welds improving

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upstateNYer
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welds improving

#1

Post by upstateNYer »

Picked up some "drops" @ my local metal supplier...using a Millermatic 175 with spoolgun...
here is a T-joint with fillet welds on both sides..bend/break test of coupon seems to be ok...comments please?!
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undercut a little on the Left..cold start side
undercut a little on the Left..cold start side
image.jpg (52.04 KiB) Viewed 9552 times
backside of T joint
backside of T joint
image.jpg (53.66 KiB) Viewed 9552 times
seems pretty strong
seems pretty strong
image.jpg (61.65 KiB) Viewed 9552 times
broken...but weld held? seems to be broken in the heat affected zone
broken...but weld held? seems to be broken in the heat affected zone
image.jpg (59.81 KiB) Viewed 9552 times
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Sabs28
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Re: welds improving

#2

Post by Sabs28 »

I have been told by many full time welders, "it isn't how nice it looks, It is how well it holds". And haveing nice looking welds is a plus. If that was me welding, it would have a BIG burn hole through it :banghead:
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Re: welds improving

#3

Post by welderbob »

Try starting and finishing you welds a little away from your weld puddle. "Create a tail in" and a "tail out". Start your weld about a half inch away, move straight , don't rush. Create your first puddle and keep moving. When you get to the end,back step over your last puddle to fill the crater and move your wire out of the puddle, letting the "hot spot" finish on a "colder" piece of metal.
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Re: welds improving

#4

Post by upstateNYer »

Thanks for the feedback welderbob,

I get the concept of cratering out to put the crater over a solid piece of weld, and you can see this in my photos. The part I am having trouble understanding is "tailing in" Kevin Morin posted a diagram of "tailing in/cratering out" in one of his posts of MIG welding, I found it on the Glenn L forum i believe. But i still am not sure I understand it. If i am welding right to left, I start my weld a little left of the right end of my workpiece, then weld right, to the end of the piece, then weld to the left over what I have already welded, continuing Left to the left end of the piece, then "cratering out" a little to the right of the left end of the piece?? SO, basically you end up having a small area of weld on either end of your workpiece that is "double welded"? Also, if I am right handed, I am pushing the puddle Right to Left with the gun very slightly angled to the right? And one other question, while I'm on a roll here...should I be preheating to prevent cold starts? I know you can slow down the wire speed at the beginning and then speed it up, but my gun doesn't have that feature, or does "tailing in" take care of this. Any feedback is very much appreciated. Also My TIG welder should be here on tuesday..so maybe I'll have some more pics to post...my first project will be an aluminum canopy frame for my boat lift....if anyone has any tips on designing a canopy frame, or has built one, PLEASE comment!!
I love this Forum!!
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Re: welds improving

#5

Post by kmorin »

upstateNYer, I think your summary of my Glen-L MIG welding posts was good, and the point taken, so I'll add a little clarification and W'rBob will also make sure I'm not overgeneralizing to help you as well.

First point is to make sure which the different weld instances we're talking about; #1 Long continuous hull seams- #2 (Interior) Framing "stitch" welds #3 Single sided versus double sided welds #4 Inside corner fillets versus outside corner welds.

The welds in #1 are best put in with a fast beginning and end so they have low masses at each end to gouge out with a carbide burr and the last series of welds in this series is the only series where the 'race course' track of my previous remarks would apply. All other welds in this type of weld seam would be run-in/tail-in for 3/8"to1/2" fast so there is little or no build up, and no change of direction and this is at the end too, instead of overlapping back into the last full puddle or the weld- whip the torch out of the puddle and let go of the trigger simultaneously. This leaves the weld tapering in and off/out and is easier to gouge out those ends as there is less to cut away.

But you would only use this method if the welds were going in a long seam that will eventually be welded continuously so #1 above and never #2.

This method does not bother to take into account the arc core crater that is present with these two in & out techniques as you've planned to cut them both out and know you will put down metal on top of both cut out areas.

Welds in case #2 are those that are put down with the racecourse track because there will not be any end prep for another welding tying in to the start and stop. So the #2 weld is where the start and stop are more critical to keep the weld sound by having good fusion and no craters to propagate into cracks or weld failures in vibration.

The speed of wire tip/gas cup at the beginning of travel of the arc and the end 'back-track' are not the same as the speed of the weld; both ends are faster by twice, or so, the regular welding speed. These areas are fast(er) to keep from depositing much metal as they are intended to transition in an out of the automatic weld mode and not to be the weld itself as much as to protect a stand-alone weld from the weakness of the cold start (beginning) and the arc core crater (end) when the process stops.

Single sided welds, in #3, are like the deck to topsides welds or bulkheads that have no access behind, or other places where one weld is all you get, some of these are continuous and some stitched, so the previous remarks apply but the key is ALL one sided welds should be beveled (in my practice and opinion). This allows the amperage to be cranked up and the travel to increase considerably and still reduce the distortion as the weld contraction face distances, and net heat imparted, are reduced so the distortion is minimized.

Double sided welds, considered in #3 as well, should be somewhat smaller than you show in proportion to the 1/8" (it looks like?) welded. The welds don't need to be as large as single sided welds (even though those should be in a bevel) since there are two root face areas on the T plate of the fillets to grip/hold/fuse/anchor the weld. Double sided welds should be put in faster rates of travel than single sided in order to make the total volume or cross section of the two welds more in proportion to the parent metal they're fusing. It will not always work to slow the wire, and reduce the welding power as the back side weld has to fuse the face fillet of a higher mass of metal since the other side's weld may already be in place so more welding power is needed to get good fusion.

Inside corner welds, case #4, are extremely common in boats, both at the hull skin to interior framing where those welds are stitched instead of continuous and at the chine where they are continuous. So these different applications call for some different weld prep and deposit in order to take into account the MIG properties and correctly adapt your technique to the welds' requirements.

Outside corner welds, the second half of case #4, are again either two sided, like the chine in most planing boats or; single sided, like the edge of a step in a deck where the last weld is only possible from an on deck location and you can't get beneath the deck of a small boat to back weld.

Here, the consideration is whether to try to keyhole or not? Further, you have to decide if the weld (usually) continuous weld will be left or dressed? Many MIG welding authorities will flatly state you cannot dress an outside single pass, aluminum MIG weld but it can be done if you keyhole effectively.

So there are more than one case to discuss.
There are more than one instance within the several cases to discuss
Welds need to be planned to be deposited in the instance of the case they will fuse.
Practicing each instance of each case is critical to be able to build a boat because the work flow will be delayed If you have to stop work or welding, and go to the bench to remember the settings, technique and handling of a given combinations of the parent metal versus welds that are implied.

The welds you show have cold starts (curled under edges), inconsistent size/face dimensions (travel speed changes) and were put down 1/3 to 1/4 too slowly (too large in cross section) but they have good cleaning action (white 'wagon tracks' along side that are not to wide or too narrow) they have good flat faces (wire speed to arc length and welding wattage is good), and they are smaller than most beginning welders (you're learning fast).

In bending coupons, cut them in the bandsaw so there is a beginning, middle, and end piece of T about 1" to1-1/2" long and these three segments are bent separately, the middle always is for 'free' as that's when the MIG process is at its best. If you're having problems in MIG the ends are where they will appear.

Do single sided bends until they will go "over and back" double sided welds are 'free'.

Practice makes better if you practice correctly but not if you repeat errors and don't know what to look for. Then your practice will reinforce imperfect welds, so get a minds' eye image of a good weld in your mind before you pull the trigger or don't pull it.

Coupons as you show or small section welds are a problem to learning. They heat up disproportionately to what the same area on a skiff would heat up. Therefore you may find yourself welding cold ont he skiff since you're using second side settings on a small piece where you've just put in a fillet and it heated to 200F but the skiff is only shop ambient plus 3deg F. This means that you need to have many coupons so they an be welded and set aside till they're room temp to the touch, otherwise the preheating will make the practice welds 'too easy' due to the preheating. But I've worked in Alaskan shops all my working life and regularly take a propane weed burner to the hull on the morning of weld out to get the overall temp up to 70-80F before beginning to clean seams and weld that day. But I don't recommend heating the entire boat to 200 or 250F like the little scraps you show will become if not cooled between practice beads.

I hope this helps to address some of your questions and make recommendations that are exact enough to turn into practice exercises so your self learning is productive?

Bob, please don't hesitate to modify my replies to widen the points I make too narrowly, we know what we're saying but we may not remember well how we learned it :deadhorse: so NY'er will benefit from having things explained in different terms.

Sorry I'm not able to illustrate the remarks at this time.

Cheers,
Kevin Morin
Kenai, AK
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Re: welds improving

#6

Post by upstateNYer »

Kevin,

THANK YOU!
I was hoping one of my posts might catch your eye! I have searched your posts on many different forums and find them to be very useful, especially to someone like myself who learns visually. I really appreciate the time you have taken to carefully explain how I can improve.
You have answered my questions and then some. I will work on faster starts and stops (to reduce the amount of gouging needed for continuos welds, and for less "buildup" on the ends of a stitch weld using the "racetrack method") and faster overall travel speed to reduce weld size, especially for double side fillet, also taking into account that the weld on the first side of a double sided weld is acting as a heat sink when the second bead is laid down, so settings need to be adjusted accordingly. I also get what you are saying about the coupon vs the real thing due to different temps., size of workpiece etc, so I will need to be able to tweak my settings accordingly, and can't rely on using the same settings I've used for my test pieces.
SO, its back to get more "drops" (hopefully in more thicknesses, last time 1/8 was all that was available), but I would imagine I should practice on 1/4, 3/16 and 1/8 as that should cover the sizes used in the boat. I will post more pics as I continue to practice and apply what I have learned. The build is a few years away as I gather my funds..so I have plenty of time to get it down.
Thanks again
NY'er
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Re: welds improving

#7

Post by kmorin »

NY'er, I'm glad that someone can benefit from my many decades of mistakes, at least its not a complete waste of everyone's time even if I tend to think of my virtually vertical learning curve as a wasted period of my time.

I'm going to remark about 'first projects' not intending to discourage you but to give you fair notice about TIG. That process is a bit more practice sensitive than MIG, not just because you're using both hands separately but because the weld 'reads' a little differently and there are different factors involved.

So tube or even square stock canopy covers, regardless if they're flat or cambered, can be a little challenging as a 'first project' with a somewhat complex welding process. I'd have to suggest some tool boxes, maybe a bracket (or ten dozen), and then some tube joint practice before jumping off the 'canopy cliff'?

One thing that a close friend of mine whom I taught to weld aluminum, did when learning was to practice his TIG with stub ends and off cuts from a local metal supplier's remnants and scarp bins. The stubs were all 4-6" or less and he made many joints to practice his TIG on tube/pipe/saddles.

All well and good. But, (and we all have one and know it's coming) when it came time to do the full sized frame work he had a very difficult time because the FULL LENGTH TUBEs blocked 50% of the access for his hands that had formerly been easy to access as he'd passed his torch through the stub ends of his practice joints! Sounds simple but beware to practice the 'real deal', like your new found caution to not rely on heating up coupons to simulate long (16-24') weld zones.

Please do not confuse this with me saying that stub-end joints are not good practice! I think you have to do these joints quite a bit to 'get your hand in'; what I'm hoping to bring about is a sense of caution to insure you set up real life practice sessions. But I'd still recommend some boxes and flat seams before you jump off on tube & pipe saddles.

What TIG power supply do you have coming, and what type of torch and controls?

Cheers,
Kevin Morin
Kenai, AK
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Re: welds improving

#8

Post by upstateNYer »

Kevin,
Again, thanks for the input! I will definitely be practicing the TIG process before diving into the canopy project. I actually was not planning on doing any TIG for a while( as i didnt have a tig welder) but my brother ( who lives over seas) bought one for the family shop, so I figured Tig might be better suited for this project as it will be made from aluminum tube/pipe. The canopy doesn't need to be very strong, except to hold up to the wind, as it will not be used during winter, so snow is not an issue..however..i will not take your advice lightly...again this project will be a ways down the road as I continue to practice mainly MIG welding until I get it down a little better..but i figure both processes will be used for the boat when the time comes.

The welder is an Everlast power tig 250ex, not a red or blue machine i know, but very well priced, and gets pretty good reviews. The machine is fairly robust AC/dc.with Pulse, AC frequency and Balance settings, Up slope/down slope, pre flow/post flow. 250 amps. with a I will be using a weldcraft w20 water cooled torch.

NY'er
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Re: welds improving

#9

Post by alanf »

I have a question about the racetrack or up and back start and stop technique. With mig alum you need to push the gun when ever possible, do you pull travel to the start of the weld and then continue the weld bead with the typical push motion? Or is there some significant gun manipulation to maintain a push feed throughout the entire weld?
Alan
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Stitch Welds; NOT continuous seams

#10

Post by kmorin »

Alan, the reason to term the technique a racecourse is that the weld is done in an a VERY approximate oval where both ends 'double back'.

This weld, a stitch applied to intermittent or staggered welds only takes into account the cold start and hot stop of a typical MIG weld. The torch in a right to left weld does drag for the first short time and not regularly formed initiation puddle. The purpose is to allow the wire to form the arc (light up) but not to make a full puddle so the arc is moved to the right not the left, even though the torch is held leaning right so it can gas cover to the left, and the beginning point is just 'inside' the final weld by one puddle or about 1/2" to 3/8" inch.

This 'light and move to the right' is faster than the rest of the weld in order to have lower wire deposit volume and NOT to form a full puddle that will chill the puddle about to fuse this are into the parent metal. So this movement is twice as fast as the rest of the weld, that means there is little 'junk' to weld over.

The weld 'officially' or actually begins one puddle to the right of the 'light up' by then the wire is lit, the arc has heated the parent metal and the gas is hot and cleaning the area to be welded. The torch direction is then reversed at the (real) beginning of the bead and the weld is deposited to the right covering the area used to 'light up'.

A run in block can be used too, where a scrap is place to the right of the puddle and used to initiate the arc BUT.. when that scrap is broken upward the weld is not as attractive.

At the end of the weld, the double back as WelderBob has described it above, is to allow the naturally occurring 'crater' to be only on top of cold weld. So, this means the end of the weld or 'effective' end of the aluminum MIG weld is the point where the torch is reversed travel at the end and doubled back onto the next to last puddle of the weld.

Aluminum welding DC or AC both have a arc core. The arc core is a column of molten metal where the arc's heat and electron stream is creating a molten puddle which will not freeze or chill into solid metal if stopped too fast. In TIG the core is slowly filled by dropping weld current allowing the puddle to chill with solid non-gas contaminated metal from the bottom up by slowly (well, gradually) lowering the overall wattage (amperage) so the parent metal conducts heat away from the puddle. As the amperage is lowered by downing the pedal or lowering the slider on the torch, the puddle will solidify from the bottom up and all the bubbles of (gas) contaminants surface and are swept off by hot argon.

Thus in TIG the way to stop a crater in aluminum is to gradually drop the amperage so the puddle chills bottom to top. But in MIG, unless you have torch mounted controls for the wire and voltage, the only way to get a clean stop is to put that last puddle onto the adjacent (already cooled) last puddle of the weld bead.

The term racecourse is an attempt to remind welders of the technique for welding stand alone stitches like longitudinals, bottom rails not pressure tested, and other framing elements where the weld schedule requires welds that are not going to end up continuous.

I hope this helps? If not please let me know and I'll try to field any questions.

Cheers,
Kevin Morin
Kenai, AK
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Re: welds improving

#11

Post by ReelSong »

Mike, I just wanted to say once again how much I appreciate your explanations given on this forum, I have learned so much from your answers that I feel like I'm in a b oat building school every time I read. While some newer machines like our pulse have a c rater fill function setting, I find myself using the process you explained more often then changing settings. Thank you again for the time you take to answer so many technical guestions.
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Re: welds improving

#12

Post by welder »

Who is Mike?
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Re: welds improving

#13

Post by alanf »

Thanks very much for the added detail Kevin. Your reply has made clear to me the "racetrack" movement. One of my students (high school shop class) is building a 16' or so alloy skiff ..... and I am not a welder by trade. We are fortunate to have a local boatbuilder that is willing to provide advice and help when needed! Thanks again.
Alan
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Re: welds improving

#14

Post by welder »

Alan, keeps the pictures coming and does your student follow the forum?
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Re: welds improving

#15

Post by aluminumdreamer »

I agree with Welder, lets see more photos! Curious to see how this turns out.

Nate
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Re: welds improving

#16

Post by alanf »

I will update photos as we progress, but remember we are talking about a school project.... things proceed slowly. The student can only work after school as he has finished metal shop for the semester. We are presently kerfing and fitting some channel stock for stringers. If I post updates, should I start a new thread... don't want to derail this welding thread.
Alan
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