Different types of steel Flashcards
What is structural steels?
Structural steels account for 80% of the steel making industry. Typicallty used direct after hot trolling, they have requirements on the yield strength or other qualities.
Can be welded with arc welding technique.
Two sub categories are:
* Basic steel: Simple alloying elements. Only requirement is that S and P is lower than 0.05%.
* Quality steel: Small amount of alloying alements. High yeild and ultimate tensile strangth, toughness and weldability.
What is reinforcing steel?
Eurocode 2 regulates this field (concrete).
Two classes of rebars are the used with the same level och strength
B450C & B450A
What is the minimum requirement for reinforcing steel?
The ratio between the Ultimate Tensile Strength and the Yield Strength (ft/fy) is also defined in the Eurocode 2 as it is a preliminary means of expressing the ability of a material to plastically deform: this value is 1 for brittle materials and higher for ductile materials
Rebars diameter sin teh range 6-40 mm
Today, only steels with high weldability can be used and, thus, the chemical composition is strictly assessed: C < 0.22; P < 0.05; S < 0.05; Cu < 0.8; N<0.012
What does nominal mean?
Using the term nominal we indicate that this level of strength is the minimum that has been expected for steels belonging to this class.
What does the term characteristic mean?
Since every real steel produced by any steelmaking shop has variable properties, it is necessary to introduce the concept of this term.
The mechanical properties of rebar steel can have a certain scattering according to the fluctuations in chemical composition. The characteristic value is a value below which the designer can expect to find a defined percentage of the population of recorded data for that specific property.
What is Plain carbon steel, Low alloyed steel and medium-high alloyed steel?
- Plain carbon steel: with Mn content below 1wt%
- Low alloyed steel: with Mn above 1% or other alloying elements below 5% (low alloyed steel)
- Medium-High alloyed steel: If at least one of the alloying element is present with a concentration higher than 5% (i.e. stainless steels). A letter “X” indicates that the steel is a medium to high alloyed one.
How is steel for pre stressed concrete fabricated?
Hot forming
Cold forming
Quenched and tempered
What is steel for pre stressed concrete?
Typically the yield strength of these steels is very high (1000-1800 MPa)
Cannot be welded due to high carbon content (0.9%)
High carbon content gives high strength
What is special with steel for pre stressed concrete?
- Stress relaxation is the core of prestressed concrete.
- Consequence: If the stress state decreases, also the prestress level inside the PSC structure decreases accordingly, thus the entire resistance of the structure is lowered.
