Advice welding smal parts of SS

[Robert1998]

Hello.

I have to weld some small stainless steel parts. Outside corners, inside... I´m triying to make all the parts of the same thickness, 2mm

This is an example



the question is, for example on the outside corners, I use around 45 amps, and I get a small puddle, but in a few seconds, the area gets red hot and I think tis is not OK.
I´m not very skilled with TIG and I used to weld big parts, so the red hot thing is new for me.

Any advice?

Thank you

best regards

 

[Brad93]

you need copper backer bars

aluminium in a pinch but copper is best

 

[Brad93]

Take copper flat bar and file one corner off to a small chamfer.

Aluminium angle works okay too.

 

[Robert1998]

Hello, thanks for your answer, but I have no idea what are you talking about.

I can imagine it is a copper piece to attach to the part to be welded to act as a heat radiator?

 

[Brad93]

Hello, thanks for your answer, but I have no idea what are you talking about.

I can imagine it is a copper piece to attach to the part to be welded to act as a heat radiator?

Yes to act as a heat sink behind the weld.

 

[Robert1998]

Ahh ok, I´ll try that.

Thank you

 

[Robert1998]

Another question. I´m going to run argon inside the part while welding. Being a small part. How many liter per minute or CFM do you recommend?

 

[chrismac]

Another question. I´m going to run argon inside the part while welding. Being a small part. How many liter per minute or CFM do you recommend?

Just a trickle, will be enough, especially if you can make up taper blanks to fit in the holes to help hold the argon in.

What are you welding on the items above, the washer onto the other part, remember some times low amps and slow travel speed is not always the coolest method either, hot and fast can have less heat input, you need to get yourself up to speed to handle that though. some pictures of the finished item would be good?

 

[Brad93]

You need to have somewhere for the argon to go if you purge it, and that needs to be the highest point ideally.

 

[chrismac]

You need to have somewhere for the argon to go if you purge it, and that needs to be the highest point ideally.

well pointed out!! it was a long day, the things you take for granted are important parts not to be missed like the vent I missed!

 

[Robert1998]

Ok, remember I´m not a welder and it is my first time with stainless.

this is the set up



This is the result



Why are so dark? I have use 308L filler wire (from a MIG machine) and the base metal is 304..

And one question, I have this pore. The point of weld them with TIG is to be sure the welds are air tight. Could this pore go deeper to the joint or is it superficial)

 

[chrismac]

I bet your torch does not have the nice gas lens set up, after a wire brush though they will mostly clean up fine, your tail off is either non existent or too fast, does the amps slope off/down when you stop? if not thats how you got a pore, you dont want pores, just run over it again, 308l filler is correct for 304 stainless steel.

Your certainly not starting out on the easiest thing for sure,

 

[Popcorn]

You just need to get 'FASTER' it's so dark coz you cooking the stainless

 

[Robert1998]

Thank you for your answers and help. I'll work on that

 

[Brad93]

Ok, remember I´m not a welder and it is my first time with stainless.

this is the set up



This is the result



Why are so dark? I have use 308L filler wire (from a MIG machine) and the base metal is 304..

And one question, I have this pore. The point of weld them with TIG is to be sure the welds are air tight. Could this pore go deeper to the joint or is it superficial)

That's a wormhole or pinhole, you need to set your downslope to something like 1.5-2 seconds then play the arc around and taper out to ensure the puddle solidifies slowly.

 

[Brad93]

Your arc length is too long. You need to keep the tungsten closer to the work - I can tell this because of the shape of the bead and how it looks like the ripple wants to run away from the joint and into the base metal.

A longer arc causes heating of a larger area, as more energy is being put into the job and naturally the cone of the arc is larger.

For small parts like that the tip of your tungsten needs to be within 1mm of the job at all times. Personally I'd use something like a 1.0 or 1.2mm filler wire to keep the joint nice and small.

If you have a spare one of those parts, pop it in the post, and I'll weld it to give you some basis of settings. Seeing that the part is a chamber you won't be able to use chill bars to this means heat management is going to be really important.

 

[Brad93]

Sometimes on stainless you can get little slag islands follow the weld along, and then when you stop create an 'eye' like you see there as the pool has frozen. Its impurities from the weld/base metal or contaminants that have been mopped up by the silicon or other deoxidants in the wire.

More common with LSi fillers (more common as MIG wire). LSi fillers have increased wetting and puddle fluidity due to the addition of silicon.

 

[Robert1998]

Thank for all your help and advice. I'll try again being more careful whit all your advice

 

[Misterg]

Would pulse help here (to reduce heat input)?

 

[Robert1998]

Ok, I know I have overheated the weldings. And I got these nodules in the other side. What are they?



The pictures have benn taken after using pickling fluid to clean SS steel. They all were black and after the solution some become grey and others remain black.

Are they iron oxide? I mean, they have grow, so, I think they cant be just steel, so maybe they contain oxigen. That is important because this part is meant to operate under high vacuum, so, it it contains oxigen it will gassing that oxigen ruin the vacuum