Cast Aluminum Alloy

[Olivero]

Hello fellow welders,

Got a question on a cast aluminum alloy. What I got here is a GD-A1Si8Cu3 cast, and its broken so I am wanting to weld it back together, I have done it before using 5356 and I believe I used 4043 once but its not holding up all that great after a while plus it gets used for about 8 hours every night. So i am trying to get a perfect (or as good as possible) filler for it that matches its chemical composition to be the best fit. But Im not sure which to use.

Any suggestions?

[H80N]

Hello fellow welders,

Got a question on a cast aluminum alloy. What I got here is a GD-A1Si8Cu3 cast, and its broken so I am wanting to weld it back together, I have done it before using 5356 and I believe I used 4043 once but its not holding up all that great after a while plus it gets used for about 8 hours every night. So i am trying to get a perfect (or as good as possible) filler for it that matches its chemical composition to be the best fit. But Im not sure which to use.

Any suggestions?

copper bearing aluminum alloy..???... Oh Boy..

What is the part and working environment ....??? temps... ???

could you post some pics...???

[Olivero]

Wow, sounds interesting.

Its for a carpet cleaning machine, nothing fancy at all, Cannot imagine it going above 130 degrees max near the brush.

Keeps saying "error uploading picture"

[Hobart Aluminum]

Olivero,
Based on the info I could find the GD-A1Si8Cu3 contains 7.5-8.5% Si and 2.0-3.5% Cu. The closest matches I could find on the Hobart Filler Metal Selection Chart were 380 with 7.5-9.5% Si and 3.0-4.0% Cu, and 319 with 5.5-6.5% Si and 3.0-4.0% Cu. The chart lists 2319 and 4145 as the two filler alloys for welding both of those castings so I would look at evaluating either of those. Hobart does not currently offer either of those filler alloys so I would check with your local welding distributor and if they can't provide it you might be able to find it online and possibly even eBay.

If you can locate those filler metals I would strongly recommend removing all previously deposited weld metal before performing the repair again. Part of the reason its cracking is because aluminum/copper alloys are very crack sensitive and the most crack sensitive range is where copper is at 3% (see page 27 in the Hobart Guide for Aluminum Welding). When you weld with 4043 or 5356 you are diluting the base metal and somewhere between the 100% weld metal and 100% base metal the mixture is still in the danger zone.

2319 contains 5.8-6.8% copper and 4145 contains 3.3-4.7% copper. Both of those filler metals are adding copper to the weld deposit and shifting it further from the peak of the crack sensitivity curve. 4145 actually has a better cracking rating and this is due to the very high level of silicon it contains (9.3-10.7%). This does a couple of things: 1) lowers the solidification temp of the weld deposit--you want the filler metal to be the last thing to solidify and 2) the excess silicon helps fill in any cracks that may start to form. Most metals contract when they solidify but silicon actually expands upon solidification. I believe aluminum shrinks about 7% and silicon expands about 3% upon solidification if I remember correctly.

I hope this helps.

[Olivero]

Hey, Hobart.

Glad you came into the discussion. Yeah, that helps a lot.

So based on what you wrote, I should go with the 4145 for this?

[H80N]

Airgas lists 4145 TIG rod....

BUT.... it's $27.02 /US pound.... 10lb minimum.................YIKES..!!!!!!

http://airgas.com/product/Welding-Products/Filler-Metal/TIG-Rod-%28GTAW%29/TIG-Rod---Aluminum/p/ATC414536125

[Olivero]

Yup, been trying to see if I can get a sample from Crowne or AlcoTec, no luck so far. Guess I will have to buy the 1 pnd tubes that Crowne makes for $38.00 -.-

Don't even know if its gonna work, hate spending money on a maybe.

[aametalmaster]

How about a pic of the part for a "plan B"...Bob

[H80N]

Here is an interesting AWS paper that deals with crack sensitivity and filler matching in Copper bearing Aluminum alloys

https://app.aws.org/wj/supplement/07-2003-HUANG-s.pdf

[Olivero]

AAMetal Master, I am trying to get a picture up but it won't load it

[aametalmaster]

AAMetal Master, I am trying to get a picture up but it won't load it

Know the feeling. Ever since the new forum style the picture loading really sucks. That's why I don't post many pics because its such a pain in the butt...Bob

[Olivero]

Yeah, can't upload any picture at all........ So frustrating, do you know of a way to do it?

[ryanjones2150]

Try using the phone app. Has been working for me. Not that I upload a lot of pictures, but I tested it and it works fine.

[aametalmaster]

Try using the phone app. Has been working for me. Not that I upload a lot of pictures, but I tested it and it works fine.

Dang now I have to buy a smartphone just to do something that used to be so easy before the "new" forum switch. Trust me I for one loved posting pics but its a real pain in the *** sizing them to fit the new forum. So I don't do much with them. Just show off somewhere else I guess...Bob

[Olivero]

Haha, guess that's the way now, resizing. Yeeeah. I guess I won't post any for a while then.