Welding 1.5mm 316L SS Box problem

[RubberDuck]

I'm experimenting with different types of welding positions and amperage while trying to weld inside and out a 200X200X70mm box.
My initial problem is that the other side of my weld looks like a complete burnt crisps... (i don't know the professional term for it)
I know i can solve this buy using a gas shield, but it's a box, though small, i'm trying to figure how to do it without gas shield.
Will lowering the amperage improve the result? if so, what will be the range for 1.5mm?

 

[Drains]

Aye, you need a purge. You can use Solar Flux instead though.
http://www.solarflux.com/

 

[Shox Dr]

That or thermal tape. However at 1.5mm I'd be welding from the outside (copper backing strip on the inside- optional).

The 'burnt crisp' look is called sugaring, and will come off with products such as Antinox

Edit; A bit of 15mm copper tube would do, it doesn't have to touch the inside of the corners

 

[RubberDuck]

How is sugaring avoided with a copper backup? copper just sucks the heat out of the weld while purging gas also inhibits oxygen which causes the oxidization and thus sugaring. What am I missing here?

 

[hotrodder]

Heat + O2 are needed for the metal to scale (sugar/coke etc). Heat sink will lower the temp at the back of the weld, limit the 'easy access' to the air and if the heat sink fits tightly keep air out. In either case the heat and travel speed need to be balanced i.e. too hot or too slow and they won't do much

A heat sink can also be used to purge a small area... think lots of small holes in a bit of copper tube with argon flowing through it or some sheet ally/copper shaped to so that it can be clamped/taped to the part and argon flowed down the back of the weld

Another way that can be quick, easy and look good is a closed corner and an autogenous weld, ideally pulsed. All depends on what's acceptable for the job/customer...

 

[RubberDuck]

Will an Aluminium strip work i this scenario?

 

[Shox Dr]

Another way that can be quick, easy and look good is a closed corner and an autogenous weld, ideally pulsed. All depends on what's acceptable for the job/customer...

Two of us used to autogenously weld up extraction filters for commercial kitchens, it was a baffle with expansion box in the middle to catch the grease, the ends were welded, all in 0.9mm 316 DP1 and all seams polished back in. Far from easy.

However a good fit in 1.5mm with more tacks than you think needed and you'll be surprised how easy it is, holding a rod just in case you need to cool it down a bit. A good sharp clean tungsten is a must

 

[hotrodder]

Yeah, not much margin for error with sub 1mm stainless especially if largish flat sections. Don't mind the welding, especially hate the regraining though

Will an Aluminium strip work i this scenario?

Could do, especially if it's reasonably thick flat bar. Angle or something bent to fit the joint even better still. As Shox said tacks are one of the key bits along with a nice sharp tungsten and very short arc length, ideally no longer than the tungsten dia

 

[RubberDuck]

That or thermal tape. However at 1.5mm I'd be welding from the outside (copper backing strip on the inside- optional).

The 'burnt crisp' look is called sugaring, and will come off with products such as Antinox

Edit; A bit of 15mm copper tube would do, it doesn't have to touch the inside of the corners

The copper tubing is a great idea, i was mind set on how to obtain an angled copper piece
Or a piece of copper plate...
Copper tubing is much more common and simpler to use on corners.

 

[Hitch]

A bit of aluminium angle works quite well for inside and outside corners as it has a nice sharp corner.
The hardest part is clamping it in place tightly against the joint without making it impossible to weld up.