metallurgy

Question 1

What is the carbon content range in steel?

Answer 1

.1 to 1.86%

Question 2

What is the definition of ferrous metals?

Answer 2

Ferrous metals contain Iron. Ex. iron, steel, cast iron, stainless steels, tool steel.

Question 3

What is the definition of non-ferrous metals?

Answer 3

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.

Question 4

What happens when you spark test high carbon steels EX. Tool steel or cast iron?

Answer 4

With higher carbon steels the sparks become shorter and more spread out or “branched”

Question 5

What happens when you spark test low carbon steels like wrought iron?

Answer 5

Lower carbon steels spread out less “branch less” and are longer.

Question 6

What is the name for cooled hot iron?

Answer 6

Pig Iron

Question 7

What is used to fuel a blast furnace?

Answer 7

Coke which is refined coal

Question 8

What is a flux?

Answer 8

is a material that melts and combines with impurities in order to remove them. Limestone and Lime are examples of a flux.

Question 9

What are the five major operations of a blast furnace?

Answer 9

1. Deoxidize the iron ore.
2. Melt the slag.
3. Melt the iron.
4. Carbonize the iron.
5. Separate the iron from the slag.

Question 10

In the United States which is the most common furnace used to make steel?

Answer 10

Basic Oxygen Furnace.

Question 11

What are the benefits of continuous casting?

Answer 11

Eliminates processing ingots, blooms, billets, & slabs. Much more efficient, production can be virtually continuous.

Question 12

Why do we use coke instead of coal?

Answer 12

Coal often has impurities such as sulfur and phosphorous refining it into coke removes the impurities.

Question 13

What is the difference between gray cast iron and white cast iron?

Answer 13

Gray cast iron is cooled slowly

White cast iron is cooled quickly and is more brittle.

Question 14

What is one benefit of small amounts of sulfur in steel?

Answer 14

Sulfur improves the machining qualities of steel (detrimental to hot forming)

Question 15

Define Tensile Strength

Answer 15

is the ability of a metal to resist being pulled apart.

Question 16

Define compressive strength

Answer 16

is a measure of how much squeezing force it can withstand before it fails.

Question 17

Define Hardness

Answer 17

is the quality which allows a metal to resist penetration.

Question 18

Define Elongation

Answer 18

is a measure of how much a metal will stretch before it breaks.

Question 19

Define Ductility

Answer 19

is the ability of a metal to be stretched.

Question 20

Define Brittleness

Answer 20

opposite of ductility a brittle metal fracture if bent or struck.

Question 21

Define toughness

Answer 21

Is the ability to prevent a crack from propagating.

Question 22

What is the melting temperature of aluminum?

Answer 22

1220 F

660C

Question 23

What is the melting temperature of aluminum oxide?

Answer 23

5000F

2760C

Question 24

what is the melting temperature of mild steel

Answer 24

2462-2786F

1350-1530C

Question 25

What are the four factors of great importance when heat treating metals?

Answer 25

1. The Temperature?
2. The Length of time held at that temperature
3. The Rate of Cooling
4. The material surrounding the metal.

Question 26

What is the definition of Ferrite?

Answer 26

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.

Question 27

What is the definition of Cementite?

Answer 27

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.

Question 28

What is the definition of Pearlite?

Answer 28

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.

Question 29

What is the definition of Austenite?

Answer 29

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.

Question 30

What is the definition of Martensite

Answer 30

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.

Question 31

What carbon content and above can be successfully hardened with a heat treatment?

Answer 31

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.

Question 32

What is the definition and reason for Annealing.

Answer 32

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.

Question 33

What is the definition and reason for Normalizing.

Answer 33

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.

Question 34

What is the definition and reason for Tempering.

Answer 34

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.

Question 35

What is the definition and reason for Spheroidizing.

Answer 35

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.

Question 36

What is the definition and reason for Surface Hardening

Answer 36

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.

Question 37

What is the definition and reason for Case Hardening

Answer 37

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.

Question 38

What is hot shortness?

Answer 38

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.

Question 39

What is meant by a critical temperature for a metal?

Answer 39

A point where a phase change occurs or a crystalline structure change occurs. Ultimately a critical temperature is a temperature where a metal goes through a change. this is important as heating to a critical temp and then cooling is the basis of heat treating.