1 of 15

Troubleshooting Welds

2 of 15

Learning Goals

We can…

Identify weld flaws and defects

Describe methods to correct flaws and defects

3 of 15

Porosity

Porosity – Pinholes in the weld as a the result of gas bubbles trapped in the weld metal; can weaken the weld

Caused by:

Excessive arc length
Excessive travel speed
Faulty electrodes
Incorrect polarity
Unclean metal
Inadequate welding amperage

So, what can I do?

Shorten arc length
Keep the puddle molten for longer
Use dry electrodes
Clean the base metal

4 of 15

Undercut

Undercut – Welding arc removes base metal but fails to replace it with weld metal; can weaken the weld

Caused by:

Too high of a current
Too long of an arc length
Improper rod angle
Excessive travel speed

So, what can I do?

Reduce the current
Shorten the arc length
Use a smaller diameter electrode
Change the electrode angle

5 of 15

Spatter

Spatter – Speckles of molten metal surrounding the weld

Caused by:

Excessive current
Excessive arc length

So, what can I do?

Reduce the amperage
Shorten the arc length

6 of 15

Incomplete Penetration

Penetration – The distance that the fusion line extends below the surface of the material being welded

Caused by:

Fault joint design
Insufficient welding current
Too large an electrode
Excessive travel speed

So, what can I do?

Checking the joint carefully
Increase the weld current
Reduce the weld speed
Use a smaller electrode

7 of 15

Cracks

Cracks – Line running through the weld; weakens the weld

Caused by:

Parent metal / filler metal composition and compatibility
Parent metal thickness
Stresses acting on the weld from external restraint
Joint geometry and fit up
Heating and cooling rate of the weld
Base metal and weld hydrogen content

Sources of hydrogen include: oil, grease, dirt, rust, paint, moisture, etc

So, what can I do?

Ensure the correct electrodes are being used
Ensure moderate metal thickness
Ensure proper joint fit
Clean the base metal

8 of 15

Slag Inclusion

Slag Inclusions - slag that is trapped in the deposited weld metal; can weaken the weld

Caused by:

Improper welding technique
Arc blow
Lack of cleaning
Too low of current
Too high of current
Rapid cooling
Flux running ahead of the puddle

So, what can I do?

Preheat the metal
Increase the welding current
Increase the weld area
Change ground clamp placement
Adjust the electrode angle
Run AC current

9 of 15

Arc Blow

Arc blow – a wandering arc due to an imbalance in the magnetic field surrounding the arc

The magnetic field is generally stronger near where the ground clamp is located and when the arc moves nearer to this concentration of magnetic force it is deflected.

Caused by:

Ground clamp location in relation to the arc
High amperage
Thicker plates, corners, deep grooves, start and finish of joints

So, what can I do?

Use the backstep method to create a continuous weld by performing a number of short welds
Reduce current
Change current to AC
Change location of the ground clamp
Wrap ground cable around the workpiece and pass ground current through it to neutralize the magnetic field
Maintain a short arc
Adjust the electrode angle against the blow

Thermal Blow - arc is lags the direction of travel due to it’s reluctance to move to the colder plate ahead; puddle helps to create a more conductive path for the arc to follow

Other magnetic field:

Magnetism - A force that acts at a distance and is caused by a magnetic field. All magnets contain a north and south pole; both poles attract ferrous metal like iron, nickel and cobalt; opposite poles will attract each other; like poles will repel each other

Magnetic fields will generate an electrical current at right angles to the magnetic field when passed through a conductive coil of wire. The field must be rotating to generate the power but when it is, it will produce alternating current electrical power. This is possible due to the magnetic field inducing current into the wire when it crosses the flux field of the magnet. When passing through the north pole of the magnet power will travel in one direction and when crossing the south pole power is induced in the opposite direction. Consequently the direction of the current alternates when generated.

10 of 15

Arc Blow

11 of 15

Distortion

Distortion – This is the warping of metal

Caused by:

Non-uniform heating and cooling of the joint
Residual stresses caused by the shrinkage of the weld metal as it cools

So, what can I do?

Control amount of heat

Use intermittent welds when possible

Minimizing the number of weld passes helps to control residual stresses
Back step welding sequence to control heat input
Use clamps, fixtures, strong backs and other methods to maintain fit up and joint alignment
Pre bend or offset the joints to allow weld shrinkage to pull them back into alignment
Preheat the joint
Use post weld heat treatment to relieve residual stress caused by welding

12 of 15

Distortion

1.

2.

3.

4.

5.

6.

7.

13 of 15

Other Weld Flaws & Defects

Underfill – occurs when the molten metal does not fill the entire gap or joint; can weaken the weld

Excess Reinforcement – occurs when too much molten metal is deposited into the weld joint; increases weld costs

14 of 15

Troubleshooting Welds

A B C D E F

Normal
Current too low
Current too high
Speed too fast
Speed too slow
Arc too long

15 of 15

Troubleshooting Welds

Normal

Too Low

Too High

Too Low

Too Slow

Too Fast