What type of steel for grate ?

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ianrichards
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What type of steel for grate ?

Post by ianrichards » Fri Dec 08, 2017 7:43 pm

Rather than having a bespoke cast iron grate made for my Lune Valley boiler, I am rather taken with the idea of using steel bars that can be easily lifted out of the grate frame individually and replaced as needed.
Mild steel bars are obviously best avoided, but would something like 316 (A4 in the UK) be worth trying?
I know that 310 or 309 would be more suitable, but they are proving difficult to source and the cost could well be prohibitive.
If, at the end of the day this solution doesn’t prove suitable, I’ve designed the frame so that a cast iron grate can be easily inserted.
TIA
Ian
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Re: What type of steel for grate ?

Post by cyberbadger » Fri Dec 08, 2017 9:17 pm

I don't know which specific alloy, but I have heard that the live steamer ride -on scale locomotive folks have found that at least one stainless steel alloy works pretty well for grates.

I have pictures of crappy mild steel grates glowing cherry red from my first boiler of ill repute. they distort like crazy.

-CB

P.S. Nyitras current grates are not quite suitable for heavy coal use. They are made from 1" asme-spec boiler stays. If I decide to start using coal regularly, I'll go stainless
Last edited by cyberbadger on Sat Dec 09, 2017 12:24 am, edited 1 time in total.
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barts
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Re: What type of steel for grate ?

Post by barts » Fri Dec 08, 2017 9:38 pm

ianrichards wrote:Rather than having a bespoke cast iron grate made for my Lune Valley boiler, I am rather taken with the idea of using steel bars that can be easily lifted out of the grate frame individually and replaced as needed.
Mild steel bars are obviously best avoided, but would something like 316 (A4 in the UK) be worth trying?
I know that 310 or 309 would be more suitable, but they are proving difficult to source and the cost could well be prohibitive.
If, at the end of the day this solution doesn’t prove suitable, I’ve designed the frame so that a cast iron grate can be easily inserted.
TIA
Ian
Coal fires are quite hot, so mild steel will not work very well at all as you know. 316 is quite resistant to high temperatures, so will likely last for a while. One method that has protected the steel and helps prevent clogging w/ slagging coal is to use stainless angle rather than bars; the tip of the angle is pointed down. The grate ends up looking like this: V V V V V V V V

Ash will collected in the 'V's, helping to insulate the stainless steel from the worst of the fire, and once a piece of slag falls between the bars, it will end up in the ash pan rather than cooling off and getting stuck. Note that the highest temperature conditions will be obtained when the damper is closed suddenly after steaming hard; letting the fire cool off more slowly should help prevent sagging grate bars. If a support can be rigged in the middle of the grate for the angled bars, the chance of sagging will be much reduced.

If you can figure out how to make one fit, stock cast iron drain grates can be used with good success - that's what it's in Rainbow, stuck in a round Scotch furnace. After it sags too much or rusts out, they're readily available at non-bespoke prices for many years as they're stock sizes.

https://www.google.com/search?q=olympic ... 88&bih=785

Note also that there still various sorts of grates and grate bars available in the UK, from which it would seem possible to construct a proper cast iron grate w/ replaceable pieces:

https://heatingpartswarehouse.co.uk/pro ... are-front/

Note the grate bars are available in 10 and 12 inch lengths:

https://heatingpartswarehouse.co.uk/pro ... -iron-bar/

- Bart
-------
Bart Smaalders http://smaalders.net/barts Lopez Island, WA
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Re: What type of steel for grate ?

Post by Mike Rometer » Fri Dec 08, 2017 10:28 pm

Stainless every time for me.

I space mine at approx. 50/50% air to bar and so far have had no trouble. I don't use individual bars but prefer sections which can be swapped around and or inverted in the f/box. I've got one that has lasted for over 25 yrs in a 7 1/4" loco, and shows no sign of not doing so for at least as long again.
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Re: What type of steel for grate ?

Post by ianrichards » Fri Dec 08, 2017 10:49 pm

Mine is all set up for 50/50 air to steel.
What sort of stainless are you using?
Thanks
Ian

Mike Rometer wrote:Stainless every time for me.

I space mine at approx. 50/50% air to bar and so far have had no trouble. I don't use individual bars but prefer sections which can be swapped around and or inverted in the f/box. I've got one that has lasted for over 25 yrs in a 7 1/4" loco, and shows no sign of not doing so for at least as long again.
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Re: What type of steel for grate ?

Post by Mike Rometer » Sat Dec 09, 2017 8:52 am

ianrichards wrote:Mine is all set up for 50/50 air to steel.
What sort of stainless are you using?
Thanks
Ian

Mike Rometer wrote:Stainless every time for me.

I space mine at approx. 50/50% air to bar and so far have had no trouble. I don't use individual bars but prefer sections which can be swapped around and or inverted in the f/box. I've got one that has lasted for over 25 yrs in a 7 1/4" loco, and shows no sign of not doing so for at least as long again.
Sorry Ian, pass on that one, it's too long ago to remember, but probably 316 as that is readily available.
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Re: What type of steel for grate ?

Post by Mike Cole » Sat Dec 09, 2017 9:18 am

Hi Ian
I use flat bars of stainless, sorry do not know what grade. I use a much greater air gap. My bars are spaced at 4 times the thickness apart, for burning mostly wood they work fine. I have also spilt the grate up in to 3 sections so to fit in and out of the firebox door.
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Re: What type of steel for grate ?

Post by ianrichards » Sat Dec 09, 2017 9:57 am

Thanks gentlemen, I knew I’d get the advice I needed.
I had planned on using 15x15, but would this be overkill?
Could I get away with 15 wide and 10 high, what do you reckon?
Thanks
Ian
Mike Cole wrote:Hi Ian
I use flat bars of stainless, sorry do not know what grade. I use a much greater air gap. My bars are spaced at 4 times the thickness apart, for burning mostly wood they work fine. I have also spilt the grate up in to 3 sections so to fit in and out of the firebox door.
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Re: What type of steel for grate ?

Post by Mike Cole » Sat Dec 09, 2017 10:03 am

[quote="ianrichards"]Thanks gentlemen, I knew I’d get the advice I needed.
I had planned on using 15x15, but would this be overkill?
Could I get away with 15 wide and 10 high, what do you reckon?
Thanks
Ian

I would say much too big, my bars are no more than 3mm think by 15(maybe 20) high. They have lasted one season with out any damage. I use mostly wood but have used coal a few times
Mike Cole
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Re: What type of steel for grate ?

Post by ianrichards » Sat Dec 09, 2017 10:12 am

Excellent, I’d rather go thinner.
The grate’s outer frame is made of angle and have fitted to the fore and aft angles a row of spacers to drop the bard between.
These spacers provide a gap of 15mm.
So, what section steeldo you reckon I should use, bearing in mind that it needs to be 15mm wide?
Thanks
Ian
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