Civil Engineering Materials: Steel, Aluminum, and Composites

Vocabulary flashcards covering the production, properties, metallurgy, testing, and corrosion of steel, along with introductory concepts for aluminum and fiber-reinforced polymer (FRP) composites.

Steel

An alloy of iron and carbon and other elements that is the $3rd$ most used construction material after concrete and asphalt.

Blast Furnace

An equipment developed in the $18th$ century used for the mass production of iron from iron ore.

Limestone

A material used in a blast furnace to remove impurities from iron ore during the reduction process.

Slag

Molten rock and impurities that are skimmed off the top during the production of pig iron.

Basic Oxygen Furnace

A furnace used to refine pig iron into steel, capable of processing $300$ tons in $25$ minutes.

Killed Steel

A term used to describe steel that has been completely deoxidized using materials like aluminum, ferrosilicon, or manganese.

Continuous Casting

A newer way of forming steel into products such as rolled shapes, plates, and bars without casting into ingots first.

Cast Iron

A high-carbon iron alloy with a carbon content of $>2\%$ which causes the material to be brittle.

Structural Steel

Low carbon steel ($0.15\%-0.27\%$ carbon) prized in civil/construction for its ductility.

Allotropic

A property of steel meaning it possesses different crystal structures (such as BCC and FCC) at different temperatures.

Crystal Lattice

An orderly $3-D$ pattern in which a metal's atoms are arranged while in a solid state.

BCC (Body Centered Cubic)

The crystal lattice arrangement containing $9$ atoms that steel assumes at room temperature.

FCC (Face Centered Cubic)

The crystal lattice arrangement containing $14$ atoms that steel assumes at higher temperatures, known as austenite.

Grains

Crystals formed when molten steel solidifies, the orientation of which forms grain boundaries in the metal.

Austenite

An FCC-dominated microstructure of steel formed at high temperatures.

Ferrite

A low carbon component of steel that is characterized as being soft and ductile.

Cementite

A high carbon component of steel characterized as being hard.

Pearlite

A microstructure formed below the transition temperature that is a combination of ferrite and cementite.

Heat Treatment

A process of controlled heating and cooling to change the physical and mechanical properties of steel.

Annealing

A softening process where steel is heated above the austenitic temperature and slowly cooled to room temperature to increase ductility and toughness.

Normalizing

A softening process involving heating above the austenitic temperature and slowly cooling to make the steel softer and more workable.

Hardening

A process involving high heat followed by rapid quenching to change grain structure into martensite.

Quenching

The rapid cooling of steel in water, brine, or oil to induce specific changes in grain structure.

Martensite

A grain structure of steel that is very strong but brittle, produced through rapid cooling.

Tempering

The process of reheating quenched steel to lower temperatures and then quenching again to reduce brittleness.

A615, A616, A617, and A706

The four types of steel (billet, rail, axle, and low alloy) used to manufacture reinforcing bars for concrete.

ASTM A416 Grade 270

A type of steel for pre-stressed concrete with an ultimate strength of $270\,ksi$.

Charpy V Notch Impact Test (ASTM E 23)

A test measuring the toughness or fracture energy of a metal specimen using a pendulum.

High Hardness

A material property measuring resistance to small dents and scratches, often required for machine parts and tools.

Anode

The positive electrode in a corrosion cell where metal goes into solution and corrosion occurs.

Cathode

The negative electrode in a corrosion cell required for an electric current to flow.

Electrolyte

A liquid, such as moisture in the air or salt water, that supports the flow of electrons between electrodes.

Cathodic Protection

A corrosion protection method involving the electrical connection of steel to a sacrificial metal that loses electrons first.

Metallic Bonds

Bonds where atoms share electrons with many neighboring atoms, resulting in high conductivity and tight packing.

Bauxite

The main raw material used in the production of aluminum.

Matrix

The continuous phase of a microscopic composite (usually a polymer) that surrounds, binds, and protects the reinforcing phase.

Dispersed Phase

The reinforcing component of a composite (such as fibers) that is generally harder and stiffer than the matrix phase.

FRP (Fiber Reinforced Polymer)

A subgroup of composite materials consisting of fibers like glass, carbon, or aramid in a polymer matrix like epoxy or vinyl ester.

Thermosetting Resins

Plastics used in FRP matrix that can deteriorate at high temperatures and cannot be easily reshaped after manufacturing.

There are mix designs for steel

False steel is not mixed like concrete; it has defined properties and grades.

Pig Iron

Iron that has been reduced from iron ore in a blast furnace, typically containing a high carbon content and used as a raw material for making steel.

Carbon (coal or coke)

Used in a blast furnace to reduce iron ore to pig iron

Refining Pig Iron and Scarp to Steel

Remove excess carbon and other impurities by oxidation in another furnace

High Carbon in Steel

>.2%

Medium Carbon in Steel

.8-2%

Structural Steel Low Carbon

.15-.27%

Microstructures of Steel

ferrite, perlite, cementite, austentite

Allotropic

Different Crystal structures at different temperatures

Most common lattice structures in metal

Body Centered Cubic and Face Centered Cubic

At Higher temperatures what cubic structure is more common?

Face Centered Cubic

When does Body Centered Cubic Become more common

When the steel cools below the transition temperature

Ductility

Materials ability to stretch, bend or be drawn to a thin wire without breaking

Below the transition temperature steel

both ferrite and pearlite

Pearlite

Combination of ferrite and cementite

Steel Alloy

Steel + alloying metal to change properties

What percentage of steel composition are elements other than iron

5

Grade of structural steel is determined by

Mechanical properties and chemical composition

Structural applications low carbon

<.3%

Structural applications medium carbon

.3%-.6%

Charpy V Notch

Measures toughness

Hexagonal Close Pack (HCP)

17 atoms

Grain Boundary

Act as crack inhibitors and increase toughness

Flaws and Defects

Weak spots, reduce toughness

Small grains

Formed by rapid cooling, increase toughness

Advantages of Aliminum

1/3 density of steel, high strength to weight ratio, good thermal and electrical conductivity

Materials used to deoxidize pig iron

Aluminum, ferroslilicon, manganese, etc

Modulus of elasticity for steel

30000 ksi

Modulus of elasticity for aluminum

10000 ksi

Whisker fiber

Very thin single crystals, high cost poor bond

Fibers

Glass, carbon, boron, ceramic, etc

Fiber reinforced polymer rebars, strengthen and wrap partially damaged columns and bridge supports, fiber reinforced concrete

Civil/construction applications of microscopic composited

Fiber reinforced polymers (FRP) are made up of

Glass( most common) carbon, and aramid (kevelar)