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Line H: Metallurgy > Depth Questions Line H Exam > Flashcards

Depth Questions Line H Exam Flashcards

1
Q

What are the melting and freezing points of pure metal?

A

They are the same. Aka only pure metals have a temperature where they are equilibrium between a solid and liquid phase.

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2
Q

What are the melting and freezing points for alloys and mixture metals?

A

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,

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3
Q

In ferrous metals, what is the main ingredient?

A

Iron.

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4
Q

Common examples of non-ferrous metals are:

A

Copper, Nickel, Aluminum and Titanium

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5
Q

Common examples of ferrous metals are:

A

Cast iron, Carbon Steel, Alloy Steel, and Carbon Steel

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6
Q

The toughness of steels decreases as the temperature…

A

Decreases.

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7
Q

What term is used to describe the rate at which heat is conducted through material?

A

Thermal Conductivity.

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8
Q

Describe malleability.

A

The ability to deform under compressive forces without breakage.

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9
Q

Describe ductility.

A

The ability to deform and stretch without breakage under tension.

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10
Q

When performing a heat treatment, which provides a finer grain structure?

A

Normalizing.

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11
Q

When performing a heat treatment, which process does not refine the grain structure?

A

Stress relieving.

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12
Q

The process of strengthening a metal by changing its shape without the use of heat is called what?

A

Cold working.

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13
Q

What is elongation?

A

How much a workpiece can be pulled without fracturing.

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14
Q

Define the difference between elastic and plastic deformation.

A

Elastic deformation is where the material returns to its original shape once the stress is removed.

Plastic deformation is irreversible.

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15
Q

What is the difference between testing for elongation and testing for tensile strength?

A

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.

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16
Q

What is Yield Point?

A

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.)

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17
Q

What is Yield Strength?

A

Yield strength is the amount of force needed to reach the yield point.

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18
Q

What is UTS?

A

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.

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19
Q

How do you calculate UTS?

A

** 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.**

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20
Q

What is the CVN test?

A

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.

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21
Q

What’s the difference between strength and toughness?

A

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.

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22
Q

What is the melting point of steel?

A

1535 °C (2800 °F).

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23
Q

What is steel mainly an alloy of?

A

Carbon and iron.

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24
Q

How is pure iron made?

A

Pure iron is made by reducing the ore and removing impurities in a blast furnace.

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25
Q

What is pig iron?

A

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.

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26
Q

Can pig iron be used for anything as it is?

A

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.

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27
Q

How is cast iron made?

A

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.

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28
Q

Is white cast iron generally harder or softer than grey cast iron?

A

Harder. Although it is important to note white cast iron is extremely hard but also extremely brittle.

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29
Q

How is white cast iron made?

A

White cast iron is made by rapidly cooling it (faster than grey cast iron production).

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30
Q

Describe cementite in reference to white cast iron.

A

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.

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31
Q

Can white cast iron be machined and/or welded?

A

No. Due to the cementite’s wear resistance, welding or machining white cast iron is a no go.

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32
Q

What is white cast iron used for?

A

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.

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33
Q

Why is white cast iron important?

A

White cast iron is the origin of malleable cast iron.

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34
Q

What are the three classes of steel (based on their level of deoxidation).

A

Rimmed
Semi-Killed
Killed

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35
Q

What level of deoxidation is killed steel?

A

Killed steel is fully deoxidized.

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36
Q

What elements are used to refine killed steel?

A

Normally with silicon and aluminum.

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37
Q

Is there gas formation in killed steel? Does this gas compensate for shrinkage?

A

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.

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38
Q

What forms on the top of a killed steel ingot?

A

A cavity or “pipe”. This concave formation must me removed prior to rolling.

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39
Q

What is the process called when removing a cavity/ pipe from a killed steel ingot?

A

Cropping.

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40
Q

How is the shape of a semi-finished steel form changed?

A

It is changed in the forming process.

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41
Q

What are forming processes more commonly referred to as?

A

Hot and Cold rolling.

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42
Q

At what temperature is cold rolling/ working done?

A

Below the recrystallization temperature of the material. AKA it varies.

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43
Q

What is the physical difference between steel that has been cold rolled vs. steel that has been hot rolled?

A

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.

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44
Q

What is Galvanizing?

A

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.

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45
Q

What is the largest use of zinc?

A

Zinc is most used in the galvanizing process.

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46
Q

What is hot dipping?

A

Hot dipping is a galvanizing process that, as per the name, involves submerging the material in a bath of molten zinc.

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47
Q

What must be done prior to hot dipping?

A

Pickling and fluxing.

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48
Q

At what temperature is the molten zinc during the galvanizing process?

A

450° C

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49
Q

How are galvanized sheets and strips’ corrosion resistance improved?

A

They are often painted to improve corrosion resistance as well as the aesthetic of the piece.

50
Q

What happens if you weld directly onto galvanized steel?

A

The creation of zinc oxide fumes.

51
Q

What characteristic should the filler metal used during the welding process share with galvanized steel?

A

Filler metal should have galvanizing qualities similar to those of the base metal, as well as be low in silicon.

52
Q

What are structural shapes and bars referred to as?

A

Raw or plain material.

53
Q

How are bars produced?

A

The desired shape of such are made by passing blooms and billets through hot rolls reducing their cross section.

Some shape bars are circular, square or rectangular, hexagonal, and pentagonal.

54
Q

How are structural shapes (excluding bars) produced?

A

Structural shapes are made by passing hot blooms through a series of grooved mill rolls.

Some structural shapes produced are W, S, tee, channel, and angle.

55
Q

What does it mean when material is labelled “carbon steel”?

A

Carbon steels or plain carbon steels have carbon as the sole alloying element.

56
Q

What are the three classifications carbon steel can be under?

A

Low
Medium
High

57
Q

What is the carbon content of low carbon steel?

A

0.5-0.15%

58
Q

What is the carbon content of medium carbon steel?

A

0.15-0.30%

59
Q

What is the carbon content of high-carbon steel?

A

0.50-0.80%
and
0.80-1.0%

60
Q

What happens when the carbon in steel is increased?

A

The hardenability is also increased. Although after a certain point, too much carbon makes the steel become extremely brittle.

61
Q

What happens when very little carbon is in steel during the welding process?

A

The cooling rate is not quick enough to harden the steel.

62
Q

How can hardening (the mostly unwanted after affect of welding on medium-high carbon steels) be prevented?

A

By pre and/ or post heat treatment. This allows the process to cool at a more controlled rate.

63
Q
A
64
Q

In the CSA G40.21, what does type W indicate?

A

Weldable steel. For general welded construction where low temperature toughness isn’t a huge concern.

65
Q

In the CSA G40.21, what does type WT indicate?

A

Weldable steel. For welded construction where good low temperature toughness is a prime consideration.

66
Q

In the CSA G40.21, what does type R indicate?

A

Atmospheric corrosion-resistant structural steel. For welded construction where low temperature toughness isn’t a huge concern.

67
Q

In the CSA G40.21, what does type A indicate?

A

Atmospheric corrosion-resistant structural steel. For welded construction; low temperature toughness isn’t a prime consideration.

68
Q

In the CSA G40.21, what does type AT indicate?

A

Atmospheric corrosion-resistant weldable notch tough steel. For welded construction; low temperature toughness is a consideration. Toughness category must be specified.

69
Q

In the CSA G40.21, what does type Q indicate?

A

Quenched and tempered low alloy plate. High yield strength steels. Welding procedure is critical if the properties of the plate are not adversely affected.

70
Q

In the CSA G40.21, what does type QT indicate?

A

Quenched and tempered low alloy notch tough steel plate. Toughness category must be specified. Welding procedure is critical if the properties of the plate are not adversely affected.

71
Q

Describe SA-36

Type or Grade:
UTS no.:
Minimum Specified Tensile ksi (MPa):
Welding P. no.:
Group no.:
ISO 25608.:
Nominal Composition:
Product form:

A

Type or Grade: N/A
Ultimate Tensile Strength: K02600
Minimum Specified Tensile ksi (MPa): 58 (400)
Welding P. no.: 1
Group no.: 1
ISO 25608.: 11.1
Nominal Composition: C-Mn-Si
Product form: Plate, bar, and shapes.

72
Q

What section of the ASME Code has been adopted?

A

The “P” number grouping system for welding procedure qualifications. This basically means a bunch of steels are now classified under one group. One qualified procedure on one steel is valid for all the steels in the same group.

73
Q

What does ASME code mean?

A

American Society of Mechanical Engineers Boil and Pressure Vessel code.
This code covers the design and construction of boilers and pressure vessels.

74
Q

How many sections are in the ASME code?

A

11, which is broken into two parts.

75
Q

How many parts are in the section of the ASME code? What is specified in such?

A

The second section is broken into four parts.

Here specifications on ferrous and non ferrous materials, welding rods, electrodes and other filler metals, and material properties permitted.

76
Q

Are the steel designations in the ASME code the same for ASTM the same?

A

Yes, but with minor differences.

77
Q

What percentage of chromium is in stainless steel?

A

Over 10%

78
Q

What does chromium do in stainless steel?

A

Chromium provides corrosion protection by forming a thin layer of chromium oxide on the surface.

79
Q

What is a cool feature about the chromium oxide corrosion resistant layer on stainless steel?

A

If the metal surface is scratched or machined, the chromium will reform to fill the exposed gap.

80
Q

Are all stainless steels 100% corrosion resistant?

A

No. Although chromium oxide helps be a barrier for that issue, some environments do not work in favour for the chromium oxide.

Because the corrosion resistant needs oxygen to reform/ form, some environments that lack said oxygen will cause corrosion to occur anyways.

81
Q

What is stainless steel made up of?

A

Iron and chromium.

82
Q

What is a common method of testing hardness?

A

Scratch and file tests.

83
Q

How is scratch method used?

A

The scratch method can be done with a fingernail, knife, or file. The ease at which the material is scratched gives a rough indication of its hardness.

84
Q

Can you use any file for a file test?

A

No. A machinist’s hand file should be used solely for the testing purpose.

85
Q

Aside from Rockwell and Brinell hardness tests, what would that be called?

A

Indentation test.

86
Q

What is Rockwell?

A

Depth of penetration of an indenter under a large load compared to the penetration made by a preload.

B tests for softer materials
C for harder materials

87
Q

What is Brinell?

A

A ball is pushed into the metal, the Brinell number is calculated through a table.

88
Q

How does low carbon steel react with a file?

A

Easily bites into it.

100 on Brinell hardness.

65 on Rockwell B
16 on Rockwell C

89
Q

How does medium carbon steel react to a file?

A

Bites into it with pressure.

212 on Brinell hardness.

90
Q

How does high-carbon steel and high alloy steel react to a file?

A

Bites into it with difficulty.

294 on Brinell hardness

31 on Rockwell C

91
Q

What is used to carry out a melting point test?

A

A Templistik™ or a pyrometer is used.

92
Q

How do you determine the melting point of metal?

A

Firstly looking at a provided chart, melting will happen at different speeds and temperatures.

ie. Aluminum melts faster than carbon steel.

93
Q

How does one limit the trials needed to find the melting point of metal?

A

By using a Templistik™ that has a temperature just below the melting point of the metal being observed.

94
Q

How does finding the melting point on a Templistik™ work?

A

The Templistik™ is marked just below the melting point, found on chart, then it is heated. If the mark changes just before the metal melts, the melting point is what was suspected from the provided chart.

95
Q

What is weldability?

A

Weldability is the capacity of a material to be welded under given fabrication conditions to perform satisfactorily in the intended service.

96
Q

All cast irons are weldable except for…?

A

White cast iron.

97
Q

What temperature should all materials be brought up to to remove moisture, hydrogen pick up?

A

21°C

98
Q

Read Aluminum pg 68

A
99
Q

Read Stainless Steel pg 68.

A
100
Q

What is the relation of normalizing to annealing.

A

Normalizing is very similar to Annealing but provides a harder structure.

101
Q

Describe Quenching and Tempering.

A

These are processes to produce a hard structure that has adequate toughness and ductility.

Quenching gives high hardness but poor toughness
Tempering restores toughness while keeping some hardness and strength.

102
Q

At what temperature is stress relieving carried out at?

A

625-650°. The entire weld area is held at this temperature for generally 1 hour per inch of thickness.

103
Q

When is thermal stress relieving usually avoided? What happens if one was to do it anyways?

A

Thermal stress relieving is usually avoided on materials that have been quenched and tempered. Although if still done the temperature must not exceed tempering temperature.

104
Q

What is Aluminums density/ cubic metre (or cubic inch)

A

2,700kg/cubic metre (0.1lb/cubic inch)

105
Q

How are mechanical properties (using aluminum) produced?

A

Alloying, heat treating, or combination.

106
Q

Aluminum’s weight is approximately what fraction of steels?

A

Aluminum’s weight is approximately 1/3 that of steel.

107
Q

What is the melting range of the oxide film of aluminum compared to the aluminum itself?

A

Approximately 3 times higher.

108
Q

Approximately how much greater is the thermal and electrical conductivity of aluminum compared to steel?

A

Approximately 4 times greater than steel.

109
Q

Due to aluminum having higher thermal conductivity, higher heat inputs are needed for fusion welding. What should be done prior to welding thicker aluminum material?

A

Preheating. This is to compensate for the heat input required for welding.

110
Q

Is it true most stainless steels can be readily welded?

A

Yes. But only if the correct welding consumables and procedures are used.

111
Q

What polarity is best used for stainless steel electrodes?

A

Reverse polarity. (Electrode positive), some may also be welded with AC.

112
Q

What is the melting temperature and thermal conductivity of the austenitic stainless steels compared to carbon steels.

A

The melting temperature and thermal conductivity is much lower, making it easier to melt during welding.

113
Q

How much heat is required to make the same size weld on stainless steel compared to carbon steel?

A

Less heat is required to make the same size weld. Lower thermal conductivity leads to greater concentration of heat during welding.

114
Q

What is a downside to welding in stainless steel.

A

Thermal expansion is 50% greater than compared to carbon steel, meaning risk of distortion is much greater.

Carbide precipitation.

115
Q

What is the main problem during welding of austenitic stainless steels?

A

Carbide precipitation.

116
Q

How is carbide precipitation handled?

A

Highly oxidizable elements are frequently used. These elements are known as stabilizers.

117
Q

What is the tolerance to oxygen of stainless steel welding compared to carbon steel welding?

A

Stainless steel welding is less tolerant to oxygen than carbon steel welding.

118
Q

What can occur when oxygen is available while welding chromium?

A

Chromium oxide is formed. This oxide isn’t fluxed out easily and can cause defects in the weld.

119
Q

Is chromium oxide (refractory oxide) a liquid when exposed to oxygen during the welding process?

A

No. Unlike iron oxide, chromium oxide is not liquid at the temperature of the weld pool.

120
Q

How is chromium oxide countered?

A

Shielding is required in the reverse side to prevent contamination.

ie root run on a pipe weld.

Line H: Metallurgy (2 decks)

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