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35 Cards in this Set
- Front
- Back
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At room tempture what crystal structure is steel?
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BCC (body centered cubic)
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When does the crystal structure change from BCC to FCC?
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During the transformation range
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The ability to change from one type of crystaline structure to another?
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allotropy
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above the transformation temperature steel is made of?
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Austenite
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Steel exsists in the what form(s) below the transformation temperature?
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pealite and ferrite.
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What is pearlite made of?
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Ferrite and cementite in alternation layers.
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what are some properties of ferrite?
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very ductile, low carbon
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what are some properties of cementite?
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Hard, high carbon
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At what temperature(s) is the transformation range?
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1333-1670, depending on the carbon content
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Adding more carbon does what to the transformation temperature of the steel?
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Decreases the transformation temperature
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To get a higher transformation temperature the carbon content must be?
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low
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what happens to steel containing less then 0.8% carbon when the temerature drops below the transformation temperature?
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ferrite starts to form along the grain boundaries of the austenite
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Islands of carbon-enriched austenite surrounded by ferrite are created as what drops?
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temperature
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When the carbon content of the austenite reaches 0.8% it transforms into what?
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Pearlite
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When austenite is allowed to cool solwly, it undergoes an allotropic transformation into a mixture of what?
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Ferrite and Pearlite
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If austenite is cooled to quickly is creates what?
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Martensite
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Distorted body centered tetragonal lattce (BCT) crystaline structure is displayed in what kinda of steel?
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Martensite
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What are some propertires of martensite?
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Very hard, Very Brittle
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Acicular (needle-like) structure is?
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Martensite
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What are two ways Martensite can be formed?
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quenching, and rapid heat transfer
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Low carbon steel has how much carbon?
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0 to .3%
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Medium carbon steel has how much carbon?
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.3% to .6%
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High carbon steel has how much carbon?
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.6% to .8%
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Can martensite be formed in low carbon steel?
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no
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What is the Tendency of the steel to form martensite called?
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Hardenability
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Rapid heat transfer can be controlled by what?
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Preheating
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Annealing produces?
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soft and high ductitity steel
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During annealing, what range is the steel brought to?
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the austenitic range
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during annealing how is the metal cooled and under what conditions?
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very slowly, and in the oven or an insulated container
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What is the difference between normalizing and annealing?
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In normalizing the steel is allowed to cool in sill air
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stress relieving occures below what?
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the transformation temperature
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what temperature is the steel brought to in stress relieving?
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900 to 1250 degrees F
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In SAE-AISI designation system what do the first two numbers mean?
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The steels major alloy
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In SAE-AISI designation system what do the last two numbers mean?
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the carbon content
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explain what ER70S-5 means
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ER = Electrode
70 = Minimum tensile strengeth in 1000 psi S = Solid -5 = Cehmical composition |
