HAZ for welding headed stud to plate 1

[dik]

One of my current projects has the contractor welding 3/4" dia headed studs to an existing plate. The existing plate is HDG. I need the coating ground off prior to welding the stud. How far beyond the stud surface should the zinc be removed. I've usually used 1/2", but am thinking this may be inadequate. The fillet weld is 5/16.

 

[lexpatrie]

You could specify removal to match the minimum shelf for the weld size if you wanted, I'm not aware of any standards, the galvanized is "hazardous" but it's the zinc vapor so a mask or other PPE (onus on the welder, not you) and ventilation I'm under the impression suffices, the galvanzing doesn't NEED to be removed for the weld quality that I know of, it's hazardous reduction for the welder.

Two coats of zinc rich paint applied after the welds cool and hot work precautions but again, not exactly on you to specify some of that.

I think the zinc rich paint will be sacrificial before the HDG, conversationally.

 

[dik]

Thanks lex... that's already covered. I will likely stay with my 1/2", then. For normal welding, I use 1".

From my notes:

-IF WELDING OF HDG STEEL IS REQUIRED, REMOVE ALL GALVANIZING FROM AREAS TO BE WELDED TO PROVIDE 1" MIN BASE METAL AROUND ALL WELDS. WORK SHALL BE DONE IN ACCORD WITH AWS RECOMMENDATION WZC. PROVIDE VENTILATION AS REQUIRED. CLEAN FINISHED WELD AND TOUCH UP WITH TWO COATS OF ZINC RICH PRIMER. PRIMER SHALL OVERLAP EXIST GALVANISING BY 1/2" MIN.

 

[dik]

the galvanzing doesn't NEED to be removed for the weld quality that I know of

If using a 'stud gun' for welding, the zinc can cause real problems.

 

[Retrograde]

If using a 'stud gun' for welding, the zinc can cause real problems.

Why is that? I have been told by a competent welder that galvanizing doesn't need to be removed, similar to what Lex said above. What is different about stud gun welding?

 

[HTURKAK]

AFAIK , the only restriction is the welding of galvanized components directly to stainless steel is not allowed. In your case , the concern should be HSE rather than strength.
The following para. from the book ; The Everyday Pocket Handbook on Welded Joint Details for Structural Applications.

Fumes and Gases. Many welding, cutting, and allied processes produce fumes and gases which may be harmful to health. Avoid breathing the air in the fume plume directly above the arc. Do not weld in a confined area without a ventilation system. Use point-of-welding fume removal when welding galvanized steel, zinc, lead, cadmium, chromium, manganese, brass, or bronze. Do not weld on piping or containers that have held hazardous materials unless the containers have been inerted properly.

 

[dik]

Thanks HTURKAK... I've often HDG stainless steel BAR connections to structural steel, HDG for NEMA electrical connections to equipment frames.