Lecture #7 - Steel Flashcards
What is steel?
Alloy consisting primarily of iron but contains carbon and some other elements.
What happens when you increase carbon content of steel?
Ductility and weldability decrease, strength increases
Name the 4 operations required to produce most metals.
Mining, ore preparation, metal extraction from ore, refining the metal
How is steel made?
Extract, proportionate, mix iron ore, limestone coal. Add on top of blast furnace and cook very hot. Remove Molten iron from bottom of furnace and blow full of oxygen. Remove impurities and solidify.
What are 2 ways to form steel?
Casting, hot-rolling.
What are ferrous metals? Name 3
Any metal that contains iron. Cast iron, wrought iron, steel.
What is the carbon content of cast iron?
2 to 4%
What is cast iron?
Older material in terms of construction, very brittle and hard to work with, strong in compression but not in tension, usually not weldable and brittle.
What are non-ferrous metals? Name 3
Metals that do not contain iron. Copper, lead, aluminium.
What is wrought iron?
Strong in tension and weaker in compression, malleable and soft, need special techniques for welding.
What is the carbon content of wrought iron?
Very little or none
Name steel properties.
Carbon content of less than 0.25%, used in structural applications, equally strong in tension and in compression, ductile and not prone to failure.
What is the divding point between low-alloy and high-alloy steel?
5% total non carbon, iron+carbon+non carbon 5%
What is added to stainless steel?
Add nickel and chromium to form long-lasting oxide layer.
What is type WT?
Weldable Notch-Tough Steel
What is Type R?
Atmosĥeric Corrosion Resistant Steel
What is Type W?
Weldable Steel
What is done to galvanized steel?
Dipped in molten zinc for corrosion protection.
What is Type A?
Atmospheric Corrosion Resistant Weldable Steel
What is Type AT?
Atmospheric Corrosion Resistant Notch-Tough Weldable Steel
What is Type QT?
Quenched and Tempered Low Alloy Notch-Tough Steel Plate
What is Type Q?
Quenched and Tempered Low Alloy Steel Plate
What is Type WT used for?
Same as Type W but when you need it to be notch tough at low temps
What is Type W used for?
Whenever you don’t need notch tough steel, includes buildings, bridges, etc.
In steel tension tests, what are other factors that affect material response?
Load cycling, loading rate
What is Type R used for?
Can give building exterior nice rust colour due to oxidization
What is the difference between true strain and engineering strain?
True strain accounts for the changing cross-sectional area of the specimen as load is applied, whereas engineering strain only considers the original cross-sectional area
What does linear behaviour mean in terms of stress-strain curve?
As stress increases, strain increases proportionally
What does elastic behaviour mean in terms of stress-strain curve?
When the load is removed, the strain returns to 0
What is the proportional limit?
The point at which the behaviour of the steel remains linear
What is the elastic limit?
The point at which the behaviour of the steel remains elastic
Are the proportional limit and elastic limit the same? If not why do we pretend they are
No, but doesn’t make a big difference and is a lot easier to model when you do that.
What is the Modulus of Elasticity? What is its other name?
Slope of the stress-strain curve, Young’s Modulus
What is yield strength?
The stress at the point at which the strain is 0.02% of the total strain
What is ultimate stress?
The largest amount of stress the specimen experiences
What is the Modulus of Resistance? What is another name for this?
Measure of energy absorbed by a material up to the time it yields under load, area under stress-strain curve up until yield point. Strain energy per unit volume
What is toughness?
Ability of steel to resist impact when its been damaged, represented by the area under the stress-strain curve
What is hardness?
Ability of a material to resist abrasion or penatratoin on its surface
What is strain hardening?
Rise of stress as strain increases after failing (in true stress)
What happens when the load is removed from the specimen?
If in the elastic region, specimen will fully bounce back with no permanent damage. If in the plastic region, material will be permanently damaged. This damage is called residual or plastic strain.
What test is used to test Notch-Tough steel?
Charpy V-notch test
What is necking?
When a lot of strain ends up in one concentrated area of the material/specimen
What is the difference between engineering and true stress after necking occurs?
In engineering stress, stress decreases after necking but in true stress stress increases after necking because it accounts for the fact that the load and the cross-sectional area both became a bit smaller.
What is ductility? Why is it important?
Ductility is a material’s ability to plastically deform without fracture
What is percentage elongation?
Measure of strain in percentage, measure of ductility
What is ASTM A6?
Standard Specififcations for General Requirements for Rolled Structural Steel Bars, Plates, Shapes, and Sheet Piling
What is ASTM A36?
Standard Specification for Carbon Structural Steel
