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Inspection and Testing

Radiography

[Drawbacks]

The time element in

developing the negative and

obtaining the necessary

information

Impracticability of taking the

welded parts to the X-ray

machine with the attendant

time element involved

Not all faults are revealed

Interpretation of radiographs

requires a highly skilled

technician

Peel Test Shown in the figure:

Visual Inspection

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Peel Test and Chisel Test

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Button Size as a Measure of

Weld Quality

Button

Diameter

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Modes of Failure in Spot Welds

Full Button Irregular Button

Interfacial Failure

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Long Life Test

-- on 1.3-mm Thick 6009-T4 Arc Cleaned/Conversion-Coated Sheet

with Truncated Cone Electrodes and Current Stepping

Percent

Heat(%)

Button

D

iameter(mm)

Undersized

Buttons/Strip

Number of Welds

[Reference: SAE

840291, Patrick,

Auhl, and Sun]

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Shear-Strength Data for Long

Life Test

-- on 6009-T4 Arc Cleaned/Conversion-Coated Sheet

Number of Welds

ShearStrength(kN/S

pot)

[Reference: SAE 840291,

Patrick, Auhl, and Sun]

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Minimum Tensile-Shear Strength

of Spot Welds in Aluminum Alloys

[Reference: Resistance Welding Manual, p.11-26, RWMA]

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Resistance Spot Weld

Radiographs 1 mm Sheet

[Reference: Joining of Aluminum Alloys 6009/6010, Hoch]

6009/6009 5182/5182 2036/2036

Small

Cracking

Large Center

Porosity

Large

Cracking

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Types of Defects Revealed by Radiography

Undersize nugget

Inadequate diameter

Inadequate penetration

Oversize nugget

Excessive diameter

Excessive penetration

Odd and misshapen nuggets

Extent of Alclad inclusion

into the nugget

Extrusion of the nugget

Cracking of the nugget

Porosity

Expulsion from faying

surfaces

Segregation of eutectic in

parent material

Electrode pickup Size or extent or granular

zone

Nugget penetration

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Setup Procedures and Suggested Schedules [Step 1] Insert electrode of

proper size and tip contour

for the gauge combination.

Align electrodes.

[Step 2] Set pressure gage

for suggested welding force,and check with an electrode

force gauge.

[Step 3] Adjust the control

to provide the approximate

suggested weld and

postheat time.

[Step 4] The welding

currents shown are

approximate and intended to

be a guide. The magnitude of

the welding current is usually

controlled by a heat dial orphase-shift control.

[Step 5] Check the machine

for consistency of operation

by making and testing twentysingle spot tension-shear

specimens and five

macroscopic examination

specimens.

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Typical Oscillograph Record during

Welding

Voltage

Force

Forge ForceWelding Force

Displacement

Current

1 V

1 kN

0.25 mm

5.0 kA rms

0.1 sec

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Typical Oscillograph Record

Current

Force

Displacement

Voltage

5.2 kA RMS

0.7 kN

0.2 mm

1.0 V (p-t-p)

Zero line

for force

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Resistance Spot Weld Data

[Reference: Guidelines

to Resistance SpotWelding Aluminum

Automotive Sheet,

p.9, The Aluminum

Association]

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Shunting Effect on 2024-T

AlcladFactors Influencing

Shunting

Effect Include: Thickness and

resistance of the alloy

being welded

Shunting effect

increases as the stock

thickness and

resistance decrease

Surface resistance of[Reference: Resistance Welding Manual, p.11-19, RWMA]

ShuntPathResistance,

Microohms

JointStrength,

lb/we

ld

Weld Spacing, in.

JointStrengthShuntResistance

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Suggested Minimum Weld Spacing

Edge and Flange Distance

[Reference: Resistance Welding Manual, p.11-20, RWMA]