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PostPosted: Thu Jan 10, 2013 10:55 pm 
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I have a nice set of Mavic GP40 rims with large flange Record hubs. Unfortunately, they're let down by a slightly pitted surface on the spokes. I assumed they would be stainless spokes given they are good quality wheels and it would seem strange to build them with normal steel spokes.

So I wondered, how can you really tell stainless from normal steel? A bit of googling and I discovered Stainless won't magnetise. I've just tried this on the pitted spokes and a magnet sticks. Tried it on a stainless spoke and it doesn't.

Well, I thought it was interesting :lol:


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PostPosted: Thu Jan 10, 2013 11:41 pm 
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Actually some stainless steel is magnetic it entirely depends on the chromium and nickel content. Spokes should have a high nickel and chromium content so Austinite should form which is not magnetic.

Stainless brake cables however are magnetic. Campag cable are weakly magnetic but cheaper cables are more magnetic but are still stainless steel.


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PostPosted: Thu Jan 10, 2013 11:42 pm 
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We had this at A level back in1978 about the magnetic / paramagnetic properties of steel. Austenitic / marstenitic ..... and the rest. nightmare. :(

Just glad it wasn't on the question papers..

Shaun


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PostPosted: Fri Jan 11, 2013 12:25 am 
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Martinsite is a phase formed when carbon is traped in the body centred cubic structure of ferrite under quenching. This results in a stretched crystal which results in the hardness you get when carbon steel is quenched. Stainless steels have very low carbon contents and are not quenched so no martiniste should ever form.

Austinite and ferrite are the two main phases in all steels but in normal steel Autinite forms when the steel is heated to above 1000 C. It all a bit fuzzy now but that is what I seem to remember from my student days.


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PostPosted: Fri Jan 11, 2013 12:33 am 
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Didn't get any better whern I went to uni and had all those phase diagrams to remember :(

Shaun


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PostPosted: Fri Jan 11, 2013 9:50 am 
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.What I disliked was crystalography <111> planes ad all that. I never got my head around it.


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PostPosted: Fri Jan 11, 2013 2:05 pm 
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They'll be chrome plated normal steel then if they're not really dull. The wheels are probably too old for stainless spokes. My early 80s wheels were built with chrome spokes as it looked better than the "rustless" option - their mid-80s replacements had stainless which had become more widely used by then.

Mark.


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PostPosted: Fri Jan 11, 2013 2:08 pm 
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like mark sez! Chrome looked good as they twinkled in the sun, but chroming made them brittle. I wrestled for years between good looking but brittle v dull galvanised but durable


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PostPosted: Fri Jan 11, 2013 2:33 pm 
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I went for good looking / chrome every time :D

Shaun


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