Silver or Stainless?

[Steve WithnellParticipant @stevewithnell34426]

Posted by Sid Herbage on 20/10/2011 00:59:22:

 

I bet a few people have also been fooled by some of the imported “brass wire brushes”.

 

Many of these will handily stick to a magnet.

 

J&L sell real brass wire brushes, which are also useful!

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Robin Woodward on 20/10/2011 10:20:17:

Hi All,

 

Nick just took me back to 1970………………………………………………..

 

 

I vaguely remember the terms “Face Centre Cubic” and “Body Centre Cubic” as regards where the atoms are and this may have something to do with the strength of the Magnetic forces, I am sure there are some who have a better grasp of the theory than I do after 40 years who can answer this.

 

Rob

 

Hi Rob, you are thinking of the Allotropy of Iron in which;

at room temperature ferrite has a “body centered cubic” structure and is magnetic, and will only take 0.006% carbon into solution.

 

If the Iron is heated above 720 to 920 degrees C (according to carbon content) it’s structure changes to “face centered cubic” and it becomes non magnetic and will take carbon into solution. The name given to iron in this changed state is Austenite.

 

Regards Nick.

[Anonymous]

The temperature at which an iron-carbon ‘mix’ changes from ferromagnetic to paramagnetic is known as the Curie point. For pure iron it is about 770°C, and varies as the carbon content increases. The Curie point is not related to the phase change from BCC to FCC.

 

For low carbon steels the change in magnetism with increasing temperature is a useful indicator of the phase change temperature, but is only an indicator. The two effects are unrelated; they just happen to occur at similar temperatures.

 

Regards,

 

Andrew

[Author]

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