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Metals Tech > Volume 4 > Flashcards

Volume 4 Flashcards

1
Q

What does the number 75 mean in SAE 1075?

A

0.75 percent carbon content.

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2
Q

Break down and explain the meaning for the digits in SAE number 9235.

A

9 = silicon-manganese. 2 = 2 percent silicon-manganese 35 = 0.35 percent carbon (C).

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3
Q

Explain the metal designation of number AA 4024.

A

4 = main alloy of silicon. 0 = no major modifications. 24 = specific series within the 4 series.

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4
Q

What type of aluminum is identified by AA number 1100, and what is the percentage of aluminum?

A

Pure aluminum. 99.00 percent.

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5
Q

Why was the unified numbering system developed?

A

To find a single classification sustem.

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6
Q

How many digits are there in the UNS?

A

Five.

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7
Q

How does the UNS group metals?

A

Into 18 families.

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8
Q

What does the UNS not do?

A

The UNS does not establish a requirement for things such as form, condition, property, or quality.

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9
Q

When performing a chemical analyis on a metal, what are you trying to determine?

A

Identity and percentage of the elements that make up the metal.

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10
Q

Why can’t pure metals be hardened by heat treatment?

A

Their structure changes very little when they are heated.

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11
Q

Define ferrous.

A

A metal that contains iron as its main alloying element.

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12
Q

Define nonferrus.

A

A metal that does not contain iron as its main alloying element.

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13
Q

Is bronze ferrous or nonferrous?

A

Nonferrous.

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14
Q

Is copper ferrous or nonferrous?

A

Nonferrous.

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15
Q

Is gray cast iron ferrous or nonferrous?

A

Ferrous.

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16
Q

Is chrome-molybdenum steels ferrous or nonferrous?

A

Ferrous.

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17
Q

Is carbon steel ferrous or nonferrous?

A

Ferrous.

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18
Q

Is magnesium ferrous or nonferrous?

A

Nonferrous.

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19
Q

Is brass ferrous or nonferrous?

A

Nonferrous

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20
Q

To what does the term “alloy steel” refer?

A

A ferrous metal that cantains a main alloying element other than carbon or iron.

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21
Q

Why are mechanical properties important to metals technologists?

A

Becuase these are the properties that we have some control over. They can be changed by cold working and heat treating.

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22
Q

What determines the mechanical properties of a metal? How is it changed?

A

They are detemined by the type of grain structure that is present in a metal. By controlled heating and cooling (heat treating).

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23
Q

What is the differance between a mechanical mixture and a solid solution?

A

In a mechanical mixture, the components are clearly visible; in a solid solution, they are not.

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24
Q

Define Brittleness.

A

Tendency to fracture or break with little deformation, bending, or twisting.

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25
Q

Define Ductility.

A

Ability to be elongated without breaking.

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26
Q

Define Hardness.

A

Resistance to deformation or penetration.

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27
Q

Define Shear strength.

A

Resistance to a cutting force.

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28
Q

Define Strain.

A

604

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29
Q

Define Stress.

A

This is the force (or pressure) which tends to shear, compress, or pull a metal apart, depending on the direction and nature of the applied load. Stress that causes a metal to be stretched is called tensile stress. Stress that causes a metal to compact is called compressive stress. Stress that causes a metal to divide into layers is called shear stress. Flexing, or bending, is an example of a combination of tensile and compressive stresses. Torsion, or twisting, is an example of shear stress

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30
Q

Define Tensile strength.

A

Resistance to being pulled apart by a slowly applied force. Resistance to stretching.

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31
Q

Define Toughness.

A

Resist repeated blows without breaking.

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32
Q

Define Wear resistance.

A

Ability to resist abrasive action.

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33
Q

When hardness increases, what happens to the other mechanical properties?

A

Generally, as hardness increases, it affects tensile strength, shear strength, wear resistance, and brittleness. Toughness increases with hardness up to a point.

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34
Q

What is a casting?

A

A product formed by pouring molten metal into a mold.

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35
Q

What is a wrought product? How does it differ from a casting?

A

A product that is formed while in a solid state.

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36
Q

What are the methods of shaping?

A

Rolling, forging, drawing, extruding, and piercing.

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37
Q

Tendency to fracture or break with little deformation, bending, or twisting.

A

Brittleness.

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38
Q

Ability to be elongated without breaking.

A

Ductility.

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39
Q

Ability to resist abrasive action.

A

Wear resistance.

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40
Q

Resistance to deformation or penetration.

A

Hardness.

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41
Q

Resist repeated blows without breaking.

A

Toughness.

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42
Q

Resistance to being pulled apart by a slowly applied force.

A

Tensile strength.

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43
Q

Resistance to a cutting force.

A

Shear Strength.

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44
Q

Resistance to stretching.

A

Tensile strength.

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45
Q

What is the best way to identify metals when using spark testing?

A

Compare an unknown material with a known sample.

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46
Q

How do you perform a spark test?

A

Hold a piece of metal against a grinding wheel.

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47
Q

Why is tensile testing done?

A

To determine yield strength, yield point, shear strength, and elastic limit.

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48
Q

What is the relationship between shear strength and tensile strength?

A

Shear strength is approximately 60 percent of tensile strength.

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49
Q

Why is hardness testing done?

A

To determine approximate tensile strength value, the results of heat treatment, and the condition of the metal before heat treatment.

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50
Q

What is the minor load of the Rockwell tester?

A

10 kg.

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51
Q

How is hardness determined by the Rockwell tester?

A

By measuring the difference in depth penetration between minor load and major load penetration.

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52
Q

Of what materials are penetrators made?

A

Diamond (Brale) penetrator or a hardened steel ball penetrator.

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53
Q

How is metal prepared for testing on the Rockwell hardness tester?

A

The metal must be smooth and level, and free from burrs and roughness.

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54
Q

Can round stock be tested on a Rockwell tester? Explain.

A

Yes. Grind a small, flat surface and use a crotch-type anvil.

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55
Q

What scale produces the highest hardness readings?

A

C-scale.

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56
Q

What must you do if you find a chipped Brale penetrator?

A

Replace the penetrator.

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57
Q

What is used to check the accuracy of the hardness tester?

A

The test blocks.

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58
Q

How do you prevent damage to the Brale or steel ball penetrators?

A

By always ensuring the protective cap is on the penetrator before changing the anvil or performing maintenance on the machine.

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59
Q

What does the passivation process remove?

A

Free iron contamination on the surface of the stainless steel.

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60
Q

What can particles of iron or tool steel and abrasive particles do if left on the surface?

A

Cause corrosion.

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61
Q

Which passivation solution is the overwhelming choice of users?

A

Nitric-acid-based solution.

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62
Q

What is the most commonly specified verification test and how can you tell if the process was successful?

A

Copper sulfate test, visually examine, any copper (pink) color indicates the presence of free iron and the test is considered unacceptable.

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63
Q

Why do regulators recognize the relative safety of citric acid formulations?

A

It is biodegradable and rinse waters can go to the drain if they meet local pH regulations.

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64
Q

Which type of peening is convenient for small areas where corrosion rework has been accomplished?

A

Roto peening.

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65
Q

What tools are required for rotary peening?

A

A pneumatic drill or high speed grinder; a flap wheel; an air regulator for the drill or grinder; a tachometer; an Almen gauge and Almen test strips.

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66
Q

What is essential to achieve the required peening intensity?

A

The flap wheel must be operated at the required speed under load and the proper flap deflection maintained throughout the peening process.

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67
Q

How can you keep the flaps from tearing when they drop over the edge of the part?

A

Use a hard rubber material clamped in place at the edges of the part being peened.

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68
Q

When visually inspecting a peened area with a 10X power magnifier, how can you tell if complete coverage and saturation have been accomplished?

A

Every portion of the critical surface will show visible evidence of plastic flow to demonstrate complete coverage and saturation which is indicated by the complete obliteration of the original surface finish and overlapping peening impressions.

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69
Q

What is an advantage of brush-plating and why?

A

The equipment is mobile and the work can be done locally in the workshop mostly without disassembling the part to be repaired.

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70
Q

From what are anodes usually made?

A

They are usually made from a material inert to the plating solution such as graphite, stainless steel and 90 percent platinum/10percent iridium.

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71
Q

What is the difference between selective plating deposits and tank electroplated deposits of the same thickness? What is a result of this?

A

Most selective plating deposits are significantly harder and less porous. Wear and corrosion resistance are greatly increased.

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72
Q

What personal safety equipment should be used when using solutions?

A

Eye safety glasses or goggles, rubber or nitrile gloves, and a rubber apron if necessary.

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73
Q

What is the purpose of circulating the air in a furnace?

A

To circulate air around the part, maintain an even temperature on the part, maintain accurate temperature control.

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74
Q

Which type of furnace can be used for the higher temperatures?

A

Still air.

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75
Q

Name the types of atmospheres that can be found in heat-treating furnaces.

A

Reactive, inert, carburizing, or vacuum.

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76
Q

Why would you use a furnace with a reactive atmosphere?

A

Because it is economical to use.

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77
Q

What type of metals requires an inert atmosphere for heat treating to prevent contamination?

A

Reactive metals.

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78
Q

What is the main purpose of the hearth plate?

A

To protect the heating elements underneath it.

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79
Q

Why would you place your workpiece on a grid rack, and not directly on the hearth plate, when you are heat treating?

A

To enable even heating and prevent overheating of the parts.

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80
Q

Why are fire bricks used?

A

To line the inside of the furnace and act as insulation.

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81
Q

What should you do if you find broken firebricks during your inspection?

A

Replace them.

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82
Q

Why must new firebricks be dried out under controlled conditions?

A

To prevent cracking and chipping.

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83
Q

What must you look for when inspecting the furnace extension leads?

A

Shorts.

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84
Q

Who performs calibration on an electronic pyrometer?

A

PMEL.

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85
Q

What is your main source document when performing heat treatment operations?

A

TO 1–1A–9.

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86
Q

What could happen if one part of the metal is heated more rapidly than another?

A

Uneven expansion occurs, which causes distortion or cracking.

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87
Q

When is a preheat recommended?

A

When heating parts above 1300F.

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88
Q

What determines the soak time when heat treating?

A

The type of metal and the part thickness.

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89
Q

What item must accompany all newly fabricated parts when they are being heat treated?

A

A coupon.

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90
Q

List the different types of quenchants.

A

Brine (salt water), water, oil, still air, and the furnace.

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91
Q

Name the four common heat treatment operations performed on carbon and alloy steel.

A

Annealing, normalizing, hardening, and tempering.

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92
Q

Why might you anneal a piece of metal?

A

To enable forming operations or to remove internal stresses.

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93
Q

Why is normalizing recommended before hardening?

A

Normalizing before hardening assures the best results when hardening, provided the hardening operation is performed correctly.

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94
Q

Describe the normalizing process.

A

It is achieved by heating metal to a temperature above its upper critical point, soaking at that temperature, and cooling to room temperature in still air.

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95
Q

What must carbon and alloy steels contain in order for them to be hardenable by heat treatment?

A

Carbon.

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96
Q

What happens when the carbon content goes above .80 percent?

A

There is no increased hardenability beyond that point.

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97
Q

The soak time for hardening is based on what?

A

The part thickness.

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98
Q

What are the two main reasons for tempering?

A

To reduce brittleness that results from the hardening process and (2) to allow you to meet a specific hardness specification.

99
Q

Into how many groups are stainless steels divided? What are they?

A

Four. Ferritic, austenitic, martensitic, and precipitation hardening.

100
Q

What is the only heat treatment process applied to ferritic stainless steels?

A

Annealing.

101
Q

How are austenitic stainless steels hardened?

A

By cold working.

102
Q

If you want to achieve maximum hardness when heat treating martensitic stainless steels, what is the determining factor? What does the process closely resemble?

A

The carbon content. It is the same as for plain carbon and low alloy steels.

103
Q

What is one of the more important alloying elements added to aluminum?

A

Copper.

104
Q

What happens as the copper content increases?

A

The ability to harden the aluminum increases.

105
Q

What do the different temper identifiers indicate?

A

What processes have taken place to the aluminum alloy.

106
Q

What process has taken place with AA2024-T6?

A

Solution heat treated and then artificially aged.

107
Q

What are the three main heat-treating processes you can perform with aluminum alloys?

A

Annealing, solution heat treating, and precipitation hardening.

108
Q

When putting aluminum through a severe cold working process what should you do? Why?

A

Do it in steps and anneal it after each step to remove the stresses of the previous cold-working operation.

109
Q

Describe the annealing process for most aluminum alloys.

A

Soak it for at least one hour, within the temperature range of 750 to 800F. Cool the furnace load at 50F per hour, until it reaches 500F.

110
Q

Successful solution heat treatment of aluminum alloys depends on what?

A

Putting the copper into a solid solution and trapping it there by quenching.

111
Q

What happens to solution heat treated aluminum when it is naturally aged? How long does it take?

A

It will reach a temper of –T4. Approximately 96 hours at room temperature.

112
Q

How can you stop natural aging from occurring?

A

Put the part in a freezer.

113
Q

How is artificial aging accomplished?

A

Artificial aging consists of heating the alloy to an elevated temperature, soaking the metal until precipitation is complete, and then cooling it in air.

114
Q

What causes blistering when heat treating aluminum alloys?

A

Overheating.

115
Q

What effect, if any, does oversoaking have on aluminum alloys?

A

It ruins the corrosion resistance of clad products.

116
Q

Name two things to which nickel alloys are resistant?

A

Highly heat and corrosion resistant.

117
Q

What effect does the addition of alloying elements have on nickel alloys?

A

Corrosion resistance, hardness, tensile strength, yield strength, and notch toughness (resistance to cracking) increase.

118
Q

What determines the soaking period for annealing nickel-base alloys?

A

The chemical composition.

119
Q

How is age hardening accomplished with nickel-base alloys?

A

By holding the alloy at temperatures between 900 and 1600F and then furnace or air cool.

120
Q

List the three basic procedures for heat treating titanium alloys.

A

(1) Stress relieving, (2) annealing, and (3) solution treating, quenching, and aging.

121
Q

Why are titanium alloys stress-relieved?

A

To remove residual stress developed during fabrication.

122
Q

How are strength and ductility produced when you are heat treating titanium alloys?

A

By solution treating, quenching, and aging.

123
Q

What happens if the rate of cooling is too slow when quenching titanium alloys?

A

There is a loss of strength.

124
Q

When is solution heat treatment of beryllium-copper necessary?

A

When the material has been subject to welding, brazing, or a fabricating process that makes it unsuitable for age hardening.

125
Q

What does age hardening do to beryllium-copper?

A

It develops the mechanical properties that are desired in beryllium-copper alloys.

126
Q

At what pressure does free acetylene become explosive?

A

29.4 psi.

127
Q

Why should you store acetylene cylinders upright?

A

To keep the acetone from escaping.

128
Q

At what pressure is an acetylene cylinder considered empty?

A

When the cylinder has 4 cu. ft. of gas remaining.

129
Q

What safety features prevent you from accidentally cross-installing an O2 regulator on an acetylene cylinder?

A

Left hand threads and a female fitting.

130
Q

Why must you handle O2 cylinders carefully?

A

O2 is under great pressure, and if a valve is broken or the cylinder is pierced, the cylinder could become a projectile.

131
Q

Where are full acetylene cylinders stored?

A

In a cool, dry, well ventilated building; separated from empty cylinders; and separated from O2 cylinders.

132
Q

What must you do to a cylinder after it has been emptied?

A

Replace the safety cap, mark the cylinder MT, and secure it in the area with other empty cylinders.

133
Q

Which side of the two-stage regulator reduces cylinder pressure to intermediate pressure?

A

High pressure.

134
Q

What’s a check valve? What’s a flashback arrestor?

A

Valves to keep the gases flowing in one direction; are installed on the acetylene line and prevent a flashback from burning through the gas line and into the cylinder

135
Q

How can you distinguish an O2 hose connection from an acetylene hose connection?

A

The torch hoses have different colors and the O2 connection has right-hand threads. The acetylene connection has left-hand threads and it has a groove machined on the wrenching surface.

136
Q

Where do gases combine in the oxyacetylene torch?

A

Mixing chamber.

137
Q

What are the two main advantages of using an equal-pressure torch?

A

(1) The flame is easy to adjust. (2) Has a low susceptibility to flashbacks.

138
Q

Why should you crack cylinder valves before you connect the regulators?

A

To blow out any dirt that may be lodged in the outlet.

139
Q

How much do you open each cylinder valve after you install the regulators?

A

Open acetylene valves no more than 1½ turns, and open the O2 valves fully.

140
Q

When lighting the torch, which torch valve do you open first?

A

Acetylene.

141
Q

How should you hold the striker to protect yourself from burns when you light the torch?

A

Keep your hand at one side of the tip.

142
Q

How should you hold the torch when you light it?

A

So the flame is directed away from anything flammable, the cylinders, the hoses, and yourself.

143
Q

How can you recognize a carburizing flame?

A

The presence of three distinct flame cones.

144
Q

What’s the temperature of a carburizing flame?

A

Approximately 5,700°F.

145
Q

Compare the gas volume of an oxidizing flame to that of a neutral flame.

A

The gas volume is one-to-one for a neutral flame, and slightly more than 1 volume of O2 to 1 volume of acetylene in an oxidizing flame.

146
Q

Give the type and temperature of the hottest welding flame.

A

Oxidizing; 6,300F.

147
Q

During emergency equipment shutdown, which valve must you close first? Why?

A

Acetylene; so you extinguish the flame because the O2 won’t burn without the acetylene.

148
Q

What’s the first thing to do when disassembling a welding set?

A

Ensure the gas supply is shut off.

149
Q

What should you do to the cylinder after you disconnect the regulator?

A

Replace the cylinder valve safety cap.

150
Q

What equipment do you use for testing a welding set for leaks?

A

A jar of soapy water and a brush.

151
Q

How do you test the hoses?

A

Submerge them in a bucket of clear water and watch for bubbles.

152
Q

How can you detect a “creeping” regulator?

A

You’ll see a gradual rise in the working pressure gage after the cylinder valve is opened.

153
Q

If a #1 tip is smaller than a #2 tip, which tip cleaner should you use to clean the #2 tip? Why?

A

1 tip cleaner; to keep from enlarging the orifice.

154
Q

Why should you use a straight back-and-forth movement when cleaning a tip?

A

To keep from enlarging the orifice.

155
Q

How can you remove accumulated slag on the face of an oxyacetylene cutting tip?

A

Open the O2 valve and clean the tip with a file wrapped in an emery cloth.

156
Q

At what temperature do you silver solder to create a bond between the base metal and the filler material?

A

Between 1,175 and 1,600F.

157
Q

What determines the strength of a soldered joint?

A

Joint fit-up and the quality of the bond between the filler metal and the base metal.

158
Q

What type of bond forms when you silver solder a joint?

A

Mechanical bond.

159
Q

List the reasons for using flux for silver soldering.

A

It reacts chemically with surface films, such as oxides, reducing them and cleaning the metal surfaces to receive the molten silver alloy; it forms a protective film during the soldering cycle, protecting the material from oxidation at the elevated temperatures required for soldering; and it helps the silver alloy flow freely.

160
Q

What’s the recommended joint clearance for silver soldering?

A

Between 0.002” and 0.005”.

161
Q

Why is it necessary to completely clean the metal surface and filler rod when silver soldering?

A

To ensure uniform capillary attraction throughout the joint.

162
Q

What type of flame do you use for silver soldering?

A

Neutral to slightly carburizing flame.

163
Q

How does a cutting torch work?

A

It mixes O2 and acetylene in definite proportions; burns the mixture in a preheating flame, which preheats the work; and then it directs a jet of high pressure O2 to cut the metal.

164
Q

What are the prime disadvantages of using a cutting attachment?

A

It’s recommended for intermittent use, not continuous use, and for cutting materials ½” thick or less.

165
Q

What’s the purpose of the outer orifices on a cutting tip?

A

Preheating.

166
Q

How does the high-pressure O2 stream affect the red-hot metal?

A

It combines with the hot metal to burn it to an oxide.

167
Q

What’s the term for the space in the metal that results from cutting?

A

The kerf.

168
Q

What must you do to high C tool steels to cut them properly with oxyacetylene?

A

You must preheat the entire section you’re going to cut.

169
Q

How should you adjust the flame for cutting?

A

Adjust the preheating flame to neutral using the torch needle valves; then open the cutting O2 valve and adjust the flame to neutral again.

170
Q

List the two processes you can use to cut Cr and stainless steel.

A

(1) Torch oscillation. (2) Waste plate.

171
Q

List four safe cutting practices.

A

Any four of the following: (1) Never dismantle or salvage Mg parts with an oxyacetylene cutting torch. (2) Never cut used drums, barrels, tanks, or other close container containers unless they’ve been cleaned and properly vented. Ensure all plugs, caps, and bungs have been removed before you cut. Cut cleaned drums, barrels, tanks, and so forth, as soon as possible after they’ve been cleaned. This lessens the possibility of fumes building up. (3) Never cut material in a position that permits sparks, hot metal, or the severed section to fall on the cylinder and hose, or on your legs or feet. (4) Move combustible materials to a safe location at least 25 feet away from the work area. Set up guards to protect shop personnel and equipment. (5) Always wear proper clothing, boots, gloves, and face-shield. (6) When you stop cutting for short periods, release the regulator adjusting screw; close the complete set down when you leave the job.

172
Q

When straight-line cutting, what should you use for making long cuts?

A

A guide bar.

173
Q

Explain how to pierce a piece of metal.

A

Preheat the metal, raise the torch about ½” above the normal position for cutting, and slowly add cutting O2.

174
Q

What does PAC use to cut metal?

A

Ionized gases at high pressures to melt and cut away the molten metal.

175
Q

What type of PAC torches are available?

A

Gas-cooled and water-cooled styles.

176
Q

What type of gasses are required for cutting nonferrous metals?

A

Inert gasses.

177
Q

Name four advantages of PAC.

A

Any four of the following: (1) Cuts at high production rates (up to 300 IPM). (2) Cuts ferrous and nonferrous material. (3) Produces ready-to-weld cuts without grinding preparation. (4) Makes slag free cuts on C steels, stainless steels, nickel, monel, cast iron and steel, clad materials, Cu, Al, Mg, and titanium. (5) Makes clean cuts on workpieces up to 5” thick.
(6) Cuts with a small HAZ, which reduces distortion and warpage.

178
Q

What is the correct torch height when cutting?

A

Approximately ⅛” to ¼” above the parent material.

179
Q

What color is steel when it has reached its upper forging limit?

A

Lemon.

180
Q

At what temperature do you strike the final forging blows?

A

1300 °F.

181
Q

Define drawing.

A

Working a piece of material to increase its length, increase its width, or decrease its cross section.

182
Q

What steps do you take to draw round stock to increase the length?

A

Square, octagonal, and then round again.

183
Q

When you stress relieve a workpiece, how much of the material cross section should you heat?

A

The entire cross section.

184
Q

What color should appear on the steel chisel before you perform the final quench?

A

Blue.

185
Q

What is weldability?

A

The capacity of a metal to be welded together and its performance after being welded.

186
Q

What four items contribute to material weldability?

A

(1) Joint design. (2) Welding process. (3) Chemical, physical, and mechanical properties of the base metal. (4) Properties of the filler metal.

187
Q

When you’re determining which welding process you’re going to use, what items should you consider?

A

Base metal, type of weld, material composition, and weld position.

188
Q

What’s the minimum C content that steel must possess to require preheat treatment and postheat treatment?

A

0.55 percent.

189
Q

What are some drawbacks to welding superalloys?

A

Lower strength of fusion welded joints can limit long-term weld performance; cleanliness of the base and filler metals can affect weldability; and S and lead, when introduced into the heated metal, cause severe cracking.

190
Q

Which aluminum groups are predominately not weldable? What are the exceptions in these groups?

A

The 2XXX and 7XXX groups. 2219, 2519, 7003, 7005, and 7039.

191
Q

Which aluminum group is prone to cracking but can be readily welded with the proper technique?

A

6XXX

192
Q

How do Zn and Al affect the weldability of Mg alloys?

A

Alloys with 1 percent Zn or more tend to crack; alloys with up to 10 percent Al weld easily and won’t crack.

193
Q

What determines if titanium is titanium “unalloyed”? In what condition should you weld unalloyed titanium? How can you increase its strength after welding?

A

If the titanium is at least 98.5 percent pure; annealed condition; cold work it.

194
Q

What is the HAZ in a metal?

A

The portion of the base metal that doesn’t melt, but has its mechanical properties altered by the welding heat.

195
Q

What does recrystallization in the HAZ affect?

A

Metal’s grain size, tensile strength, hardness, ductility, and corrosion resistance.

196
Q

What five factors dictate the size of the HAZ?

A

(1) Metal type. (2) Metal T. (3) Joint type. (4) Welding process and technique. (5) Quantity of heat.

197
Q

What causes hot tearing?

A

When metal is weak and has limited plasticity at high temperatures.

198
Q

How can you control hot tearing?

A

Preheat; control temperature between weld passes; and weld with as little strain as possible on the joint.

199
Q

What causes cold cracking?

A

Occurs when hydrogen dissolves in the weld.

200
Q

What increases a metal’s susceptibility to underbead cracking?

A

Increased CE.

201
Q

What’s porosity?

A

The cavities and holes in the weld caused by trapped gases.

202
Q

What are the main causes of incomplete fusion?

A

Inadequate heat and oxides or foreign materials trapped in the weld.

203
Q

What are the most common causes of incomplete penetration?

A

Not enough heat at the root of the material, poor joint preparation, and improper cleaning.

204
Q

What causes undercutting?

A

Incorrect torch and electrode angles.

205
Q

What’s thermal expansion? Thermal conductivity?

A

The rate at which a metal expands when it’s heated; the speed at which a metal heats.

206
Q

Describe backstepping.

A

Start a given distance from the end of the weld, and weld to the end. After cooling the joint, step back a given distance and weld to the beginning of the previous starting point.

207
Q

How can you increase speed to reduce distortion and residual stresses?

A

Ensure the joint fits up tightly; use smaller electrode and lower heat output during multipass welding; and weld in the flat position.

208
Q

Define Fusion zone.

A

The area of weld metal that has penetrated beyond the surface of the base metal.

209
Q

Define Root.

A

The portion of the weld metal deposited at the bottom of the joint.

210
Q

Define Leg.

A

The dimension of the weld extending on each side of the root of the joint.

211
Q

Define Face.

A

The outer surface of the weld reinforcement.

212
Q

Define Toes.

A

The edges of the weld face.

213
Q

Define Penetration.

A

The distance from the original surface of the base metal to the point at which fusion ceases.

214
Q

Define Throat.

A

The distance through the center of the weld from the root to the face.

215
Q

What’s the minimum required penetration for a groove weld?

A

100 percent through the base metal regardless of metal thickness.

216
Q

For strength, what groove weld should you select for welding heavy sections?

A

Single U groove.

217
Q

At what distance should you make the tack welds on a rigid groove weld?

A

Every 1½″ along the seam.

218
Q

Which lap joint is the weakest?

A

Single-fillet lap.

219
Q

Which lap joint is welded from both sides?

A

Double-fillet lap.

220
Q

Which lap joint is the best to use under stress?

A

Offset lap.

221
Q

What are the specifications for the legs of a single-fillet lap joint?

A

Upper leg 1T, lower leg 1½ T.

222
Q

What should be the shape of the face of a lap weld?

A

Slightly convex.

223
Q

How should you prepare the edges on ½″ plate if you’re going to weld the T-joint form both sides?

A

Prepare the edges of the vertical sheet with a double-V 45° bevel.

224
Q

When you weld a T-joint, why do you space the vertical sheet above the horizontal sheet?

A

Permits the welding heat to reach the entire joint for proper fusion.

225
Q

What should the legs measure on a T-joint made from ½″ plate?

A

1½” T.

226
Q

Name the four welding positions.

A

(1) Flat. (2) Horizontal. (3) Vertical. (4) Overhead.

227
Q

Describe the flat position.

A

When you weld at an incline of less than 45°and the weld face is horizontal.

228
Q

Describe the horizontal position.

A

When the weld bead runs horizontally and the workpiece has an incline of 45° to 89°.

229
Q

Describe the vertical position.

A

When the weld runs vertically and the workpiece has an incline of 45° or more.

230
Q

How do you control the flow of the molten pool when you weld a vertical joint?

A

Point the torch at a 45° upward angle.

231
Q

When you weld in the overhead position, how can you control the puddle?

A

Use less heat and smaller diameter filler rods.

232
Q

What are the requirements for the 6G weld position?

A

The axis of the pipe joint is at an approximately 45° angle to the horizontal and the tube cannot be rotated during the welding process.

233
Q

What factors should you consider when setting up for arc welding?

A

Type of work you’re going to do, type of machine you’ll use, type of electrode required, type of current available, and safety precautions.

234
Q

When are you particularly susceptible to severe shock from AC and DC open circuit voltages?

A

When you or the machine are wet, or if the machine isn’t properly grounded.

235
Q

What can happen if you subject the welding cables to currents higher than their rated capacity?

A

You’ll damage the cable insulation and leads.

236
Q

What’s the significant difference between an E–7024 electrode and an E–10024 electrode?

A

The rod composition is the same; the coating on the E–10024 electrode is thicker; and the tensile strength is higher.

237
Q

What’s the meaning of the electrode number E–12040?

A

SMAW electrode with 120,000 psi tensile strength; can be used to weld in the flat, horizontal, overhead, and vertical down positions.

238
Q

What’s the correct electrode lead angle?

A

10° to 20° in the direction of travel.

239
Q

What is the first thing you must do to start welding a bead? How do you do this?

A

Strike an arc. It is done like striking a match.

240
Q

What happens if your arc length is too long?

A

You overheat the plate in a general area and cause the puddle to be wide and shallow. You also cause the electrode to spatter a great deal.

241
Q

What is the common name of the engine-driven generator?

A

Portable welder.

242
Q

What is an advantage of the portable welder?

A

It is capable of generating its own electricity. It can power lights and other shop equipment.

243
Q

List the safety concerns with a portable welder.

A

Engine exhaust, fuel hazards, moving parts, trailer safety, towing, and when the trailer is uncoupled.

244
Q

The portable welder operates on what type of voltage?

A

Constant amperage or constant voltage.

Metals Tech (5 decks)

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