GTAW On Mild Steel Flashcards
How should you lay the beads when surface welding for buildup work
Blend them together so they form a solid layer of weld metal
Is it necessary (yes or no) to remove the following from the mild steel base metal before welding with GTAW
- millscale
- loose rust
- oil
- varnish
- soapstone markings
- no but is can be done to reduce undercut on the cap pass
- yes
-yes - yes
- no
Identify the following for GTAW on mild steel
Most common electrode type
Electrode preparation shape
Current type
EWTh 2
Conical
DCSP
DCEN
What shielding gas is most often used for GTAW on mild steel
Argon
What size of gas nozzle is recommended for any GTAW application
The smallest nozzle whose lip does not melt in the heat of the arc yet allows good visibility and adequate gas shielding
An appropriate electrode stick out for GTAW
Maintains a gas shield around the electrode and molten weld metal
Advantage and disadvantage of touch start
Adv: DC without high frequency
Disv: may contaminate the electrode
Advantage and disadvantage of high frequency start
Adv: start without contamination
Disv: ceramic nozzles must be used
Advantages and disadvantages of lift start
Adv: no high frequency required
Disv: machine design must be compatible
Name two techniques used for adding filler rod with GTAW
Dip feed
Continuous
Changing the inclination of the electrode holder in relation to the direction of travel
Changes the depth of penetration of the weld
In what positions can you do surface welding with GTAW
All positions
Describe the purpose of tailing out prior to breaking the arc
Prevent cracking in the weld crater
How is the work positioned for a 1F tee joint
Each member at 45 to the horizontal plane
Given the choice what position should you use for the most productive fillet welding
1F
What is the recommended electrode angle for a 2F weld on 10 gauge material
45 degree to the vertical and horizontal planes
What is the likely weld progression for a single pass 3F weld on 10 gauge material with GTAW
Uphill
As a general rule at what thickness of material should joint preparation be considered for full penetration groove welds when using GTAW
3/16
What is the recommended electrode inclination for 1G weld
0-15 forehand
Describe the dip technique of adding filler rod
Filler rod is added at the leading edge of the puddle until the desired fill is attained and then removed from the puddle to progress forward
What is fall through
A localized area of excessive penetration
What is the max electrode extension used for GTAW and why
Do not extend the electrode beyond 1/4 bc this may result in inadequate gas
What is likely to happen if a keyhole forms in the 1G position
Fall through
What is meant by suck back and how may it occur
Suck back refers to an area of root bead that has been drawn into the groove leaving the root side concave in contour. Caused by overheating the root pass during the second pass application.
- travel speed to slow
High current settings for overhead positions
Excessive arc length
Failure to add filler rod deep enough into the backside of the groove
3 actions may be used to increase root bead penetration
Change electrode inclination
Slow the travel speed
Shorten the arc length
Increase amp
Add filler metal closer to back of groove
Change configuration of land and gap
In multi pass welds which pass is more susceptible to cracking
The root pass
A procedure used to help prevent weld bead crater cracking is
Tailing out prior to breaking the arc
What is the purpose of pre setting the 2G weld on a plate
Compensates for shrinkage caused by stringer bead multi pass welding
What is the recommended bevel angle range for a single vee groove weld prep on a pipe
30-37.5
How many tacks are recommended for joining 6” nominal pipe size
4
If the gap is unequal after the first two tacks have been places on a pipe joint you should
Place the third tack at the widest location to even out the gap
Which of the following would be most effective in reducing accidents caused by portable grinders kicking back
Keep both hands on the grinder and clamp the work
