How to use a datasheet to develop a heat treatment

Larrin

Knifemaker / Craftsman / Service Provider
Joined
Jan 17, 2004
Messages
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Good write up, but I feel this beginning part is inaccurate/misleading. It has been proven by my self and others that some carbon steels from NJSB are not ready to be heat treated as provided.

Forging, Normalizing, and Annealing

These steps are only required for bladesmiths that are forging their blades. Steel comes forged and annealed from the manufacturer so if the blade is being produced for stock removal the steel is ready for drilling, grinding, and heat treating.
 
Good article for me to read. I don’t understand all the data sheets so I do look at the recommended HT recipes from the suppliers and people like you. That can make scratch my head as well. Case in point.
8670 Looks like AKS chart to get around 62r you would temper at around 150. The other recommended tempers here are around 400. So what’s makes the difference in the same metal the supplier? I have been using Larrins recommendation.

kinfe engineering
1525 for 10 minutes temper at 400
8670 Pops
Hardening

Austenizing temperature - 1,550
Hold/Soak Time - 3-10 minutes
Expected Rc (as quenched) - 63-65

Oil Quench - Parks 50

Tempering

Temper twice for 2hrs.

300°F - 325°F - 62-63
375°F - 400°F - 61-62


8670 Heat Treat Information: AKS
Austenitize: Heat to 1,560°-1,635° and hold for 5 minutes. Quench in oil.

Temper: Temper twice for two hours each time. Use the chart below to select the tempering temperature.
8670-TC.gif
 
I would wager a bet that the chart is actually in C° not F°. No o e tempers at 100-200°f. Lowest we have ever gone on any steel is 250°.
 
The 1560-1635F austenitizing range seems to come from Bestar. It is definitely higher than is necessary, I'm not sure why they recommend so hot. I just tested a bunch of 8670 coupons and by 1600-1625F the toughness drops.
 
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