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How much expansion?

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Bruce Edney30/01/2016 03:53:54
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167 forum posts
53 photos

Hi folks

I have a ring of cast iron about 155mm ID 210mm OD and will be 12mm thick. If I heat it to say 300 deg C can some tell me approx what size the ID would increase to?

Thanks

Bruce

pgk pgk30/01/2016 07:11:21
2661 forum posts
294 photos

I think that it's as simple as looking at the missing central disc i.e cast iron 155mm long.

coeff expansion I found was 0.0000112 / degC so from say 20C to 300C for 155mm = 155 x 289 x coeff = 0.48608 for a new id of 155.48608.

Roger Head30/01/2016 07:32:24
209 forum posts
7 photos

pgk pgk is correct, 'cept for the typo

155 x 280 x coeff = 0.48608 for a new id of 155.48608.

There are slight variations quoted for different types of CI, and the CTE changes with temperature, but the effects are small and would only change the ID by one or two thou. The following horrible link brings up pages 295-298 of the Iron Castings Handbook which shows the effect.

https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&ved=0ahUKEwjLyqaV-9DKAhXDKWMKHVXTB2kQFghKMAk&url=http%3A%2F%2Ffiles.engineering.com%2Fdownload.aspx%3Ffolder%3Db1e13803-7e48-479f-ae19-67666ee8c97b%26file%3DIron_Castings_Handbook_4th_Edition_-_Thermal_Expansion.pdf&usg=AFQjCNFrTGDj2Ee1KzAXqlWC-xbRgmYQIg&sig2=ZTACQ5c2_EgulHd2JODncA&bvm=bv.113034660,d.cGc&cad=rja

Roger

Bruce Edney30/01/2016 08:03:14
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167 forum posts
53 photos

Thanks guys

Looks like I have to do a bit more machining

Bruce

pgk pgk30/01/2016 08:10:17
2661 forum posts
294 photos

If they gave out degrees in typo I'd have a first.. thanks for the correction.

Michael Gilligan30/01/2016 08:43:50
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23121 forum posts
1360 photos

Roger,

I present your 'horrible link' in friendlier forms, for those of a nervous disposition:

**LINK**

Thanks for finding it.

MichaelG.

Roger Head30/01/2016 11:15:44
209 forum posts
7 photos

Yeah, thanks Michael. I know, I should have done that.

Interesting to see Fig 2 in that reference and read of Ni-Resist. I used Invar in some laser opto-mechanics in the past (20 years ago), but I was never aware of a casting alloy. I wonder what's available now...

Roger

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