inspector 362
Lincoln Electric procedure hand book of arc welding makes two references to maximum interpass temperatures
The first is for A514 where it gives the max. interpass temperatures for material up to 1-1/2" inclusive is 400 degrees and 450 for greater thicknesses.
The second seems to be a rule of thumb. Max. interpass temperatures may exceed minimum by 100-200 degrees.
I'll keep looking.
Lew
Hi
If you look at 3.5 Minimum preheat and interpass temperture requirements, table 3.2 gives minimum preheat and interpass temperature.
5.6 Preheat and Interpass temperature.
5.21.7 Temperature Limitations
And Annex XI will help you
Mike
The information in the previous post was taken from D1.1 2002.
Mike
Inspector 362
AWS Welding Handbook states:"Generally the interpass temperature should be maintained within 150 degrees of the preheat temperature.
Lew
Actually, the reason I ask is that almost all of the reports to be filled out ask for a minimum and maximum interpass temperature
I don't recall D1.1 addressing maximum interpass temps. I qualify our PQRs to D1.5 and I use the maximum recorded interpass from the testing which we limit to 500 deg F. I really don't know why we use a 500 deg limit, probably because of the various ASME wpss our company has.
Chet Guilford
Inner pass can have direct impact on Yield strength and should be determined by a PQR.
We have some procedures that have the same preheat and inner pass temps.
The interpass temperature is allways the MAXIMUM interpass temperature.
Preheat-/working temperature is allways the MINIMUM temperature.
Best regards
Happy
(This is not true, see replies below. However, I didn´t want to delete the post, since in that case the replies would make no sence)
Hello Happy,
I am of the impression that the reason they label this paragraph 3.5 "Min. Preheat and Interpass Temp. Requirements" is because welding can get interrupted (change of shifts, lunch time, etc...) and they want you to maintain a min. of whatever temp the Table 3.2 calls for. If you go to lunch and the temp falls below the min interpass temp. then you have to get out the rose bud and heat it back up before you can continue welding.
I haven't ran across a Max. interpass temp. chart in D1.1 but I would think your acceptable weld profiles would limit how much heat you can input and still maintain the acceptance criteria. At some point you'll have to stop and let it cool a little to keep the weld metal in the groove. Also see Paragraph 5.6 for another explanation of this thought. I believe the steels that may have a Max. preheat and interpass temp might would be Quenched or Tempered steels, but don't quote me as I'm not 100% sure about that.
I guess if I had to guess at a max temp for preheat or interpass on mild steel I would say that paragraph 5.26.2 would give an indication if you were approaching 1200F, that would be the top end temp for most mild steels. I keep a 1150F temp stick in my welders pocket for checking the temps when they are heat straightening so they won't violate the 1200F limit. Hope I was able to explain myself without offending. :)
John Wright
Hi John!
You are right. There is a difference between working/preheat temperature and minimum interpass tempeature: the minimum interpass temperature caould be higher than the preheat temperature.
No offence taken!
Lew sums it up below.
Best regards
Happy
The minimum interpass temperature is at least as high as the minimum preheat temperature. On sensitve base metals the minmum interpass tempwerature must be sufficient to prevent cracking, while the maximum must be controlled to provide mechanical properties
To maintain this balance these varibles must be considered; time between passes, base mealt thickness, preheat temperature, ambient conditions, heat tranfer characteristics and heat input from welding.
Which poses another question,about heat input. I think I'll post that question now.
Lew
Thanks Lew!
Also se my post to John above.
Best regards
Happy
I failed to follow a basic rule here. I did not read the question correctly and jumped in too fast. The MAXIMIM was missed by me entirely. I apologize and promise to read and re-read before offering my 2 cents again.
Mike
MBLAHA,
The question was worded kinda tricky. Like the old " If 1/3 of a Dollar is $.33 then whats 1/3 of a Dollar and a half"?
Most of us think of inner pass as a MAX to start with pre heat as a MIN.
Who ever designed the forms he is filling out got it confused also.
RonG
AWS D1.1, Annex E, forms is where they are found. I know it sounds like I am nit-picking, but that question on almost all forms that I have seen, ask for it. I am beginning to come to the belief that it is only for insertion if required for base metals that need it. But, even software producers that have record generating capabilities get their information from somewhere.
I have no literature in front of me to back it up, but it seems to me that years ago when I wrote some prequalified procedures, I used ASM Book 6 which, if I am remembering correctly, had references to maximum recommended temperatures. Since all I ever deal with is basic structural steels, 500°F is the number that sticks in my head and what I have on my current prequalified WPSs. It has to do with not crossing into a range where the metalurgy of the steel transitions which if I remember correctly is around 600°F. Remember that part of the CWI training/test that I knew almost nothing about! Hardest part of test!!! Anyway, hope that gives you another place to research. If I am remembering the correct book, ASM 6 is a book packed with a wealth of welding information and I need to find a copy to put into my personal library. Costs about $175 new, I think.
Where can I look for this book?
Available through American Society for Metals (http://www.techstreet.com/cgi-bin/detail?product_id=246403).
Also can be found on e-bay occasionally. Try used bookstores on-line for older versions of this book also (I think '71, '80 & '93 is most current edition).
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