Normalizing fo SCM415H steel

Normalizing is the simplest yet a very typical heat treatment process.
We are making gears+shafts for two wheelrs.
I faced problem with Normalizing of Gears & Shafts of Steel grade (JIS)
SCM415 or SCM420. Problem is after 'Normalizing' specified
Microstructure is Uniform distribution of Perlite+ferrite with bainite
< 10% & hardness limits are 80-90HRB.
I normalizing a load of 200kgs of SCM415 gears in an Electric
Normalizing f/c (heating with electrical heater) with cycle : 870=B0C -
70minutes - forced air cooling.
If I start forced air cooling just after taking the load out from the
f/c it results in Hardness in the range 84-92HRB with Bainite >25%
If I start forced air cooling after 3 minutes when the charge is out
from f/c it resulst in very good microstructre but with hardness
Ambient temp. now a days is 25-30=B0C.
Any solution to this problem.
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in article, Sunil at wrote on 2/3/06 2:37 pm:
Can't you just split the difference and start the cooling after, say, 1 or 2 minutes? Surely that will give better hardness and less bainite?
Reply to
Dave Herbal
Forced air cooling is gas quenching - NOT Normalizing.
Normalizing is allowing an austenized load to cool in still air so that cooling is faster than annealing (unless isothermal) and slower thn quenching, See Peter Payson Book "The Annealing of Steel" or "The metallurgy of tool steels" for more insight.
Reply to
in article, Ed at wrote on 9/3/06 3:20 am:
That's what i figured, but if he lets is normalise for 3 mins, then air quenches, he's not hitting the hardness range. Judging by that, a full normalise isn't going to hit it either.
Reply to
Dave Herbal

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