-base or tin-base alloys used for things like bearings, jewellery, miniature figures, fusible plugs, some medals and metal type.

Some of the metals that make up a white metal alloy are antimony, tin, lead, cadmium, bismuth, and zinc. Not all of these metals are found in all white metal alloys but are mixed to achieve a desired goal or need.

As an example, a base metal for jewelry needs to be castable, polishable, have good flow characteristics, have the ability to cast fine detail without an excessive amount of porosity and cast at between 230 °C and 300 °C