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I have a supplier who has cast zinc products for us with surface defects that are unacceptable. The supplier is proposing a grinding operation to remove ~1/8" deep x 1" diameter area of the casting to be filled with aluminum Blueshield ER5356 3/64" wire. The zinc casting is a zinc aluminum alloy but I don't have any more detail on the chemistry, it's a supplier-controlled spec. This product is installed outdoors and must last decades in service. I've never come across this type of repair process and I'm concerned about adhesion and long-term degradation. Does anyone have experience with this type of repair process?
Reply:More details might be useful. What kind of objects are they, what size are the parts and do they need the metal surface showing or could they be painted/coated? Are you saying they first need grinding before having the surface rebuilt by MIG welding and if so, is that because dimensions are critical? No idea about the relative proportions (mostly Zn vs Al)? If you need to approve such a repair, shouldn't the supplier be obligated to give more information to base the decision on?
Reply:The zinc casting is a spherical shape that is cast around a zinc-coated steel insert. The steel insert is too big and is protruding from the zinc casting. The grinding is meant to shorten the steel insert because it is prone to rusting, then build up the profile with the aluminum filler metal. We've tried surface treatments that have not worked and the only alternative is to melt the zinc casting off and start again. My question essentially is should I be worried about adhesion between the aluminum filler metal and the zinc casting.
Reply:You need to know the with the cast are made of and the thickness too. Dave
Originally Posted by Ian_in_Canada
I have a supplier who has cast zinc products for us with surface defects that are unacceptable. The supplier is proposing a grinding operation to remove ~1/8" deep x 1" diameter area of the casting to be filled with aluminum Blueshield ER5356 3/64" wire. The zinc casting is a zinc aluminum alloy but I don't have any more detail on the chemistry, it's a supplier-controlled spec. This product is installed outdoors and must last decades in service. I've never come across this type of repair process and I'm concerned about adhesion and long-term degradation. Does anyone have experience with this type of repair process?
Reply:
Originally Posted by Ian_in_Canada
The zinc casting is a spherical shape that is cast around a zinc-coated steel insert. The steel insert is too big and is protruding from the zinc casting. The grinding is meant to shorten the steel insert because it is prone to rusting, then build up the profile with the aluminum filler metal. We've tried surface treatments that have not worked and the only alternative is to melt the zinc casting off and start again. My question essentially is should I be worried about adhesion between the aluminum filler metal and the zinc casting.
Reply:The wire or rod needs to match the color of the casting. If the company want to a epoxy they would have used the epoxy too. Any time you working castings (not iron) they typically do get painted. Myself I would use sticks / rod made from same casting with TIG so color is same. But some casting can find wire the same color too.Dave
Originally Posted by Oldiron2
Have you tried/considered high quality epoxy? Grind the steel down below the wanted surface, leave a very rough surface, and use a product made by a good company like Devcon to build it up. I have literature somewhere about coatings designed to be wear-resistant when lining the insides of coal chutes and such, so suitable products are available. As stated, more knowledge of the alloy is needed for members here to give a valid opinion about compatibility.
Reply:
Thanks for the feedback folks. Alternate repair methods like epoxies, etc are not an option. Long story short we are either doing a weld repair or re-melting the castings and re-casting. I've got a copy of the material cert for the casting below, it's a Zamak #3 alloy with 4% aluminum. Again, the question is just whether or not the aluminum filler metal will adhere long term to the zinc weight in sub-zero outdoor use.
Reply:I would tig weld with same Zamak #3 alloy and pick a bar of Zamak #3 alloy. There maybe a wire with that alloy but I do not know of mig wire. Dave
Originally Posted by Ian_in_Canada
Thanks for the feedback folks. Alternate repair methods like epoxies, etc are not an option. Long story short we are either doing a weld repair or re-melting the castings and re-casting. I've got a copy of the material cert for the casting below, it's a Zamak #3 alloy with 4% aluminum. Again, the question is just whether or not the aluminum filler metal will adhere long term to the zinc weight in sub-zero outdoor use.
Reply:
Originally Posted by smithdoor
.... If the company want to a epoxy they would have used the epoxy too. ...
Reply:Here is a mig wire zinc it may match the color.https://www.superwireindustries.com/...re-158925.htmlDave
Originally Posted by Ian_in_Canada
I have a supplier who has cast zinc products for us with surface defects that are unacceptable. The supplier is proposing a grinding operation to remove ~1/8" deep x 1" diameter area of the casting to be filled with aluminum Blueshield ER5356 3/64" wire. The zinc casting is a zinc aluminum alloy but I don't have any more detail on the chemistry, it's a supplier-controlled spec. This product is installed outdoors and must last decades in service. I've never come across this type of repair process and I'm concerned about adhesion and long-term degradation. Does anyone have experience with this type of repair process?
Reply:I don't think any electric arc process will work. The zinc will gas causing large porosity defects.What about flame heating and melting zinc stick (the type used for galvo repair) over the surface and then filing/sanding to shape?
Reply:It does have problems but can be done. I would not use stick welding. But is about same as brazing. Dave
Originally Posted by Woznme
I don't think any electric arc process will work. The zinc will gas causing large porosity defects.What about flame heating and melting zinc stick (the type used for galvo repair) over the surface and then filing/sanding to shape? |
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发表于 2022-3-3 15:51:21