amp- thickness

[knoba]

Sparkey
You woulden't hit a girl now, would you? (...batting eyelashes fiercely..)

Most certainly not! ...well ...not with my digital appendages, anyway.

...and what lovely eye's, you've got too ...Sparkey... (...flexing arm muscles fiercely.. )

dai
think i been on it

aproxx 1mm per 40amps

Good enough, Dai! (...approx 35a per mil - give or take)!

 

[abnormalsheep]

Hi,

I have a bit of an extension to this question.

I'm looking at an Inverter Fusion 160amp welder to finish replating my narrowboat (5mm & 4mm...ish). One welder told me I need no more than 150amps, I guess based on using E6013 electrodes.

Another, with marine experience, told me that after the first filler weld, the overlapping welds are best with 4mm rods (I'm intending to do 3 welds as standard). I'm a bit dubious after reading comments here about 4mm rods making holes in 4mm steel, but with a chunky bead already set I'm wondering if that point still stands?

As for the question extension, the Inverter Fusion states it's capabilities of using 4mm, but I'm curious what the average amp requirements would be, if the welder could really handle it?

Marine welder also told me I ought to get a 200amp welder, but if the 160 reckons it's up to it then it might be sufficient? Reviews of it seem pretty positive anyway, albeit hard to find!

Thanks for any comment!

 

[dobbslc]

This thread is 7 years old mate! I'd start a new one in the right section for a better response.
Welcome to the forum

 

[Richard.]

Hi,

I have a bit of an extension to this question.

I'm looking at an Inverter Fusion 160amp welder to finish replating my narrowboat (5mm & 4mm...ish). One welder told me I need no more than 150amps, I guess based on using E6013 electrodes.

Another, with marine experience, told me that after the first filler weld, the overlapping welds are best with 4mm rods (I'm intending to do 3 welds as standard). I'm a bit dubious after reading comments here about 4mm rods making holes in 4mm steel, but with a chunky bead already set I'm wondering if that point still stands?

As for the question extension, the Inverter Fusion states it's capabilities of using 4mm, but I'm curious what the average amp requirements would be, if the welder could really handle it?

Marine welder also told me I ought to get a 200amp welder, but if the 160 reckons it's up to it then it might be sufficient? Reviews of it seem pretty positive anyway, albeit hard to find!

Thanks for any comment!

It is an old thread but it’s a new question and sometimes these old threads could do with a little revive.
1st question. I don’t think you need a 4mm rod for welding 4 and 5mm thick material and I don’t think it warrants a multi pass either unless these are prepped full pen joints where your rooting through.
Standard run square edged butt, lap and fillet joints are going to be perfectly performed on that gage with single runs from a 3.2 electrode 100-135 amps (joint,rod type, position depending).
Second question. If you do want to use a 4mm rod I do agree with your friend in this case a 200 amp unit is really the tool for the job. While a 160 amp will burn them, you are going to be maxing that unit out and unless we are talking about a rare case with 2-3 stitches your machine duty cycle is going to be taking one for the team.
A 4mm rod wants 140-175 amps.

 

[abnormalsheep]

Thanks Richard!

I did decide to revive a thread rather than start a new one, as when I did a search about amps this is the thread that popped up, and as it didnt quite answers what I was looking for, I'm not sure it answers the OP question either, so now there is a very thorough answer that has been very helpful to me, and possibly anyone else looking for the info.

The standard for boat welds is three welds, and although the first welder (who advised no more than a 150amp welder) also suggested just doing a cap on the existing single weld.... part of me really wants to do it as properly as possible!

So I'm sort of planning to do a seam weld (making up my own terminology here), and then another between that weld and the base plate, then another on top of the central weld to the side plate. Would a 3.2 be sufficient at higher amps to make a rock solid water tight weld?

On the older, thinner, rustier metal with remnants of bitumen, I'll probably use lower amps initially until I'm welding mostly from weld to the new steel...?

My main concern is significant penetration and fusion with the first welds. If they crack, my boat sinks! May make another more relevant post about this.

Anyhow, I suppose OP has been sufficiently answered:

4mm rods unnecessary on 4mm plate, probably way too big, unless being welded on top of existing 3.2mm seams therefore needing a higher ampage welder than a 160amp, that may manage but suffer the effort. On top of a 3.2mm the 4mm would be much stronger, although 3.2mm is sufficient.

I suppose there is also the issue that although a 4mm on top of 3.2mm would work, there is still risk of the heat needed for the 4mm burning through the 4mm steel, or cutting in?

Anyway, many thanks Richard!

 

[abnormalsheep]

Another note re: first question: tis a fillet joint, or onesided tee joint.

 

[Richard.]

No problem. However
The boat building standard might suggest a 3 run fillet joint but good welding practice wouldn’t.
The aim of a square edged fillet is to match your fillet leg length closely with the thickness of the material. Over reinforcing the joint say a 10mm leg on 5mm material can effect the integrity of the joint in a negative way by creating a stress riser. It’s a common misconception that more weld more strength and it’s simply not the case. Unless I was governed by wps with a good reason as to why, I would be doing those joints with a single pass roughly 5mm leg weld 3.2 low hydrogen rod. (Assuming its steel) Trust me you don’t need to worry about fusion and penetration with MMA. If you do it properly you won’t sink
Just be careful before ploughing in tonnes on unnecessary weld metal into those joints. It doesn’t work like you would think. See bad sketch below of what I would be doing with your joint. (Z-leg)

 

[Richard.]

On top of a 3.2mm the 4mm would be much stronger, although 3.2mm is sufficient.

This is incorrect as well. The diameter of the rod makes no bearing to the strength of the weld achieved. Bigger rod = higher deposits. You need more current to burn a bigger rod and more material put down can increase strength if the joint requires that volume of material but like I said your welding on relatively thin (in the MMA world) gage plate. You can easily achieve a 5mm leg fillet with a 3.2. You could do it with a 2.5 (not ideal as travel will be slower) but it will do your job no problem. If you need a bigger gage fillet go 4mm or multiple pass
Bigger rods are there to be more productive on thicker gages

 

[abnormalsheep]

Hmmm... pretty convincing reasons to trust your opinion, although I still feel a kind of vulnerability by only having one seam!

The existing seam was done in pretty poor conditions (dark & dusty with lots of power cuts) and I'm a little concerned about their quality although I have been reassured with the second opinion of another welder. He suggested simply to use a wire wheel and cap them if I really wanted to. Didnt think there was much need to grind it out completely.

I've also been told that each weld weakens the steel, so the less runs the better for the strength of the joint.

Dunno why I feel so worried about cracking.

I've found holes in a few of the welds inside, done by the same original welder, and we'd spotted a few on the outside.

Wondering what the best course of action might be: wire wheel, locate holes and fill, or grind welds back to a T and do another seam all round, just to be sure.... as holes may be missed.

Thanks again for sharing your knowledge Richard

 

[Arclikeharrypotter]

For 4mm I'd use a single pass 2.5. But a 3.2 would also work just don't expect to be burning it in a 130A!

A good single pass weld with sufficient penetration and fusion is more than suffice. If you'e concerned about your first pass lacking any of the above then slapping 2 extra passes won' solve your issues.

 

[abnormalsheep]

Will have a look see how wide the leg is on the existing welds... was just thinking that if the first seam was a 2-3mm leg, then the triple welds could then extend it to a 5mm leg

 

[abnormalsheep]

I'm aware that the first seam (possibly only seam) is the most important in terms of fusion.

160amp welder would do alright with 3.2 rods, at 130amps tops I suppose. Plates I think are 5mm and 6mm, or 4mm and 5mm.

Wonder why its a boating standard to do three welds if it contradicts general welding practice

 

[Richard.]

Will have a look see how wide the leg is on the existing welds... was just thinking that if the first seam was a 2-3mm leg, then the triple welds could then extend it to a 5mm leg

With a 3 run fillet you will struggle to get under an 8mm leg
If the existing welding is no good just like mr potter said covering it up won’t do any more help than sweeping the dirt under the carpet. You need to cut it out or risk it for a biscuit
Your concerned about cracking and I wouldn’t be. Hydrogen cracks are rare but can be taken out of the equation with hydrogen controlled consumables and use them, store them correctly.
High stress cracking.... well every weld has its limits but tbh a 5mm plate I’d expect to bend abit first before a good MMA weld went bang in which case your design, material thickness should be looked into rather than the weld.
Boat welding standard......I know zip diddly squat about.
My advice can only be based on good general welding practices which would suggest a 3 run fillet (8-10mm) to be unsuitable for 4-5mm plate.
However. @Hood has built lots of boats. He will know the standard and if he says it’s 3 run as the norm and explains why then that’s what it is. Seems odd.
Done a 5mm fillet here on some 10mm plate. There is no reason I can see why weld sizes like these wouldn’t be sufficient.

 

[Richard.]

I've also been told that each weld weakens the steel, so the less runs the better for the strength of the joint.

Sorry to keep bouncing on your quotes but this is incorrect too.
Every time you add a run on top of another you do 2 things. You purify the weld metal further obviously because your dilution with the parent is less the more runs you put in but most importantly you refine the grain structure further with each run. This is a good thing as it creates toughness in the joint. However as I said before too much reinforcement generates stress risers at the weld toes.

 

[abnormalsheep]

Well I've definitely learnt a few somethings today, much appreciated!

I guess those 2 reasons may also be some of the reasons for multiple passes. I hope Hood pops up to share his thoughts about it!

Heading back to the yard now to check legs and such. Will try and get some photos up here. Aware that I have somewhat hijacked the OP, but all vaguely relevant still!

If the existing weld isnt quite equivalent to steel thickness maybe a simple cap weld would be sufficient to clear up any potential faults/holes.... as originally recommended by second opinion on the yard?l

Is an interesting discrepancy then, perhaps.... that it doesn't aid reinforcement to lay welds on top (on the basis it goes beyond ideal leg length) but it would purify and smooth grain of the existing weld.... therefore smoothing a few of my concerns?

 

[Richard.]

The op hasn’t been on the forum since 2012 so I’m sure he won’t mind the hi jack.
Hood will be on soon to clear up the boat building standard.
It’s all finer details really. You’ll find the extended leg length or slightly hotter/colder runs in most welded up stuff makes no difference whatsoever to the “proper” way because generally we over engineer stuff. The difference in strength between an oversized fillet to a correct sized fillet will probably never be noticed if I’m being completely honest on your application because you have probably built it to withstand 5x the amount of force it’s ever going to receive. So with this in mind there is no point (unless hood says differently) to putting 3 runs in there despite the positive or negative effects because it’s going to take you 3 times longer to build it.

 

[Hood]

Will have to have a read later on to see what this is all about but I probably don't have a clue anyway as it is mainly Alu I do and from a quick skim this seems to be steel.

 

[Richard.]

If the existing weld isnt quite equivalent to steel thickness maybe a simple cap weld would be sufficient to clear up any potential faults/holes.... as originally recommended by second opinion on the yard?

It really depends on what the holes are. You can’t just hide a major weld defect with another weld. I wish you could but it will always come back to haunt you. If the holes are simply missing welded areas then yes give a smoothing over with a grinder and fill em in hot.
If it’s cluster porosity or slag traps then the defect needs to come out. You will risk stress cracking if you leave such things and weld over them.

 

[Arclikeharrypotter]

A few pictures of the defects and exactly what you'l be welding would be helpful. Is the hole just a missed bit of weld, or porosity, slag trap.

Forgive me if this offends but you've mentioned concerns of cracking, and sinking your boat. Would this not be a better job to out source to someone who already has the required skill set and knowledge.

 

[Hood]

I am finiding it hard to understand what you are actually welding. Is it bulkheads or ?
As @Arclikeharrypotter says, some pics of what you are wanting to do would be good.

As said I don't really do much in the way of steel welding of hulls, usually the boatyards welders that do them as it is they who have them up the slipway, I get the Alu stuff from them.
I have cut out and replaced sections of corroded hull from some boats but it has just been single pass welds from both sides. It has been a long time since I have done anything like that or in fact even been inside the hull of a steel boat but from memory the ribs are just stitched and I think bulkheads are usually just a single pass.