Flashcards in metallurgy Deck (39):
What is the carbon content range in steel?
.1 to 1.86%
What is the definition of ferrous metals?
Ferrous metals contain Iron. Ex. iron, steel, cast iron, stainless steels, tool steel.
What is the definition of non-ferrous metals?
Non Ferrous means that the metal does not contain iron or does not contain significant amounts of iron. Zinc, Copper, Brass, Bronze, Aluminum, Magnesium, Titanium, & Lead.
What happens when you spark test high carbon steels EX. Tool steel or cast iron?
With higher carbon steels the sparks become shorter and more spread out or "branched"
What happens when you spark test low carbon steels like wrought iron?
Lower carbon steels spread out less "branch less" and are longer.
What is the name for cooled hot iron?
What is used to fuel a blast furnace?
Coke which is refined coal
What is a flux?
is a material that melts and combines with impurities in order to remove them. Limestone and Lime are examples of a flux.
What are the five major operations of a blast furnace?
1. Deoxidize the iron ore.
2. Melt the slag.
3. Melt the iron.
4.Carbonize the iron.
5. Separate the iron from the slag.
In the United States which is the most common furnace used to make steel?
Basic Oxygen Furnace.
What are the benefits of continuous casting?
Eliminates processing ingots, blooms, billets, & slabs. Much more efficient, production can be virtually continuous.
Why do we use coke instead of coal?
Coal often has impurities such as sulfur and phosphorous refining it into coke removes the impurities.
What is the difference between gray cast iron and white cast iron?
Gray cast iron is cooled slowly
White cast iron is cooled quickly and is more brittle.
What is one benefit of small amounts of sulfur in steel?
Sulfur improves the machining qualities of steel (detrimental to hot forming)
Define Tensile Strength
is the ability of a metal to resist being pulled apart.
Define compressive strength
is a measure of how much squeezing force it can withstand before it fails.
is the quality which allows a metal to resist penetration.
is a measure of how much a metal will stretch before it breaks.
is the ability of a metal to be stretched.
opposite of ductility a brittle metal fracture if bent or struck.
Is the ability to prevent a crack from propagating.
What is the melting temperature of aluminum?
What is the melting temperature of aluminum oxide?
what is the melting temperature of mild steel
What are the four factors of great importance when heat treating metals?
1. The Temperature?
2. The Length of time held at that temperature
3. The Rate of Cooling
4. The material surrounding the metal.
What is the definition of Ferrite?
Ferrite is practically pure iron and can contain a maximum of 0.02% at 1341C. it is present in all steel and cast iron. Ferrite is body centered cubic in structure and is ductile & tough.
What is the definition of Cementite?
Cementite or Fe3C has a high carbon content of 6.69% and is in-turn very hard and brittle. Cementite is found in all steels and cast irons.
What is the definition of Pearlite?
Pearlite is a combination of ferrite and cementite which forms in alternating layers. Pearlite always contains 0.77% carbon. If a steel has a carbon content above 0.77% cementite and pearlite will form. Below Ferrite and pearlite. Pearlite is very ductile.
What is the definition of Austenite?
Austenite is a high temp form of steel and cast iron. Austenite is stable above 1341C and will change into ferrite, cementite, pearlite, and martensite based on carbon content and cooling rates. Austenite is non magnetic and face centered cubic in structure.
What is the definition of Martensite
Martensite is a glass like in its grain structure and is formed from rapidly cooling from the austenite range. Martensite is very hard and brittle.
What carbon content and above can be successfully hardened with a heat treatment?
a 35 point steel or 0.35% carbon and above can be hardened.
a 10 point steel or .10% carbon has little cementite and lots of ferrite. steels with lots of ferrite cannot be hardened. however heat treatment can alter their structure and grain size.
What is the definition and reason for Annealing.
Annealing is a heat treatment that leaves the metal in the softest condition. Annealing is done to soften metal, make steel machinable, & relieve internal stresses. Annealing works by heating metal to the critical temperature holding for a set time, furnace cool below critical temperature and then air cool.
What is the definition and reason for Normalizing.
Normalizing develops ductility and relieves stresses, just to a lesser extent than annealing. Normalizing works by heating above critical temperature, hold for some time, and cool in still air to room temp. Normalizing is cheaper than annealing as there is less need to use a furnace.
What is the definition and reason for Tempering.
Tempering is used to improve the properties of martensite specifically by making martensite more ductile and tough while retaining hardness and strength. Tempering is done by quenching from the austenite region, reheating to between 400 C to 1300C and then cooling in air.
What is the definition and reason for Spheroidizing.
Spheroidizing is a heat treatment to improve ductility in high carbon steels. Spheroidizing groups cementite together into small spheres while the rest of the steel is ferrite. To spheroidize steel you heat to just below critical temperature, hold, and then slowly cool to room temperature.
What is the definition and reason for Surface Hardening
Surface hardening is a process where the outer surface is heated & quenched to harden it while the internal structure remains ductile & tough. Example drive shafts, or gears.
What is the definition and reason for Case Hardening
Casehardening is a process where carbon is added to the outer surface of a part. The part is heated to its critical temperature, in a carbon rich environment often carbon monoxide, and held there for a set length of time. The carbon penetrates 1/64" per hour. Case hardening can be prevented in areas by covering with copper. the part is then quenched and tempered to harden the piece and then relieve stresses.
What is hot shortness?
Hot shortness is the property of some non ferous metals to become weak when heated but still solid. Often the slightest load or shock can distort these metals. Ultimately when working with metals that are prone to hot shortness it is advisable to clamp and fully support them. Examples, copper or aluminum.