TIG partial rectification problem?

I am hoping you people can shine some light on this problem I'm having with trying to AC TIG weld Aluminium.

I am using a home built high frequency unit (based on a Miller HF15) with a AC transformer stick welder (230 volt primary supply, 46 volt open circuit secondary, 50-160 amp) and pure Argon with 2.4mm zirconiated tungstens. Normally when stick welding I can run it at 160 amp if I'm careful, and not blow the 15amp fuse in the shed fuse box.

The problem is when I try to TIG Aluminium I can't "dial in" over about 80 amps on my power source with out blowing the 15 amp fuse. I am putting this problem down to partial rectification producing a DC current that the welder is trying to overcome by drawing extra current in the primary. The welder gets hot quite quickly resulting in the temperature overload kicking in. I am wanting to get to at least 125amps so I can try and weld 3mm (1/8 inch) aluminium.

I have tried including a 12 volt battery (as per Lincoln Electric recommendations) in the welding circuit but soon removed this due to the large amount of hydrogen gas produced and rapid rise in temperature of the battery.

Have also tried my mates stick welder as the power source, it's a little more "industrial" than mine, same problem.

So my question is, does anyone have any suggestions to overcome / reduce this problem. Or is there something other than partial rectification causing the problem?

Thanks in advance, questions welcome.

Reply to
Bruce
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Buy a REAL Tig welder ??

Reply to
Never_Enough_Tools

Ignore the previous poster. Apparently he couldn't offer anything intelligent to say, so he tried to be snotty/funny/etc. People like him ruin a lot of good newsgroups.

So, you are saying you can use the same setting on steel without the problem? Perhaps the much lower resistance of the aluminum is causing the current in the secondary to be significantly higher than indicated.

Never_Enough_Tools wrote:

Reply to
Gerald Cooper

ooh, that stings....

Buy a REAL Tig Welder......

I fail to see how my suggestion is not THE most intelligent solution to the problem...???

Why try to do a job with a jury rigged piece of shit ????

Reply to
Never_Enough_Tools

That would require more intelligence.

Some people like to experiment. Some people have limited funds.

Reply to
Boris Mohar

If I'm using the arc welder as a stick welder then I can run it up to

160amps. Have tried using it with a AC/DC rectifier with the high frequency connected for a short period and there didn't seem to be any problems.

Perhaps the much lower resistance of the aluminum is causing

Didn't think so as theres not enough heat to melt a butt join on 1/8 5083 alloy.

As a side note, Miller still manufuature high frequency stabilisers for use with their power sources as this is the prefered method for TIG welding heavier aluminium sections.

Thanks for your reply

Reply to
Bruce

I am taking a guess here but obviously running 160A with stick you are on the edge of the 15A breaker. What about the argon changing the voltage of the "arc". If the voltage goes higher by a few volts then the input power is higher assuming the constant current component stays relatively constant. As you probably know the open-circuit voltage is not what appears across the arc. Billh

Reply to
billh

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