Volume 4 Flashcards
(244 cards)
1
Q
What does the number 75 mean in SAE 1075?
A
0.75 percent carbon content.
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).
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.
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.
5
Q
Why was the unified numbering system developed?
A
To find a single classification sustem.
6
Q
How many digits are there in the UNS?
A
Five.
7
Q
How does the UNS group metals?
A
Into 18 families.
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.
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.
10
Q
Why can’t pure metals be hardened by heat treatment?
A
Their structure changes very little when they are heated.
11
Q
Define ferrous.
A
A metal that contains iron as its main alloying element.
12
Q
Define nonferrus.
A
A metal that does not contain iron as its main alloying element.
13
Q
Is bronze ferrous or nonferrous?
A
Nonferrous.
14
Q
Is copper ferrous or nonferrous?
A
Nonferrous.
15
Q
Is gray cast iron ferrous or nonferrous?
A
Ferrous.
16
Q
Is chrome-molybdenum steels ferrous or nonferrous?
A
Ferrous.
17
Q
Is carbon steel ferrous or nonferrous?
A
Ferrous.
18
Q
Is magnesium ferrous or nonferrous?
A
Nonferrous.
19
Q
Is brass ferrous or nonferrous?
A
Nonferrous
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.
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.
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).
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.
24
Q
Define Brittleness.
A
Tendency to fracture or break with little deformation, bending, or twisting.
25
Define Ductility.
Ability to be elongated without breaking.
26
Define Hardness.
Resistance to deformation or penetration.
27
Define Shear strength.
Resistance to a cutting force.
28
Define Strain.
604
29
Define Stress.
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
30
Define Tensile strength.
Resistance to being pulled apart by a slowly applied force. Resistance to stretching.
31
Define Toughness.
Resist repeated blows without breaking.
32
Define Wear resistance.
Ability to resist abrasive action.
33
When hardness increases, what happens to the other mechanical properties?
Generally, as hardness increases, it affects tensile strength, shear strength, wear resistance, and brittleness. Toughness increases with hardness up to a point.
34
What is a casting?
A product formed by pouring molten metal into a mold.
35
What is a wrought product? How does it differ from a casting?
A product that is formed while in a solid state.
36
What are the methods of shaping?
Rolling, forging, drawing, extruding, and piercing.
37
Tendency to fracture or break with little deformation, bending, or twisting.
Brittleness.
38
Ability to be elongated without breaking.
Ductility.
39
Ability to resist abrasive action.
Wear resistance.
40
Resistance to deformation or penetration.
Hardness.
41
Resist repeated blows without breaking.
Toughness.
42
Resistance to being pulled apart by a slowly applied force.
Tensile strength.
43
Resistance to a cutting force.
Shear Strength.
44
Resistance to stretching.
Tensile strength.
45
What is the best way to identify metals when using spark testing?
Compare an unknown material with a known sample.
46
How do you perform a spark test?
Hold a piece of metal against a grinding wheel.
47
Why is tensile testing done?
To determine yield strength, yield point, shear strength, and elastic limit.
48
What is the relationship between shear strength and tensile strength?
Shear strength is approximately 60 percent of tensile strength.
49
Why is hardness testing done?
To determine approximate tensile strength value, the results of heat treatment, and the condition of the metal before heat treatment.
50
What is the minor load of the Rockwell tester?
10 kg.
51
How is hardness determined by the Rockwell tester?
By measuring the difference in depth penetration between minor load and major load penetration.
52
Of what materials are penetrators made?
Diamond (Brale) penetrator or a hardened steel ball penetrator.
53
How is metal prepared for testing on the Rockwell hardness tester?
The metal must be smooth and level, and free from burrs and roughness.
54
Can round stock be tested on a Rockwell tester? Explain.
Yes. Grind a small, flat surface and use a crotch-type anvil.
55
What scale produces the highest hardness readings?
C-scale.
56
What must you do if you find a chipped Brale penetrator?
Replace the penetrator.
57
What is used to check the accuracy of the hardness tester?
The test blocks.
58
How do you prevent damage to the Brale or steel ball penetrators?
By always ensuring the protective cap is on the penetrator before changing the anvil or performing maintenance on the machine.
59
What does the passivation process remove?
Free iron contamination on the surface of the stainless steel.
60
What can particles of iron or tool steel and abrasive particles do if left on the surface?
Cause corrosion.
61
Which passivation solution is the overwhelming choice of users?
Nitric-acid-based solution.
62
What is the most commonly specified verification test and how can you tell if the process was successful?
Copper sulfate test, visually examine, any copper (pink) color indicates the presence of free iron and the test is considered unacceptable.
63
Why do regulators recognize the relative safety of citric acid formulations?
It is biodegradable and rinse waters can go to the drain if they meet local pH regulations.
64
Which type of peening is convenient for small areas where corrosion rework has been accomplished?
Roto peening.
65
What tools are required for rotary peening?
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.
66
What is essential to achieve the required peening intensity?
The flap wheel must be operated at the required speed under load and the proper flap deflection maintained throughout the peening process.
67
How can you keep the flaps from tearing when they drop over the edge of the part?
Use a hard rubber material clamped in place at the edges of the part being peened.
68
When visually inspecting a peened area with a 10X power magnifier, how can you tell if complete coverage and saturation have been accomplished?
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.
69
What is an advantage of brush-plating and why?
The equipment is mobile and the work can be done locally in the workshop mostly without disassembling the part to be repaired.
70
From what are anodes usually made?
They are usually made from a material inert to the plating solution such as graphite, stainless steel and 90 percent platinum/10percent iridium.
71
What is the difference between selective plating deposits and tank electroplated deposits of the same thickness? What is a result of this?
Most selective plating deposits are significantly harder and less porous. Wear and corrosion resistance are greatly increased.
72
What personal safety equipment should be used when using solutions?
Eye safety glasses or goggles, rubber or nitrile gloves, and a rubber apron if necessary.
73
What is the purpose of circulating the air in a furnace?
To circulate air around the part, maintain an even temperature on the part, maintain accurate temperature control.
74
Which type of furnace can be used for the higher temperatures?
Still air.
75
Name the types of atmospheres that can be found in heat-treating furnaces.
Reactive, inert, carburizing, or vacuum.
76
Why would you use a furnace with a reactive atmosphere?
Because it is economical to use.
77
What type of metals requires an inert atmosphere for heat treating to prevent contamination?
Reactive metals.
78
What is the main purpose of the hearth plate?
To protect the heating elements underneath it.
79
Why would you place your workpiece on a grid rack, and not directly on the hearth plate, when you are heat treating?
To enable even heating and prevent overheating of the parts.
80
Why are fire bricks used?
To line the inside of the furnace and act as insulation.
81
What should you do if you find broken firebricks during your inspection?
Replace them.
82
Why must new firebricks be dried out under controlled conditions?
To prevent cracking and chipping.
83
What must you look for when inspecting the furnace extension leads?
Shorts.
84
Who performs calibration on an electronic pyrometer?
PMEL.
85
What is your main source document when performing heat treatment operations?
TO 1–1A–9.
86
What could happen if one part of the metal is heated more rapidly than another?
Uneven expansion occurs, which causes distortion or cracking.
87
When is a preheat recommended?
When heating parts above 1300F.
88
What determines the soak time when heat treating?
The type of metal and the part thickness.
89
What item must accompany all newly fabricated parts when they are being heat treated?
A coupon.
90
List the different types of quenchants.
Brine (salt water), water, oil, still air, and the furnace.
91
Name the four common heat treatment operations performed on carbon and alloy steel.
Annealing, normalizing, hardening, and tempering.
92
Why might you anneal a piece of metal?
To enable forming operations or to remove internal stresses.
93
Why is normalizing recommended before hardening?
Normalizing before hardening assures the best results when hardening, provided the hardening operation is performed correctly.
94
Describe the normalizing process.
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.
95
What must carbon and alloy steels contain in order for them to be hardenable by heat treatment?
Carbon.
96
What happens when the carbon content goes above .80 percent?
There is no increased hardenability beyond that point.
97
The soak time for hardening is based on what?
The part thickness.
98
What are the two main reasons for tempering?
To reduce brittleness that results from the hardening process and (2) to allow you to meet a specific hardness specification.
99
Into how many groups are stainless steels divided? What are they?
Four. Ferritic, austenitic, martensitic, and precipitation hardening.
100
What is the only heat treatment process applied to ferritic stainless steels?
Annealing.
101
How are austenitic stainless steels hardened?
By cold working.
102
If you want to achieve maximum hardness when heat treating martensitic stainless steels, what is the determining factor? What does the process closely resemble?
The carbon content. It is the same as for plain carbon and low alloy steels.
103
What is one of the more important alloying elements added to aluminum?
Copper.
104
What happens as the copper content increases?
The ability to harden the aluminum increases.
105
What do the different temper identifiers indicate?
What processes have taken place to the aluminum alloy.
106
What process has taken place with AA2024-T6?
Solution heat treated and then artificially aged.
107
What are the three main heat-treating processes you can perform with aluminum alloys?
Annealing, solution heat treating, and precipitation hardening.
108
When putting aluminum through a severe cold working process what should you do? Why?
Do it in steps and anneal it after each step to remove the stresses of the previous cold-working operation.
109
Describe the annealing process for most aluminum alloys.
Soak it for at least one hour, within the temperature range of 750 to 800F. Cool the furnace load at 50F per hour, until it reaches 500F.
110
Successful solution heat treatment of aluminum alloys depends on what?
Putting the copper into a solid solution and trapping it there by quenching.
111
What happens to solution heat treated aluminum when it is naturally aged? How long does it take?
It will reach a temper of –T4. Approximately 96 hours at room temperature.
112
How can you stop natural aging from occurring?
Put the part in a freezer.
113
How is artificial aging accomplished?
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
What causes blistering when heat treating aluminum alloys?
Overheating.
115
What effect, if any, does oversoaking have on aluminum alloys?
It ruins the corrosion resistance of clad products.
116
Name two things to which nickel alloys are resistant?
Highly heat and corrosion resistant.
117
What effect does the addition of alloying elements have on nickel alloys?
Corrosion resistance, hardness, tensile strength, yield strength, and notch toughness (resistance to cracking) increase.
118
What determines the soaking period for annealing nickel-base alloys?
The chemical composition.
119
How is age hardening accomplished with nickel-base alloys?
By holding the alloy at temperatures between 900 and 1600F and then furnace or air cool.
120
List the three basic procedures for heat treating titanium alloys.
(1) Stress relieving, (2) annealing, and (3) solution treating, quenching, and aging.
121
Why are titanium alloys stress-relieved?
To remove residual stress developed during fabrication.
122
How are strength and ductility produced when you are heat treating titanium alloys?
By solution treating, quenching, and aging.
123
What happens if the rate of cooling is too slow when quenching titanium alloys?
There is a loss of strength.
124
When is solution heat treatment of beryllium-copper necessary?
When the material has been subject to welding, brazing, or a fabricating process that makes it unsuitable for age hardening.
125
What does age hardening do to beryllium-copper?
It develops the mechanical properties that are desired in beryllium-copper alloys.
126
At what pressure does free acetylene become explosive?
29.4 psi.
127
Why should you store acetylene cylinders upright?
To keep the acetone from escaping.
128
At what pressure is an acetylene cylinder considered empty?
When the cylinder has 4 cu. ft. of gas remaining.
129
What safety features prevent you from accidentally cross-installing an O2 regulator on an acetylene cylinder?
Left hand threads and a female fitting.
130
Why must you handle O2 cylinders carefully?
O2 is under great pressure, and if a valve is broken or the cylinder is pierced, the cylinder could become a projectile.
131
Where are full acetylene cylinders stored?
In a cool, dry, well ventilated building; separated from empty cylinders; and separated from O2 cylinders.
132
What must you do to a cylinder after it has been emptied?
Replace the safety cap, mark the cylinder MT, and secure it in the area with other empty cylinders.
133
Which side of the two-stage regulator reduces cylinder pressure to intermediate pressure?
High pressure.
134
What’s a check valve? What’s a flashback arrestor?
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
How can you distinguish an O2 hose connection from an acetylene hose connection?
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
Where do gases combine in the oxyacetylene torch?
Mixing chamber.
137
What are the two main advantages of using an equal-pressure torch?
(1) The flame is easy to adjust. (2) Has a low susceptibility to flashbacks.
138
Why should you crack cylinder valves before you connect the regulators?
To blow out any dirt that may be lodged in the outlet.
139
How much do you open each cylinder valve after you install the regulators?
Open acetylene valves no more than 1½ turns, and open the O2 valves fully.
140
When lighting the torch, which torch valve do you open first?
Acetylene.
141
How should you hold the striker to protect yourself from burns when you light the torch?
Keep your hand at one side of the tip.
142
How should you hold the torch when you light it?
So the flame is directed away from anything flammable, the cylinders, the hoses, and yourself.
143
How can you recognize a carburizing flame?
The presence of three distinct flame cones.
144
What’s the temperature of a carburizing flame?
Approximately 5,700°F.
145
Compare the gas volume of an oxidizing flame to that of a neutral flame.
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
Give the type and temperature of the hottest welding flame.
Oxidizing; 6,300F.
147
During emergency equipment shutdown, which valve must you close first? Why?
Acetylene; so you extinguish the flame because the O2 won’t burn without the acetylene.
148
What’s the first thing to do when disassembling a welding set?
Ensure the gas supply is shut off.
149
What should you do to the cylinder after you disconnect the regulator?
Replace the cylinder valve safety cap.
150
What equipment do you use for testing a welding set for leaks?
A jar of soapy water and a brush.
151
How do you test the hoses?
Submerge them in a bucket of clear water and watch for bubbles.
152
How can you detect a “creeping” regulator?
You’ll see a gradual rise in the working pressure gage after the cylinder valve is opened.
153
If a #1 tip is smaller than a #2 tip, which tip cleaner should you use to clean the #2 tip? Why?
#1 tip cleaner; to keep from enlarging the orifice.
154
Why should you use a straight back-and-forth movement when cleaning a tip?
To keep from enlarging the orifice.
155
How can you remove accumulated slag on the face of an oxyacetylene cutting tip?
Open the O2 valve and clean the tip with a file wrapped in an emery cloth.
156
At what temperature do you silver solder to create a bond between the base metal and the filler material?
Between 1,175 and 1,600F.
157
What determines the strength of a soldered joint?
Joint fit-up and the quality of the bond between the filler metal and the base metal.
158
What type of bond forms when you silver solder a joint?
Mechanical bond.
159
List the reasons for using flux for silver soldering.
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
What’s the recommended joint clearance for silver soldering?
Between 0.002” and 0.005”.
161
Why is it necessary to completely clean the metal surface and filler rod when silver soldering?
To ensure uniform capillary attraction throughout the joint.
162
What type of flame do you use for silver soldering?
Neutral to slightly carburizing flame.
163
How does a cutting torch work?
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
What are the prime disadvantages of using a cutting attachment?
It’s recommended for intermittent use, not continuous use, and for cutting materials ½” thick or less.
165
What’s the purpose of the outer orifices on a cutting tip?
Preheating.
166
How does the high-pressure O2 stream affect the red-hot metal?
It combines with the hot metal to burn it to an oxide.
167
What’s the term for the space in the metal that results from cutting?
The kerf.
168
What must you do to high C tool steels to cut them properly with oxyacetylene?
You must preheat the entire section you’re going to cut.
169
How should you adjust the flame for cutting?
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
List the two processes you can use to cut Cr and stainless steel.
(1) Torch oscillation. (2) Waste plate.
171
List four safe cutting practices.
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
When straight-line cutting, what should you use for making long cuts?
A guide bar.
173
Explain how to pierce a piece of metal.
Preheat the metal, raise the torch about ½” above the normal position for cutting, and slowly add cutting O2.
174
What does PAC use to cut metal?
Ionized gases at high pressures to melt and cut away the molten metal.
175
What type of PAC torches are available?
Gas-cooled and water-cooled styles.
176
What type of gasses are required for cutting nonferrous metals?
Inert gasses.
177
Name four advantages of PAC.
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
What is the correct torch height when cutting?
Approximately ⅛” to ¼” above the parent material.
179
What color is steel when it has reached its upper forging limit?
Lemon.
180
At what temperature do you strike the final forging blows?
1300 °F.
181
Define drawing.
Working a piece of material to increase its length, increase its width, or decrease its cross section.
182
What steps do you take to draw round stock to increase the length?
Square, octagonal, and then round again.
183
When you stress relieve a workpiece, how much of the material cross section should you heat?
The entire cross section.
184
What color should appear on the steel chisel before you perform the final quench?
Blue.
185
What is weldability?
The capacity of a metal to be welded together and its performance after being welded.
186
What four items contribute to material weldability?
(1) Joint design. (2) Welding process. (3) Chemical, physical, and mechanical properties of the base metal. (4) Properties of the filler metal.
187
When you’re determining which welding process you’re going to use, what items should you consider?
Base metal, type of weld, material composition, and weld position.
188
What’s the minimum C content that steel must possess to require preheat treatment and postheat treatment?
0.55 percent.
189
What are some drawbacks to welding superalloys?
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
Which aluminum groups are predominately not weldable? What are the exceptions in these groups?
The 2XXX and 7XXX groups. 2219, 2519, 7003, 7005, and 7039.
191
Which aluminum group is prone to cracking but can be readily welded with the proper technique?
6XXX
192
How do Zn and Al affect the weldability of Mg alloys?
Alloys with 1 percent Zn or more tend to crack; alloys with up to 10 percent Al weld easily and won’t crack.
193
What determines if titanium is titanium “unalloyed”? In what condition should you weld unalloyed titanium? How can you increase its strength after welding?
If the titanium is at least 98.5 percent pure; annealed condition; cold work it.
194
What is the HAZ in a metal?
The portion of the base metal that doesn’t melt, but has its mechanical properties altered by the welding heat.
195
What does recrystallization in the HAZ affect?
Metal’s grain size, tensile strength, hardness, ductility, and corrosion resistance.
196
What five factors dictate the size of the HAZ?
(1) Metal type. (2) Metal T. (3) Joint type. (4) Welding process and technique. (5) Quantity of heat.
197
What causes hot tearing?
When metal is weak and has limited plasticity at high temperatures.
198
How can you control hot tearing?
Preheat; control temperature between weld passes; and weld with as little strain as possible on the joint.
199
What causes cold cracking?
Occurs when hydrogen dissolves in the weld.
200
What increases a metal’s susceptibility to underbead cracking?
Increased CE.
201
What’s porosity?
The cavities and holes in the weld caused by trapped gases.
202
What are the main causes of incomplete fusion?
Inadequate heat and oxides or foreign materials trapped in the weld.
203
What are the most common causes of incomplete penetration?
Not enough heat at the root of the material, poor joint preparation, and improper cleaning.
204
What causes undercutting?
Incorrect torch and electrode angles.
205
What’s thermal expansion? Thermal conductivity?
The rate at which a metal expands when it’s heated; the speed at which a metal heats.
206
Describe backstepping.
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
How can you increase speed to reduce distortion and residual stresses?
Ensure the joint fits up tightly; use smaller electrode and lower heat output during multipass welding; and weld in the flat position.
208
Define Fusion zone.
The area of weld metal that has penetrated beyond the surface of the base metal.
209
Define Root.
The portion of the weld metal deposited at the bottom of the joint.
210
Define Leg.
The dimension of the weld extending on each side of the root of the joint.
211
Define Face.
The outer surface of the weld reinforcement.
212
Define Toes.
The edges of the weld face.
213
Define Penetration.
The distance from the original surface of the base metal to the point at which fusion ceases.
214
Define Throat.
The distance through the center of the weld from the root to the face.
215
What’s the minimum required penetration for a groove weld?
100 percent through the base metal regardless of metal thickness.
216
For strength, what groove weld should you select for welding heavy sections?
Single U groove.
217
At what distance should you make the tack welds on a rigid groove weld?
Every 1½″ along the seam.
218
Which lap joint is the weakest?
Single-fillet lap.
219
Which lap joint is welded from both sides?
Double-fillet lap.
220
Which lap joint is the best to use under stress?
Offset lap.
221
What are the specifications for the legs of a single-fillet lap joint?
Upper leg 1T, lower leg 1½ T.
222
What should be the shape of the face of a lap weld?
Slightly convex.
223
How should you prepare the edges on ½″ plate if you’re going to weld the T-joint form both sides?
Prepare the edges of the vertical sheet with a double-V 45° bevel.
224
When you weld a T-joint, why do you space the vertical sheet above the horizontal sheet?
Permits the welding heat to reach the entire joint for proper fusion.
225
What should the legs measure on a T-joint made from ½″ plate?
1½” T.
226
Name the four welding positions.
(1) Flat. (2) Horizontal. (3) Vertical. (4) Overhead.
227
Describe the flat position.
When you weld at an incline of less than 45°and the weld face is horizontal.
228
Describe the horizontal position.
When the weld bead runs horizontally and the workpiece has an incline of 45° to 89°.
229
Describe the vertical position.
When the weld runs vertically and the workpiece has an incline of 45° or more.
230
How do you control the flow of the molten pool when you weld a vertical joint?
Point the torch at a 45° upward angle.
231
When you weld in the overhead position, how can you control the puddle?
Use less heat and smaller diameter filler rods.
232
What are the requirements for the 6G weld position?
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
What factors should you consider when setting up for arc welding?
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
When are you particularly susceptible to severe shock from AC and DC open circuit voltages?
When you or the machine are wet, or if the machine isn’t properly grounded.
235
What can happen if you subject the welding cables to currents higher than their rated capacity?
You’ll damage the cable insulation and leads.
236
What’s the significant difference between an E–7024 electrode and an E–10024 electrode?
The rod composition is the same; the coating on the E–10024 electrode is thicker; and the tensile strength is higher.
237
What’s the meaning of the electrode number E–12040?
SMAW electrode with 120,000 psi tensile strength; can be used to weld in the flat, horizontal, overhead, and vertical down positions.
238
What’s the correct electrode lead angle?
10° to 20° in the direction of travel.
239
What is the first thing you must do to start welding a bead? How do you do this?
Strike an arc. It is done like striking a match.
240
What happens if your arc length is too long?
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
What is the common name of the engine-driven generator?
Portable welder.
242
What is an advantage of the portable welder?
It is capable of generating its own electricity. It can power lights and other shop equipment.
243
List the safety concerns with a portable welder.
Engine exhaust, fuel hazards, moving parts, trailer safety, towing, and when the trailer is uncoupled.
244
The portable welder operates on what type of voltage?
Constant amperage or constant voltage.
