Non-Magnetic?

3

30-30 Cal.

Joined
Jan 1, 2004
Messages
243
What, exactly, is meant by the term "non-magetic" when it comes to knives? As in " During heat treatment, heat the knife to the non-magetic point. Sounds silly, I know, but I just noticed most, well hell, all of my knives, both production and custom, will allow a magnet to stick weakly to them. since these are excellent knives by well known makers, I assume they did the job correctly and it is my understanding of the term non-magnetic, that is the issue.

Regards,

Dave
 
Moving to Shop Talk. These guys are good at explaining what non magnetic is.
Randy
 
Non magnetic is what hapens to the steel when it is heated to critical temperature during the heat treating process. The steel no longer draws to a magnet. Thats the temperature where the steel changes and you are at the correct temperature. Just a little more heat and you are ready to quench the steel. Once its cool again it will draw to a magnet like your knives do know.

SOmeone else can better explaine this but I thought I'd give it a shot :D
 
rlinger said:
Brian, edit out that molecule thing before Mete sees it ;) . He's going to lecture you on that. No molecular structure in steels.
Click to expand...

:D

Brain add to it,, it should be just above the point...
 
Ooooh, now I get it! I assumed that once they were non-magnetic they would stay non-magnetic. Thanks for the reply, Brian.

Dave
 
I've got you all trained !! The Curie temperature is 1414F, it is the temperature where the steel is no longer magnetic.It's a handy way to determine that the steel has reached the hardening temperature [above the critical temperature.
 
mete said:
I've got you all trained !! The Curie temperature is 1414F, it is the temperature where the steel is no longer magnetic.It's a handy way to determine that the steel has reached the hardening temperature [above the critical temperature.
Click to expand...

OK Robert
1414F is above or belolw critical temperature :confused: and we'er talking O1,,
why am I believing
critical temperature is about 100 deg's above the Curie temperature..have I been wrong :confused: ;)
 
i thought some little boogie mens shadows started dancing at critical temp!
 
Looking at the iron carbon diagram A1 is 1333F and Curie is 1414F. Off hand I do not know if this[Curie] changes for O-1.The A1 will change with changes in composition.
 
It would all be so easy if things would just work in a way that we would like them to :grumpy: . One of the problems is that the iron-carbon equilibrium diagram is only good under equlilibrium conditions. Rate of heating will heavily influence the Ac temps and alloying elements will really move things around. We have a discussion going over on the SFI metallurgical forum about how alloying pushes the eutectoid point to lord knows where.

The curie temperature could be a full blown discussion unto itself and presents many conundrums and paradoxes that leave me scratching my head. But it does appear to be a point that is more constant than the other points of the Fe-FeC3 diagram. The Curie point of iron does appear to be 1414F. (at least until you reach Delta iron- one of those head scrathing things) which makes it a good guide to get you in the neighborhood, you then need to adjust for how much more carbon or ferrite you may need to dissolve. The best way to play it is if you are not over heating things let the tmperature do its thing and soak it.

Just remember that the non magnetic thing is only good for a ball park on the rising heat. Heat a piece of steel to non magnetic and then let it cool while testing with the magnet, then tell me if you would EVER quench a pice of steel at the color that the magnet finally started sticking again :eek: Ac and Ar are not the same ;)
 
Hey Dan
Now I got it.Couldn't remember the term being used before.
(would all be so easy if things would just work in a way that we would like them to . One of the problems is that the iron-carbon equilibrium diagram is only good under equlilibrium conditions. Rate of heating will heavily influence the Ac temps and alloying elements will really move things around. We have a discussion going over on the SFI metallurgical forum about how alloying pushes the eutectoid point to lord knows where.

The curie temperature could be a full blown discussion unto itself and presents many conundrums and paradoxes that leave me scratching my head. But it does appear to be a point that is more constant than the other points of the Fe-FeC3 diagram. The Curie point of iron does appear to be 1414F. (at least until you reach Delta iron- one of those head scrathing things) which makes it a good guide to get you in the neighborhood, you then need to adjust for how much more carbon or ferrite you may need to dissolve. The best way to play it is if you are not over heating things let the tmperature do its thing and soak it.

Just remember that the non magnetic thing is only good for a ball park on the rising heat. Heat a piece of steel to non magnetic and then let it cool while testing with the magnet, then tell me if you would EVER quench a pice of steel at the color that the magnet finally started sticking again Ac and Ar are not the same )
TJ
 
TJ Smith said:
Hey Dan
Now I got it.Couldn't remember the term being used before.
(would all be so easy if things would just work in a way that we would like them to . One of the problems is that the iron-carbon equilibrium diagram is only good under equlilibrium conditions. Rate of heating will heavily influence the Ac temps and alloying elements will really move things around. We have a discussion going over on the SFI metallurgical forum about how alloying pushes the eutectoid point to lord knows where.

The curie temperature could be a full blown discussion unto itself and presents many conundrums and paradoxes that leave me scratching my head. But it does appear to be a point that is more constant than the other points of the Fe-FeC3 diagram. The Curie point of iron does appear to be 1414F. (at least until you reach Delta iron- one of those head scrathing things) which makes it a good guide to get you in the neighborhood, you then need to adjust for how much more carbon or ferrite you may need to dissolve. The best way to play it is if you are not over heating things let the tmperature do its thing and soak it.

Just remember that the non magnetic thing is only good for a ball park on the rising heat. Heat a piece of steel to non magnetic and then let it cool while testing with the magnet, then tell me if you would EVER quench a pice of steel at the color that the magnet finally started sticking again Ac and Ar are not the same )
TJ
Click to expand...

who said that?? :confused: :) OK where's your quote tags TJ ? :p
 
Here is the quote tags.
Kevin R. Cashen said:
It would all be so easy if things would just work in a way that we would like them to :grumpy: . One of the problems is that the iron-carbon equilibrium diagram is only good under equlilibrium conditions. Rate of heating will heavily influence the Ac temps and alloying elements will really move things around. We have a discussion going over on the SFI metallurgical forum about how alloying pushes the eutectoid point to lord knows where.

The curie temperature could be a full blown discussion unto itself and presents many conundrums and paradoxes that leave me scratching my head. But it does appear to be a point that is more constant than the other points of the Fe-FeC3 diagram. The Curie point of iron does appear to be 1414F. (at least until you reach Delta iron- one of those head scrathing things) which makes it a good guide to get you in the neighborhood, you then need to adjust for how much more carbon or ferrite you may need to dissolve. The best way to play it is if you are not over heating things let the tmperature do its thing and soak it.

Just remember that the non magnetic thing is only good for a ball park on the rising heat. Heat a piece of steel to non magnetic and then let it cool while testing with the magnet, then tell me if you would EVER quench a pice of steel at the color that the magnet finally started sticking again :eek: Ac and Ar are not the same ;)
Click to expand...
 
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