Recurring cracking

[Jlg]

I've just seen your replies, having welded & ground out the slag inclusions and again etc etc.

JLG, I have no doubt it is my lack of skill and depth of knowledge. I'd do welding evening classes, but all the good ones have been axed.

Coincidentally, I did a couple of practice beads on a piece of scrap, then ran beads & more beads over the finished area to fill it, as it had developed a slight concavity.

Now it's all ground down just the odd pinprick of void but these are in the build-up layers. I was planning on fairing cosmetic blemishes with epoxy fairing compound (as used on boats) -any reason why that is a bad idea?

ALHP, that is good advice to take time out, which to some extent JLG is suggesting too. My welder is an RT110B & won't go to 120. I really ought to take time to play with the settings.

I had a look to see why I would choose 50V or 80V, but as yet haven't found an answer.
Cheers

You don't need to go to 120 it's over power for the rods I just did it to show you that you shouldn't be blowing holes in 3mm 80-90a I found worked just fine as to the 50v or 80v it just gives easier starting of the rods and helps with cellulose rods

 

[Jonathan Webb]

You don't need to go to 120 it's over power for the rods I just did it to show you that you shouldn't be blowing holes in 3mm 80-90a I found worked just fine as to the 50v or 80v it just gives easier starting of the rods and helps with cellulose rods

Thanks.

So if mine was melting away, I was going too slowly?

I'll get some scrap and take some time to do the same thing but with different settings.

 

[Jlg]

Thanks.

So if mine was melting away, I was going too slowly?

I'll get some scrap and take some time to do the same thing but with different settings.

I'd say you were just keeping in one spot to long

 

[Turbo]

You now have quite a wide gap to fill with a 2.5mm rod & looking at your weld it is fusing either one side or the other of the joint. You need to have a pool of molten metal that ties in both edges of the weld. You could go slower with the 2.5 to build up the pool but you run the danger of things getting too hot.

If it were me I would use a 3.2mm rod at around 90-100a, it will make a bigger weld pool with less slag. An alternative would be to run 2 welds between each edge & the backing strip with your 2.5's, removing the slag after each run. Then if needed run a cap weld between those 2 welds to fill up any hollow.

 

[Jonathan Webb]

Turbo

You now have quite a wide gap to fill with a 2.5mm rod & looking at your weld it is fusing either one side or the other of the joint. You need to have a pool of molten metal that ties in both edges of the weld. You could go slower with the 2.5 to build up the pool but you run the danger of things getting too hot.

If it were me I would use a 3.2mm rod at around 90-100a, it will make a bigger weld pool with less slag. An alternative would be to run 2 welds between each edge & the backing strip with your 2.5's, removing the slag after each run. Then if needed run a cap weld between those 2 welds to fill up any hollow.

Turbo, I did the latter. Took me more than 3 runs though.

 

[Turbo]

Turbo

Turbo, I did the latter. Took me more than 3 runs though.

How did it turn out?

 

[Jonathan Webb]

How did it turn out?

At close of play on Tuesday it looked ok. Weather was vile yesterday so it stayed under wraps. Hopefully I'll get another session today. Maybe the stresses of manhandling do it -whether to subject it to stress, to see or to handle it carefully to avoid?

 

[Brad93]

In my opinion.

This is a skill issue. The welds above clearly have multiple discontinuities.

MMA is not the best process for sheet metal work. It is difficult to produce a butt weld with adequate penetration with a 2.5mm electrode on 3mm sheet.

You say you've used a backing bar? How thick was that?

Are you using decent rods and which welding machine have you got?

Ignore what Runnach is saying about ceramic backing tiles, you're working in your backyard not in a bloody ship yard.

 

[angellonewolf]

im not that great at welding but if was me and i needed it to look good i would set up a 3mm sheat make some cuts to mimmic what you need to do and weld them instead of mucking up the work get them right then do the weld you need to do

yes on a lot of stuff only needs holding together put the welder in the right ish settings and make little ajustments as needed but when needs to be good first strike as above

 

[zeppelin builder]

View attachment 140411
At close of play on Tuesday it looked ok. Weather was vile yesterday so it stayed under wraps. Hopefully I'll get another session today. Maybe the stresses of manhandling do it -whether to subject it to stress, to see or to handle it

Guilty of murder by 5 inch grinder id say

no small wonder it keeps splitting use a sanding disc and drag it backwards in long smooth motion
and welding 2/3 mm plates should be no problem with or without a backing strip
get a pro welder to show you where your going wrong or you never going to get it

 

[Rrunnach]

Good advice should never be ignored, Brad. You never know, the poster may have access to backing tiles and, if not, at least the poster knows they exist and, not only for "BLOODY SHIPYARD" use.

Poster is using decent rods, pay attention, please.

 

[Brad93]

Good advice should never be ignored, Brad. You never know, the poster may have access to backing tiles and, if not, at least the poster knows they exist and, not only for "BLOODY SHIPYARD" use.

Poster is using decent rods, pay attention, please.

You never fail to **** someone off do you rrunnach.

Just because they’ve got bohler written on them doesn’t mean they’re decent. Anyhow I think we’ve already deduced this is a technique issue.

The guy is welding 3mm mild steel why on God’s earth would you use ceramic backing for something so simple. And with stick. I’ve never seen ceramic backing used with electrodes and can’t imagine an application for it. Flux core yes a very useful tool.

Your useless advice never ceases to amaze me - the guy is working in his garden. Is he gonna start using single use consumables to do some art.

Dear god this forum gets worse day by day.

 

[Jonathan Webb]

Brad,
What can actually be seen above is the new surface I laid down by running multiple beads to counteract the slight concavity that had developed, presumably through repeated grinding.

I had run welds along the valley sides, (hopefully) joining each side to the backer, then more passes to fill. When I smoothed that off. I saw the depression over 30mm or so, which I filled as described above. That big void is cosmetic and I ran out of time that session. I ground & drilled out & filled any voids/slag inclusions during the above process.

Yes it's a skill issue. MMA may not be the best process, but it's what I've got. As you say, it's in my garden not a workshop although I thought MMA was at home on metal of this guage and that the 2.5mm should be a reasonable match for 3mm sheet. Most of the work is joining external angles, there are two short butt welds as unavoidable exceptions.
However, the welds definitely feel & look better at the higher current, so I'm hopeful that this has resolved it.

The backing piece is the same sheet, 3mm.

The rods are what I understand to be decent: Bohler 6013 and the machine is now a Oxford RT110B. I started off though with my 30 year old SIP made in England weldmate.

As of close of play today, there was no cracking. :-)

 

[Rrunnach]

Touchy touchy, Brad. I guess you should go back and read my post. I have also used tiles on various applications, including MMA. But hey ho. My advice is just that, advice. Take it or leave it. But you should take a chill pill. All responses from various individuals were civil and, given with the best intentions. Until you butted in (excuse the pun.)

Anyways, appears the OP has achieved a sound weld, good for him and his perseverance.

Have a good evening Brad.