Ok I'm making a part for a test stand fixture. I need to create basically a rod with a threaded end in it. Our company wants to use sch80 304 stainless pipe for the rod itself. I need to machine and weld in a plug that will have a 3/8-16 threaded hole into the end of the pipe. I have a chunk of 416 stainless. Can I just TIG them together is there anything special like preheating that I would need to do in order to weld these two different types of stainless to each other? Is it just a terrible idea? I'm open to any other suggestions as well.Thanks,Matt
Reply:Just off the top of my head, I would do a test piece and use 309 for the filler, see how it does.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Why not just get a piece of 304 to match the 304 pipe?304 is austentitic and 416 is martensitic. 304 is generally weldable without too much difficulty (with the right filler alloy, like the 'standard' 308). 416 is a hardenable martensitic alloy, that is weldable with some major pre-heat and controlled post-heat and slow cooling (to prevent weld cracking from the alloy getting hard after welding).But 416Se (free-machining selenium grade of 416) is NOT considered weldable.Also, the 416 has way less corrosion resistance to most environments than the 304. So you should double-check your alloy selection to verify the correct material properties (strength and corrosion resistance especially in stainless steels).What size/diameter pipe are you trying to put that 3/8-16 female thread into? Maybe you could weld a 304 3/8-16 nut into the pipe? The best laid schemes ... Gang oft agley ...
Reply:Because I have the piece of 416 already, we had it laying in our stock. And like most other companies right now we're on something of a spending freeze. And we would have to either order this in or travel about 45 minutes to get a piece of stainless. None available locally. Interesting to know that there are non weldable grades of stainless though. 1/2" sch 80. Might be able to weld a nut in. It has to be dead nuts square and we want it to look decent too though so the plan was to machine a shoulder onto the plug that will fit the ID of the pipe within a thousandth or so to keep it aligned while we weld it in. The rest of the plug will be turned to match the OD of the pipe and the joint will be ground then so it looks as close to a single piece of metal as possible. We want to stay with pipe instead of solid stock to cut down on the weight as much as possible.Last edited by mjmiller1824; 03-31-2009 at 12:59 PM.
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ead-nuts square and within a thou?The PIPE isn't toleranced that close! Yes, there are LOTS of unweldable or difficult to varying degrees of weldable alloys, stainless or other types of steel or metals. Maybe true the pipe ID, turn a stainless 3/8-16 nut from hex to round, build-up the od of the now threaded cyulindrical plug, return the OD of the threaded plug back to desired dimension, insert into trued-up pipe ID, weld, hope threads stay true enough. The best laid schemes ... Gang oft agley ...
Reply:The ID of the pipe has been reamed on the lathe, squared off and measured at .545" Id already Already. I'm not trying to blow smoke here, I'm trying to figure out the best way to do this. I'll look into the nut way but I've had bad luck welding nuts that small into things. If it was onto a plate that would be one this this is a bit different (I think anyway).
Reply:I think you're better off investing 90 minutes to drive to where there's some 304 stainless plate you can use.The reason 400 series martensitic stainless steels are hard to weld is not only that they form martensite (a hard, brittle microscopic structure), but they undergo a fairly significant volume change as a part of that transformation. I'm almost willing to guarantee that your 416 stainless component will distort unless you jump through some major hoops and use a bunch of pre-heat and slow cooling after welding. It'll be faster and easier to make that drive, than it will be to figure out how to make the 416 stainless you have, work in this application.In this case, 'A bird in the hand is NOT worth more than the 2 in the bush'...Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Cool, I'll talk to the boss when he gets back from vacation. If the 416 really isn't a good idea then I'll get the 304. Thanks.
Reply:Just drive or have delivered the 304 (or whatever) piece that you really need/want and be done with it.As I said above : 416 is a hardenable martensitic alloy, that is weldable with some major pre-heat and controlled post-heat and slow cooling (to prevent weld cracking from the alloy getting hard after welding).
Reply:A flick of the mouse wheel and i missed your post Moonrise. If I'd seen it, I wouldn't have repeated what you said. Originally Posted by MoonRiseJust drive or have delivered the 304 (or whatever) piece that you really need/want and be done with it.As I said above : But if that 416 is ACTUALLY 416Se (free-machining 416), then the 416Se is considered unweldable.It's all well and good (sometimes) to use what you have. But sometimes it will take less time and money to go get what you really need instead of trying to 'make-do'.
