nickel base alloys. resistance welding lesson objectives when you finish this lesson you will...
TRANSCRIPT
Resistance Welding
Lesson ObjectivesWhen you finish this lesson you will understand:•
Learning Activities1. View Slides; 2. Read Notes, 3. Listen to lecture4. Do on-line workbook
Keywords
Nickel Base Alloys Can Be Divided into Categories• Commercially Pure Nickel• Solid-Solution Alloys• Precipitation-Hardenable Alloys• Dispersion-Strengthened Alloys (ThO2)• Ni-Ti Shape Memory Alloys
Pure Nickel - Alloy 200
• Food processing equipment• Caustic handling equipment• Chemical Shipping drums• Electrical & electronic parts• Susceptible to graphitization at grain boundaries at elevated temperatures.
Alloy 201
• Used for service above 600F because:• Has low carbon which promotes increased resistance to graphitization at elevated temps
Solid Solution
Nickel - Copper (400, R-405)• Resistance to Sea Water, chlorination• Naval Application, Chlorination Plants, Water meter parts, pump shafts, feed water heaters
Nickel-Chromium (600, 601, 690, 214, 230, G-30, RS-330)• Corrosion Resistance at Elevated Temp• Furnace muffles, heat treating equipment, nuclear steam tubing, heat exchangers, aircraft engine components
Nickel-Iron-Chromium (800, 800HT, 825, 20Cb3, N-155, 556)• High Temp Strength, Resistance to Oxidation• Heat exchangers, carborizing fixtures, pickling tank heaters, spent nuclear fuel element recovery, hydrofluoric acid production
Solid Solution
Cobalt-Chromium-Nickel-Tungsten (L-605, 188, S-816, 54Co-26Cr)• Sensitive to Copper contamination
Nickel-Chromium-Molybdenum (C-22, C-276, G, S, X, 622, 625, 686)• Corrosion resistance at room temp
Nickel-Molybdenum (B, B-2, N, W)• Low temp corrosion resistance, some acids• Cryogenic Service
Precipitation-Hardenable AlloysGamma Prime Precipitate
Nickel-Copper Alloys (K-500)• Resistant to Sea Water, Chlorine• Pump shafts, impellers, oil well drill collars, electronic components, springs•Sensitive to strain age cracking
Nickel-Chromium (713C, X-750, U-500, R-41, Waspalloy)• Al-Ti-Nb strengthening• Good high temp oxidation• Gas turbine components
Nickel-Iron-Chromium (901, X-750)• Forging applications• generally not welded
Thorium Dispersion Strengthened Nickel
TD Nickel• High Temperature Strength • Thermal Shock Resistance – Used for Turbine components
Can have considerable loss of strength in weld, due to agglomeration or growth of thoria dispersoid.
TD NiCr• High Temperature Strength•Oxidation and Sulfidation Resistance
Fansteel Metals Division Bulletin,
Ni-Ti Shape Memory Alloy
• 55Ni- Bal Ti• Reversible Martensite
Potluri, N. “Joining of Shape Memory Alloys” Welding Journal, March 1999
Spot Welding
Electrical Resistance Range from 9.5 to over 130 micro-Ohm Cm(1-13 times that of Plain Carbon Steels)• Welding Current similar to steel for low resistance• Current lower for higher resistance alloys• Short Weld Time• Because of short time, generally no atmosphere required
Strength Range from 0.8 to 3.8 times Plain Carbon SteelFor Lower Strength Materials• Same Force LevelsFor High Strength (at Elevated Temp)• Higher Forces
a. Expulsion = Force too lowb. Electrode Mushroom = Force too high
Because of wide variations in propertiesExact welding conditions vary widely
Spot Welding
Resistance Welding Manual, RWMA
For thin material up to 0.06”If tip sticking go to 10o
For heavier material 0.06-0.125”
5-8”
Spot Welding Thicker Gage 73Ni-16Cr-7Fe-3Ti
Resistance Welder Manufacturers Association Bulletin # 26
Spot Welding Thicker Gage 73Ni-16Cr-7Fe-3Ti
Resistance Welder Manufacturers Association Bulletin # 26
Thickness
Spot Weld Defects
Hot Cracking• lower S&P• forge force
Coring• higher R in GB• Constitutional Liquation• Reduce particles in HAZSulfur HAZ Surface Cracking
•Oil, Grease, Marking Pencil on Surface
Resistance Welding Manual, RWMA
Projection Welding
Seldom Projection Welded because ProductionRuns are usually small
Higher Weld Forces and longer weld times required than for Plain Carbon Steel
because of higher elevated Temperature Strength
Seam Welding
Upper Electrode Wheel
Workpiece
Lower Electrode Wheel
Throat
Knurl or FrictionDrive Wheel
Roll Spot Weld
Overlapping SeamWeld
Continuous SeamWeld
[Reference: Welding Handbook, Volume 2, p.553, AWS]
Intermittent Pulse, Intermittent Roll, Forge Force Possible
No Intermittent Roll, No Forge Possible
Class 1 or 2 RollsBurnished to PreventSticking
Flash Welding
Higher upset force because of higher hot strength than plain carbon steel
Higher Clamping Forces because higher upset forces
Die burn = Insufficient Clamping Force
Resistance Welding Manual, RWMA
High flashing speeds (parabolic vs. linear) and shorter flashing times used to minimize weld contamination.
Flash Welding
Jaw spacing less because higher resistance
Upset distance sufficient to get all molten material out
Higher resistance may cause some centerline melting
Resistance Welding Manual, RWMA
Flash Welding
Current Flow During UpsetIf flashing current is cut off before upset, oxide forms at centerline
Resistance Welding Manual, RWMA
Resistance welding Electrode to Spark Plug
Nickel (typically Inconel 600) Sheath Copper Core Electrode
Weld to Steel Plug Body
Chiu, R, “Spark Plug with Copper Cored Ground Electrode and a Process of Welding the Electrode to a Spark Plug Shell” US Patent 5,530,313 Jan 25, 1996
Welding of a current collector in a Ni-Cd Coil Wound Battery
Nakamaru, H, et al, “Cylindrical Storage Battery” US Patent 6,013,389 Jan 11, 2000
Ni
Cd
Separator
Nickel strip (3&4) resistance spot welded to nickel plated steel collector plate (7&8)
Method For Replacing Blade Tip of Directionally Solidified and Single Crystal Blades
(Tips to prevent leakage of Compressed Air Between Blade and Shroud)
Rene N5 (single Crystal)Rene 142 Dir. Solidified
Blade Cross Section
ResistanceWeld
Air Holes
Bewlay, B, et al “Method for Replacing Blade Tips of Directionally Solidified and Single Crystal Turbine Blades”, US Patent 5,822,852 Oct 20, 1998