Adding to existing undersize fillet weld
Adding to existing undersize fillet weld
(OP)
Have a situation where existing welds that connect standard shear connection clip angles to beam webs are undersized. The connections are of filler beams to spandrel beams. Need to get a 1/4" leg size on the weld, and at present have only 1/8 to 3/16".
The simplest thing to do seems to be to get the primer and slag off the as-built welds, and then give them another pass. However, the this seems like it may take more skill than is available. The structure is up, and the work will be difficult and partly overhead. I am concerned that getting a thicker leg size may not be possible.
The clip angles are 5/16" thick, beam web is 3/8" thick.
Anyone ever had this problem? Any suggestions? Thanks for
any comments.
The simplest thing to do seems to be to get the primer and slag off the as-built welds, and then give them another pass. However, the this seems like it may take more skill than is available. The structure is up, and the work will be difficult and partly overhead. I am concerned that getting a thicker leg size may not be possible.
The clip angles are 5/16" thick, beam web is 3/8" thick.
Anyone ever had this problem? Any suggestions? Thanks for
any comments.





RE: Adding to existing undersize fillet weld
No preheat is required unless the steel is Grade 55 ksi or above. Your legs and thicknesses are small enough to avoid that.
I would make sure that during the welding, the beam will not loose its support due to temporary melted weld material...perhaps a temporary screw jack column under the beam would be a good idea.
RE: Adding to existing undersize fillet weld
RE: Adding to existing undersize fillet weld
Repairing an installed structure can be expensive, but worse than that it is more difficult to maintain the same quality standards as in the shop. You could potentially solve one problem and make others.
If you have not done so already I would do some calculations to determine if the current weld size is or is not fit for purpose. If the main failure criterion is fatigue the bigger welds may not increase the life of the structure indeed the lower standard of welding may make its life shorter.
TERRY
RE: Adding to existing undersize fillet weld
Please explain about steel Grade 55 ksi. Is this minimum tensile or yield strength?
RE: Adding to existing undersize fillet weld
Preheat's main purpose is to control cracking due to high cooling rates of steel. Thus, a thicker plate has a larger "heat sink" that can draw heat away from a fresh weld and initiate cracks. Also, for the chemistry of the steel, the higher the carbon content (as well as the presence of other elements) the lower the critical cooling rate and the greater necessity for preheating. Higher grade steels tend to loose ductility more with cooling.
The Lincoln Elec. Co. offers the following in their Procedure Handbook:
Hardenability can be expressed in terms of a "carbon equivalent" (Ceq) Various formulae have been developed (empirical) that give this number once you know the recipe for the steel:
Ceq = %carbon + (%Mn/6) + (%Ni/15) + (%Mo/4) + (%Cr/4) + %Cu/13)
(valid only if alloy contents are less than the following:
0.50%C
1.60% Mn
3.50% Ni
0.60% Mo
1.00% Cr
1.00% Cu
Approximate preheat temperatures:
Ceq up to 0.45% - ....preheat is optional
Ceq 0.45 to 0.60% ....200 to 400 deg F
Ceq over 0.60% ....400 to 700 deg F
AWS table 4-3 would probably be the governing "code" rule, however.
RE: Adding to existing undersize fillet weld
Rod