Chapter 13 Flashcards
Heat Treatment of Steels (47 cards)
Define phase.
Equilibrium Diagrams
A homogenous component of a metal alloy.
Explain an equilibrium phase diagram.
Equilibrium Diagrams
A graph showing phase relationships that occur in a metal alloy as it slowly cools from the molten state.
A metal that is completely pure is considered to be _ _ _ _ _ _?
Equilibrium Diagrams
Single Phase!
What is a binary alloy?
Equilibrium Diagrams
A metal with two components shown on its equilibrium graph.
Is there a such thing as a pure metal?
Equilibrium Diagrams
Nope, can’t be done.
Name when metal solution contain three major alloys.
How about four?
Equilibrium Diagrams
Ternary!
Quaternary!
What is the line called that is used to identify the percent alloy a metal has on a phase diagram at a certain temperature?
AKA?
Equilibrium Diagrams
Tie line!
Isotherm
Define lever law calculations.
What do they help predict?
Equilibrium Diagrams
Determines percentage of each phase present in alloy at specific temperature (like liquid + solid alpha) by divided left of fulcrum length (vertical line from given % alloy) on tie line by total tie line length to get % liquid.
Microstructures!
Overall, what do phase diagrams predict for metallurgists?
Equilibrium Diagrams
Whether one metal is soluble in another, whether metal will be weldable to other metals, to select materials for new alloys (must have significant solubility), and long term stability of an alloy (whether has stable solid solution or not in which structure would change over time).
What is the point on the equilibrium phase diagram in which the composition has one melting point?
What do you call a metal at this point?
Equilibrium Diagrams
The Eutectic point!
A Eutectic or easy-melting metal
What are the percent limits of carbon for a material to be considered steel?
Morphology of Steel
0.06% to 2.0% carbon
What is the name for Fe3C?
Morphology of Steel
Cementite
Cemetite is largely present in _ _ _ _ _ _ _ form. Alternating between _ _ _ _ _ _ _ and _ _ _ _ _ _ _ .
This form is also known as…
Morphology of Steel
Lamellar! Ferrite and Cementite.
Pearlite!
At what percent carbon is the eutectoid where the metal’s grains are 100% pearlite?
Morphology of Steel
0.8 % Carbon
True or False:
Steels and irons are usually heat treatedunder equilibrium conditions.
What does this mean for diagrams?
Morphology of Steel
FALSE.
Only relevant for slow heating and cooling (for hardening and softening)
What is the ability of a steel to go from BCC to FCC at high temperatures?
Morphology of Steel
Allotropy
Quench hardening of steel is only possible at what minimum of carbon content?
0.6% carbon
What are the 3 requirements for quench-hardening steels?
1) Heat to austenitic temperature range
2) Sufficient carbon content (0.6%)
3) Rapid quench to prevent formation of equilibruim products
What are the 3 main reasons for heat treating?
Reasons for Heating Treating
1) Hardening
2) Softening
3) Conditioning
Difference between direct hardening and diffusion treatment (both are hardening).
Reasons for Heating Treating
Direct hardening happens for steel that meet the carbon content and temp requirements that are quench, while metals without sufficient carbon can harden using diffusion treatment by adding alloys (may not even need to be quenched).
What 3 qualities would be best for an automobile spring?
Reasons for Heating Treating
High yield strength (to hold car up without giving), high strength (to prevent creep) and toughness
Steel springs usually direct hardened & double tempered to 47 HRC.
What element/alloy makes steel into stainless steel?
Reasons for Heating Treating
Chromium (Cr)!
Why are some stainless steels hardened, trapping chromium in solution?
Reasons for Heating Treating
To obtain their maximum corrosion resistance.
Think CrO!!
Can hardening steel improve coefficients of thermal expansion or magnetism?
Reasons for Heating Treating
Yes, in fact!
