Fudging tempering time?

weo

weo

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Sep 21, 2014
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Hello all. I think I was able to infer the answer after my researching time/temperature relationship during tempering, but didn't find a direct answer to this specific question, so I'm asking it for both myself and future makers who may have the same specific question.

Is fudging tempering time minutes going to be detrimental to my heat treat? For example, is two 1 1/2 hour tempering cycles going to be detrimental? Or, when running short on time, should we let our plans be delayed?

Thanks
 
Everything I've ever read leads to not enough time is bad, longer times not, provided you don't go over temp.
 
I'll let the "real" gurus respond if they see something wrong here - "IF" you've only got 3 hrs, then allow first temper to be 1 hr, then 2nd temper the full 2 hrs. Some alloys will work with first temper with only 15 to 30 minutes, but last temper really needs to be full 2 hrs. Allow me to say this is from my reading of the "real" gurus, NOT my own testing or experience.
 
Thanks, guys. I would still like an answer to my question, but today I put off my appointments to get the two 2-hour sessions
 
You didn't state what steel you are asking about ( and that matters), but as a general rule:
One hour is the minimum.
Two hours is enough.

If you have only three hours, do as Ken suggested.
In most cases there will be no harm from one shorter temper, and in many knife steels, two one hour tempers are sufficient. The higher that alloy content, the more you need the two hours.
 
Thanks all.
Today I was using only 15N20, but most of the time it's damascus involving O1, 1080, 1095 or 5160.

Stacy - can you give a definition of what you're referring to as "higher alloy content"?
 
Weo, Stacy is talking about ingredients in the steel. The more ingredients the “higher” the alloy. In very general terms.
 
Thanks Mr McPherson, but I know what he's talking about in general terms, I was referring more to the specifics: is it how many different elements? Is it the percentage of elements?

For example, in one of my reference books, it says that O1 is:
C - .85-1.00
Mn - 1.00-1.40
Si - 0.10-0.40
Cr - 0.40-0.60
V - 0.15-0.30 (possibly)
W - 0.40-0.60
This is 5 additional ingredients compared to plain carbon steel, so is this 5 extra considered high alloy or is it high alloy if the percentages of each ingredient are on the top end?
 
Larrin could explain it better, but a very simplified way to say it is higher amounts of carbide forming elements like C, Mo, Cr, V, W need longer temper time. It is not the number of alloying ingredients, but the percentage. When the alloying gets over 4% it takes mote time for the shifting of structures in tempering.

5160 has .60% carbon and 1% chromium. D2 has 1.5% carbon and 12% That would make D2 a high alloy steel. All stainless steel is high alloy.


Here is a graph I built showing the alloy content of 1095, O-1, D-2, CPM-S35VN, and Elmax. You can see that 1095 and O-1 have low alloy content and that Elmax, D-2 and S35VN have high alloy content. You could get away with a one hour temper on the low alloy steels, but the higher ones would really need 2 hours.
http://www.zknives.com/knives/steels/steelgraph.php?nm=1095,O-1, D-2, S35VN, Elmax&hrn=1&gm=0
 
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