How much expansion?

[Bruce EdneyParticipant @bruceedney59949]

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

[Bruce EdneyParticipant @bruceedney59949]

[pgk pgkParticipant @pgkpgk17461]

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 HeadParticipant @rogerhead16992]

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 EdneyParticipant @bruceedney59949]

Thanks guys

Looks like I have to do a bit more machining

Bruce

[pgk pgkParticipant @pgkpgk17461]

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

[Michael GilliganParticipant @michaelgilligan61133]

Roger,

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

**LINK**

Thanks for finding it.

MichaelG.

[Roger HeadParticipant @rogerhead16992]

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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