[fsa]

dear expert, I want to weld sheet metal parts one is 1.2mm thick and the other is 8mm mild steel by the MIG process. please check the jpeg. the problem I am facing Is leakage between the flange and weld beads and also from the start & end points on the weld. after welding the is checked under 3bar air pressure. kindly advice how I achieved a leakage-free weld.

regards

asif

[mactec54]

dear expert, I want to weld sheet metal parts one is 1.2mm thick and the other is 8mm mild steel by the MIG process. please check the jpeg. the problem I am facing Is leakage between the flange and weld beads and also from the start & end points on the weld. after welding the is checked under 3bar air pressure. kindly advice how I achieved a leakage-free weld.

regards

asif

Should work very well, I would say it is how the weld is being applied, what amperage and wire size are you using this may be too low

[joeavaerage]

Hi,
some of the better MIG welders have settings like pre-flow and/or post-flow which refers to the shield gas flow prior to and post weld.
Others have settings, variously named, but front-porch and back-porch are common terms. Both these features are designed to control the start
and end of a weld, which is as you have discovered critical in getting a genuine gas seal.

Another technique used by pipe welders, especially food grade pipework, is to use back purging. This means the very root of the weld is flushed with Argon/CO₂
and there will (hopefully) be zero oxide inclusion in the weld metal, a sure place for a leak or a void where bacteria can lodge.

Looking at your pic I think back purging could be a useful technique for you. Probably very inexpensive to try anyway.

Craig

[mactec54]

Hi,
some of the better MIG welders have settings like pre-flow and/or post-flow which refers to the shield gas flow prior to and post weld.
Others have settings, variously named, but front-porch and back-porch are common terms. Both these features are designed to control the start
and end of a weld, which is as you have discovered critical in getting a genuine gas seal.

Another technique used by pipe welders, especially food grade pipework, is to use back purging. This means the very root of the weld is flushed with Argon/CO₂
and there will (hopefully) be zero oxide inclusion in the weld metal, a sure place for a leak or a void where bacteria can lodge.

Looking at your pic I think back purging could be a useful technique for you. Probably very inexpensive to try anyway.

Craig

Your inexperience is showing again

You don't use any purging to weld regular steel and never with Mig welding, it is only used for Tig welding of stainless steel and sometimes in special cases Crome molly tubing

[joeavaerage]

Hi matec,
you are a know-it-all jerk!

I have used pre and post flows regularly and back purging on pipework, especially irrigation pipework . I repaired and serviced welding and plasma equipment as a job for seven years, and any and all
pipework welding experts are acutely aware of pre/post flows, front porch/back porch welder settings. It was my job to make sure they worked.

Craig

[Vlod]

I think you will have difficulty in this configuration, as there are big difference in material thickness. It’s hard to see how much room you have to get to it. You might consider using TIG instead of MIG. Or perhaps weld from other side.

[mactec54]

Hi matec,
you are a know-it-all jerk!

I have used pre and post flows regularly and back purging on pipework, especially irrigation pipework . I repaired and serviced welding and plasma equipment as a job for seven years, and any and all
pipework welding experts are acutely aware of pre/post flows, front porch/back porch welder settings. It was my job to make sure they worked.

Craig

Yes, I may be, but you sure look a fool when you say someone needs to use a purge for Mig welding

Pre and post flow is normal settings for any Mig and Tig welding machines, that has nothing to do with using a purge, purging is only used for some Tig welding applications, for Mig welding you would never use a purge

[joeavaerage]

Hi,
excepting the fact that purging assists in getting leak free welds, in any material, MIG or TIG.

Craig

[deadlykitten]

hy fsa using that 3bar air test, can't you locate also the leak location ? or you only see sloooooooooooooooooooow pressure drop over time ?

if pressure los is slow, then is hard to find the spot ... above a certain value, you can locate by submerge, spray, or looking for a hole

[mactec54]

Hi,
excepting the fact that purging assists in getting leak free welds, in any material, MIG or TIG.

Craig

No, purging is not used for Mig welding

[Vlod]

Purging could be used but it’s not required in this application and you missing the point. The metal is 8 mm and 1.2mm that is the problem he is facing. The question to the welder how to approach it.
With TIG - it’s simple, one should heat the thicker plate first pointing torch on it and soon as it makes melting point turn the torch to the root and get the paddle going directing most of the heat to the thick plate.
With MIG - you don’t get just heat- it comes with the metal. If it directed to the root right the way - there is no way to heat the thick side.
The trick is to start on the thick side and approach the root when you get the proper heat. Then it depends on the wire size- if the wire is to small, you never get it hot enough and you putting melting metal on cold base. Here is you leak…

[mactec54]

Purging could be used but it’s not required in this application and you missing the point. The metal is 8 mm and 1.2mm that is the problem he is facing. The question to the welder how to approach it.
With TIG - it’s simple, one should heat the thicker plate first pointing torch on it and soon as it makes melting point turn the torch to the root and get the paddle going directing most of the heat to the thick plate.
With MIG - you don’t get just heat- it comes with the metal. If it directed to the root right the way - there is no way to heat the thick side.
The trick is to start on the thick side and approach the root when you get the proper heat. Then it depends on the wire size- if the wire is to small, you never get it hot enough and you putting melting metal on cold base. Here is you leak…

No point being missed

He only had a start and stop point problem this is easy to solve with the right setup

The metal thickness is not the problem there are hundreds of automotive manifolds made like this every year without any problems and their thickness is up to 12mm on the flange and 1.2mm to 1.5mm for the tubing thickness, they are all Mig welded some complicated systems are Tig welded, purge is never used for this unless the tubing being used is stainless steel then you should use continuous purge flow

It could be Tig welded like you say but is not need, if they have a good welder and machine to do the job

[mactec54]

Purging could be used but it’s not required in this application and you missing the point. The metal is 8 mm and 1.2mm that is the problem he is facing. The question to the welder how to approach it.
With TIG - it’s simple, one should heat the thicker plate first pointing torch on it and soon as it makes melting point turn the torch to the root and get the paddle going directing most of the heat to the thick plate.
With MIG - you don’t get just heat- it comes with the metal. If it directed to the root right the way - there is no way to heat the thick side.
The trick is to start on the thick side and approach the root when you get the proper heat. Then it depends on the wire size- if the wire is to small, you never get it hot enough and you putting melting metal on cold base. Here is you leak…

Here is a good video for you, there are many examples of how to Mig weld thick to thin material

https://www.youtube.com/watch?v=iS5GmXj2rpw

[Vlod]

You are right, he just needs a welder that has experience and he does not if he ask questions like these.
We don’t know if he clean it before welding that might be a reason too.

[fsa]

ok brother thanks for your comment and advice ..but I am still facing a tiny leakage issue please check the attached video..still looking solution.

also right now I am using an old technology selector type welding machine someone advises me to use an inverter base MIG welding machine to resolve the cold start and lack of fusion at the end

[fsa]

at last leakage, free welding has been done by CNC welding Spm thanks for everyone's advice and guidance.

regards

asif

https://www.youtube.com/watch?v=ZDaNcpYJRw4





https://www.youtube.com/shorts/lgrK7ezbLdA