spot weldability lesson objectives when you finish this lesson you will understand: concept of spot...
TRANSCRIPT
Spot weldability
Lesson ObjectivesWhen you finish this lesson you will understand:• Concept of Spot Weldability• Electrode arrangements
Learning Activities1. View Slides; 2. Read Notes, 3. Listen to lecture4. Do on-line
workbook
Keywords: Current Level, Current Range, Lobe Curve, Electrode Life, Peel Test, Nugget Size, Button Size, Interfacial Failure, Shunting Effect, Multiple Direct Electrodes, Series Electrodes, Electrode Tooling
Process Characteristics as a Measure of Weldability
• Current Level
• Current Range & Weldability Lobe
• Process Deterioration– Characterization of the loss in weld size at constant
welding conditions– Characterization of the variation in process
requirements for maintaining welds of an adequate quality
Peel Test Used As MeasurePeel Test Used As Measure
Button Size as a Measure of Weld Quality
ButtonDiameter
Modes of Failure in Spot Welds
Full Button Irregular Button
Interfacial Failure
Process Characteristics as a Measure of Weldability
• Current Level
• Current Range & Weldability Lobe
• Process Deterioration– Characterization of the loss in weld size at constant
welding conditions– Characterization of the variation in process
requirements for maintaining welds of an adequate quality
Peel Test Used As MeasurePeel Test Used As Measure
Nugget Diameter vs. Weld Current
Expulsion
SmallNuggets
AcceptableNuggets
Minimum Nugget Diameter
Weld Current
Nug
get
Dia
met
er
Nominal Current
Process Characteristics as a Measure of Weldability
• Current Level
• Current Range & Weldability Lobe
• Process Deterioration– Characterization of the loss in weld size at constant
welding conditions– Characterization of the variation in process
requirements for maintaining welds of an adequate quality
Peel Test Used As MeasurePeel Test Used As Measure
Current Range & Weldability Lobe
ExpulsionAcceptableNuggets
Small Nuggets
Minimum Nugget Diameter
Weld Current
Weld Current
ExpulsionLevel
TimeA Smaller
“Brittle” Nuggets
AcceptableNuggets
LobeCurve
Nu
gge
t Dia
met
er
We
ld T
ime
Time A
Process Characteristics as a Measure of Weldability
• Current Level
• Current Range & Weldability Lobe
• Process Deterioration– Characterization of the loss in weld size at constant
welding conditions– Characterization of the variation in process
requirements for maintaining welds of an adequate quality
Peel Test Used As MeasurePeel Test Used As Measure
Process DeteriorationMinimumAcceptableDiameter
Number of Welds
Wel
d D
iam
eter
Shunting Effect
AB
IB
IA
Itotal = IA + IB
IARA = IBRB
IB/Itotal = 1 - RB/(RA + RB)[Reference: Resistance Welding Manual, p.1-7, RWMA]
Multiple Direct Electrodes
Series Electrode
Tooling for Multiple Welding
Stud and Jam NutsEqualizing Bar
Split and Clampedto Electrode
Flexible Conductors
Slip-Fit
Lower Electrode
Welding PressureAdjustment Screw
Compression Spring
FlexibleConductors
Slip-Fit
Workpiece
(a) (b)
[Reference: Resistance Welding Manual, p.17-8, RWMA]