Welding Tips and Tricks

So at my work everynow and then we have to weld monel 400 to 316 stainless. The problem is that this combination likes to heat crack. We use either nickel 99 or iconel 82. Sometimes it works sometimes it doesn't. We also do other alloys like tantalum, hastlelloy and some other nickle alloys to 316 and these hardly ever heat crack like monel does. Just wondering why the monel heat cracks so much worse than the rest of the alloys? I have tried to ask the lead welder and engineers why this happens and they just say its monel and its a crap shoot.

I've never looked closely at the metalurgy of Monel.

My experience with metals that expand/shrink at different rates tells me to pre-heat as much as the metal will tolerate without readily oxidzing, welding it up, then insulating it for a very slow cool. Werkspace had a great suggestion... Vermiculite, available at any garden center for cheap. It's a great insulator, and will allow things like cast-iron and dissimilar metal welds to cool very slowly.

Steve S.

Well preheat is not a option in this application. The only time I run in to this combination is in our pressure sensing units. They are basically one or two seals each will get a stainless tube welded to them which is then welded to a mounting flange which is attached to a transmitter that senses the pressure in this chase. The seals have a diaphragm on them that move when the pressure is applied to them. These diaphragms are anywhere from 1 mil to 3 mil in thickness while the body of the seal is about a half in thick so a preheat would warp the diaphragm. Now some of them are made with everything monel instead of stainless but for some reason my guess would be cost some are made with stainless and monel.

Now THAT's a challenge.

Rupture discs for my application are commomly monel and 316, but from what I can tell, they are resistance-welded in a press.

Ya its not easy

Thawed after 5yrs of carbon freezing.

We're currently working on on a build that requires fusing Monel 400 (65Ni,35Cu) to 316 SS with TIG. Service temps below 600F in a non-corrosive and non-brine rich environment.

We selected ERNiCrMo-3 filler based on tech research, consult with Lincoln Electric, and recommended practices from industry. We understand the Nb/Ti content in NiCrMo-3 filler lowers the alloyed melting point and integration of end carbides. Nb essentially helps to interlock migrated grain boundaries and stabilize the austenitic matrix during solidification and combat the tendency for hot cracking.

For the metallurgically curious, the alloy composition % of NiCrMo-3 filler is provided below:

Ni (49.4), C (0.1), Si (0.5), Mn (0.5), Cu (0.5), Fe (5.0), Cr (21.5); Mo (9), Co (9), Nb (3.6), Al (0.4), Ti (0.4); P (0.022), S (0.003).

That's good information!

I take it your results are much improved?

Steve

Otto Nobedder wrote:That's good information!

I take it your results are much improved?

Steve

GTG. Shots of 1in solid hex Monel400 fused to 1/8in 304SS. Used Lincoln Electric TechAlloy 606 {ERNiCr-3} filler. End shot shows the heat tint symmetry for each weld line. Note, this filler is not/not TechAlloy 625 {ERNiCrMo-3}. Worked well.

Anyone ever try using Monel 60 to Join Monel 400 to Stainless Steel?