[TheForge] Do you know if the normalizing differ substantially from the annealing

[James Binnion]

Normalizing needs an extended soak time, 15min to 1hr depending on thickness. You need ideally to convert all crystals to austenite and there is a definite time aspect to that process.


On Jun 5, 2013, at 7:35 AM, Paul Novorolsky wrote:

> Awesome information. Thanks Mike. This is the kind of stuff I was looking for. I'll have to see if I can find that book, or one similar for a reasonable price. (I know current versions of Engineers Handbooks are quite expensive.)
> 
> Since it doesn't specify a soak time under Normalizing, can I assume more than a thorough heating through,that it isn't important here? (with a couple statements out of context, I don't want to make any bad assumptions...)
> 
> Not soaking 1hr/inch would then make multiple normalization cycles make a little more sense to me.
> 
> **Paul
> 
> On 6/5/2013 12:43 AM, Mike Spencer wrote:
>> 
>> George Dixon wrote:
>> 
>>> Do you know if the normalizing differ substantially from the
>>> annealing
>>> 
>>> Normalizing is using heat in a controlled manner to remove stress
>>> imposed by forging
>>> 
>>> Annealing is using heat in a controlled manner to remove hardness,
>>> either from work hardening or heat treating
>> 
>> 
>> I recall once mentioning "annealing" something by heating it and
>> letting it cool in air to Sam Allen.  He corrected me, saying, "That's
>> normalizing."  Since Sam is a metallurgy professor at MIT, I reckoned
>> I hadda do some reading before I pontificated again. :-)
>> 
>> Looking at Mechanical Engineer's Handbook (Theodore Baumeister,
>> ed.,1958), I see that "annealing" is treated as a broad category of
>> processes used:
>> 
>>    (1) to remove stresses; (2) to induce softening; (3) to alter
>>    ductility,toughness, electrical, magnetic or other physical
>>    properties; (4) to refine the crystaline structure; (5) to remove
>>    gasses; or (6) to produce a definite microstructure....
>> 
>> Within that category are "fuel annealing" and "normalizing".
>> 
>>     Fuel annealing:
>> 
>>     Heating iron-base alloys above the critical range, holding above
>>     that range for a proper period of time, followed by slow cooling
>>     below that range. The annealing temperature is generally about 100
>>     F above the upper limit of the critical temperature range, and the
>>     time of holding is usually not less than 1 hr for each inch of
>>     section of the heaviest object being treated.  The objects being
>>     treated are ordinarily allowed to cool slowly in the furnace. They
>>     may, however, be removed from the furnace and cooled in some
>>     medium that will prolong the time of cooling AS COMPARED WITH
>>     UNRESTRICTED COOLING IN THE AIR. [Emphasis mine]
>> 
>>     Normalizing:
>> 
>>     Heating iron-base alloys to approximately 100 F above the critical
>>     temperature range followed by cooling to below that range in still
>>     air at ordinary temperatures.
>> 
>> Other sub-topics mentioned under the general rubric of annealing:
>> Process Annealing; Patenting; Spheroidizing.
>> 
>> I once made a (finger) ring by pattern-welding a piece of
>> off-the-shelf mild steel with a piece of Volkswagen beetle front
>> torsion spring.  Let it cool in air.  File glided off as if it were
>> glass.  Re-heated, allowed to cool more slowly in forge cinders. Still
>> like glass.  I finally threw it into my kitchen range where it
>> remained red hot all evening. I left it there over night so that it
>> cooled in the coals (later, the ashes) of a dying fire. Stove was cold
>> in the morning. Retrieved from the ashes, the ring could be filed
>> fairly easily, albeit noticably harder than mild steel.
>> 
>> So in the first two tries, I was normalizing it (consistent with Sam's
>> remark) and in the stove I was "fuel annealing" it, with a long hold
>> above critical followed by very slow and even cooling.
>> 
>> VW front torsion bars are, BTW, cool material.  They're compound units
>> of ca. 1/8" x 3/4" and 1/8" x 3/8" flat strips roughly a yard long.
>> You can clamp the end of one in the vise, bend it over 180 degrees and
>> (keeping your head well out of the way!) release it. Just whips back and
>> forth.  Heat one end to red, cool in air and try the same thing.
>> Snaps off as easily as, say, breaking a candy cane or a thin strip of
>> glass.
>> 
>> 
>> FWIW,
>> - Mike
>> 
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James Binnion
jbin at well.com