Steel Flashcards
(22 cards)
What is the composition of steel?
Steel = iron + controlled carbon (~0.02% - 2.0%)
Steel is primarily made by reducing iron ore using coke and limestone in a blast furnace.
How is steel produced?
Made by reducing iron ore using coke and limestone in a blast furnace. Further processed in basic oxygen or electric arc furnace.
The production process involves several stages to achieve desired properties.
What is ferrite in steel?
Low-carbon phase, soft and ductile
Ferrite is one of the microstructures in steel.
What is cementite?
Hard, brittle iron carbide
Cementite is denoted as Fe₃C and is a significant component of steel’s microstructure.
Describe pearlite.
Alternating ferrite and cementite layers; strong and tough
Pearlite is formed during the cooling process of steel and contributes to its strength.
What is austenite?
High-temp phase; transforms on cooling
Austenite is crucial for understanding the heat treatment and transformation of steel.
What is martensite?
Quenched steel; hard, brittle (needs tempering)
Martensite is formed through rapid cooling and requires tempering to improve toughness.
What are the characteristics of mild steel?
Low Carbon < 0.25%: High ductility, good weldability
Mild steel is commonly used in construction due to its favorable properties.
What defines medium carbon steel?
0.25–0.6%: Stronger, less ductile
This type of steel is often used for automotive components.
What is the characteristic of high carbon steel?
> 0.6%: Hard, brittle, used for tools
High carbon steel is preferred for cutting tools and other applications requiring hardness.
What is the purpose of annealing?
Softens, refines grain, improves ductility
Annealing is a heat treatment process where steel (or other metals) is heated to a specific temperature, held there for a period, and then slowly cooled, usually inside a furnace.
Annealing is a crucial heat treatment process in steel manufacturing.
What is normalizing in steel treatment?
Heat treatment process where steel is heated above its critical temperature, held to allow the microstructure to transform into austenite, and then air cooled to room temperature
Normalizing helps in achieving a uniform microstructure.
What happens during quenching and tempering?
Quenching = Steel that is hard,, strong but brittle (due to the presence of martensite)
Tempering = Restores some of the toughness and ductility by transforming some of the martensite into ferrite and cementite.
This process is essential for achieving desired mechanical properties in steel.
What are the mechanical properties of steel?
High strength (400–700 MPa), elastic modulus ~200 GPa, ductile and tough
These properties make steel suitable for various structural applications.
What is general corrosion?
Uniform rusting
General corrosion occurs when metal surfaces are exposed to moisture and oxygen.
What is pitting corrosion?
Localized attack, hard to detect
Pitting is a localized form of corrosion that can lead to severe damage.
What is galvanic corrosion?
Dissimilar metals in contact
This type of corrosion occurs when two different metals are electrically connected in a corrosive environment.
What causes crevice corrosion?
Oxygen-deprived zones. The difference in oxygen levels (between outside and inside the crevice) sets up an electrochemical cell, where the inside of the crevice becomes anodic (corrodes) and the outside surface becomes cathodic (protected)
Crevice corrosion typically occurs in tight spaces where oxygen access is limited.
How can corrosion be prevented?
Coatings, cathodic protection, alloying (e.g., stainless steel)
These methods help protect steel from various forms of corrosion.
What is the Heat-Affected Zone (HAZ)?
Changes properties near welds
The HAZ can experience altered microstructures and mechanical properties due to welding.
True or False: Fatigue failure is common at stress risers.
True
Stress risers, such as welds, can lead to premature fatigue failure in materials.
What should be avoided to reduce fatigue failures in steel?
Notches, use smooth transitions
Design considerations are critical to enhancing the fatigue life of steel components.
