Steel Flashcards
What are the two main types of steel used in construction?
1) Structural steel
2) Rebar Steel for reinforcement
What does S275 mean?
Structural steel with fy = 275MPa.
How many possible levels of ductility are there?
A, B and C in ascending order where class B is rebar steel.
What is steel in construction composed of?
plain-carbon steel with low carbon contents of <0.3%.
What does structural steel favour?
Ductility over strength therefore has lower carbon content.
What does steel reinforcement favour?
Strength over ductility therefore has higher carbon content.
How do we get the iron that is required to make steel?
iron is not found as a pure metal, we find minerals rich in iron oxide and then split this from the rest of the minerals and separate the iron from the oxygen.
What is the primary processing of steel?
From iron to steel
What is the secondary processing of steel?
Smelting which is separating the metal from the ore.
What does smelting require? (2)
1) Separation of the oxide from the rest
2) High temperature and carbon, to steal oxygens away (reduction reaction).
Why are smelting and melting iron not easy?
Due to the very high temperature required.
What is equipment is able to achieve steel at high temperatures?
Blast Furnace
Describe the blast furnace process.
Lots of coke and blasted in air. Temperature is sufficient to melt iron ore. Coke provides the carbon to remove the oxygen from the oxide. Liquid slag floats over heavier liquid iron, therefore, easier to separate. Limestone provides additional carbon and Ca to bind with the slag, resulting in pig iron which has 5% carbon there cannot be called steel. Convert pig iron to steel, removing the carbon.
What was the Bessemer process?
Blowing pure oxygen instead of ai this was called basic oxygen steelmaking BOS process.
What is hot rolling?
Used to produce universal beams and columns. Steel is heated to 1200 degrees C but cools during rolling to around 750 degrees C.
What is cold rolling?
Higher-strength- lower ductility, lightweight sections. Large deformation to the grains therefore causes strain hardening. Often used for purlins and facade elements.
What is the percentage of recycled structural steel and reinforcement steel for concrete?
60% for structural and 100% for reinforcement.
How do we achieve a yield strength of 500N/mm^2?
1) Micros-alloying
2) Quenching and self-tempering
3) Cold rolling
4) Ribs are required to help bond concrete.
How can we join different profiles together?
bolt knots, rivets or pins.
What type of connections are rivets?
Permanent mechanical connections
What are the pins?
Smooth bar allowing for rotation.
What is welding?
Joining two metal parts together by supplying heat to them.
How can heat for welding be supplied?
1) Oxygen acetylene flame e.g. gas welding
2) Electric arc e.g. arc welding and stud welding
3) resistance to the passage of current.
What is the most common type of welding?
Arc welding
