Forge Heat - HELP NEEDED!!

[ErnieB]

Good Morning Folks,

One issue that has been on my mind lately is when a discussion on forging comes up, there seems to be a lot of talk about using the hottest heat when you first start to shape the steel into a blade. But as the project goes along, lower and lower heats are used. This may be a dumb question, but what exactly is meant by lower and lower heats... does it mean that the heat is controlled by backing off on the amount of gas pressure to the forge (if using a gas forge) as the process continues, or, does it simply mean keeping the blade in the forge for shorter and shorter periods of time as you are progressing? I think this might be one of the places I'm going wrong as I don't regulate the heat of my gas forge in any manner while I'm forging a blade. I can see it may be a problem for me because its harder to keep the heat of a blade under control, especially on the tip, the farther I go into the process.

Since it seems I've kinda' hit a wall as far as forging, I felt the best thing to do is back off, re-evaluate what I have been doing, both right and wrong, to this point, and try to get some answers to the uncertainties and questions I have. What I'm saying here is no matter what I try, blades that I forge mostly turn to crap. I normalize according to how everyone says I should - anneal the same way, but nothing seems to help. Hopefully, I can began with a fresh start and have a little more success than I've been having. THIS BY NO MEANS SAYS I'VE LOST ANY OF MY DESIRE TO MAKE KNIVES! Its just that I have a lot of guestions and I though I'd start with this one.

Thanks in advance for all your help.

[Peter_E_Ryt]

What do you mean they turn out like crap? Grain structure is off, knife edge holding ability is bad, the blade is brittle, the are cracks in the blade, the steel is warped, it looks ugly? Knowing what is happening would help.

For grain structure: I'm not qualified for that

Edge Holding: comes from hardness and the type of metal. Maybe you're tempering at too high of a temperature, or not quenching properly

Strength: it's too hard or too soft- tempering problem

Cracks: stressed steel from quenching, or forging to cold generally

Warped: happens when quenching if everything isn't even- even then it'll sometimes happen.

Looks ugly: practice- mine don't look great, but they sure look one hell of allot better than the first.

I'm not sure about the heat thing though.

Hope this helps.

[plain ol Bill]

Ernie I'll throw in my 2 cents worth here. By heat control I know I adjust the heat output of the forge by turning the gas flow and air volume down. I (and Ed) have thermocouples in our forges so we know what the heat output is. I have full control of my forge from 2300 degrees to 1350 degrees by this method. This allows normalizing for grain control with each heat being a little lower than the previous.
Personally I forge at high temps and then normalize to reduce grain structures. There are metals out there that do like lower forging heats than I use such as 52100 but I do not use them myself (at least not yet anyway)/

[ErnieB]

Sorry about the lack of info I provided folks.

I'll start by saying that I have only ever used 5160 for forging and all my forged knives are ending up with two problems. First, they always warp and secondly, the edge remains too soft. Something that I should point out at this time is when make knives out of 0-1 via the stock removal method, I don't have these problems. BTW. I have one of the Carolina Forge Knifemaker's forges

After forging the knives to shape, I normalize them is still, room temperature air. I anneal them by heating them in the forge to just above critical and then burying the entire knife in vermiculite for 18-24 hrs. before HT'ing.

I them heat them with a torch to critical and quench them in a 2 gal. tank of vet grade mineral oil pre-heated to 145-150 degrees. Unless they are really small knives, I edge quench using a limiter plate in my tank. I then submerge the blade, standing on its edge, and allow it to cool with the oil. I do this process three times.

As far as tempering, I do that in a toaster oven preheated to 400 deg. with the knife standing on its edge in the oven. I leave the knife in for 1 hour. This process is also repeated 3 times. I will say I have possibly messed this process up in the past by not getting the knife from the quench to the temper soon enough.

That's my proecess in a nut shell. but I'm still not getting the edge to harden and the warping problem varys from just a little to real bad. I knew the first time I read about using lower and lower heats I had never done that before and as I said in my 1st post, when I'm forging a blade, the farther I go the harder it is to keep the heat of the blade under control. I do have a pressure guage on my gas feed line to the forge - could I use that to lower the heats? To get a thermocouple to work at those kinda temps, would I have to go with one of the super-expensive digital read-out types?

Thanks for you help guys...