Question about Stainless Steel Rings and Cooking temperatures

I've got a gas cooktop that for some unfortunate reason, the manufacturer decided to make the "grates" which sit on the cooktop and
hold the pot above the flame, much taller than they need to be. As a result, it takes an inordinate amount of time to heat anything. Boiling water takes way too long. Each grate appears to be cast, with a ring that has five fingers extending upwards, then converging in the center, providing a surface on which to set the pan.
Being the resourceful type, I cut a ring on my lathe (from an old brake rotor) and some fingers from 1/4" by 3/4" iron stock and tapered them on the mill, and after a bit of drilling an tapping, had a replacement "grate" that sits on the standard cooktop mount ring, but is short enough to put most of the heat on the bottom of the pan, not around the sides. After using this single iron grate for well over a year, it has (of course) rusted, and I've pretty much given up on finding a decent enameling solution, and besides, creating the first one took me way longer than I expected, and I really don't have enough time in my schedule to make five...
Thus, I'm at the point where I'm thinking about having some rings cut from 1/4" or 3/8" Stainless, along with some fingers, and bolt together a set of five of these grates, made of SS.
Can Stainless take this sort of heat without significant discoloring or rusting? What type of Stainless should I be using? Where can I get rings cut? They would need to be about 8.7" OD, 8.1" ID, and .250" or .375" Thick. I need five total. I can provide exact size, but right now, I'm not close to the cooktop to be able to measure the one I already made to test the concept.
I live in Hawaii, on the Big Island (the southernmost island) and we don't have much industry here, so I wouldn't expect to find anyone in the state that could do this, so I will need to look somewhere on the mainland.
Thanks --Rick
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Can you get some 1/4" S.S. rod, roll the rings, bend the fingers, & weld, or spot weld, or hi-temp silver solder the fingers in place???
Rick Frazier wrote:

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Jerry:
To make the rings from 1/4" rod, you'd have to make two rings that fit closely within each other (so the little feet that actually space the ring above the mount would fit in place and allow air flow to the burner). If I can't find someone to cut rings from appropriate tubing or sheet, I may mock one up in iron to see how they would work.
Thanks --Rick
jerry Wass wrote:

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wrote:

How about making them out of ceramic? Should be pretty easy to turn on a potters wheel then cook in a kiln.
Gunner
That rifle hanging on the wall of the working-class flat or labourer's cottage is the symbol of democracy. It is our job to see that it stays there.         - George Orwell
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Gunner:
Most of the ceramic clays available here seem to be more brittle than I'd like for holding up a large pot of hot water.....
However, there might be other applications where ceramics would work.
Thanks --Rick
Gunner wrote:

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wrote:

Reason I mentioned this is Ive seen any number of such ceramic goodies used in Mexican cooking, as well as in Asia for holding woks and such. They seemed tough enough to hold a large menudo pot under full boil <G> No idea what sort of clay was involved though.
Gunner

That rifle hanging on the wall of the working-class flat or labourer's cottage is the symbol of democracy. It is our job to see that it stays there.         - George Orwell
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321 Stainless steel would be the cheapest solution. It is designed to take repeated heat cycles for exhaust tubing and jet engine parts.
Inconel 625 or 718 would be even better. The best I can think of would be Inconel C-276
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310 stainless would be the best bet for withstanding a lot of heat, but I don't think you need to worry about any stainless. Don't you have some stainless pots and pans? How do they do?
I agree with Jerry. You should be able to get some rings rolled and the fingers welded on. Or better yet, you can probably figure out how to bend a piece of stainless so it does the whole thing. Get some steel straping used to band crates and see if you can't figure out how to bend a piece to do what you need.
Dan

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I agree that SS should be OK. However, don't compare with pans as they're water cooled remember. At least they should be unless you're cooking is like mine.
John
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The stainless support is not directly watercooled, but it is in contact with the pot so it is somewhat cooled. My cooking must be like yours however. I find stainless pots hold up even when the contents boil dry.
Dan
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Dan Caster wrote:

...

A couple times, I've noticed a serious design problem with tea kettles ... they stop whistling when the water's all gone, so if you're out of the room a few minutes too many and miss the first bit of whistle it goes away. Then the blue paint on the bottom of the tea kettle transfers onto the surface of the burner, or the spout falls off...
-jiw
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Dan Caster wrote:

Good idea. Sort of a 3-leaf clover shape. Bob
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snipped-for-privacy@rickfrazier.com says...

I'd expect either 304 or 316 SS (the most common alloys) would work fine, with 316 being a bit more resistant to high temperatures. Either will take on a heat tint much like the tempering colors seen on carbon steel, but I don't think you'll get any scaling below a red heat. I'd go with the 3/8" stock, which will conduct the heat away from the area directly in the flame, helping to keep the temp down.
The old SS Shipmate propane stoves had stainless steel grates, and seemed to be OK.
Lots of boats where you are, so I'm sure you can find a good SS fabricator to make what you need.
Ned Simmons
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Rick Frazier wrote:

I bought some 304 SS rod on eBay and TIG welded a replacement barbeque grill. (No, don't tell me how much money I wasted, I am learning the fine art of TIG welding, and the old grill was somehow lost. It was an opportunity to make about 50 TIG welds.) I had no worries whatsoever of overheating the stainless with a barbeque! You have to get it yellow hot, BRIGHT yellow, before it really loses strength.
Rust? That's what Stainless Stell is all about, it does NOT rust! Even when hot. If the stuff has to keep a mirror shine, then you have a problem. It will discolor a bit, like just about anything that is exposed to flames.
Jon
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wrote:

Stainless will discolor quite a bit if it's heated above about 700 deg C.
My pulsejet engines regularly run at a red-yellow heat and they rapidly turn a golden brown (initially) then a slate grey shortly afterwards.
Within a few minutes of hard running at these temperatures, most of the chrome is driven out of the stainless, leaving a nickel-iron alloy which has a rough (slightly porous) surface -- probably as a result of the loss of chrome.
In fact, after the first few runs, the inside of the engines are coated with a layer of green powder which I assume to be some kind of oxide of chromium.
After all the chrome is lost, rubbing a finger over a (cooled) engine produces a black powder which I expect is a form if iron oxide resulting from the oxidation of the remaining iron.
Eventually, once the iron too is oxidized away, the alloy becomes very brittle and cracks -- a single point of failure rapidly forming a maze of very fine cracks that spread like a crack in safety glass.
Of course I'm using very thin material -- just 0.020"-0.040" so it's pretty easy to drive all the chrome out. With thicker material it would probably take a lot longer.
However, I doubt your application would raise the SS to these kind of temperatures and because your material would be much thicker, the discoloration would likely be more superficial.
-- you can contact me via http://aardvark.co.nz/contact / Need a cruise missile? http://www.interestingprojects.com/needamissile.shtml
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