A36 Weld Shrinkage

Date 01-23-2009 14:18

Zeek,
if your great concern is distortion, then a double V joint is the best one, rather than a J or K, as I suggested on the other section of the forum.
I've got with me a booklet published by Lincoln and titled (in English) "The welding shop foreman's handbook", where a chapter is dedicated to how to prevent distortion. The book is printed, not in electronic format, but I can fax you the interesting pages if you let me know your fax number, including area code. The book is written in Spanish, but this shouldn't be any problem, because I've heard that a good part of welders in the US are hispanic.
Another place you can draw information from is the TWI's site (www.twi.co.uk). TWI is The Welding Institution of the United Kingdom.
A word of advice: it's been awful expensive to cold roll two pieces of steel 33 inches long and 2.25 inches thick, so, don't start welding until you've planned a good welding sequence so as to minimize distortion, and I stress the word "sequence", rather than "procedure", because procedure will guarantee the weld quality, regardless of warpage, and sequence will guarantee the weld straightness.
Giovanni S. Crisi
Sao Paulo - Brazil

By aevald

Date 01-23-2009 15:51

Hello Professor Crisi, certainly agree with your last comments on this post. The proper sequence will certainly be of importance to the overall success of his project. Best regards, Allan

By CHGuilford (****)

Date 01-23-2009 17:38

One thing we do to minimize distortion is to use a 2/3 - 1/3 depth bevel and weld the 2/3 side first. (For 2.25 inch thick you probably want 1.5 and .75 depths)
This places the root and next 1 or 2 passes near the centerline of the plate so that weld shrinkage does not tend to cause bending - which causes most of the visible distortion in welding.
Maintain your preheat, weld out the root and if you can, halfway out the large groove side. Then backgouge the shallow side to sound metal and put a few passes in there. As you build thickness, you gain more resistance to bending.
It is important to maintain your preheat through the thickness and avoid having one side hotter than the other.

To figure shrinkage I use Lincoln Electric's formulas:
Transverse shrinkage = 0.10 (weld cross sectional area divided by weld thickness)

I don't know the formula for axial shrinkage but I don't think that shrinkage will cause you much of a problem, 2.25 is pretty stiff.

By G.S.Crisi (****)

Date 01-23-2009 18:57

Chet,
I agree entirely with you on the 2/3 and 1/3 depth bevel. As a matter of fact, it's lilke that that the Lincoln handbook I've mentioned recommends to weld thick plates.
However, the Lincoln hadbook says to weld the 1/3 side first and, after it's completed, weld the 2/3 side. It's written like that on the handbook.
Giovanni S. Crisi

By CHGuilford (****)

Date 01-26-2009 18:06

Giovanni,
I wonder if that's a typographical error?

Lincoln has been in welding for far longer than I've been alive so there certainly know more that I do. However, if that is not an error, then I don't understand their reasoning.

By G.S.Crisi (****)

Date 01-29-2009 16:38

Chet,
it's not a typo mistake. The booklet is in written format and I can't send it by e-mail. If scanned, it'll loose some of its accuracy.
I can send it to you by air mail, but for this I need to know your address. You can put it as a private message to me in this same Forum, if you prefer.
Giovanni S. Crisi