Not logged inAmerican Welding Society Forum
Hey All,
Looking to get some clarification if possible.
We're a pedestrian/light vehicle (non-highway/roadway) bridge manufacturer in the midwest. We're currently working on PQRs to be able to bid on projects for the NY DOT. Most of the material we use is Tubular A709-50W (A588), aka Weathering Steel, also use plate and I-beam shapes as designed. The process we are testing with is FCAW-G using 81T1-Ni1 wire and 75%/25% Argon/CO2.
So, as for the question: Heat Input requirements. According to New York's Steel Construction Manual, Section 709:
"The minimum heat input during welding of A709-50W (A588) steel shall be 35 kilojoules per inch for
material from ⅜ inch to ¾ inch in thickness and 50 kilojoules per inch for material over ¾ inch in thickness.
The heat input for A709-HPS70W, regardless of material thickness, shall be a minimum of 40 kilojoules per
inch and a maximum of 90 kilojoules per inch. The Contractor shall calculate the minimum and maximum
welding heat inputs for various welding procedures and submit these values to the DCES for approval as part
of the welding procedure specification."
I am trying to discern if the heat input minimum is 'per pass' or 'aggregate average of all passes' and whether that would exclude root and cover passes as described by AWS D1.5 Clause 5.12?
Trying to maintain that level of heat input throughout seems to be a challenge with the wire we're using. The travel you have to use to achieve that, lends itself to allowing slag to get trapped in the weld toes, specifically on the root pass.
Any advice would be greatly appreciated.
Adam - Shop QC/CWI
Adam,
first thought
why FCAW-G? and not just GMAW?
takes the slag out of the problem
as far as heat input
I always used per pass for our stuff
now Al will tell me I am wrong and stupid
sincerely,
Kent
For weathering steel, New York seems to only allow FCAW with an E8XT-1-Ni1 wire (at minimum on the top two covering layers). -Sec. 706.2, Table 706.2 and Sec. 707(a)
At least that is my interpretation of those sections.
By kcd616 
Date 05-17-2016 02:25
Edited 05-17-2016 02:31
Adam,
my thoughts
in a shop use GMAW
same quality and more $$$$$$$$$$$$ for everyone
in the field use FCAW NO gas
this is how everyone makes $$$$$$$$$
this is why we do jobs to make $$$$$$$$$$$$$$
again just IMHO
sincerely,
Kent
edit: yes flux, Kent is counting beans again
I think it's per pass. If going below 35kJ can cause problems (ie hydrogen concentration), then a cold root pass could be detrimental.
Tyrone
No matter how you do it, someone will take issue with the methodology you use. I qualify one PQR using high heat input (Q), and a second using low heat input.
Since FCAW is a semi-automatic process, there is some variation from one pass to the next. I record the parameters for each bead. The goal is to weld using the same Q for each bead, but there is a human holding the gun.
The data is processes using MS Excel and the Statistical Analysis tool to determine the mean values. The ranges for the WPS are based on the calculated mean values.
I had one fellow insist I had to clamp the gun to a Buggo so every bead would be identical. The code doesn't say that.
Best regards - Al
Interesting way to determine the range for WPS. You would need to take measurements from multiple Weldors to get data to calculate the mean and std dev of the population to get a better range. I never thought of doing it that way. I'll give that a shot next time.
Tyrone
A same sample size of 30 is consider to be a valid sample size. A single thick test plate requiring more than 30 beads is a valid sample. However, multiple welders, welding a number of welded samples works if notch toughness is not a consideration. If that is the case, I have used the welder qualification effort to expand the range for procedures that do not need to meet notch toughness requirements.
Al
Hey Al,
You don't use multiple welders for notch toughness due to the cost? or the narrower allowable?
Tyrone
The testing regiment for qualifying a WPS for notch toughness is more involved than simply qualifying a welder. The cost of qualifying a WPS for notch toughness is also considerably higher for qualifying the WPS with notch toughness. If a contractor wants to have each welder weld a test assembly, each using different parameters, and if each test plate is subjected to all the testing needed to qualify the WPS for notch toughness, more power to them. There is a case that can be made that testing many assemblies will present a case of diminishing returns on the investment. In other words, the cost of testing several test assemblies will not extend the usable range of welding parameters in direct proportion to the cost of the additional tests.
Yes, it all boils down to money when all is said and done.
Best regards - Al
Wanted to post some of the answers I have received from an inspector that handles NYDOT specific code concerning some of these questions I had, in case anyone else runs in to it.
The Heat Input minimum is per pass, including Root(s) and Covers. If the PQR does not maintain the 50 KJ/in per pass on Test material Thickness over 3/4", but stays above the absolute minimum of 35 KJ/in, the WPS would be limited to 3/4" Thickness for CJP Groove Welds, and unlimited Thickness for Fillet Welds. Again this seems to be just for A709-50W steels.
Al - Exactly right on the semi-in consistence of FCAW/GMAW welding. We use the PQR worksheets specifically for that reason. To make life a bit easier, I created a Excel spreadsheet that will calculate out the Heat Input factors, as well as set up our weld parameters in a format my boss prefers.
As to the use of a Bugg-O, we have been attempting to use one for these tests, but find you loose some of that human ability to adjust as you proceed.
Adam
Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill
