304 exhaust setups

[Brad93]

I use mine as amperage control whilst welding, works for me. 0.9mm

 

[HughF]

I used to use a pedal for everything, recently switched to fixed current and a torch switch, for my DC stuff (after having some pointers from @Richard. ) consistency and quality has improved a lot.

 

[Richym]

tried with the torch switch today. and pulsing I'm getting there. I've watched few videos and seen people laying the filler rod in front. is this good practice?

 

[Richard.]

tried with the torch switch today. and pulsing I'm getting there. I've watched few videos and seen people laying the filler rod in front. is this good practice?

Some results pics would be nice rich.

 

[Brad93]

tried with the torch switch today. and pulsing I'm getting there. I've watched few videos and seen people laying the filler rod in front. is this good practice?

Lay wire technique can work well in some cases, mainly cover passes or caps. For the root or first pass you really need to watch the puddle melt in to the parent material so you have good penetration and depth of fusion.

 

[whm_fab]

I’m a little late to the party here but hopefully I might be able to add something to help the op get better, although there has been some excellent advice by brad and Richard etc so far.


I suppose just to clarify a few points firstly, as the guys have already said, back purging on thin wall stainless, or any exotic alloy is an absolute must! Anyone who says they can butt weld thin wall stainless tubing on 35-40amps and not get sugaring on the backside, is frankly talking rubbish.

You will get discolouration and sometimes sugaring when tacking thin wall stainless at 40a.

If you are welding it at an amperage or speed that will not penetrate through 1.5mm wall or less stainless, you’re in big trouble shortly down the road.


On the filler side of things, it’s a bit of a double edged sword.

It is very possible and fully acceptable to butt weld stainless tube autogenously and have it as strong as the base metal IF, and that is a bit IF, there is NO, and im talking not even mocroscopic air gaps or chamfers on the tube. When the tube is butted together is should be very very difficult to even see where one tube meets the other the fit-up is so good. Then, generally with pulse, an autogenous weld with no undercut is possible with full penetration that is as strong as the parent metal.

As I make manifolds for often very expensive and important race/rally cars, I send off a few samples to be tested in 2014 for my own knowledge – 1.2mm wall 304 and 321, few samples without filler, few samples with. Each one was x-rayed, bent, stretched until it yielded. In general, the autogenous welds were as strong as the base material.
The samples with the filler were stronger than the material, so it's all relative.

What it comes down to really is longevity. There is more chance of failure in a shorter time period with no filler, but that doesn't necessarily mean that it is a flawed technique - F1 exhausts are autogenously welded .6mm inconel. And they are expected to fail after a certain amount of hours use.
Obviously that's not ideal for 99% of retail customers.

Unless a customer specifies to me that he doesn't want filler to save weight or whatever then I will always use a filler.

When Im building manifolds for f3 cars for example IL use 1mm or 1.2mm wall 304 or 321 with a .8mm filler or sometimes 1mm.
38ish amps, clean clean clean and clean again. Hand file each tube end for a nothing but perfect fit, and purge absolutely everything , Everytime

 

[Richard.]

I’m a little late to the party here but hopefully I might be able to add something to help the op get better, although there has been some excellent advice by brad and Richard etc so far.


I suppose just to clarify a few points firstly, as the guys have already said, back purging on thin wall stainless, or any exotic alloy is an absolute must! Anyone who says they can butt weld thin wall stainless tubing on 35-40amps and not get sugaring on the backside, is frankly talking rubbish.

You will get discolouration and sometimes sugaring when tacking thin wall stainless at 40a.

If you are welding it at an amperage or speed that will not penetrate through 1.5mm wall or less stainless, you’re in big trouble shortly down the road.


On the filler side of things, it’s a bit of a double edged sword.

It is very possible and fully acceptable to butt weld stainless tube autogenously and have it as strong as the base metal IF, and that is a bit IF, there is NO, and im talking not even mocroscopic air gaps or chamfers on the tube. When the tube is butted together is should be very very difficult to even see where one tube meets the other the fit-up is so good. Then, generally with pulse, an autogenous weld with no undercut is possible with full penetration that is as strong as the parent metal.

As I make manifolds for often very expensive and important race/rally cars, I send off a few samples to be tested in 2014 for my own knowledge – 1.2mm wall 304 and 321, few samples without filler, few samples with. Each one was x-rayed, bent, stretched until it yielded. In general, the autogenous welds were as strong as the base material.
The samples with the filler were stronger than the material, so it's all relative.

What it comes down to really is longevity. There is more chance of failure in a shorter time period with no filler, but that doesn't necessarily mean that it is a flawed technique - F1 exhausts are autogenously welded .6mm inconel. And they are expected to fail after a certain amount of hours use.
Obviously that's not ideal for 99% of retail customers.

Unless a customer specifies to me that he doesn't want filler to save weight or whatever then I will always use a filler.

When Im building manifolds for f3 cars for example IL use 1mm or 1.2mm wall 304 or 321 with a .8mm filler or sometimes 1mm.
38ish amps, clean clean clean and clean again. Hand file each tube end for a nothing but perfect fit, and purge absolutely everything , Everytime

Nicely said mate. Some good advice there. Would be good to see more of your stuff on here.

 

[whm_fab]

Thanks Richard I do my best to get online when I can!
I will post some photos over the weekend of different examples, tube prep a weld with filler and without on the outside and the backside and the difference if you have the tiniest gap or chamfer

 

[M K]

Some good info and comments on here, great to hear from people with lots of experience

I do a few exhausts and always use filler but can never get it looking as good as others

Just finishing one at the moment, 1.5mm 304 stainless welded at about 50amps, 1.6mm 308L filler rod

This was not back purged as the customer wants to keep costs down, yes there is a little sugaring but they are not bothered by that as it's only their road car toy

My fit up is pretty good but do you think I'd get a better weld with 0.8mm or 1mm filler rod?

Thanks
Marc

 

[Gizmo.Y]

I would drop down a filler size, i found i got better results using 316 1.0mm rod on 304 stainless. (Below picture is an intake tube, but some principle)

 

[HughF]

I would agree, 1mm filler, 316 is all I use...

 

[Richard.]

Yes giz is bob on a 1mm filler will be far more suitable for a 50amp current range.
1.6 fillers don't really come in to there own until you into the triple digits.

 

[whm_fab]

i would also agree on the 1mm, you're far to cold for 1.6. but you are never going to get the results you want without purging - it will always be sucking impurities in from the back side.

But i have to argue, keep the costs down? it uses about a 5er's worth of gas to purge that tube. if a customer told me not to purge that tube i would either A)do it anyway, or else B) thank him for his inquiry and tell him he should try somewhere else. You are compromising your product which looks like you have put alot of effort into by letting the customer tell you how to weld it, you're the welder! Tell them this is the process, this is the price, thats how its done, there is no short cuts take it or leave it.

I wouldn't ever remotely even consider welding this wall stainless without purge, ever.

 

[Mee]

Nicely said mate. Some good advice there. Would be good to see more of your stuff on here.

+1

You are compromising your product which looks like you have put a lot of effort into by letting the customer tell you how to weld it, you're the welder

It rather defeats the object of employing you to do it properly in the first place.

 

[german8rcoupe]

I don't get the multiple slice bends....one mandrel bend would take care of that with less welding and imho look much nicer.
I am going to look out some old pics to see if I can find some internal shots of my exhaust stuff to show no sugaring......don't like being called a **********.

 

[M K]

Thanks for the reply to my post people

I agree I think I will stick to purging with no other opinion from the customer and they either pay the price which will account for the time and bit more gas etc or have to go elsewhere.

I have just ordered some 1.0mm 308l filler so will post some update pics of how I get on with that, purged and not purged

As for the multiple bends I agree it's a lot more work but it meant I could order one lot of straight tubing without having to order bends and wait for them to be delivered as and when I worked out what I needed

If I have spare money when I get a job like this as it's my hobby work not my day job then I order a few of each bend so I have more than what's needed but didn't have the spare cash to buy in advance on this one

My welding is 100% self taught so I am the first to admit I'm far from the best and doing ok and learning everyday from reading topics like this

Very helpful

Thanks
Marc

 

[whm_fab]

keep up the good work, nice job, im 100% self taught too, although i did do a 'night course' purely to practice with all the free material and get a massive discount on the tests - id say i went through a metric ton of stainless in a few week nights

you should consider buying good mandrel bends though unless people are actually asking you to do pie cuts - the time to cut and sand them, never mind the welding time is colossal compared to mandrel bends.

where most people think purging is expensive is they are lashing small tubes with tons of gas. for a tube you posted above i would purge that for 5mins at 5lpm and drop it to 2lmp so there is just a positive pressure in the tube to stop oxygen coming back in. you wont even barely notice it on your gas bill if you do it right.

dont every stay quiet, ask questions. keep up the good work.
remember, there are no such thing as stupid questions

 

[Richard.]

I guess it depends on how tight that bend has got to be, material you use and radius size required as to whether it's better to lobster back the bend or use a mandrel bend from 1 piece.
Done nicely the lobster back can look really good and can be a good way to achieve a sudden direction change with a tight radius bend.

 

[Gizmo.Y]

ProFusion do a nice range of Tight Radios bends

 

[Richard.]

ProFusion do a nice range of Tight Radios bends

They might do but there is always a bigger radius with a pre bent tube than can be achieved by using a lobster back technique. So it really does depend on where the thing has got to go and whether a mandrel bend can be used