welding thick walled tube

Date 01-21-2014 01:00

I have a 6 foot piece of 3.5" OD X .625 wall 513 steel tube, nothing special, very weldable carbon tube.
I have two collars that must be welded to this tube.
Each collar is a 2" thick piece of T-1 (ASTM A514) HSLA steel about 10" X 10" square footprint. These pieces are welded towards each end of the tube.
Any problems with using an all around weld to make the joint?

I am not worried about the operating services stresses, but more so the post weld induced stresses due to restraint of the collars and the all around weld.
There is about a .050 gap between the collars and tube, the collars have a machined ID, where the tube is mill finish.
Weld process is shielded arc, with a typical shop wire, 70 ksi strength.

Any potential problems?

Would it be better to split the collars and weld them as two haves - even though it's more expensive?

Thanks

By swsweld (****)

Date 01-21-2014 21:56

Billz,
I would recommend a higher than normal preheat due to the thickness and material combination.
200F min preheat and interpass temperature and 450F max interpass should get you in the ball park. Check the weldment in 48 hours for cracking. This material is prone to cracking. We used HSLA on MRAPS and these temperature ranges worked well but we were not welding collars. I understand your concern.

Also, LH electrodes treated properly is essential. You don't want to introduce hydrogen into the welds from the rods.

Wish I could suggest a certain wire, we used 110KSI and other companies used 70KSI for the same materials and had WPS/PQR's to qualify it.
The preferred process was FCAW but lots of SMAW was done as well.

By billz

Date 01-21-2014 23:23

Thanks for the input.

Do you think it matters much if the collars were split by 1" , using a 1" small piece of CF flatbar welded in to fill this gap?
Would this create less restraint and therefore less stress due to welding?

The wire used is Lincoln arc 712C .045" dia., the T-1 has a 250 degree F preheat call out.

By swsweld (****)

Date 01-22-2014 19:16

billz,
The .050" gap should be sufficient to allow for the thermal expansion. I don't think the FB is necessary but...you might want to do one without, before you do both, that is if you have the time to go that route.
I'd plan for a slow, gradual cool down also.

By welderbrent (*****)

Date 01-22-2014 03:52

Billz,

1) What type of weld? I presume a fillet weld? What size is called out?
2) According to D1.1-2010 Table 4.9 your ASTM A514 (T1) is actually 175°F. But, I would personally go with about 200-250° with the size material you are talking about. The steel tube is not as critical (?) as the mass of the T1. Concentrate the pre-heat flame on the heavy material.
3) You are talking about GMAW with .045 and 70ksi? The recommended for that is an ER110S filler. While it can be done with the correct process and procedure depending upon the application, it is a little questionable.

Now, finally, the reason for my (?) in #2 above and some other hesitancy in an answer, 513 steel tube? There is no 513 shown in ASTM nor in the Pre-Approved D1.1 Table 3.1 or 3.2. Is it by chance A53? If so, then the 70ksi filler could be workable. That will depend upon application/usage and/or job specifications.

I would not be that concerned with the stresses. Mostly eliminated with the proper pre-heat and inter-pass temps. Again, depending upon the usage and how you would weld that split, or piece removal, back in...you will create more stress from that than just welding it like it is.

Have a Great Day, Brent

By billz

Date 01-22-2014 18:18

Thanks for the replay,

I did goof up, the tube is A519, CDS 1018 material, not 513
The weld is a fillet weld.
The wire meets the AWS 71T-12 spec, ultimate strength 70-90ksi, with 79ksi being typical.
There is enough weld for the service loads, so I used a wire that would not be too hard even if welded slightly improperly.
In running test, I have found the weld can become very hard - sometimes harder than the spec says it should become, so in this case I erred on the safe side.

I know allot of folks weld solid, round collars on tube, but the welder I am using had concerns about this, so I am addressing his concerns by getting more inputs.