I can also have this HIP'd for you. We HIP Ru/Re/Ir/Os.
Casting Rhodium
- Thread starter Jshapco2
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Follow Lou's advice. It's the definitive answer you're looking for. I've been waiting for him to respond.
Dave
Dave
Darkthirty
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Hot Isostatic Pressing. More education!Welcome to us
Casting Rhodium is exceedingly difficult due to the high temperature needed.
Why cast and machine?
Do the product have stringent dimension criterias?
I believe most parts of Rhodium is sintered.
What is a HIP process?
I found it on Google after I asked
You can melt it with a TIG torch. It takes a lot of current, a lot of power, and skill with the torch so you don’t melt through the bottom of whatever you’re consolidating. I do it mostly with platinum and pt-rh wire to make plate that I roll into sheet, but the process should work with Rhodium. See the attached article from Johnson Matthey, and the pic of a pt billet made from 4, 4mm wires. The end product is a 3mm solid bar. The challenge is to weld >50% to a liquid without melting through the bottom. I elevated 2” from the welding table by a pt wire stand to avoid any introduction of contaminants, and a pt sheet to catch any spilled metal.
I’m new, so I’m including pics to show that I’ve actually done everything I’m describing.
The 3rd picture is my pt setup, less the welding table (fire brick for oxy-ac): it’s simple and it works. The dirty spots are bits of soot and the results of being flame sprayed by a torch. I don’t clean working pgm items unless I’m melting them. I use an OxyAc torch as a high-oxygen flame drives out anything that is not pt. The XRF report is for the high o2 melt. I use about 2:1 oxy:ac — basically I experimented until I got the most separation of contaminants from the pt, which is a bit more than what’s required for the hottest flame.
I wear a #8 shield for eye protection with the high O2 work, a P100 mask anytime I weld, and I only work with pgm powders when they’re wet. I put slurries in a pouch, dry them and weld the pouch shut before I press, sinter, and melt.
I haven’t done the quantitive work for my method: I don’t know my losses yet. I’ll post my results if their instructive, cautionary, or merely interesting, when I process my next batch/pouch.
I’m new, so I’m including pics to show that I’ve actually done everything I’m describing.
The 3rd picture is my pt setup, less the welding table (fire brick for oxy-ac): it’s simple and it works. The dirty spots are bits of soot and the results of being flame sprayed by a torch. I don’t clean working pgm items unless I’m melting them. I use an OxyAc torch as a high-oxygen flame drives out anything that is not pt. The XRF report is for the high o2 melt. I use about 2:1 oxy:ac — basically I experimented until I got the most separation of contaminants from the pt, which is a bit more than what’s required for the hottest flame.
I wear a #8 shield for eye protection with the high O2 work, a P100 mask anytime I weld, and I only work with pgm powders when they’re wet. I put slurries in a pouch, dry them and weld the pouch shut before I press, sinter, and melt.
I haven’t done the quantitive work for my method: I don’t know my losses yet. I’ll post my results if their instructive, cautionary, or merely interesting, when I process my next batch/pouch.
Attachments
Rhodium sputtering targets are isostatically hot-pressed in foil, then machined to final dimensions. I’m pretty sure that solid Rh metal would need to be ground as it’s too hard & brittle to cut with a tool
If you're going to TIG Pt, just do so on a block of copper with a depression milled into it.
Jshapco2
New member
Thank you all so much.
A 50mm disk 5mm thick at the melting point of Rh is going to radiate all of the input power as heat & light once it’s incandescent. I’m not confident that a block of copper can passively dissipate that much energy without sublimating or melting copper. I haven’t tried it. I use a 300amp setting on a idealarc TIG welder to weld 5mm Pt and I have to put the pedal on the floor to get it going. It takes almost as much power to keep it hot. I’ve welded billets larger than 50mm, but those have been more than 3mm thick.
I don’t have any experience welding pure Rh. I don’t think a copper block will be able to sink heat fast enough to not lose copper. The risk of getting copper in or on your Rh seems substantial: there’s not a lot of room between the BP of copper and the MP of Rh.
If someone has experience welding Rhodium, Iridium, or Palladium objects, especially larger objects, with TIG, I’d like to know how that turned out. If I learn anything interesting when I next melt/weld PtRh next month, I’ll post it here.
Thanks for responding. I was just saying that TIG melting Pt on a large block of copper is a hygienic method of melting platinum buttons.
I actually have some experience in the arc melting of different metals, not much, but I've melted Ir, Ru, Os, Pt, Rh, Hf and Zr, Ta, Nb and even W. I agree that at a certain point, radiative losses far exceed conductive losses. This means the top zone is absorbing and radiating most of the heat and that loss is more than the loss of the melt zone at the bottom to the copper. The huge delta creates a frozen skull that prevents migration of Cu into the melt pool.
You aren't going to sublimate or melt copper if it provides enough of a thermal sink and the delta is great enough. I use a 3"x3" by 20" block of copper, it's dozens of lbs if I'm just doing a quick melt with our TIG at the shop. I've melted 12 g chunks of iridium with it. When I melt up a couple ounces of iridium, the copper does get warm. My actual arc melting furnace has a water cooled shell and water cooled copper hearth and a water cooled 6 mm diameter tungsten electrode. That can melt about 300 g of iridium at 600 amps. That requires more of a procedure to use.
In general, you can't put enough heat into the copper with the water running to mess it up. I say that with a caveat, because the arc melter I have (and some members here are personally familiar with it as they helped clean it up before it went out to a specialist) had its hearth all pockmarked from starting the arc without ever cooling the hearth.
Usually Ir is welded with EBM welding not TIG. PtRh should behave very similar to Pt in melting. In fact, TIG welding Pt (or even oxyhydrogen welding it) is in my opinion, quite enjoyable.
One of these days I'd like to start making some videos of some of the fun sides to this profession. I wish I knew all the A/V stuff that some people here do because we've done some silly things that are entertaining.
I actually have some experience in the arc melting of different metals, not much, but I've melted Ir, Ru, Os, Pt, Rh, Hf and Zr, Ta, Nb and even W. I agree that at a certain point, radiative losses far exceed conductive losses. This means the top zone is absorbing and radiating most of the heat and that loss is more than the loss of the melt zone at the bottom to the copper. The huge delta creates a frozen skull that prevents migration of Cu into the melt pool.
You aren't going to sublimate or melt copper if it provides enough of a thermal sink and the delta is great enough. I use a 3"x3" by 20" block of copper, it's dozens of lbs if I'm just doing a quick melt with our TIG at the shop. I've melted 12 g chunks of iridium with it. When I melt up a couple ounces of iridium, the copper does get warm. My actual arc melting furnace has a water cooled shell and water cooled copper hearth and a water cooled 6 mm diameter tungsten electrode. That can melt about 300 g of iridium at 600 amps. That requires more of a procedure to use.
In general, you can't put enough heat into the copper with the water running to mess it up. I say that with a caveat, because the arc melter I have (and some members here are personally familiar with it as they helped clean it up before it went out to a specialist) had its hearth all pockmarked from starting the arc without ever cooling the hearth.
Usually Ir is welded with EBM welding not TIG. PtRh should behave very similar to Pt in melting. In fact, TIG welding Pt (or even oxyhydrogen welding it) is in my opinion, quite enjoyable.
One of these days I'd like to start making some videos of some of the fun sides to this profession. I wish I knew all the A/V stuff that some people here do because we've done some silly things that are entertaining.
He is not going to weld it, "only" melt it.
goldandsilver123
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Not nearly enough mass!!
goldandsilver123
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goldandsilver123
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Just got a 5500 g (58x more mass than the other copper mold) block o copper, improvised a "guard-rail" and tried to TIG melt Platinum, it went really well:
XRF didn't show any copper on the bottom of the button.
Don't know what the black soot is, it's electrolytic copper and the melt was done under plenty flow of argon with gas lens.
I will drill this copper and make it water cooled.
Bottom:
It is hard to say what the black is.
I once had a Tig nozzle explode on me during welding.
It literally separated and shot the electrode and rear end straight into the ceiling.
When I inspected it after it was sooted like it had been burnt with a rich Acetylene flame.
But it could not be we was using pure Argon.
Maybe some kind of stray plasma hot enough to decompose the Teflon rings?
