Q2) When welding in the overhead position, what keeps liquid metal from spilling?
Q3) In what position is this weld if it is 6 inches off of the ground?
Q4) In oxyacetylene welding (OAW), which flame type is best for welding structural steel?
Q5) In arc welding, what is the primary difference between electrodes and filler rods?
Q6)
Q7)
Q8)
Q9)
Q10)
A1) 0
A2) surface tension
A3) overhead
A4) carburizing, reducing, neutral, oxidizing
A5) only filler rods ever supply filler metal, only electrodes ever supply filler metal, only filler rods are ever part of the electrical circuit, only electrodes are ever part of the electrical circuit
A6)
A7)
A8)
A9)
A10)
FOCUS TAKE-AWAYS:
1) Why over-sizing fillet welds is bad practice:
-more material (leg size squared)
-more time (number of passes)
-shrinkage stresses worse - increased risk of lamellar tearing (see also AISC manual 8-17 "excessive welding")
-alternative to upsizing: make the welds continuous instead of stitching them (in other words, don't stitch unless you have to or your weld size is already the minimum possible)
*Note that lower strength weld metal will result in less tendency to crack (but may also result in the need for a larger weld).
2) Why CJP welds can be problematic:
-need backing rod
-backing rod itself needs to be attached (temporarily or permanently)
-removable backing rods need to be removed
-left-in-place backing rods can cause stress concentrations
3) What alternative to CJP may be used for a butt joint to develop member tensile strength?
Base metal strength = 50 ksi
Electrode strength = 70 ksi
Member thickness = T
Member width = weld length = L
Effective throat = E
Tensile yielding of gross section:
PhiPn = 0.9FyAg = 0.9 x 50 ksi x L x T
Strength of PJP weld:
PhiRn = 0.8(0.6FEXX) = 0.8 x 0.6 x 70 ksi x L x E
E for equivalent strength = (0.9 x 50 x T) / ( 0.8 x 0.6 x 70) = 1.34 T (not possible)
Why is submerged arc welding (SAW) more limiting in terms of root face, effective throat? (AISC Table 2.1)...per DG 21, it has "inherently deep penetration"
Distinguish:
-Base metal thickness = T
-Throat = groove depth = depth of preparation = S
-Root face = f = T-S (minima for this exist in prequalified joints)
-Effective throat = E = weld size specified by engineer = probable depth that fusion will be achieved
Depth of Groove = t - min root face
Max effective throat (regardless of process and joint shape): depth of groove - 1/8"
4) What's the deal with the strength increase for transverse welds?
From: Laura Dolak mailto:ldolak@hpse.com
Sent: Friday, April 25, 2014 8:38 AM
To: Solutions Center
Cc: Alex Montalbini
Subject: load direction vs. weld strength
Hi AISC,
Quick question for you: why are welds stronger when they are loaded transversely as opposed to longitudinally?
(See 14th ed manual page 8-8.)
Any resources welcome.
Thank you!
LAURA K. DOLAK, SE, LEED AP BD+C
HALVORSON AND PARTNERS
600 WEST CHICAGO AVENUE SUITE 650 CHICAGO, ILLINOIS 60654
T: +1 312 981 2054 F: +1 312 274 2401 W: HALVORSONANDPARTNERS.COM
Sketch.pdf
From: Solutions Center mailto:Solutions@aisc.org
Sent: Monday, April 28, 2014 5:57 AM
To: Laura Dolak
Subject: RE: load direction vs. weld strength
Laura,
The length of the rupture path increase when the fillet weld is loaded transversely as opposed to longitudinally. I have attached a sketch to illustrate.
I hope this helps. Please let me know if you have any additional questions.
Sincerely,
Carlo Lini, P.E., LEED AP BD+C
Staff Engineer
American Institute of Steel Construction
866.ASK.AISC
5) What's the deal with decrease in strength for long fillet welds?
6) Code language: min and max sizing based on thickness of material being joined
7) How can welds be made more sustainable?
