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Up Topic Welding Industry / Technical Discussions / Welding SS to galvanized CS
- - By jwright650 (*****) Date 04-25-2013 11:23
Customer has some stone and precast panels on the exterior of their building and wants us to to weld some 304 SS L6x4x3/4's and Plate to a galvanized frame built out of heavy channel shapes.

Any advice on this?

I checked with the AGA and they don't recommend mixing SS with anything that has been galvanized and for good reason(LMC). I'm nervous about tackling this due to the heavy stone and precast that will be hanging across the front of the entrance to this building.

1)Contamination of the SS with CS is a given, everything we have toolwise has seen CS everyday of it's life. This L6x4 has to be purchased as a L8x4 and cut down to a L6x4.
2)Grinding the galvanizing off the CS in the areas to have the SS welding concerns me as you can never get 100% of the galvanizing off.
3)Thirdly, my welder's are not checked out for respirator use.
I don't like how this is shaping up, but I've got to deal with it in the best manner possible. I've got to have a little talk with our sales folks and get them to let me know ahead of time when they are going to place me in these types of situations so I can get prepared way ahead of the material hitting the shop floor and a shipping deadline looming over my head.
Parent - By TimGary (****) Date 04-25-2013 11:52
You might notify them of your concerns and point out that the accelerated corrosion from dissimilar metals electrolysis will negate the benefit of using SS anyway, to talk them into using CS and/or mechanical fastening.

Tim
Parent - By OBEWAN (***) Date 04-25-2013 12:25
My first guess is that there might be issues with hot cracking if fillet welds are required, but 304 may be more forgiving on this issue.  A 312 filler might help mitigate the concerns if you have the option to use it.
Parent - By jwright650 (*****) Date 04-25-2013 17:49
Purchasing agent tells me that nobody makes a 3/4" thick angle.....now we might have to weld two plates together to make a "angle"...this keeps getting better and better.
Parent - By tazmannusa (**) Date 04-26-2013 03:14
In the milk barns we weld lighter gage stainless to galvanized quite a bit. good old 6011 works for that, being that your welding 3/4" thick material I think what I would do is grind and burn off the galvanized then weld it up with 309
Parent - By welderbrent (*****) Date 04-26-2013 03:55
I'm with some of the others here John,

1) Grind the galvanizing off as clean as possible/reasonable in the area of welding; about 1 1/2 - 2" beyond weld area.
2) Burn off further with a torch to clean more out of the bonding area; often, after grinding, workers think they are down to steel when they have only smoothed and shined up the zinc.
3) Checked out or not, make them wear a good fume rated respirator; not just cheapy dust mask.
4) Use small volume fan to keep the fume plume away from the welder's breathing area.
5) Weld away, 309 sounds like a good place to start.
6) Coat area with good cold galv. 

Good luck.

Have a Great Day,  Brent
Parent - - By ozniek (***) Date 04-26-2013 03:58
Hi John

As with just about anything, you will be able to get a technical solution to this problem. (Prof Crisi has also made some good suggestions about burning off the galv etc.) You just need to go through a proper risk assessment process, and then do some trials to make sure that everything has been taken care of. I think you have a good handle on the problems you are facing, so you will be able to provide the solutions also. (Liquid metal embrittlement of the welds if not all Zinc is removed; Health hazards; Galvanic corrosion; Corrosion of the carbon steel following the whole process; Contamination of the stainless steel) Once you have done all the preparation work, you may find that you will end up loosing money on the project, but that is another debate. Usually the contractor can re-negotiate some "scope change" if things like dealing with hazardous substances were not included in the quote from the start.

Regards
Niekie
Parent - By welderbrent (*****) Date 04-26-2013 14:04
Yeah, that (what Niekie said). 

Have a Great Day,  Brent
Parent - By jwright650 (*****) Date 04-26-2013 12:25
UPDATE 4/26/13: After sending an RFI we find that other trades have already sent in RFIs about these same issues(SS L6x4x3/4 not available, and the LMC concerns). We proposed using CS material exclusively and then galvanizing the entire frame for corrosion resistance.
So now we wait and see where this goes from here.

Thank you for ALL of the replies, they are helpful to reinforce my concerns, as I don't want to be the QC manager that frets over the small things.

I like to be the guy who CAN DO and when given enough time to prepare, I like to think that I can make things happen and have them go well for our company.
- - By 803056 (*****) Date 04-25-2013 21:00
Nothing good can come of this.

All the literature I've read says that welding galvanized carbon steel to stainless steel is not a good idea.

Al
Parent - - By OBEWAN (***) Date 04-25-2013 22:29
That's what I was thinking too, but I tried to be a little more positive since it seems like the customer is not too open to other options.  My impression is that it could be a crack city project.
Parent - - By G.S.Crisi (****) Date 04-25-2013 23:07
I've put dozens of posts on this Forum saying that it is not Good Engineering Practice to weld galvanized steel to itself or to another material without removing the zinc coating first.
Zinc melts at a much lower temperature that iron and when you strike the arc, zinc will melt inmediately, and in the presence of air will produce a yellow fume of zinc oxyde that is harmful to human health. This is one problem.
The second one is that the molten zinc will mix up with solid iron (Materials Science call this phenomenum "Diffusion") and the weld won't be a sound one.
Before attempting to weld galvanized steel you must burn completely the zinc coating with a torch. Of course, this will produce the yellow fumes as well, from which you should protect yourself, but once the zinc coating has been removed, you can proceed safely with the weld.
Once the weld has cooled down, you should paint it with a zinc rich paint.

Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By OBEWAN (***) Date 04-26-2013 01:41
I forgot about removal of the coating.  One safe option might be grinding.  Zinc poisioning is no fun.  I got it once working on an automotive weld process experiment using a robotic spot weld set-up in a small closed weld lab.  Keep lots of milk handy!
Parent - - By 803056 (*****) Date 04-26-2013 14:43
Water is just as effective as milk and a lot less expensive if the objective is to drown yourself once you are sickened by the zinc fumes.

Milk is not going to help prevent metal fume fever while welding galvanized steel. A good respirator will help.

Keep the milk for after the job is completed. Cold milk and Oreo cookies always helps.

Al
Parent - - By jwright650 (*****) Date 04-26-2013 15:29
Al, I know lots of guys who swear by milk helping them deal with the side effects of welding galvanized.
I would rather prevent it to start with by not breathing it in vs dealing with the effects of over exposure after the fact.
We use the 3M 8512 and 8514 disposable masks to filter out those tiny metal particles when welding galv'd, but I didn't have anything on hand at the moment to help with the hexavalent chromium if we had to deal with the stainless steel. I did get a Miller P100 respirator from a LWS yesterday that fits under the hood and has changeable cartridges for welding on SS.
Parent - - By 803056 (*****) Date 04-26-2013 16:30
I would chalk it up to the "placebo effect."

The inhalation of the fumes causes metal fume fever. Unless the milk is inhaled, I don't see it doing much other than soothing the throat by causing an increase in secretions, i.e., mucus, which coats the throat.

I have worked on projects that specified the welders and helpers had to have free access to milk when they were welding or were grinding hot dipped galvanized materials. They all drank milk and they all got metal fume fever.

Al
Parent - - By welderbrent (*****) Date 04-26-2013 17:36
If I remember the routine correctly...

Part of having metal fume fever is also that the body takes the zinc and utilizes it in the system.  While a proper amount of zinc as a trace mineral is good and even necessary for the body, this process causes the zinc to be absorbed in toxic levels and from a source that is not good for the body.  As is the case with many other vitamins and minerals as well, the presence of counteracting minerals helps relieve this condition.  The calcium and other ingredients in milk 'SUPPOSEDLY' contribute to absorbing excess zinc and drawing it out of the system. 

The problem:  It would be akin to drinking a couple of gallons of milk EACH DAY within a short time period during and immediately following the performance of welding the galvanised parts.  As stated by Al, the mucus from the milk brings along other problems to some of us with various allergies and even lactose intolerance. 

You are better off seeking the advice of a naturpathic physician to see what suppliments could be used and in what amounts to flush your system of toxic levels of zinc if you were so foolish as to attempt the welding without proper material preparation, proper ventilation, and proper protection with a properly fit respirator.

Have a Great Day,  Brent
Parent - By 99205 (***) Date 04-27-2013 22:48
A small fan "sucking" the fumes away always worked for me.  I was just too cool (stupid) to wear a respirator.
Parent - - By CWI555 (*****) Date 04-26-2013 16:34
You can weld anything with the farm code... just sayin
Parent - By 803056 (*****) Date 04-26-2013 16:37
That's is true.

Al
Up Topic Welding Industry / Technical Discussions / Welding SS to galvanized CS

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