"smoothing" welds

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Hello all,TIG question: I do repairs and some minor fabrication on aluminum fishing equipment, and there are some places where the net rides over the aluminum where it must be very smooth, or it will catch the finer meshed nets. On the last job I did, I was widening the stern rollers, and instead of using the flapwheel to smooth out the welds after, I experimented with going over them again with the TIG torch, but with no filler, and smoothed the bead out that way. I was pleased with the results, but I wonder if that method will ruin the integrety of the weld?The end result was a smooth seam with no ripples in it, that was only slightly raised above the parent aluminum. Obviously I would only try this in spots where it is challenging to use the flapwheel or the wire wheel and where it has to be very smooth. Is this a mistake?-RyanLast edited by Ryan McEachern; 05-23-2007 at 03:04 AM.
Reply:i dunno if its a mistake but it sounds good and dont see why it would weaken the weld.
Reply:re-melting a weld can cause problems. some metals 'lose' some of their alloying elements when welded (boiled off due different melting temps) and so filler often contains a higher percentage of these elements to compensate. with aluminium the fillers contain excess to dilute the weld and prevent cracking- Al is crack sensitive when certain amounts of copper, magnesium and/or silicon are presentas you're talking marine aluminium i assume you're welding 5052, 5083 or similar. i would guess that if you used 5356 filler you should be fine as the would contain an excess of magnesium. if you welded with 4043 it's possible (remember i'm guessing here) that the weld ended up containing magnesium silicide and may be susceptible to stress corrosion cracking. as an aside magnesium silicide is the reason that filler must be used with 6061- the weld WILL crack if 6061 is fusedi would stick to sanding the weld smooth or altering your technique to leave a smoother weld. good reputations take time to aquire and are easily lost
Reply:Now ya got me thinking.....  Hotrodder,  I honestly never thought about it and don't know, but if remelting a weld can cause problems how does that work with multiple pass welds?  Would a joint with a single larger pass be stronger than the same joint with multiple passes since you are actually remelting and adding more heat to the joint with the extra passes.  Just curious....I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Wow, another nice thing about all those time zones! Sure don't have to wait long for an answer on this Forum. Thanks for the cautions hotrodder. I am indeed using 5356. The reason I asked for input is that sometimes when I am modifying an existing piece of equipment, it gets really hard to access parts of the weld with the grinder. Of course, if it is hard to get in there with the grinder AFTER the weld, then it was hard to get it clean BEFORE the weld, so I often am working with less than perfectly clean aluminum. (hence the need to smooth out some sections better). I will try to borrow the digital camera form the "admiral" and get her to help me post some pictures so you can see what I am talking about, but an example would be a 12 inch butt weld where the last 2 inches are covered by a piece of tubing coming down on an angle, making it hard to get the grinder in there right. It seems that I can get the smaller TIG torch into tighter spots than I can get the grider into, but maybe I would be better off investing in larger and smaller grinders to get into tougher spots.Thanks.-Ryan
Reply:Reheating the weld is not good.  Aluminum welds are not as strong as the parent metal.  By reheating the area you increase the area that has lost its heat treatment.  If the area is highly stressed you could expect failure later on.  If the area where the net rides is not highly stressed you should be OK.  Often the only proper repair on damaged or cracked aluminum is to cut out the piece and insert new.  Talk to someone that has done aluminum fishboat repairs over the many years.  There are quite a few of them floating around after the aluminum fishboat boom and the fast ferries.  Also a die grinder with a carbide burr is your friend.  Use the burrs with the course spiral flutes designed for aluminum.  Gloves and faceshield are a must as the slivers are deadly.
Reply:Never "go over" a weld to smoothen things out unless your adding more filler  No no no.. Grinders and flatwheels are the only option..Don't forget the canning wax......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Got to love your cat, looks kind'a like mine. Keep up the good posts Zap!
Reply:Hammack, multiple pass welds have filler added with each pass so no problems. remelting a weld without adding filler is what can cause problems- loss of alloying elements etc. depositing a large amount filler in one pass requires more heat input/mm than several passes with lower deposition rates. trying to deposit too much filler in one pass will also give far more distortionRyan, a die grinder would work well for preping the area to be welded. a power file (small slimline belt sander) would work too and be a better choice for smoothing welds in difficult access areas5*** series Al is not heat treatable but the HAZ will be annealed after welding. the hotter it gets, the larger the annealed section will be
Reply:Great info guys, thanks.-Ryan
Reply:Originally Posted by zapsterNever "go over" a weld to smoothen things out unless your adding more filler  No no no.. Grinders and flatwheels are the only option..Don't forget the canning wax......zap!
Reply:Originally Posted by zapsterNever "go over" a weld to smoothen things out unless your adding more filler  No no no.. Grinders and flatwheels are the only option..Don't forget the canning wax......zap!
Reply:I thought it was fine for regulare cold steels, but not for alloys/aluminum/etc...at least that was what I came away with when I asked the same questions a few months ago.ThermalArc 185MillerMatic 180 w/ AutosetVictor Cutskill Oxy/AcetyleneThermal Dynamics Cutmaster 38and spite!
Reply:Zap, I can't help but call you on this one.Can you add any information as to WHY one should "Never "go over" a weld .........". My first response to your statement is "never say never"!And, what is your reasoning?
Reply:When making multiple passes, you are not remelting all the way through the previous weld.  Do a penetrant test on a single pass sample and then do a remelt sample and I think you will see the difference.
Reply:Originally Posted by brandon75173You guys are saying that even on your weave passes you are adding filler?  I generally dont add filler for a weave unless its biased to one side of the weld.  Never had any subsequent failure to speak of.
Reply:Adding filler in each process...(besides the fuse) YES!!!...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:I too always add filler, even if its taking some .023 wire when doing a near-fusion weld.  Prevents any undercut, prevents loss of material thickness from the drywash, and helps keep those alloying elements where they should be, even in mild steels.
Reply:Hotrodder your info is incorrect.... if I understand.... you are saying using 4043 can cause Mag/Sil? and 4043 also stress corosion cracking? That's how I understand your reply. If so then it is incorrect and should be that using 5356 in any application operating in excess of 150F. will see both Mag/Sil and  stress corrosion cracking.
Reply:Ric,that's why i underlined 'guessing' in my reply- i'm not a metallurgist and even if i were we don't know what alloy the base metal is, only that it's marine work and therefore (hopefully!) 5*** series. given this, only generalizations can be made- good enough to illustrate a point but not likely to be accurateanyways, by generalizing you're also incorrect. if 5356 were used to weld a 5*** series alloy where will the Si come from to create magnesium silicide? true, above 150F AND 3% Mg stress corrosion cracking can occur which pretty much rules out the use of 5356 filler for anything operating at temperature along with some of the 5*** series alloysIF the base alloy was a Mg rich 5*** series AND 4043 were used it's possible (remember, i'm guessing) that magnesium silicide could be formed in the weld- a crack sensitive chemistry. remelt a weld containing 2MgSi and it will crack- same deal as running an autogenus weld on 6061 which contains 2MgSi by design and requires the weld to be diluted with Si or Mg. each filler has advantages and disadvantages- all depends what will be done with the finished weldmenti probably still it got wrong somewhere- metallurgy makes my head hurt and now i gotta go to work