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  1. #1
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    Default Welding galv/ zinc plate steel

    First of all, I try not to. I think the stuff is horrible and prefer to not have it in my shed - however, sometimes you must (friend wants a repair; all there is in the hardware shop; other half doesn't want to paint the trellis she has asked for; bracket will be outside but hot-dip is too expensive...)
    Even when you mechanically strip the coating off there always seems to be some that you miss, and don't get me started about the insides of galv tube.

    Came across a galvaniser's association page https://gaa.com.au/welding/ and around 3/4 of the way down they talk about brazing with GTAW (TIG to us backward types).
    Key points are
    • Up the gas flow to around 12l per minute
    • tilt the torch over to 70 degrees


    I tried it with welding and it did improve things. On normal settings, the arc would spit and contaminate the electrode as soon as look at it. With gas up to 12.5l (by the ball bearing gas gauge) from the usual 7 to 9 and slightly more angle, it seemed to push the zinc fume away from the torch and I even got a half way decent looking bead.
    Still don't like the stuff but at least there is a hope that the electrode will last past the start of the arc.

    I do wonder if this technique will work on brass, as I have some of that to do one day.

    Michael

    (and yes, I had a fan going to get the fume out of the area)

  2. #2
    BobL is offline Member: Blue and white apron brigade
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    Default

    I agree galv is a PITA and mechanical abrasion doesn't or can't get at all the Zn.

    One way I have got around this problem with pipe is to completely strip off the gavl with HCl (sprits of salts) around the area of the weld.
    The easiest/most applicable case is for (very) short lengths of pipe as these can be just dunked into HCl and it will bubble away furiously while there's Zn remaining and then settle down to a more gentle bubble when it starts to attack the steel. Pull it out and neutralise it in washing soda. then wash off the soda, Weld - if its left for some time after welding remove any rust and then paint etc.

    If you try this (as well as decent eye and hand/wrist protection) I recommend
    - doing it outside as large amounts of Hydrogen are generated and
    - using a container that is much larger than the volume of HCl as the bubbles will rise up like a volcano and overflow the container onto your other half's fave bit of brick paving or kill the grass if you do it in the middle of the lawn

    Longer lengths of pipe are problematic. If the welding is only to be done at the ends of the pipe it is usually easy to strip off/out the Zn just at the ends by standing the pipe in a bucket of HCl.
    If the welding is to be done only in the middle of the pipe then the ZnO produce on the inside doesn't matter so much.
    On the outside it's possible to strip off the Zn in a specific patch by placing the pipe horizontal and wrapping some rags around the pipe on either side of the area to be welded and spraying HCl onto the area. Spraying HCl is not exactly OHS kosher, so painting it on would be safer. HCl dripping off the pipe and rages is inevitable so some sort of acid proof drip tray and a sheet of pectic under that are advised. At the start some of the acid that falls into the drip tray can be repainted back up into the pipe.

    This can become a real PITA if there are lots of pipes involved - only you can determine if its worth it.

  3. #3
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    Default

    Going off memory here, zinc (the gal coating) vapourises around the 700 degree mark, whereas the steel you want to weld becomes liquid (aka weld pool) at 1200 or so.
    So to that end, MIG or TIG brazing can allow a lower strength weldment without fusion into the base material, and still be below the zinc vapourisation temp.

    Never tried it myself. Although I know some of the non structural architectural guys use it for handrails (for subsequent powder coating), pool fences and the like.
    Last I priced up some silicone bronze mig wire it was north of 400 clams for a 15kg spool, and not available in anything smaller. TIG might be a different story though.

    Let us know how you get on with the job.

  4. #4
    BobL is offline Member: Blue and white apron brigade
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    Zm melts at 690C, if there is oxygen around it starts to burn at around 790C and boils at 900C.

  5. #5
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    Quote Originally Posted by Commander_Keen View Post
    ...Let us know how you get on with the job.
    Here is a couple of corner welds on 1mm galv steel. The only prep was to wire brush the worst of the white stuff away from the weld area.
    This using my usual settings
    P1040800.JPG
    This is with the same current etc but slightly greater torch angle and more gas.
    P1040799.JPG
    I'm convinced...

    Michael

  6. #6
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    Default Electric brazing

    Hello from the old goat.
    Silicon bronze is used extensively with gal material both by mig and tig/gas. A good info source is Wisconsin wire company in USA. It is very particular about parameters. 0.9mm runs best between 90-115A. You must keep the torch angle up or spatter goes everywhere. Unlike steel spatter this stuff sticks like poo to a blanket. Good for dissimilar metal welding too. EG black steel to SS, gal steel to SS. Also for build up by tig on cast iron axle boxes that are machined too far. Use straight argon gas. Mig build up of low stressed steel parts is good too.
    As it is electric brazing the parent material is only raised to approx 800 deg.
    Usually in stock in 5kg rolls at $145.00 plus GST but sold one yesterday so a few days away. Tig rod in 1.6 and 2.4mm held too. High corrosion resistance and strength too.
    That was long winded. It machines like copper and has 60% of brass machinability I think.
    Regards
    BC

  7. #7
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    Why not change your profile name to just Old Goat, it seems that you have to repeatedly tell us it’s the Old Goat again, why?

  8. #8
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    Default

    Riding the goat.

  9. #9
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    Default

    So I started a thread on TIG welding galvanised steel, based on this -

    Quote Originally Posted by Michael G View Post
    ...Came across a galvaniser's association page https://gaa.com.au/welding/ and around 3/4 of the way down they talk about brazing with GTAW (TIG to us backward types).
    Key points are
    • Up the gas flow to around 12l per minute
    • tilt the torch over to 70 degrees


    I tried it with welding and it did improve things.
    And you have responded with a comment about silicon bronze MIG welding brazing

    Quote Originally Posted by steamloco1954 View Post
    Silicon bronze is used extensively with gal material both by mig and tig/gas. A good info source is Wisconsin wire company in USA. It is very particular about parameters. 0.9mm runs best between 90-115A. You must keep the torch angle up or spatter goes everywhere. Unlike steel spatter this stuff sticks like poo to a blanket. Good for dissimilar metal welding too. EG black steel to SS, gal steel to SS. Also for build up by tig on cast iron axle boxes that are machined too far. Use straight argon gas. Mig build up of low stressed steel parts is good too.
    As it is electric brazing the parent material is only raised to approx 800 deg.
    Usually in stock in 5kg rolls at $145.00 plus GST but sold one yesterday so a few days away.
    Why is this relevant? I don't mind things veering a little OT, but this contributes nothing to discussing TIG welding of galvanised steel

    Michael

  10. #10
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    Default

    Yes I agree.
    Lets keep it on topic please!

    Grahame

  11. #11
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    Default Tig welding gal steel

    Quote Originally Posted by Michael G View Post
    So I started a thread on TIG welding galvanised steel, based on this -



    And you have responded with a comment about silicon bronze MIG welding brazing



    Why is this relevant? I don't mind things veering a little OT, but this contributes nothing to discussing TIG welding of galvanised steel

    Michael

    Hello Michael.
    I was replying to commander Keen's post which mentioned Silicon Bronze as filler metal suited to joining gal steel. There was also a question as to the availability of smaller spools. Some hints as to it's use were also given. Tig welding is more common in home shops now that inverter machines are well priced but info on filler metal and it's use not so. It is also a good alternative to 309 SS for dissimilar metals if heat input can be a problem.
    Regards
    BC

  12. #12
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    Quote Originally Posted by Michael G View Post
    Here is a couple of corner welds on 1mm galv steel. The only prep was to wire brush the worst of the white stuff away from the weld area.
    This using my usual settings
    P1040800.JPG
    This is with the same current etc but slightly greater torch angle and more gas.
    P1040799.JPG
    I'm convinced...

    Michael
    Interesting topic Michael and thanks for the photos. I used to tig a lot of thin gal tube, but usually by mig these days (one of the motivations for buying a mig).
    My prep has always been to grind most of the gal/zinc off (i.e. until spark pattern changes). I've never bothered with HCl. If I did, I would never do this without neutralising and rinsing as explained above, as you would inevitably get internal rust. Having removed most (but not necessarily 100%) of the gal by grinding I found that TIG was doable.
    Things I noticed:
    - yes it was still possible to get a decent weld even when the tungsten had a blob of zinc on it (not at the tip but further up)
    - whilst most of the weld was good, I would get random areas of porosity, which I attributed to zinc revapourising when the blob got too big and being pushed by the argon back into the weld. If enough zinc had been removed and I swapped tungsten before it got out of hand, I wouldn't have a real problem.
    - the welds used to sometimes have a black, almost oily look to them, but would wire brush up OK.
    - shallow welds without full burn through/penetration were fine, but the will the live quickly evaporates once drawing in zinc from the back.
    Because of the random porosity, I would never trust the welds structurally, although I never have noticed any strength issues with a zinc-influenced weld.
    I'd never seen that article before, but I did actually start using higher argon flows to good effect, but the reason I started that was because of background fan to remove fumes.
    Yes I use a respirator. Yes I have fan, but have it behind me so the weld is shielded. I can't remember ever suffering from zinc fume 'fever'.
    And a slight diversion - even though the MIG is more forgiving with gal, I still grind most of it away so that the weld edges cleanly adhere and to reduce fumes.
    Cheers
    Mick

  13. #13
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    Good to know about the options for TIG - I've tried it exactly once and regretted it.

    With MIG I find CO2 copes far better than MIG mix, even with heavy gal if you're too lazy to remove it. Does have a heap of spatter, but the welds look good.

  14. #14
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    Quote Originally Posted by RustyArc View Post
    Good to know about the options for TIG - I've tried it exactly once and regretted it.

    With MIG I find CO2 copes far better than MIG mix, even with heavy gal if you're too lazy to remove it. Does have a heap of spatter, but the welds look good.
    If it's part of the concern, you'll never get it into GMAW spray transfer with 100% CO2.
    The fume with CO2 is horrible too, due to the high energy arc. Watch this space, weld fume will become the next 'asbestos'.

  15. #15
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    Quote Originally Posted by Commander_Keen View Post
    If it's part of the concern, you'll never get it into GMAW spray transfer with 100% CO2.
    The fume with CO2 is horrible too, due to the high energy arc. Watch this space, weld fume will become the next 'asbestos'.
    The inability to spray with CO2 is often used as a selling point for Argon based mixes by the various gas supply companies. Honestly I think it's a pretty weak argument in the grand scheme of things. Spray transfer is of limited use to most people as it is a downhand only process and most handymen do not have welders/power supplies capable of spray transfer with any sort of useful duty cycle. Pulse migs have muddied the waters somewhat, but I haven't seen any set up for steel in my travels as most people seen to reserve them for Stainless and Aluminium work. I would much prefer to use a gas shielded flux core wire if I had a heavy job to handle as I can run high amps flat, vertical and overhead with little or no change, whereas solid wire is limited. I have probably run 10 times more CO2 than Argon mix and prefer it under virtually all circumstances, particularly where Duragal or actual galvanised product is concerned. CO2 provides a much better penetration profile and is far less prone to root porosity than Argon mixes and will handle rust and dirt far better than Argon mix. In my experience, most of the fumes come from the contaminants on the steel and I find CO2 welding no more or less fumey than Argon mix welding.
    On the subject of spatter, CO2 can be tuned to be almost spatter free on thin materials and what spatter you do get is relatively easily removed unlike the Argon mix spatter that sticks tenaciously. Add this to the clear price advantage of CO2 and for me, the choice is easy.
    For my personal usage at home, I run CO2 shielding gas with either .9mm ES6 solid wire or 1.2 or 1.6mm Kobelco DW - 100 fluxcore for the big jobs. At work, I run Supagas Argon 10 for one reason and one reason only, that being several ongoing jobs we have welding y12 deformed bar to 75X10 flat in the downhand position with the final product to be galvanised. Wire feed maxxed out and voltage 2 steps from flat out and let her rip.
    I definitely agree though that welding fumes are often overlooked. There are so many options available now that were not about when I started my trade. You certainly don't need the full on Adflow hood as a hobbyist, but there are now several affordable respirators aimed at welders that will fit under a standard shield.

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