I have been using my recently bought SIP 130 MIG welder over the past
couple of weeks. At first I used it in'gasless' mode with cored wire
but in the last few days I've been in a sheltered area so switched to
working with gas and ordinary wire.

When I swapped over I forgot to switch polarity and I didn't notice
this for quite a while. I did eventually realise and changed to the
correct polaity. To be quite honest I couldn't really tell the
difference, what effect does the polarity have in MIG welding?

--
Chris Green )

wrote:
I have been using my recently bought SIP 130 MIG welder over the
past
couple of weeks. At first I used it in'gasless' mode with cored
wire
but in the last few days I've been in a sheltered area so switched
to
working with gas and ordinary wire.

When I swapped over I forgot to switch polarity and I didn't notice
this for quite a while. I did eventually realise and changed to the
correct polaity. To be quite honest I couldn't really tell the
difference, what effect does the polarity have in MIG welding?

IIRC the main difference is in weld penetration, others include torch
temperature.

MrCheerful

MrCheerful wrote:


IIRC the main difference is in weld penetration, others include torch
temperature.

The metals being welded can also affect the required polarity. And
aluminium needs AC....

Steve

On 28 Aug 2003 20:12:13 GMT, wrote:

what effect does the polarity have in MIG welding?

Same as any process - the +ve electrode gets hotter

For MIG welding in spray-transfer mode, it's important to have the
wire running hot and the torch +ve, or else you won't get a spray
(which leads to globular transfer, poor penetration, and premature
baldness)

If you're using dip transfer on thin sheet, then it doesn't matter
which way you run it. Besides which, the voltage (and thus the power)
is lower anyway. For cored wire, running the wire over-hot can
disrupt the shielding effect of the generated gas - but even then,
thin sheet isn't fussy.

MIG keeps the same polarity for all metals. TIG uses a -ve torch, to
stop the tungsten melting. Welding aluminium (or magnesium) with TIG
(but _not_ MIG) uses AC, to get a "scrubbing" action on the weld pool
to break up the oxide film.

Andy Dingley wrote:
On 28 Aug 2003 20:12:13 GMT, wrote:

what effect does the polarity have in MIG welding?

Same as any process - the +ve electrode gets hotter

For MIG welding in spray-transfer mode, it's important to have the
wire running hot and the torch +ve, or else you won't get a spray
(which leads to globular transfer, poor penetration, and premature
baldness)

If you're using dip transfer on thin sheet, then it doesn't matter
which way you run it. Besides which, the voltage (and thus the power)
is lower anyway. For cored wire, running the wire over-hot can
disrupt the shielding effect of the generated gas - but even then,
thin sheet isn't fussy.

Thanks for the explanations, I'm working on fairly thin material so it
would seem that polarity isn't all that critical.


MIG keeps the same polarity for all metals. TIG uses a -ve torch, to
stop the tungsten melting. Welding aluminium (or magnesium) with TIG
(but _not_ MIG) uses AC, to get a "scrubbing" action on the weld pool
to break up the oxide film.

Well my instructions definitely say:-
+ve torch for using MIG with gas.
-ve torch for using MIG gasless with cored wire.
This is a SIP 130DP, specifically designed to be used for both gas and
gasless MIG welding. It's also marked up on the welder itself.

--
Chris Green )

Chris,

Where do you buy your gasless wire, please?


Rgds Richard

wrote:

I have been using my recently bought SIP 130 MIG welder over the past
couple of weeks. At first I used it in'gasless' mode with cored wire
but in the last few days I've been in a sheltered area so switched to
working with gas and ordinary wire.

When I swapped over I forgot to switch polarity and I didn't notice
this for quite a while. I did eventually realise and changed to the
correct polaity. To be quite honest I couldn't really tell the
difference, what effect does the polarity have in MIG welding?

--
Chris Green )