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Thread: Help with corner to corner join
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23rd June 2015, 07:01 PM #1Senior Member
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Help with corner to corner join
If you wanted to weld two plates of 3mm steel with an arc welder in a corner to corner weld. After you do the tac welds.
Which size electrode? 2 or 3mm? Would the 3mm be too thick & hot?
And what gives better penetration, a straight weld down parallel to the sides & maybe a few more runs? Or across in zig zag? Would this 2nd way really distort the straightness of the seel compared to the straight down runs?
thanks
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23rd June 2015, 07:22 PM #2SENIOR MEMBER
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Approach depends a bit on whether it's an outside corner joint or an internal (fillet) joint, but I think the response is the same.
I'd use the 2mm electrode.
In this case, zig zag weaving will probably get more penetration (well... burn through really) because you'd be dwelling the same area longer than a series of parallel runs. Having said that - you'be flat out fitting 3 runs into a 3mm outside corner. One straight run is what you'd aim for - not the easiest weld if you're just learning.
Even for a fillet joint (where you need a bit more heat), the 2mm electrode, no zig zag is really still the go on thin material.
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23rd June 2015, 09:11 PM #3GOLD MEMBER
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Is the weld going to be horizontal or vertical? Will it be supporting any sort of load? The reason I ask, is that if you're not a proficient welder, you could be in trouble. Vertical downs are a real problem as slag inclusions are quite easy to get but hard to get rid off, making for a weaker joint if it is load bearing. Not doubting/knowing your skill, but making you aware of any problems.
Kryn
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24th June 2015, 05:07 PM #4
Hi Tegmark,
Please! A bit of a description from you of what you have and what you want to achieve. Extra info will help us, help you the most effectively.
Do you know if its 304 or 316 S/S? most common)
Do you have electrodes already, if so what brand and certification type are they?
Your welding machine-is it AC transformer, or DC-helps a lot
As the other blokes have mentioned, what will you fabrication be used for? This info can dictate joint types, material sizes and from that how it will be welded.
We don't mean to be difficult.
Its just us showing some caution so people don't get themselves /or others hurt by accident or lack of knowledge.
There a couple of issues to be dealt with here.
Ok! do we assume external open corner joint
Welding of stainless steel -> electrode type,electrode diameter, welding polarity
Distortion - there are ways to minimize the effects of distortion- dependent on those other factors
Vertical down welding- not recommended for high strength application
Application of the stainless steel welded product.- there's a lot of difference between welding a tin can and welding the Titanic.
There will be a ton of help for you if you can come back with some more info.
Cheers
Grahame
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24th June 2015, 07:23 PM #5SENIOR MEMBER
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Grahame - what's with the stainless steel thing? did I miss something?
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24th June 2015, 07:27 PM #6Senior Member
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Hi,
I have Weldcorp 2.5mm Mild Steel rods, DC arc 130A & the steel is typical sheet. this fab/tube 25cm long 40x60mm will be placed onto a tripod like a pedestal fan only very strong, holding an upright beam of wood 2M high to hold some weight around 40KG on top. Put it another way 2mm stock tube was strong enough, but too hard to weld onto tripod because of how thin it was. Hope this helps
Cheers
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24th June 2015, 07:35 PM #7SENIOR MEMBER
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24th June 2015, 08:47 PM #8
Great info Tegmark
OK we can get down to business
Weight around 40KG. A reasonable welded /fabricated structural tube of 250L x 60W x 40 deep will have no difficulty in supporting 40KG.
That means the joint design can be open external corner say one plate slightly overlapping the other-see the pic -not exactly your job but turn it sideways and imagine thinner plate.
Electrodes need to be ( 2.6 for 3mm thickness) stainless to weld stainless. Expensive I know, but I have seen smaller packs of 10 for sale at Total Tools.I am sure there are T T branches in Melbourne - give them a call for pricing.Others may have smaller packs in SS , maybe Bunnings.Sorry but your MS electrodes will not weld stainless.
DC Welder is good but reverse the normal polarity - electrode positive - switch the electrode din plug to the + socket.
Amps- on an open joint maybe around 75 -80- try same joint on scrap for practice.
Welding tack it ALL up first.When tacked start short runs maybe 25mms long and oppose them. Run 1 on one side and them run 2 on diagonal opposite as far away as you can get-it spreads the heat and then the cooling out- makes for less distortion.
Don't fully weld - leave as much gap as your short bead - run 25mm then space 25mm- mark it all out first but oppose those short welded beads.- again helps to minimise distortion
When you do your practice you will find out about how smooth S/Steel electrodes are to use.
Safety- make sure you wear s/ glasses under helmet - as some brands of SS electrodes spit the red hot flux off a few seconds after arc finish - about the time you lift the helmet. Believe me getting your eyeball scraped by a emergency doc after this hits it, is not for you.
I have probably missed something but I think that is most of it.Our other welder may have an input for you.
Ask plenty of questions
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24th June 2015, 10:34 PM #9GOLD MEMBER
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24th June 2015, 11:56 PM #10
Thanks for noticing
No, Its old tired fella who was jumping between two different posts and whose blood sugar is presently way too high. When I made stuff ups they are good uns.
Duhh! Oopps sorry blokes
Disregard all S/S references- I'll be off hiding with embarrassment under a rock somewhere!
Ok to fix it up.
Use the M/S electrodes on M/s. Mild steel electrode runs electrode negative, amps probably around the same for starters and you may have to reduce 5 or so as plate temp increases or just periodically dunk it in water, You won't hurt it.. its only LC steel.
Probably still a good idea to to keep the distortion prevention thing. Single bead, only to minimise heat input and therefore distortion.Also keep a short arc length gain to minimise heat inputs.
The main thing is to get in and have practice on a scrap piece that is pretty much the same thickness, joint, position etcetera.If it blows through on the amps suggested just keep adjusting them down. On an amps for amps basis inverters will run the same electrode on lower amps input than a transformer will.
I notice I also failed to mention the optimum welding position - horizontal.
Same deal, tack it all up first then start the short beads, 25mm run 25mm space. It looks sexy if marked out for bead and they are all equal.
Again Sorry about that.
Off to check my blood sugar levels
Grahame
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25th June 2015, 06:27 PM #11Senior Member
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