Heating stainless

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I am thinking I will need to heat the stainless 2 1/2" pipe in order to flare about 1 1/2 inches of it out to 3" to match a header flange.  Can I do that with oxy-acetylene or is there something I need to be concerned or watch out for?
Reply:The only problem I can visualize is having enough hands to heat it evenly enough to get a good even flare. Almost a forge application. You'll need a helper who understands what you want to achieve.
Reply:Thanks.  Yes I agree it's going to be difficult, but right now I'm going to take my time and think it through - I'll figure it out.  So heating the stainless with the oxy acetylene won't weaken the metal?
Reply:So heating the stainless with the oxy acetylene won't weaken the metal?
Reply:Excellent. thanks!One more question; welding mild steel to 304L stainless, I use 309 wire and use the tri-mix for stainless? (or the 75 25).
Reply:Originally Posted by DaddySSExcellent. thanks!One more question; welding mild steel to 304L stainless, I use 309 wire and use the tri-mix for stainless? (or the 75 25).
Reply:Good information, thanks, much appreciated!
Reply:I actually forge stainless all the time- usually I use a big propane forge, but thats just because I have one- you can do it fine with an oxy fuel torch-  a rosebud is good, as you can heat a lot at once.To slightly flare pipe, the easiest way is to just pound it up on the horn of an anvil- but if you dont have an anvil, you can use a ball pein hammer and pound the inside of the open end, working your way around a few times.304 will discolor, but it wont get much softer just from heating- but if you quench it in water while it is red, it will anneal, and get a little softer- not enough to change what you are doing, but I can tell the difference when bending 304 with the hossfeld, annealed vs factory.For welding, I use straight argon- works fine, and is a lot cheaper and easier to get than trimix. Trimix, which has helium in it, will get the weld a little hotter, for better penetration in some situations, but that should not be a problem with something as thin wall as pipe or tubing- its more of a concern with 1/2" thick and up. I dont like the mess, and the pinholes, you get with a co2 mix when welding stainless. Personally, I would tig it, as it is just more neat and clean.
Reply:Thanks for the info, that's helpful.I wish I could tig it, but I only have a mig.
Reply:Originally Posted by Ries304 will discolor, but it wont get much softer just from heating- but if you quench it in water while it is red, it will anneal, and get a little softer- not enough to change what you are doing, but I can tell the difference when bending 304 with the hossfeld, annealed vs factory.
Reply:that flare is an easy job, just take the piece to any muffler shop.  $10 and 5min you will have a professional flare with no discoloration, hammer marks or carbide precipitation.Have we all gone mad?