120103d Exam Jan 20 93.33% Flashcards
When adjusting wire tension on the drive rolls (drive roll tension) at what point do you have enough pressure? explain
once you have a positive continuous feed without deforming or scarring the surface of the wire.
In what direction do you blow out the liner when changing a spool of wire?
a) in the direction of wire travel
(machine to gun)
b) in reverse direction of wire travel
( gun to machine)
b) in reverse direction of wire travel
( gun to machine)
What does arc hunting mean?
chips have built up in the liner
- happens often on flexible steel coil liners
If blowing out a liner does not fix the arc hunting problem what should you do?
- soak the liner in solvent that leaves no residue then blow it out with clean compressed air
- or replace liner
For fillet welds what is the correct electrode angle in relation to the joint?
a) 1/4 the angle
b) 1/2 the angle
c) 3/4 the angle
b) 1/2 the angle = 90 degrees
Explain the 2 following terms
Forehand
Backhand
Forehand points the electrode in the direction of travel
Backhand points the gun at the back of the puddle
When you change electrode inclination what weld characteristics are changed?
weld profile and depth of penetration
When using forehand is the bead shape
a) flatter & less penetration
b) convex & less penetration
c) concave & more penetration
d) concave and less penetration
a) flatter & less penetration
When using back hand is the bead shape
a) flatter & less penetration
b) convex & less penetration
c) concave & more penetration
d) concave and less penetration
c) concave & more penetration
- narrower bead with a higher crown
When using no inclination is the bead shape
a) flatter & less penetration
b) convex & less penetration
c) concave & more penetration
d) concave and less penetration
d) concave and less penetration
At what backhand inclination range do you obtain max penetration?
a) 5-10 degrees
b) 15-20 degrees
c) 18- 25 degrees
d) 20-25 degrees
b) 15-20 degrees
What electrode extension length is recommended using GMAW short circuiting?
a) 1/4”
b) 3/16”
c) 3/8”
d) 1/2”
c) 3/8”
What problems can be caused by slow travel speeds using GMAW & short circuiting metal transfer
Large weld beads and possible overlaps with lack of fusion
When travel speed is increased using GMAW & short circuiting metal transfer what problem may occur?
possible undercut at the toes of the weld
What happens to your arc in GMAW if the ground connection is inadequate?
an unstable arc
Explain stubbing
when the electrode (wire) comes in contact with the base metal but fails to start an arc immediately.
What is generally the cause of stubbing?
excessive wire feed speed, low arc voltage or heavily scaled base metal
or with GMAW excessive slope settings
Explain Arc Hunting
when the wire feed becomes erratic and an unstable arc develops
What is generally the cause of arc hunting?
from severe drag in the conduit liner or contact tip
- causes unstable rate of wire feed speed, and some cases wire pile up
What is the main thing to ensure to prevent arc hunting?
ensure the wire guides and drive rolls are properly aligned
What causes porosity?
A reaction with atmosphere, moisture or other contaminations
Match the porosity causes to the remedies
Causes
C1. Lack of gas coverage due to drafts, the nozzle is clogged with spatter or loss of gas flow
C2. Excessive Tip to work Distance
C3. Excessive gas flow
C4. Foreign material on surface of filler and base metal
C5. Excessive current or voltage
Remedies
R1. Move Gun closer to work to reduce electrode stick out and nozzle to work distance
R2. Check for shielding gas flow. If needed in crease the flow using a wind break or remove spatter build up from the nozzle.
R3. Reduce gas flow
R4. Use settings recommended for filler metal used
R5. Clean and protect wire from dirt and remove rust, oil and other contaminants from the weld joint.
C1 - R2
C2 - R1
C3 - R3
C4 - R5
C5 - R4
Match the Undercut causes to the remedies
Causes
C1. Incorrect electrode angle
C2. Travel Speed to fast
C3. Insufficient pause time on the edges of weave beads
Remedies
R1. Increase side wall pause time
R2. Point towards the undercut
R3. Slow down to allow puddle to blend with base metal
C1 - R2
C2 - R3
C3 - R1
What is a weld failure that is of concern using GMAW. What testing method is it difficult to detect with
Lack of fusion & it is hard to detect using x-ray
What is the only weld test method that is accurate for GMAW processes?
a) Radiographic
b) magnetic
c) bend test
d) ultrasonic
c) bend test
What is the major cause of cold lap (lack of fusion) using GMAW?
carrying a large bead with slow travel speeds.
sometimes referred to as pillowing effect
( little to no penetration of the base metal as the bead absorbs the force and heat of the arc without transfering it to the base metal)
Match the Causes of lack of fusion with the Remedies
Causes
C1 - Improper manipulation of electrode holder
C2 - Puddle to large
C3 - Welding current is to low
Remedies
R1 - Reduce wire feed and move wire from the centre of the puddle to the leading edge to increase travel speed
R2 - Increase current settings or reduce electrode stick out
R3 - Work wire into the side wall or leading edge of puddle - do not allow the puddle to do the fusing
C1 - R3
C2 - R1
C3 - R2
What does WFS stand for
Wire feed speed
Is the following statement correct? Y/N
WFS = Amperage = Penetration
Yes
Match the Causes of lack of fusion with the Remedies
Causes
C1 - Current is set to high
C2 - Excessive root opening or root face is to small
C3 - Travel Speed is to slow
Remedies
R1 - Increase travel speed to reduce heat output
R2 - Increase wire stick out and weave to control puddle action
R3 - Reduce wire feed speed (WFS)
C1 - R3 - Reduce wire feed speed (WFS)
C2 - R2 - Increase wire stick out and weave to control puddle action
C3 - R1 - Increase travel speed to reduce heat output
Match the Causes of lack of penetration with the Remedies
Causes
C1 - Root opening to narrow or root face to large
C2 - Stick out to long
Remedies
R1 - Increase root opening : increase welding current and reduce electrode stick out. Reduce root face width
R2 - Reduce electrode stick out
C1- R2
C2- R1
What is another name for slag inclusions?
Wagon tracks depending on location and shape
What are 4 causes of slag inclusions
Any of the following 6 are correct however 1-4 are most important
1. Improper electrode manipulation
2. Inadequate pre-weld cleaning
3. Inadequate interpass cleaning
4. Current setting to low
5. Preceding pass to convex
6. To much voltage on succeeding passes
What is considered to be the most serious of all weld failures?
a) Inclusions
b) Porosity
c) Under cut
d) Cracking
d) Cracking
What is the cause of cracking if the remedy is as follows;
Redesign joint; use preheat and post heat; use weave beads to increase heat input
a) Faulty design
b) Improper technique
c) To small weld bead
d) Rigidity of joint
d) Rigidity of joint
List 5 causes of Porosity within the weld bead if the problem is in the process
- Lack of shielding gas
- Improper inclination
- Air drafts
- Contact tube not centred
- Dirty base material
List 2 Causes of Stubbing
if the problem is in the process
- Excessive wire speed
- Arc voltage to low
List 2 Causes of Burnback
if the problem is in the process
- Wire speed to slow
- Voltage is to high
List 3 Causes of Unstable Arc if the problem is electrical
- loose cable connections
- badly worn or dirty contact tip
- loose work lead connection ( ground)