V-groove Dimensions

Date 01-22-2009 21:29

For that thickness, I would consider a J groove (or bevel), rather than a double V, if it'll be possible to backgouge the root pass. If not, I'd consider a K joint.
Reasons:
the amount of filler required will be much less,
the time required to complete the weld will be shorter,
the chance of distortion will be lower.
Giovanni S. Crisi
Sao Paulo - Brazil

By Zeek

Date 01-22-2009 23:29

Thanks Giovanni. The only problem we have with this particular part is clearance for cutting the groove. We basically have 2 large rolled 180° segments of A36 (about 33" high, 25" radius) that will be welded together up the 33" height. The only way we can cut this v-groove is on our waterjet machine. I think putting the J-groove in the part will prove to much more difficult for us. We were looking at using a 45° total bevel angle. However I'm concerned about the shrinkage from welding. How do you go about estimating the part shrinkage caused by welding?

By Metarinka (****)

Date 01-22-2009 23:55

shrinkage is a variable based upon heat input, temperature difference, joint configuration, material etc. that is a very long winded way of saying "depends"

are you worried about dimensional distortion changing the trueness of your rolled shape? Distortion could be reduced by preheating and performing welding at a minimum interpass temeprature.

Finally about the edge preparation. I mirror the proffessor in my opinion that a J groove would require less filler material and reduce distortion. Is it not possible to bevel by hand or milling machine?

I don't have access to D1.1 right now but off the top of my head I know root opening and face have a relatively wide range for this joint . What process are you using?

By Zeek

Date 01-23-2009 00:03

We were going to use GMAW and ER70S-6 solid wire with a 75/25 mix for shielding gas. I don't want this barrel to cloverleaf on me, so I definitely want to control the distortion in that regard. Basically the wall thickness was 2.25" inches when we sent it out for rolling and it's going to be cold rolled, so I'm hoping there won't be much reduction in thickness. Once we get this back and weld it together they are going to machine the ID so that they meet an inside diameter of 46" inches or something close. But, when they machine the ID they will only have 1/4" to play with. The minimum thickness of this part needs to be 2" after machining. So, in regards to weld shrinkage, I'm trying to make sure I do what I can to prevent this weld from shrinking the radius somewhat.

By rmkrider1 (**)

Date 01-23-2009 00:14

If the plate is 2.25" thick you could take a 1/4" all the way around which will actually give you 1/2" (to play with)

By aevald

Date 01-23-2009 00:25

Hello Zeek, I believe your shrinkage will be negligible in regards to the finished diameter after welding regardless of process. Consider the circumferential measurement difference between the projected length and a resulting length that had a 1/2" of shrinkage between the 2 weld seams (that would be excessive), this reduction in length would only alter the diameter by roughly .125" As to your choice of shielding gas, I would consider a different choice. With the 2.25" section thickness I believe you could have some serious issues of lack of sidewall fusion on the filler passes if welding parameters weren't pretty tight and the operator's skills weren't spot on. The solid wire with a form of true "spray transfer" would likely be a much better choice and reduce the likelihood of any material soundness issues. Just a few ramblings of mine for your consideration. Best regards, Allan

By Zeek

Date 01-23-2009 00:31

Thanks for the comments. Would you recommend 100% CO2?

By Metarinka (****)

Date 01-23-2009 00:40

I was in a similar situation in my facility, I switched all machines from 100% CO2 to 85/15 which allowed spray transfer around the temperature and thickness we welded at. In generall it's not possible to realistically achieve spray transfer with solid wire GMAW when using over a 20% CO2 mixture. I would reccomend 85/15, or 90/10. If you want I even have starting parameters on hand for GMAW using that exact wire.

By Zeek

Date 01-23-2009 00:55

Oh that would be great. We were hoping to start experimenting with the parameters this weekend, but if you have some recommended settings, that would definitely give us a good starting point. I would greatly appreciate that.

So, you'd recommend a mix a 85CO2/15Ar or a 90CO2/10Ar?

By DaveBoyer (*****)

Date 01-23-2009 03:38

Zeek: You want OVER 80% ARGON, not the other way around.

By aevald

Date 01-23-2009 03:49

Hello again Zeek, is there any particular code that this is being fabricated and inspected under. If so, you will likely need to qualify your welders as well as the particular procedure that you are going to use. I won't make any specific suggestions for the particular process, parameters, etc., you will likely need to determine that based upon your particular situation and the requirements of the job or applicable code. My comments on your thoughts of using the 75/25 shielding gas mixture on that thickness of plate with the solid wire are based on experiences relative to heavy plate welding that I have been involved in in the past. I would generally follow Metarinka's suggestions for shielding gas choices if you plan on using the solid wire and setting this up to be welded in a "spray" transfer mode. Here again, you should only consider making changes if you have the necessary procedures and policies in place. Best of luck and regards, Allan

By Metarinka (****)

Date 01-23-2009 07:23

Aevald and Dave Boyer offer good advice.
for clarification the gas mixtures are 85% AR 15% CO2.
In general, for production GMAW using solid wire CO2 has fallen out of favour due to excessive spatter, narrower parameter range and other undesirable effects. CO2 in volumes over 20% prohibit the use of spray transfer which is generally more desirable to weld under. From my personal experience 85/15 offered the optimal weld conditions and parameters as opposed to 100% CO2 or 100% Argon.

PM me if you want those parameters.

On the related note I'm not a fan of 95/5 Argon/oxy or any argon oxygen mixture as tend to increase the oxidation potential of the weld, or oxidize alloys during welding. I may be impartial but most of the material I use specifically denies the use of 2-5% oxygen in the shielding gas. In general you can get the same affects using CO2 or helium without significantly lower issues of oxidation

By Zeek

Date 01-24-2009 18:38

Thanks again for the advice. I sent you an PM regarding the GMAW parameters on this plate. We're still in the process of machining the joint, so it'll be a couple days before that's ready.

By Kix

Date 01-23-2009 13:58

Why don't you go with a metalcore wire (not fluxcore) and the cheaper 90/10 argon/co2 shielding gas. Time is money

By leterburn (**)

Date 01-23-2009 03:31

FWIW, We've successfully used spray transfer with 95 / 5 argon - oxygen mix - it surely wouldn't be much more cost and with 95/5 you'll also get more penetration as well as a cleaner weld... in my limited experience with spray transfer. Lucky