Welding thin stainless

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Pieter van Boven
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Post by Pieter van Boven » Tue Mar 30, 2004 4:09 pm

Viv,

go for a tig-welder if you want to weld thin stainless steel. I bought one two month's ago on a second hand internet-marked place. Some people don't know what they are selling so for me it was a bargain. I admit I am happy with it. :-)
Here's a picture.

Pieter.
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Capt Ahab
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HV ignition transformer

Post by Capt Ahab » Wed Mar 31, 2004 5:32 am

Al, I've found a similar transformer for my HF system. It isn't exactly the same but it has a 120V primary, 10KV secondary, 23 mA with mid point ground. Is there anything else I need to match up or should this work?

Oh, it is an Alanson 2721-605 if that helps.

Thanks

Al Belli
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Transformer

Post by Al Belli » Wed Mar 31, 2004 12:44 pm

Hi Capt,
The transformer unit is ok. Start with a spark gap of about .030".
I made My spark gap from two spark plugs with the ground electrodes removed, and mounted with the center electrodes facing each other.

Al Belli

Capt Ahab
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Post by Capt Ahab » Wed Apr 07, 2004 3:16 am

Al,

I just got my order of components from Hosfelt and it turns out some of the resistors I got are wirewound ones. Does it matter. I know wirewound resistors could have ill effects due to their inductance.

I should get my OBIT tomorrow and I'll give it a try.

Thanks

Al Belli
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Resistors

Post by Al Belli » Wed Apr 07, 2004 1:01 pm

Hi,

Wirewound resistors are what I used in My welder.
They work very well in this application.

Al Belli

Viv
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Post by Viv » Wed Apr 07, 2004 2:07 pm

An answer to an old question.

Avoiding weld imperfections
Austenitic stainless steel is readily welded, but weld metal and HAZ cracking can occur. Weld metal solidification cracking is more likely to occur in fully austenitic structures, which are more crack sensitive than those containing a small amount of ferrite as ferrite has the capacity to dissolve harmful impurities which would otherwise form low melting point segregates and interdendritic cracks. The presence of 5-10% ferrite in the microstructure is extremely beneficial, so the choice of filler material composition is crucial in suppressing the risk of cracking. An indication of the ferrite-austenite balance for different compositions is provided by the Schaeffler diagram. For example, when welding Type 304 stainless steel, a Type 308 filler material, which has a slightly different alloy content, is used.

Shamelessly nicked from another site

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

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Monsieur le commentaire

Raymond G
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Post by Raymond G » Thu Apr 08, 2004 12:09 am

Can anyone recommend any kind of pastelike flux that can be applied to the BACKSIDE of a stainless joint before welding to avoid the dreaded "black Crystals" or "sugar". I 've heard of the back purging approach, be seems spendy and laborious. Perhaps a better question might be, "Does anyone have a technique to avoid "sugar" on the backside of stainless welds?"

Regards,
Raymond

Capt Ahab
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Post by Capt Ahab » Thu Apr 08, 2004 2:08 am

Solar Flux type B seems to work ok but it's expensive. You can read about it at www.solarflux.com.

Larry Cottrill recommended Chromalloy which he said was only $15 per can but I've never used it.

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Post by larry cottrill » Thu Apr 08, 2004 3:41 am

Capt Ahab wrote:Solar Flux type B seems to work ok but it's expensive. You can read about it at www.solarflux.com.

Larry Cottrill recommended Chromalloy which he said was only $15 per can but I've never used it.
Captain -

That was a price from 2001, of course. It is basically a can of grey powder; you mix it up a bit at a time with water and a little milk or gelatin or some such. I just dabbed it on with a popsicle stick, which seemed to work OK. It dries in a matter of minutes [in conditioned indoor air].

After your weld cools, the flux remains as a thin film of black 'glass', strikingly similar in sheen to black anodizing on aluminum. If you want to remove it for some aesthetic reason, you need a good wire wheel and lots of patience.

L Cottrill

Capt Ahab
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Post by Capt Ahab » Thu Apr 08, 2004 5:22 am

Larry,

Sounds a lot like Solar Flux, except that with Solar Flux you have to use methanol alcohol instead of water and milk.

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Post by Capt Ahab » Thu Apr 08, 2004 5:31 am

Ok, I got my OBIT transformer today and threw together my high frequeuncy unit. IT WORKS!!! Cool...lots of sparks and arcs and stuff!!!

I'm having a bit of trouble getting enough voltage out of the secondary to strike an arc though. The only way I can get it to work is to increase the spark gap to 1/2" or so which causes it to make a heck of a racket. While experimenting, I increased the spark gap to over an inch which was really cool till it started arcing to my capacitors and catching them on fire. Luckily I ordered extras. I think I'm going to try using 1/4" copper tubing instead of heavy gauge copper wire for the large coil. I read somewhere that the diameter of the wire matters because it affects its capacitance somehow. We'll see. Anyway, thanks Al.

Al Belli
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HF unit

Post by Al Belli » Thu Apr 08, 2004 9:11 pm

Hi,
High frequency travels on the surface of conductors, so the 1/4" tube is much more efficient than a smaller diameter conductor.
You need not have the spark gap any larger than .040". The starting sparks may appear to be quite small, but with the argon flow, the arc will start very easily. Excessive high voltage will cause the emission of a lot of radio interference, and may cause the failure of the rectifiers and other components. The use of ceriated electrodes will also make the arc starting much easier.
Al Belli

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Post by Capt Ahab » Thu Apr 08, 2004 11:10 pm

Al,

About the copper tubing coils. You said 1/4" tubing for the outside and 1/8" for the inside. Are these ID or OD measurements? All they have at the hardware store is 1/4" ID and 1/4" OD. The stuff I used on my first coil was solid wire that I think was #6 and #8 gauge. Would it help to use larger diameter on the inside coil too?

I used a larger spark gap because that was the only way I could get it to work even with the Ar. With a smaller spark gap it was too weak. I'm hoping the larger diameter tubing will do the trick.

Thanks,
Ahab

Capt Ahab
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Post by Capt Ahab » Fri Apr 09, 2004 4:33 am

Al, what sort of spark plugs did you use? I originally made my spark gap from a couple of short pieces of 1/16" stainless steel TIG rod which worked as I said if the gap was 1/2" or more. I rigged up a spark gap tonight using a couple of automotove spark plugs with the metal tab removed. The spark plugs were facing electrode to electrode. This setup simply wouldn't work for me no matter what gap I used. An arc would jump the gap but It didn't seem to be exciting the coil circuit hardly at all. The plugs must have some resistance or something. I should have checked them but didn't.

-Ahab

Al Belli
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HF unit

Post by Al Belli » Fri Apr 09, 2004 1:02 pm

Hi,
Use 1/4" o.d. tube for the outside coil, ans the solid wire that You have for the inner primary coil.
The spark plugs that I used are non-resistor type spark plugs.

Al Belli

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