Asking questions about MIG/MMA heat input, penetration etc.

[Richard.]

And I am also limited to what I can get off a 13 Amp plug, (I can change it to a 20 Amp plug as I really need 16 Amps).

So I am interested in what I can and can not do with it.

I have no 10 mm plate around at the moment so I can not go in the garage and try anything, but I would ask this question, can you not get any penetration on 10mm plate with a 150 Amp Mig or will the penetration be , of in the order of 0.5mm?? What would be expected?

Adrian

Hi mate. It's a good q. I don't know the depth of penetration you'll get on it. It won't be a lot. In a joint you can control penetration and get full pen from low power simply with preps open roots, big gaps, small lands (faces) and IMO a 150 amp mig is suitable for a root run on a prepped 10mm butt joint. Penetration ain't the issue. It's fusion. The thick plate will suck the heat away very quick. If the heats not there then the fusion cannot happen.

 

[Kent]

No your right there Kent there is no substitute for hands on experience but all these things play a part and there is a lot more to it. For example knowledgable guys that qualify as "true" welding engineers design complex structures calculated in such a way to eliminate stress points. They also design the wps's which will (if followed) create welds more suitable/stronger than twiddling knobs and going by sound. If a weld fails the welding inspector will say why it's failed the metallurgist can design/improve consumables to suit. I understand your an old school fabricator and you know your stuff as you've done it long enough. You can set your machine up and lash out strong welds. Guess what I can too. I am not a qualified metallurgist or a welding engineer. But I would like to say I could be one or the other One day as I'm on the right tracks, in the right job and have got a few things already under my belt that get me on that ladder. When ever a post comes up about a guy wanting codings/quals you don't seem that keen to agree with it but things have changed since the 80's and to be taken seriously these are the things that we need to approach.

Actually Richard I am all for codings. To such an extent that I am looking to re- code myself for asme9 / bs en287-1
What I am not all for is shed loads of people auditing others and having guys in who likely can't do the job but have just memorised the theory
Reason is I still have good contacts in power generation and there is a big shortage of guys that can do more than one set task on the job
My point is more towards saying to Adrian you can think too much about this stuff
Apologies if I Co m e across a bit heavy on this at present but under a bit of constant stress at home with my youngest who has recently developed really brittle asthma ( done 7 blue light jobs in last month or two and many more scooby runs to hospital) I think it's comming out a bit in the wrong places

 

[Richard.]

Actually Richard I am all for codings. To such an extent that I am looking to re- code myself for asme9 / bs en287-1
What I am not all for is shed loads of people auditing others and having guys in who likely can't do the job but have just memorised the theory
Reason is I still have good contacts in power generation and there is a big shortage of guys that can do more than one set task on the job
My point is more towards saying to Adrian you can think too much about this stuff
Apologies if I Co m e across a bit heavy on this at present but under a bit of constant stress at home with my youngest who has recently developed really brittle asthma ( done 7 blue light jobs in last month or two and many more scooby runs to hospital) I think it's comming out a bit in the wrong places

Yeah that's awful mate especially when it's the little ones. I hope it's all ok and they get it under control. My daughter has it (not to the same extent mind) but it is worrying.

 

[Kent]

And I am also limited to what I can get off a 13 Amp plug, (I can change it to a 20 Amp plug as I really need 16 Amps).

So I am interested in what I can and can not do with it.

I have no 10 mm plate around at the moment so I can not go in the garage and try anything, but I would ask this question, can you not get any penetration on 10mm plate with a 150 Amp Mig or will the penetration be , of in the order of 0.5mm?? What would be expected?

Adrian

You can if you heat the plate up some first. Thing is you wouldn't if you had mma to hand that could satisfactory burn a 3.2!
A lot matters on a lot like the area of that 10mm. Size of the wire co2 or mix what mix arc length
A spreadsheet will be either bob on or s work of fiction
Frankly I know for fact that wps have been copied from job to job by people who know next to nothing about the why at the highest level of work and couldn't actually do the job to save thier life and will freely admit that fact to those who can
You just remember " a lot depends on a lot" if you compile such a thing and rely on running test pieces and overkill on anything important

 

[Richard.]

IMHO I personally don't think warming the plate up will have much effect on the fusion level unless you get it to the point of Glowing (which will effect the strength of the joint any how) I've not heard of people preheating thick section to aid levels of penetration/fusion. It's usually done to slow down cooling rates to avoid cold cracking. I could be wrong it's just not something I've done or heard of personally.

 

[Kent]

It's been done many times. Yes it does have its own side effects though
Not often published but it has been reasons as above I suppose and the fact that best practice means you get a bigger set

 

[Richard.]

It's been done many times. Yes it does have its own side effects though
Not often published but it has been reasons as above I suppose and the fact that best practice means you get a bigger set

Fair enough. I can only go by personal experience.

 

[TechnicAl]

Temperature and heat arent the same. You need heat to penetrate. Getting it hot will add something but not a great deal.

 

[Kent]

I think its fair to say that and you certainly cannot push things on the basis of being "able" to add a gas torch more a " might help some if " thing in a push.

Temperature and heat are not the same thing because why? temperature could be very cold or very hot right but heat has to be hot

 

[TechnicAl]

Heat is energy. Temperature is the result of energy.

"Heat has to be hot" err well you can heat something by freezing it.......starting to get complicated now and Im tired (been gardening etc all day)

google it im sure its there

 

[Richard.]

Heat is energy. Temperature is the result of energy.

"Heat has to be hot" err well you can heat something by freezing it.......starting to get complicated now and Im tired (been gardening etc all day)

google it im sure its there

No wait don't stop there Al as you've now got my attention.
How do you freeze something to add heat?

 

[TechnicAl]

stretching my memory now........enthalpy or entropy

 

[TechnicAl]

This explains it
http://littleshop.physics.colostate.edu/tenthings/FreezingWarmer.pdf

to be honest we are going miles off topic

 

[Kent]

this sort of thing reminds me why I am a fabricator, its like a riddle init ! Can you imagine here heat that up for us will you? Ok I will stick it in the freezer a while

 

[Richard.]

This explains it
http://littleshop.physics.colostate.edu/tenthings/FreezingWarmer.pdf

to be honest we are going miles off topic

We are but such things can't be left. When I hear cool stuff I only wanna know more.

 

[TechnicAl]

this sort of thing reminds me why I am a fabricator, its like a riddle init ! Can you imagine here heat that up for us will you? Ok I will stick it in the freezer a while

Thats why its important to understand it