IME 300 Exam 2
Terms
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- heating steels to a certain temperature for a certain time period followed by cooling at a certain rate
- heat treatment
- material is melted and then poured in a mold that has the shape of whatever I want to make
- casting
- any operation which involves removing of metal out of an existing piece; anything that has a nice profile was done through machining; can be done for both steels and cast irons; but for cast irons, they are first cast and then machined
- machining
- any operation which deals with plastically deforming a part to make shape A from shape B
-
forming
- when you are putting two pieces of a material together and causing those two pieces to melt and join together
- welding
- Main purpose of heat treatment of steel
- is to achieve quench hardening and tempering
- heating it to red hot; cooling quickly, usually in water; becomes hard and brittle, toughness is lost, strength and hardness is gained
- quench hardening
- regains some of the toughness lost, TOUGHNESS and STRENGTH are two of the most desired properties of your material; below 700 degrees C; after tempering, the cooling rate is not critical
- tempering
- different groups of cast irons
- gray, malleable, ductile, white
- mostly graphite, free form of carbon; least ductile out of the mostly graphite cast irons; will be gray color at fracture points; potato chips
- gray
- mostly graphite, free form of carbon; in between, not as ductile as DUCTILE, not as brittle as gray; resembles popcorn
- malleable
- mostly graphite, free form of carbon; most ductile
- ductile
- mostly iron carbon, known as “white†because it appears to be silvery white at it’s fracture point; hardest; LEAST ductile
- white
- no other elements besides carbon and iron; no intention of addition of any more elements; if it’s not an alloy steel, it’s a plain carbon
- plain carbon steel
- Tempering regains some of the _______________ lost in quench-hardening.
- toughness
- 6. In plain carbon steel in addition to carbon we may have the following unintentional elements: Silicon, Manganese, Phosphorous, and Sulfur. Which element(s) is (are) harmful and we try to eliminate?
- Sulfur and Phosphorous
- Mention at least three common elements added to steels intentionally to make alloy steels.
- chromium, nickel, tungsten
- Explain the four main reasons for adding alloying elements to steel.
-
a. Corrosion Resistance
b. Increases Resistance to unwanted tempering
c. Increase Hardenability
d. Decrease ductile to brittle transition temp.
-
i. More ductile
ii. Tougher
iii. Formed, not cast
iv. Parts are removed or cut out
v. Much higher melting temp
- steels
-
i. Difficult to form, so they are cast
ii. Low ductility
- cast irons
- when a metal is overworked and experiences stress that exceeds its yield strength
- fatigue fracture
- The maximum stress a fastener can withstand for a specific number of repeated applications prior to its failure.
- fatigue strength
- the stress value below which the material will withstand many number of load cycles
- endurance limit
- the length of time a thread lasts before breaking down or failing.
- fatigue life
- creep deformation
-
a. Plastic deformation, not recovered
b. Under constant stress above yield of strength
c. It is time dependent, does not occur right away
d. Must be above recrystalization temperature
- three examples of aluminum products
- pop can, battery, foil
-
chemical damage to a material, like rust
- corrosion resistance
-
Corrosion Resistant because the type of aluminum oxide it makes is different than the iron oxide that iron and steel makes
- aluminum alloy
- two ways to differentiate aluminum from steels
- aluminum is not magnetic, aluminum is lighter