Galvanized steel

Date 06-14-2004 03:42

Mark:
Much of this is yes in your favor, BUT if the job is of low tollerance and not critical the time addition doesn't gain the job any meaningful dollars, therefore it doesn't get done. The penetration is probably going to get to hard metal but the porosity and inclusions will be much higher and the weld will be weaker. The trick is to choose your battles wisely and be ready to recant when the matter is simply no-matter of quality just dollars.

I'm in your corner for quality, but remember the company needs to make money to make you salary payment!

Peace,
pjseaman

By jwright650 (*****)

Date 06-14-2004 11:12

I hear what you are saying, but some can use the 7018 (some use 6010 or 6011) and use a slight oscillation ahead of the puddle (about an 1/8"-5/16") and back. This volatilizes the galvanizing before diluting it into the puddle. All that zinc will melt out ahead of the puddle. This isn't what most inspectors like to see, but it can produce a decent weld for adding a galvanized bent plate for a pour stop or something other than full pen welds. I agree with you that all the galvanizing "should be" cleaned off ahead of time and the rust should be cleaned back to shiny material. The welder should keep his/her head out of the plume when welding the galvanized material.
Be objective and give the benefit of the doubt where you can (without compromising), but if the welds don't look right, fix them or at least recommend that they be addressed.
John Wright

By jwright650 (*****)

Date 06-14-2004 11:19

If you have to stick to your guns, use Paragraph 5.15 if this is a D1.1 job. It is written very loosely and can be used in your favor. Welding over galvanizing without objectionable fumes is next to impossible.
John Wright

By swnorris (****)

Date 06-14-2004 16:00

Hi Mark31,

As everyone knows, welds over galvanized surfaces have a tendency for porosity. However, small cracks may develop in fillet welds. The porosity may be within acceptable limits, but the cracking may pose a difficult problem. Investigations have revealed that weld metal cracks in galvanized steel are intercrystalline with a zinc rich layer lining the surface of the crack. On a galvanized surface, the coating is not usually uniform, and the cracking severity will vary with the varying coating thicknesses. Cracking can also be caused by restraint, especially in fillet welds, and the tendency for cracking will increase as the base metal thickness increases. To reduce restraint, the joint can be fitted with a small gap, which also allows volatile zinc to escape.
I agree with John's tip about oscillation, etc., and will add that the weld will contain porosity and possibly cracks if the zinc is not completely volatilized in the area where the weld metal is to be deposited. Also, on base metals 1/4" or thicker, insufficient penetration may be a problem with fillet welds. Always use the largest diameter electrode compatible with the base metal thickness and welding position, and with a whipping motion, concentrate on volatilizing the zinc ahead of the arc.
6010 and 6011 electrodes have been recommended for this, and as John said are sometimes used, but since most job specifications require 70 series electrodes, make sure that the job specifications allow for the use of 60 series.