120301b Flashcards
(207 cards)
1
Q
What is a key characteristic of precipitation hardenable alloys?
A
They undergo changes to their crystal structures on heating and cooling.
2
Q
What is the primary composition of Inconel?
A
About 78% nickel, 15% chrome, and 7% iron.
3
Q
True or False: Monel alloys are primarily composed of nickel and copper.
A
True
4
Q
What is the typical application of nickel alloys in the chemical industry?
A
Used in welded fabrication for equipment such as piping and storage tanks.
5
Q
Fill in the blank: Precipitation hardening is also known as _______.
A
age hardening
6
Q
What effect does adding up to 4% nickel to steel have?
A
Increases tensile strength and impact hardness without decreasing toughness.
7
Q
What are the typical service conditions for low carbon nickel?
A
Temperatures in the range of 370°C to 650°C (700°F to 1200°F).
8
Q
What is the main advantage of using commercially pure nickel?
A
Stronger and more ductile compared to carbon steel.
9
Q
What percentage of nickel produced is used in the production of stainless steels and nickel alloy steels?
A
Approximately 60%
10
Q
What is the melting point of nickel?
A
1455°C (2647°F)
11
Q
True or False: Commercially pure nickel is highly resistant to corrosives.
A
True
12
Q
What is the primary use of Monel alloys?
A
Applications requiring corrosion resistance and toughness.
13
Q
List the three main types of nickel and nickel alloys.
A
- Commercially pure nickels
- Solid solution alloys
- Precipitation hardenable alloys
14
Q
What is the typical composition of Monel alloys?
A
About 67% nickel and 30% copper.
2/3 nickel and 1/3 copper
15
Q
What is the effect of nickel on the properties of steels?
A
Increases tensile strength, yield strength, and impact toughness.
16
Q
What is the primary purpose of nickel plating?
A
To improve corrosion resistance and hardness.
17
Q
What is the tensile strength of nickel?
A
Approximately 317 MPa (46,000 psi).
18
Q
What are the characteristics of nickel, Monel, and Inconel alloys?
A
Most nickel, Monel, and Inconel alloys are solid solution alloys and are not heat-treatable. Cold working, rolling, and forming operations are used to increase their tensile strengths and alter their grain size.
19
Q
How does heating affect nickel, Monel, and Inconel alloys?
A
Heating softens these alloys, similar to copper. The rate of cooling from the annealing temperature has no effect on the hardness of these alloys.
20
Q
What is Incoloy?
A
Incoloy is an iron, nickel, chromium alloy that is not considered a true nickel-based alloy because the nickel content is below 50% (30% nickel instead). It is closely related to austenitic stainless steels.
21
Q
What are the properties and applications of Incoloy?
A
Incoloy has good oxidation resistance and strength at elevated temperatures. It is used as sheathing on electrical heating elements and for other high-temperature service applications.
22
Q
What are Nichrome alloys composed of?
A
Nichrome alloys have about 80% nickel and 20% chrome and are used as heating filaments in electrical appliances.
23
Q
What are Nimonic alloys?
A
Nimonic alloys are similar to Nichrome alloys with about 80% nickel and 20% chrome, but they also contain additions of titanium and aluminum.
24
Q
What are the properties and applications of Nimonic alloys?
A
Nimonic alloys offer excellent high-temperature resistance, high strength, and good corrosion resistance properties. They are widely used in the construction of gas turbines.
25
What are Hastelloy alloys?
Hastelloy alloys are nickel/molybdenum-based and are among the most corrosion-resistant alloys available today.
26
What is the main application of Hastelloy alloys?
Their main application is in the chemical industry for equipment to handle, transport, and store acids and other corrosive materials.
27
What is required for producing industrial gases at cryogenic temperatures?
Equipment that operates safely at very cold temperatures.
28
What is the process that separates individual gases from air?
Liquefaction of air.
29
What is the temperature of liquid oxygen?
-182.8°C (-297°F)
30
What is the temperature of liquid helium?
-269.9°C (-452°F)
31
What is crucial for fabricating cryogenic handling equipment?
Adequate resistance against brittle fracture and good impact properties at low operating temperatures.
32
What materials are used for cryogenic applications?
Copper alloys, aluminum, Monel, austenitic stainless steel, and alloy steel containing 9% nickel.
33
How do nickel and high nickel alloys respond to welding?
Most nickel and high nickel alloys respond well to conventional arc welding processes.
34
What are the mechanical properties of welded joints in nickel alloys?
Welded joints in most nickel and high-nickel alloys produce good mechanical properties in the as-welded condition.
35
Is any treatment needed after welding nickel alloys?
No treatment, either thermal or chemical, is generally needed afterwards to restore corrosion resistance.
36
What welding procedures are used for nickel and nickel alloys?
The welding of nickel and nickel alloys uses procedures similar to that of austenitic stainless steel.
37
What special attention needs to be taken when welding nickel alloys?
Joint design, joint and surface preparation, preheat requirements, and welding procedures.
38
What types of joints can be used to join nickel alloys?
Various joint types may be used, including corner joints, lap joints, and butt joints.
39
What is important for corner and lap joints in nickel alloys?
Corner joints should be fully fused and lap joints should be welded on both sides to avoid corrosion.
40
What is the most common joint type for nickel alloys?
Butt joints are the most common type used on nickel alloys.
41
What is a guideline for butt joint design in nickel alloys?
If possible, the joint should be welded from both sides to eliminate lack of fusion or crevices.
42
What should be used if welding from one side only?
Use a removable backing material, often copper, as it does not fuse to the parent metal.
43
What is the recommendation for backing materials?
Backing materials should be contoured to allow full penetration.
44
What is recommended for material thickness greater than 10 mm?
Double Vee or double U grooves are recommended to reduce weld metal and residual stress.
45
What is the recommended groove angle for butt joints in nickel and nickel alloys?
An increase of up to 40% in groove angle is common. This design helps to overcome the sluggish nature of the molten weld metal.
46
What is required for J and U groove preparations?
A larger root radius is required as it provides better accessibility to the root and joint side walls.
47
What is the recommended thickness and root radius for nickel and nickel alloy joint preparations?
T = Thickness < 15 mm; R = 5 mm - 8 mm.
48
What type of welding is generally recommended for single welded joints?
GTAW (Gas Tungsten Arc Welding) is generally recommended for smooth bead contour on the back of the joint.
49
What is an acceptable method for bevelling before welding?
Thermal cutting or bevelling with plasma arc cutting (PAC) is acceptable, provided that all heat-affected material is completely removed from the joint before welding.
50
What type of grinding wheels are required for nickel and nickel alloys?
Aluminum oxide grinding wheels are required for nickel and nickel alloys.
51
What should not be used on the surface of nickel materials?
Do not contact or scratch the material surface with iron tools, jigs, or handling equipment.
52
How should nickel products be stored?
Store nickel products on wood.
53
How should nickel and nickel alloys be handled?
Handle nickel and nickel alloys as you would stainless steels to avoid crevice corrosion.
54
What materials can cause embrittlement and accelerated corrosion in nickel alloys during welding?
Materials containing phosphorus, lead, or sulphur can cause embrittlement and accelerated corrosion in nickel alloys during welding.
55
What foreign materials should be removed before welding nickel alloys?
Foreign materials such as petroleum products, marking pencils, and temperature indicating crayons must be removed before welding.
56
Why is it necessary to remove the oxide film prior to welding nickel alloys?
The oxide film must be removed because there is a large difference in the melting points of the parent metal and oxide.
57
How can the oxide layer be removed before welding?
The oxide layer can be removed by grinding, machining, or pickling, which is washing or immersion in a mild acid solution.
58
What are the preheat requirements for welding nickel alloys?
Preheat is not required unless the ambient temperature drops below 0°C (32°F). Below that point, preheat to 21°C (70°F) for 300 mm (12") on both sides of the joint is recommended.
59
What is a characteristic of welding nickel and high nickel alloys?
During welding, the weld metal does not spread out as it does with carbon steels, requiring greater rod manipulation and a wider fit up.
60
How does thermal conductivity affect welding nickel alloys?
The higher thermal conductivity of nickel contributes to greater difficulty in achieving fusion between the filler and base metals.
61
What welding technique may aid in blending weld edges in nickel alloys?
A slight weaving technique may be employed to aid in blending the weld edges.
62
What should be limited to reduce hot cracking in nickel alloys?
Heat input should be limited to reduce hot cracking, minimize grain growth, and retain corrosion resistance.
63
In what positions can nickel and nickel alloys be welded using SMAW?
Nickel and nickel alloys can be readily welded in all positions using SMAW.
64
What is a similarity between SMAW techniques for nickel alloys and another material?
Welding techniques using SMAW on nickel alloys are similar to those used on stainless steel.
65
Why is SMAW rarely used on precipitation hardening alloys?
SMAW is rarely used on precipitation hardening alloys because it is difficult to transfer certain alloying elements like aluminum and titanium across the arc.
66
What can excessive heat input during SMAW lead to?
Excessive heat input can cause overheating of the electrode coating, resulting in serious loss of deoxidizers and gas shielding.
67
What technique should be used to lower heat input during SMAW?
Use stringer beads with a slight weave to lower the heat input.
68
What inclination is suitable for controlling molten flux during SMAW?
An inclination of 20° towards the deposited metal is suitable to control the molten flux and avoid trapping slag.
69
What can cause porosity in nickel alloy welds?
Nitrogen can cause porosity in nickel alloy welds.
70
How can the weld zone be protected from nitrogen pickup?
The weld zone must be protected from nitrogen pickup by adequate gas shielding, maintaining a short arc and minimizing manipulation of the electrode.
71
What welding processes are well suited for nickel alloys?
Wire feed processes and SMAW are well suited for welding most solid solution nickel alloys.
72
What is the primary use of wire feed processes in nickel alloy operations?
Wire feed is widely used for nickel alloy cladding operations.
73
What are the advantages of spray transfer in welding?
Spray transfer offers higher deposition rates, while pulsed spray provides advantages for all position welding.
74
What gas mixtures are generally used in wire feed processes for nickel alloys?
Argon or argon/helium gas mixes are generally used.
75
What type of electrical current is most often used on nickel alloys?
DCEP (Direct Current Electrode Positive) is most often used on nickel alloys.
76
What is the role of GTAW in nickel alloy welding?
GTAW is extensively used on nickel alloys for thin materials, root passes in single welded butt joints, and in conditions where flux residue is undesirable.
77
Why is GTAW considered the best choice for precipitation hardening nickel alloys?
GTAW provides the best protection against oxidization and prevents alloying elements like aluminum and titanium from burning out.
78
What is required when using pulse spray transfer with the welding gun?
A slight pause at each side of weave beads is required to eliminate undercut.
79
What gas is generally used for nickel and nickel alloy welding using GTAW?
Argon or argon/helium gas mixes are generally used.
80
What type of electrode is recommended for nickel alloy applications?
A 20% thoriated electrode with a conical angle of 30°-60° and a small flat apex on the tip gives good results for most applications on nickel alloys.
81
What current type is often used in GTAW for nickel welding?
Direct current electrode negative (DCEN) with high frequency (HF) start only.
82
What feature can help prevent crater cracks when breaking the arc?
If the power source is equipped with a crater out feature, you can use it to prevent crater cracks.
83
What is the maximum torch inclination to avoid air in the weld zone?
Torch inclination should not exceed 15°.
84
What should be minimized to ensure effective GTAW?
Use a short electrode extension and minimize stand-off distance.
85
What is the recommended arc length for GTAW?
Use the shortest possible arc length.
86
What type of gas nozzle should be used in GTAW?
Use a gas nozzle just large enough to deliver gas to the weld zone with low velocity.
87
How can good gas coverage be achieved in GTAW?
A gas lens may be helpful in offering good coverage with minimum turbulence.
88
What must be done for single welded open groove joints?
Single welded open groove joints must be back purged or have temporary backing.
89
Where should the hot end of the filler rod be kept during manual GTAW?
The hot end of the filler rod should be kept within the gas shield to avoid oxidation.
90
What special care should be taken with autogenous welds?
Take special care with autogenous welds as porosity can readily form due to lack of deoxidizing elements.
91
What should be considered when welding precipitation hardening alloys?
Take special care to avoid cracking and consult with the base metal supplier for specific weld procedure and heat treatment information.
92
What is SAW suited for?
SAW is suited to welding most solid solution nickel alloys.
93
What types of alloys is SAW not generally used on?
SAW is not generally used on precipitation hardening alloys and nickel/molybdenum alloys.
94
Why is SAW not used on nickel/molybdenum alloys?
The high heat input and slow cooling rate have a detrimental effect on ductility and corrosion resistance.
95
What is SAW ideally suited for?
SAW is ideally suited for nickel alloy beads and clean, defect-free weld metal.
96
What should be considered when developing cladding on carbon steel using SAW?
Consider high deposition rates and smooth, nicely blended nickel and nickel alloy welding procedures.
97
What type of flux must be used in SAW?
A specially designed flux must be used; fluxes for steel are not suitable.
98
What should be done after welding is complete?
Remove any slag or flux with non-ferrous tools or brush with a stainless steel wire wheel.
99
What is the effect of flux on weldment subjected to high temperature service?
Flux acts as an accumulator of sulphur, and melting of residual slag may cause sulphur embrittlement.
100
What is the preferred current for groove welds in SAW?
DCEP is preferred for groove welds because of greater depth of penetration and flatter beads.
101
What current is often used for surface welding operations?
DCEN is often used for surface welding operations due to higher deposition rates and less depth of fusion.
102
What should the weld bead profile be?
The weld bead should be flat to slightly convex.
103
What type of beads are more prone to centerline cracking?
Concave beads are more prone to centerline cracking under certain conditions.
104
What are the most common weld faults in SMAW of nickel and nickel alloys?
The most common weld faults are spatter and porosity. In some circumstances, cracking may also develop.
105
What is spatter in welding?
Spatter detracts from the final appearance and should be removed or prevented from occurring.
106
What are some causes of spatter?
Causes of spatter include:
1. The arc length is too long.
2. Amperage is excessive.
3. Polarity is incorrect.
4. Electrodes are damp.
5. Slag is running under the arc.
6. Arc blow conditions exist.
107
How can spatter be corrected?
To correct spatter:
1. Maintain a short arc.
2. Use amperage within the suggested current range.
3. Use the recommended polarity for the filler metal.
4. Dry or rebake to recondition the flux coating.
5. Travel faster and/or increase backhand inclination.
6. Follow procedures to counteract arc blow.
108
What is porosity in welding?
Porosity is a problem in weld metals of the chromium-free nickel-base alloys.
109
What causes porosity during welding of nickel alloys?
Nitrogen, oxygen, and carbon monoxide cause porosity. Nitrogen dissolved in the molten puddle is often the main cause.
110
What elements are added to reduce porosity?
Titanium, aluminum, manganese, and silicon are added to reduce porosity.
111
What is a key requirement for SMAW to prevent nitrogen pickup?
SMAW requires a short arc length to prevent nitrogen pickup.
112
What can cause hot cracking in welds?
Petroleum products, marking pencils, temperature-indicating crayons, cutting compounds, or other materials containing lead or sulfur may cause hot cracking.
113
What are the effects of foreign materials in the weld zone?
Foreign materials can cause hot cracking during welding or heating, and after welding, they can cause embrittlement and accelerated corrosion.
114
What can excessive heat input cause in welds?
High current settings and slow travel speeds may cause weld bead cracking.
115
What is strain-age cracking?
Strain-age cracking is the result of residual stresses that exceed the yield point of the alloy, caused by age hardening, cold working, and welding.
116
What do precipitation-hardening nickel alloys require to avoid cracking?
They require specific pre and post-weld heat treatments to avoid cracking.
117
What must be followed to avoid defects in precipitation-hardening nickel alloys?
Welding procedures must be followed to the letter to avoid cracking or other defects.
118
What is a clad steel?
A clad steel is a composite material that has been bonded on one or both sides with a thin layer of more expensive material.
119
What are the advantages of clad steels?
Clad steels provide corrosion resistance, abrasion resistance, thermal conductivity, heat resistance, and electrical conductivity.
120
What is co-rolling?
Co-rolling, also known as hot roll bonding or integral bonding, is done at the steel mill where a sheet of clad material is laid on top of a backing steel.
121
How is clad material bonded to backing material?
A clad material can be bonded to a backing material by co-rolling, furnace brazing, explosive bonding, surface welding, and casting.
122
What is the primary application of clad steels?
The widest application of clad steels is in the construction of tanks and pressure vessels.
123
What materials are commonly used for the outer shell of pressure vessels?
The outer shell of pressure vessels is commonly made from carbon steel, such as SA516 grade 70N.
124
What type of stainless steel is often used for cladding?
SA-240 type 316L austenitic stainless steel is often used for cladding.
125
What is the significance of the thickness of materials in clad steels?
When the material thickness exceeds 10 mm, the price difference between full alloy and clad materials is significant, allowing for cost savings.
126
What is a common practice for welding high alloy filler metals onto carbon steel?
SMAW, GMAW, FCAW, MCAW, and SAW are used for cladding.
127
What factors influence the choice of surface welding process?
Factors include size of job, thickness of material, position, and type of material.
128
What does Figure 11 illustrate?
It shows samples of welded cladding with SAW using a 51 mm (2") wide stainless steel strip onto carbon steel.
129
How many layers were required to obtain the required cladding thickness?
Two layers were required to obtain the required cladding thickness and to reduce dilution.
130
What does casting in welding involve?
Casting involves bringing one of the metals to a molten state and pouring it onto the other.
131
What is explosive bonding?
Explosive bonding uses the high-energy impulse of an explosion to drive two metal surfaces together.
132
How does explosive bonding work?
An explosive charge is placed on top of the cladding metal over the backing metal. The pressure generated when the two metals collide causes plastic deformation and yields a high strength metallurgical bond.
133
What is an advantage of explosive bonding?
Explosive bonding is an effective joining method for several combinations of metals.
134
What is furnace brazing?
Furnace brazing involves a thin layer of brazing material sandwiched between two cladding materials, which is then heated in a special furnace.
135
What happens to the brazing material during furnace brazing?
The brazing material flows and combines the two cladding materials.
136
What is the typical range for cladding thickness as a percentage of total thickness?
Cladding thickness may range from 5% to 50% depending upon the application requirements.
137
What is the common cladding thickness range for carbon or low alloy steels?
For the majority of industrial applications, the cladding thickness generally falls in the 10% to 20% range.
138
What are the most common clad materials on a tonnage basis?
The most common clad materials are carbon and low alloy steels clad with stainless steels.
139
What is straight chromium stainless steel used for?
Straight chromium stainless steel (400 series - 12% Cr) is used for oxidation and corrosion resistance at elevated temperatures.
140
What applications use chromium nickel stainless steel?
Chromium nickel stainless steel (300 series) is employed for architectural or decorative purposes and where corrosive conditions are not too severe.
141
What are nickel and nickel alloys used for?
Nickel and nickel alloys offer good resistance to caustic soda service applications.
142
What industries commonly use Inconel?
Inconel is used in the food and beverage industries.
143
What are copper and copper alloys used for?
Copper and copper alloys are used for applications where corrosion service conditions exist.
144
What is the advantage of clad steels?
Clad steels provide the benefits of more expensive materials at a much lower cost.
145
What does surface welding of a clad allow for?
Surface welding of a clad allows for specific size or thickness.
146
What is effective for joining several combinations of metals?
Explosive bonding is effective for joining several combinations of metals.
147
What types of steels can be used for backing?
Various types of steels can be used for backing.
148
How can cladding types and thicknesses vary?
Cladding types and thicknesses can vary depending on specific service conditions.
149
How does the preparation of clad steels differ from other steels?
The preparation of clad steels differs considerably from that of other steels.
150
What is the recommended orientation for shearing and punching clad steels?
Perform all shearing and punching with the clad side up.
151
Why is it important to keep the clad side up during shearing and punching?
This ensures that the brift for clad steels is maintained and does not dilute the intended properties of the cladding.
152
What condition should the material be in when severe bending or forming is performed?
Material should be in the annealed condition.
153
How does cold working affect the ductility of straight chromium clad steels?
The material's ductility reduces markedly with cold working.
154
What is the shear strength comparison between stainless steel and low carbon steel?
The shear strength of stainless steel is roughly twice that of low carbon steel.
155
What is the maximum cladding thickness that can be flame cut from the carbon steel side?
Most clad steels with up to 30% cladding can be successfully flame cut from the carbon steel side.
156
What is the exception for flame cutting clad steels?
Copper and copper alloy cladding cannot be satisfactorily flame cut unless the cladding is removed mechanically from the cut line.
157
What is recommended when using powder or flux injection for cutting clad steels?
Clad steels may be cut from either side using the oxyacetylene cutting process.
158
What oxygen pressure is recommended to prevent undercutting when cutting clad steels?
The recommended oxygen cutting pressure is between 48 kPa to 70 kPa (7 psi to 10 psi).
159
What type of cutting torch is required for low-pressure cutting oxygen control?
A three-hose cutting torch is required.
160
Why should a low calibration regulator be used with the cutting torch?
If using a standard two-hose cutting torch, the recommended oxygen cutting pressure would likely be exceeded before the gauge pointer moved off the pin of the dial.
161
What is the purpose of gouging or grinding in welding?
To clean metal.
162
What thickness is specified for clad materials in welding?
3 mm thick.
163
What are the two methods used for welding clad steels?
Composite welding (dual electrode) procedures and single V butt joint preparation.
164
What factors determine the choice of welding process?
Size of job, thickness of material, joint accessibility, position of welding, and whether it is shop or field welded.
165
What must be preserved within the weld zone when welding clad steels?
The properties of the cladding.
166
What can excessive dilution in welding cause?
Cracking, porosity, or other weld defects.
167
What is the recommended method to avoid excessive dilution?
Avoid penetration into the clad alloy.
168
What is the preparation requirement for the root face in welding?
It must equal the thickness of the cladding plus 16 mm to 3.2 mm.
169
What is a potential consequence of using inappropriate backing material?
It could cause a hard, brittle area in the weld, resulting in a loss of ductility.
170
What is the design goal of the welding procedure?
To prevent excessive dilution.
171
What is a full alloy weld?
A full alloy weld is a welding technique where the final layer has little or no dilution.
172
How should the groove be prepared for a full alloy weld?
The groove should be prepared from the clad side using the selected alloy filler metal to weld the groove completely.
173
What is the advantage of using a full alloy weld over a composite weld?
The advantage of a full alloy weld is that the setup is simplified, which can help reduce labor costs.
174
What thickness of clad plate is most economical to fabricate using a full alloy weld?
When fabricating clad plate 13 mm (1 inch) or less in thickness, it is the most economical to use a full alloy weld.
175
What is the root gap set at for a full alloy weld?
The root gap is set at 1.6 mm (1/16 inch) to permit full penetration with the high alloy filler metal.
176
What is the purpose of removing the cladding material in a full alloy weld?
The cladding material is removed to form a root face that allows for a good quality deposit.
177
What type of electrodes should be used to reduce dilution?
Use small diameter electrodes with low amperage settings to help reduce dilution.
178
What type of beads are often specified for this procedure?
Stringer beads are often specified with this type of procedure.
179
How is a major surface defect identified?
A major surface defect is identified when the defect is deeper than the cladding and penetrates the backing steel.
180
What procedures are generally called for removing major surface defects?
Procedures to remove major surface defects generally call for grinding or gouging to sound metal.
181
What should be done if the defect is deep enough into the backing steel?
A recommended steel electrode may be used to fill to below the cladding and the remainder is filled with the proper alloy.
182
What must be considered to avoid dilution or contamination of alloy weld metal?
Consider the possibility of dilution or contamination caused by picking up iron from the steel backing plate.
183
How can dilution be controlled?
Dilution can be controlled by using a higher alloy electrode than the cladding or by depositing thin layers of the same alloy as the cladding.
184
What is required when using SMAW for surface defect repair?
Remove all slag and perform any cleaning or brushing only with tools and equipment required for the clad material.
185
What is the responsibility of the welder in these types of repairs?
It is the welder's responsibility to choose the specified filler metals and follow the procedure closely.
186
What can result from failure to follow qualified welding procedures?
Failure to follow qualified welding procedures can result in welds with poor chemical and mechanical properties.
187
What weld defects can lead to cracking?
Weld defects such as lack of fusion, slag entrapment, or incomplete penetration can lead to cracking.
188
What effect does undercut on the clad side have?
Undercut on the clad side reduces the thickness of the clad and even a minute amount of undercut could significantly reduce the product's service life.
189
What is 1A0b-bickol Alloys?
Clad Steel with pure nickel and 1.5% carbon.
190
What is the maximum carbon content in low carbon nickel?
0.02% max carbon.
191
What are Monel Alloys composed of?
Nickel and copper.
192
What are Inconel Alloys primarily made of?
Iron, nickel, and chromium.
193
What is Incoloy Alloys' nickel content?
30% nickel.
Not a true alloy
Related to austentic stainless steel
194
What is the composition of Nicnome Alloys?
Nickel and chromium.
80% 20%
195
What are Hastelloy Alloys made of?
Nickel and molybdenum.
Most corrosion resistance
196
What is precipitation hardening?
A process involving cooling and heat treatment.
-heating to dissolve alloy
- rapid cooled
- reheat back to lower temperature
197
What is the main application of cryogenic materials?
Used in gases like oxygen, nitrogen and argon requires very cold temps for safe operation
198
What effect does nickel have at low temperatures?
It increases impacts properties and decreases toughness.
199
What is the inner content of stainless steel 304?
Contains 8-12% nickel.
200
What are the most common electrodes for SMAW?
Most common electrodes for SMAW are nickel / nickel alloy electrodes.
201
What polarity is smaw
Dcep/ Reverse polarity can affect the performance of electrodes.
202
What is the recommended preheat temperature for welding?
Preheat to 21°C (70°F) on both sides unless ambient temperature is below 0
203
What is the significance of HAZ in welding?
HAZ refers to the heat-affected zone, which should be managed to avoid defects.
204
What is the typical thickness for solid welding?
Greater than 3/8" thickness is typical for solid welding.
205
What should be done to limit heat input?
Lessen the gas coverage
206
Why do we clear 2" back?
Foreign material can deteriorate the quality of the weld.
207
What is the purpose of using an aluminum oxide grinder?
An aluminum oxide grinder is used to prepare surfaces for welding.
