Welding Problem

[Roger Mason]

Hi All,

Whilst not strictly model engineering - it is not as far off topic as some postings that I have seen, so I hope you will be sympathetic to me and my problem.

I am constructing a bracket made of angle iron welded together. Now I will be the first to admit that I am not the world's best welder. So I wonder if anyone can help me with diagnosing why my welding is so bad.

I am trying to weld two bits of this angle iron together using the MMA process. The two bits of angle iron come together at a right angle and I am trying to put a fillet of weld down in the 90 deg. corner. Each time I try it I get a bead of weld material on each side of the corner, with a deep canyon down the middle with no weld in it. The end result is this narrow canyon that is difficult to get the flux out of and the two bits of iron are not joined together.

What am I doing wrong? Is it amperage, is it angle of rod, is it length of arc, what is it?

[kingsteam9]

Roger,

As another not too good MMA welder this sounds like an old and familiar problem! My welding instructor pointed out that this usually results from not having got the weld started properly, ie not allowing the material to heat up enough at the start of the weld before moving the rod along the joint, = the two sides don't fuse as one bead, and slag gets trapped in the middle. The cure that he taught me was to increase the amps then use the sequence ' strike, pause, weld'. The pause is usually just enough to get the work piece heated up.

You might like to get your hands on a copy of 'Farm and Workshop Welding' by Andrew Pearce, which has an excellent section on MMA, with a large number of useful photos. I bought my copy through Amazon recently at well below list price, and I'd recommend it.

Robin

[havoc]

Care to tell us unwashed masses what "MMA" stands for?

[gilesengineer]

Havoc,

That's 'Stick' Welding to all of us! (Manual Metal Arc...)

Roger, if you've got a D.C. welder, you could try swapping the torch and 'earth' leads over..... Welding into a corner is known to sometimes 'repel' the weld, and swapping the polarity can sort it.

Another (easier) way is to re-orientate the job so you're welding flat, and not vertically (granted this is NOT always possible, but if you can, it makes all the difference...)

[weldsol]

Manual Metal Arc
Roger your current is too low. What size rod are you using ?
For a guide 40 amps per m.m. of electrode core wire ( not the od of the coating.
Another thing that can give a problem if using DC is arc blow (magnetic field set up )
if using electrode pos, then go to electrode neg, this will help better still will be AC as the alternating current cuts the field and collapses the magnetic field

Paul

[chris vine]

Hi Roger,

I certainly found that increasing the current helped in this situation.

The other thing that can help is to increase the voltage if you have the option. Unfortunately a lot of cheap air cooled welders have very low voltages and although the current rating on the box makes out that they are quite good, infact the industrial machines work with a higher voltage and seem to make it a lot easier.

having said all that, what I know about welding could be written on a postage stamp with a marker pen!

Chris

[weldsol]

Nov 28, 2008 19:22:22 GMT chris vine said:

Hi Roger,

I certainly found that increasing the current helped in this situation.

The other thing that can help is to increase the voltage if you have the option. Unfortunately a lot of cheap air cooled welders have very low voltages and although the current rating on the box makes out that they are quite good, infact the industrial machines work with a higher voltage and seem to make it a lot easier.

having said all that, what I know about welding could be written on a postage stamp with a marker pen!

Chris

Re voltage The ocv (open circuit voltage ) will only assist in arc stiking
Once the arc is established it is the type of coating (Rutile / Basic ? Cellulosic) give the arc voltage typical on a general purpose m.s rod (rutile ) will be around 18V
Paul

[simonwass]

You may be a little to far away, shove the rod in purposefully.
The arc and molten metal tends to go where the surface is closest, in a corner it is not at the corner.
Give it some more amps, strike the arc and hold the arc for a 1/2 second to shove some heat in, then dive in and start the weld.
Definitely not an easy weld going into a corner.

[Chris Kelland]

Hi,

Have a look at this forum,

www.mig-welding.co.uk/forum/index.php

In spite of it's title they cover all types of welding MMA, MIG & TIG also gas etc. it is a good forum where us hobby welders can get advise from the pro's. Your problem has been covered before. I think you need to develop the weld pool before moving the weld along the joint, a little increase in Amps and coax the pool to form across the joint and then move slowly and let the weld build up.

Hope this helps,

Chris.

[Chris Kelland]

Hi,

Further to my last post, have a look at this thread,

www.mig-welding.co.uk/forum/showthread.php?t=7885


Regards,

Chris.

[steamjohn248]

Basic tip from an old blacksmith that let me play with his welder when I was about twelve,

"make a bridge" i.e. make sure the weld puddle bridges the gap between the two bits of metal you are trying to glue together, once youve got the " bridge" just keep the weld puddle pushing up against it as you lay it down.

John

[Roger Mason]

Hi guys,

Thanks for all the help - I have increased the amperage setting on the welder - a DIY special! I think this has helped a little, however some of the welds look absolutely awful!

I remember an old welder who produced wonderful welds every time, said to me once, after watching my terrible efforts, "Can't you see the difference between the molten flux and the molten metal?" I couldn't tell the difference then and I still cannot. Perhaps this is my problem I have no idea where the molten metal is going, rather than the molten flux. What should I be looking for?

Hoping for more assistance with what should be a useful addition to my range of skills, but at the moment something that alludes me.


Cheers,


Roger Mason, in a very chilly St. Agnes.

[weldsol]

Hi Roger
It may be that your welding screen is too dark you want a 10 or 11 shade unless your up around 200 A which I doubt very much. You should then see the fluidity of the molten slag.

Paul

[garethp]

I'd agree with Paul - my welding skills aren't good but I found a big improvement in using one of the auto darkening shields, the one supplied with the welder was way too dark and the auto ones allow you to alter the darkness by turning a dial. Now I can see the pool and the gap in the materials - make's it much easier to control whats happening!

Gareth.

[dva]

No one seems to have mentioned it yet, so . Is the metal clean ? Electric welding hates rust. I have spent a lot of time on rusty old fabrications and have found you must have a clean, preferably rough-ground metal to work on. With gas welding this isn't so much a problem.

Dave

[weldsol]

Nov 30, 2008 12:03:09 GMT dva said:

No one seems to have mentioned it yet, so . Is the metal clean ? Electric welding hates rust. I have spent a lot of time on rusty old fabrications and have found you must have a clean, preferably rough-ground metal to work on. With gas welding this isn't so much a problem.

Dave

Totally agree with you Dave about the cleaning the material I must admit one tends to assume people have already done what is a basic requirement in any welding (a bit like painting you would not paint a dirty surface)
Paul

[Steve M. W]

Just a thought I have found that magnetic clamps sold for holding work together if to close to the weld area can cause all sorts of problems in stick & mig welding but not with my tig welder.

Steve

[weldsol]

Hi Steve the reason you have problems with MMA / MIG and not with TIG is that no metal transfer through the arc takes place with TIG.
If you have strong enough magnets and high enough amps though you can deflect the TIG arc we used to use that technique for weaving on automatic welding

Paul

[iansabey]

I'm not sure of the exact shape of the work, but, as a rule I find I get better results welding from the outside of a corner. Where possible of course.

Ian.

[Roger Mason]

Hi All,

Thanks for all the assistance you have given me with this simple welding problem.

The welding forum was very informative and some of the pictures there of disasters look exactly like my miserable attempts!

They did suggest that the right current for 2.5mm electrodes, which is what I am using is as high as 90 amps. The miserable scale on my welder is set to around 35 amps. Is there any way in which I can actually determine how much current I am using? I would have thought that more than doubling my current would just blow holes in everything.

Regarding the grade of the shades in the screen - I will have to get it out to see if the grade is written on it or not. I seem to remember a long time ago I replaced the original shade with one a bit lighter and that helped

One reply on the welding forum suggested that if you saw bright liquid (said to be molten flux) and dull liquid (molten metal) all mixed up and swirling around you have already made a mess of the weld. Well this is what I see all the time!

As for cleanliness - the metal has the black mill scale on it, and no rust.

I think maybe I should stick to bolted construction!

Thanks for all the help.


Cheers,


Roger Mason, in St.Agnes.