Hardening and tempering

[DC]

I was watching "Forged in Fire". They were all using the same steel. Some blades chipped and others folded. Since somebody other than the contestant tempers the blade(a sore point with me) could the tempering be causing the failures. Put another way if two people use the same steel and one hardens his blade at a higher temperature could different tempering methods make both blades survive?

[KHalverson]

In my opinion yes.
There is just way too many variables between 3_4 different smiths to let 1 individual govern a temper .

[burchett.donald]

Every steel has a recipe...So many variables...So many recipes...What steel were they using...

[DC]

Sorry, I can't remember. I've only ever used truck springs and that was long ago. It's just always bothered me that we don't get to see or even hear about the tempering that's done on that show. A guy loses a chance on 10 grand because his blade chips. It may not even be his fault. I may be wrong on this because I only heard the "someone else is tempering" from one spot. I wish they would explain a bit.

[bubby]

The mastersmith does the tempering on all blades. They know what steels they used and watched them forge them, it seems most of the chipping comes from to thin an edge profile most of the time. They also use a even heat oven to treat them and make sure of the temps.

[KHalverson]

Also edge geometry comes into play.
U see some guys use a flat Scandinavian grind.
Then it chips chopping cow bones.

[DC]

The mastersmith does the tempering on all blades. They know what steels they used and watched them forge them, it seems most of the chipping comes from to thin an edge profile most of the time. They also use a even heat oven to treat them and make sure of the temps.

I wonder why they chose to do it like that? Maybe because of the wide choice of steels, some contestants may be working something new to them but still, tempering is an integral part of blade making. My suspicious mind makes me think they could steer the outcome that way. I'm not accusing them of that but it's there.

[bubby]

It could be because of the mystery steel they use and the fa t that a lot of the Smith's only use known steel that they figure that they know how it should be tempered

[jim l.]

It's been my experience that steel type is only one aspect of the heat treat. Granted that certain steels require very specific heat treat regimens. That said, the steel provided to the contestant  is usually hardened by quenching oils (also provided).

Many of the variables come into play such as normalizing, quench temperatures (how hot was the steel - white hot, dull red, yellow) which determine grain structure, and temperature ranges used for thermal mass of the steel. How thick was the blade at each cycle for even thermal saturation. A 1/4 in. thick piece of steel will require more saturation time than a 1/8 in. thick piece. If both pieces are tempered for the same period of time, the thinner piece would probably be softer.

Part of the "trick" in the show is paying attention to the parameters. Many people can hammer out a blade, but will they be able to make it to parameter and stand up to the tests. I:E - "this knife will need an edge profile that will be able to withstand the shock and vibration of hacking a piece of oak 10 x 10 (axe?) but be able to slice through a pork shoulder human analogue (chef's knife?) .

The Smiths have to come up with appropriate edge geometry, cross section, and steel hardness. The tempering I believe is standardized by the Master Smith(s) to accommodate the "ideal" tempering cycle to meet steel provided and parameter requirements.

Besides, the period when the temperature takes place is when they eat lunch. 

[Mesophilic]

I can usually tell which knives will fail just based on the color they go into the quench and the blade profile.  Surprises me the credentials of some of the individuals and the simple mistakes they make.  I really don't think I could do better, but have higher expectations of guys who work steel full time.  Maybe it's just that they sre handicapped without their computer controlled Evenheat furnaces.

[TRiggs]

If you want a good heat treat then you should do it in proper order, use clean oil for your quench
#1 heat your quench oil ! ! ! !
#2 thermo-cycle your blade 3 or 4 times this will tighten the grain of the steel
#3  Heat your blade until it is not magnetic anymore
#4 Quench the blade slowly moving in figure 8's
#5 Pull it out when it won't burn your eyebrows off,  all that flame in the quench is for show and it's dangerous, it should be hot when it comes out but not on fire.
#5 pop it into your oven and bake  @ 400 for2 hours then 300 for an hour, then 200 for 1 hour and let it cool off in the oven.
Some on Forged in Fire you will see thermo-cycle there blades most don't and they never have a chance to temper the blade that takes a few hours and if you watch it you can see each Smith quench is own blade and I have never seen a tempering oven on the show.

[Mr. Woolery]

Dieselcheese said something I was about to comment on.  I watched an older episode with my kids a few days ago and all the contestants were given identical steel (W2 round stock) to start with.  One guy put his blade into the quench at a screaming yellow heat, the judges commented on it being really hot.  He pulled it out still red hot, then put it back in.  It must have been close to 1800 degrees (though I know the camera doesn't really tell the truth at those temperatures, so I'm only guessing). 

In the testing, his blade had a chip come out of it.  Now, I don't know what sort of test it is to baton the blade against a huge steel nut, but that's what you have to expect on this show.  The other blade it was compared to did not chip. That smith had hardened at a much lower temperature. 

I am honestly surprised to see very few examples of smiths checking their blades with magnets before quenching.  I know some do, but counting on a trained eye in an unfamiliar shop with studio lights, camera crews, all the stress of the deadline, and the often rather whacky parameters to the challenge is counting on a trained eye that is being asked to work in the worst circumstances.  A magnet would make life so much simpler. 

But I do think it would be better to allow the smiths to do their own tempering.  It would be a more genuine comparison, I think.

-Patrick