Depth Questions Line H Exam Flashcards
What are the melting and freezing points of pure metal?
They are the same. Aka only pure metals have a temperature where they are equilibrium between a solid and liquid phase.
What are the melting and freezing points for alloys and mixture metals?
For alloys and mixture metals, the temperatures where melting starts are lower than the temperature where melting is completed, this depends on the range of alloying elements,
In ferrous metals, what is the main ingredient?
Iron.
Common examples of non-ferrous metals are:
Copper, Nickel, Aluminum and Titanium
Common examples of ferrous metals are:
Cast iron, Carbon Steel, Alloy Steel, and Carbon Steel
The toughness of steels decreases as the temperature…
Decreases.
What term is used to describe the rate at which heat is conducted through material?
Thermal Conductivity.
Describe malleability.
The ability to deform under compressive forces without breakage.
Describe ductility.
The ability to deform and stretch without breakage under tension.
When performing a heat treatment, which provides a finer grain structure?
Normalizing.
When performing a heat treatment, which process does not refine the grain structure?
Stress relieving.
The process of strengthening a metal by changing its shape without the use of heat is called what?
Cold working.
What is elongation?
How much a workpiece can be pulled without fracturing.
Define the difference between elastic and plastic deformation.
Elastic deformation is where the material returns to its original shape once the stress is removed.
Plastic deformation is irreversible.
What is the difference between testing for elongation and testing for tensile strength?
Elongation testing is to measure how much the material can stretch or lengthen before it breaks.
Tensile strength testing is to determine the maximum force that a material can withstand while being stretched before it breaks.
Elongation is for stretching, tensile is for strength.
What is Yield Point?
The yield point is the moment when a material starts to deform permanently. Up to this point, if you stop pulling on the material, it will return to its original shape.
**The yield point marks that critical stretch right when it starts to stay deformed. **
(pulling on a piece of elastic; it snaps back until stretched too far, then it stays stretched.)
What is Yield Strength?
Yield strength is the amount of force needed to reach the yield point.
What is UTS?
UTS stands for Ultimate Tensile Strength.
UTS is the maximum stress (due to tensile loading) a material can manage without fracture. After this point, no matter how little, any additional load will cause fracture.
How do you calculate UTS?
** UTS = F/A **
** F is the maximum force (or load) applied to the material during the tensile test.**
** A is the original cross-sectional area of the material.**
What is the CVN test?
The Charpy V-notch test (CVN) is a way to measure the impact strength and toughness of a material, which tells us how well it can absorb energy and resist breaking when hit by a sudden force.
What’s the difference between strength and toughness?
Impact Strength: Focuses on resistance to a sudden impact.
Toughness: Shows overall energy absorption and plastic deformation ability, telling how much total energy the material can take before fracturing.
What is the melting point of steel?
1535 °C (2800 °F).
What is steel mainly an alloy of?
Carbon and iron.
How is pure iron made?
Pure iron is made by reducing the ore and removing impurities in a blast furnace.
What is pig iron?
Pig iron is produced in the first step of steel production. Pig iron is the product of smelting iron ore with a high-carbon fuel and reductant such as coke.
Can pig iron be used for anything as it is?
No. This iron is too brittle to be useful due to the amount of impurities, so it is transferred to a specific furnace for further production, such as to make cast iron or steel.
How is cast iron made?
Cast iron is made by remelting pig iron in a cupola furnace alongside scrap steel and other elements. The melted iron modified to composition specifications (added material) and then cast (hence the name) into shapes for later usage.
Is white cast iron generally harder or softer than grey cast iron?
Harder. Although it is important to note white cast iron is extremely hard but also extremely brittle.
How is white cast iron made?
White cast iron is made by rapidly cooling it (faster than grey cast iron production).
Describe cementite in reference to white cast iron.
All the carbon in the white cast iron, due to the rapid cooling, is in the form of cementite. White cast iron with cementite (Fe3C) has no graphite and is very hard, resistant to wear, and brittle.
Can white cast iron be machined and/or welded?
No. Due to the cementite’s wear resistance, welding or machining white cast iron is a no go.
What is white cast iron used for?
White cast iron can be used for hardfacing applications to improve wear resistance on the softer surfaces of more ductile irons. White cast iron can be used for rollers and crushers.
Why is white cast iron important?
White cast iron is the origin of malleable cast iron.
What are the three classes of steel (based on their level of deoxidation).
Rimmed
Semi-Killed
Killed
What level of deoxidation is killed steel?
Killed steel is fully deoxidized.
What elements are used to refine killed steel?
Normally with silicon and aluminum.
Is there gas formation in killed steel? Does this gas compensate for shrinkage?
No and no. There is no gas to compensate for shrinkage as the killed steel ingot is uniformed in composition, meaning it is consistently made up throughout it its entirety, without the partial separation of alloy parts, known as segregation, one may find in rimmed steel.
What forms on the top of a killed steel ingot?
A cavity or “pipe”. This concave formation must me removed prior to rolling.
What is the process called when removing a cavity/ pipe from a killed steel ingot?
Cropping.
How is the shape of a semi-finished steel form changed?
It is changed in the forming process.
What are forming processes more commonly referred to as?
Hot and Cold rolling.
At what temperature is cold rolling/ working done?
Below the recrystallization temperature of the material. AKA it varies.
What is the physical difference between steel that has been cold rolled vs. steel that has been hot rolled?
Hot worked steel has slightly rounded edges.
Cold worked steel is more uniform and square with higher dimensional control and a high quality surface finish.
What is Galvanizing?
Galvanizing is the process of coating a piece of metal with zinc. Galvanizing produces a durable coating of zinc that is bonded to the steel.
What is the largest use of zinc?
Zinc is most used in the galvanizing process.
What is hot dipping?
Hot dipping is a galvanizing process that, as per the name, involves submerging the material in a bath of molten zinc.
What must be done prior to hot dipping?
Pickling and fluxing.
At what temperature is the molten zinc during the galvanizing process?
450° C
