1084 Tempering Times

[mdubs]

Maybe a little introduction first. I'm a 3D modeler by trade from the Pine Barrens in NJ, but come from a long line of blacksmiths going back from what I can find about 6 generations of Von Warning males in Hamburg, Germany up until my great grandfather Warning (shortened at Ellis) in Maria, PA. It ended with him having only only girls. Being a little disillusioned with dealing in purely hypothetical craft, I wanted to make something tangible and useful and thought back to the stories my father told me about his grandpa Warning at the forge.

So I've been lurking around these forums for a while now learning everything I can and it's been an amazing resource. I've gotten my first two knives to the point where they're ready to be tempered and read as many guides to HT as I could find and one thing seems to vary and I can't find the pattern. Tempering times seem to change from 1 to 2 hours from guide to guide and I'm not sure what the difference is. Logan Pearce's tutorial for instance has it at 395 for 1 hour x 3 while I see a lot of others say the same temp range but at 2 hour cycles.

I was really hoping someone could shed some light on this. I'd really appreciate it. I'd hate to mess something up this far along and honestly don't relish re-hardening as my access to the torch is limited.

And just because I hate posts with no pictures here are the blades sanded to 220 before I stated HT

 

[Bo T]

I've read that there are a lot of variables when heat treating your steel. The composition of 1084 can vary from batch to batch. Your austenizing temperature, soak time, normalizing process, quench speed, type of quench, temperature control, and probably some things I didn't think of or am not aware of can all effect your final product. You could make some small test pieces to test and develop a method based upon your results. You could temper at a lower temperature, say 350 F, and see if the blade is to brittle along the edge. You can always temper again at a higher temperature.

 

[Stacy E. Apelt - Bladesmith]

1084 is pretty simple as far as the alloying goes. Austenitize at 1500°F, temper twice at from 350-450°F ( I use 450° , and get great results.). The time required for a proper tempering is probably only one hour, buy most metallurgical procedures use two hours to assure complete transformation of any retained austenite and full tempering of the brittle martensite. This should be repeated to temper the new martensite formed by the converted austenite. A third temper does no good on anything but a very complex steel, like the super steels and high alloy stainless.

Bo's advice on tempering low and testing the edge for chippiness is a good practice if getting the highest hardness on the edge is important. However, there is a very small difference in the hardness between one that is chippy and one that isn't. If the edge is chippy, raise the temper50° and try again. When you get an edge that holds up to testing ( brass rod, whittling wood, cutting cardboard ) that is the point to stop raising the temper. If the edge is still chipping at 450°, take a look at your edge, perhaps it is too thin?

 

[ricky_arthur]

I have been doing 2 tempers at 400 degrees for 2 hours each. Works for me. I had a guy bring me a 1084 blade back yesterday, He said, "I skinned out a lion (mountain lion)with this yesterday"

I thought Uh Oh, something must be wrong.

He handed it to me as he finished,..."This thing is still razor sharp"
and it was.
He wants another knife.

ETA I will add this with all respect to Bladsmith,

if you are not getting good results with a lower tempering temp, 50 deg is alot to jump. From everything Iv'e seen and read even 10-20 degrees can make a marked difference so I wouldn't jump in such high increments.

 

[mdubs]

Thank you all very much for the straight forward and simple answers.

The time required for a proper tempering is probably only one hour, buy most metallurgical procedures use two hours to assure complete transformation of any retained austenite and full tempering of the brittle martensite. This should be repeated to temper the new martensite formed by the converted austenite. A third temper does no good on anything but a very complex steel, like the super steels and high alloy stainless.

This was exactly the information I was looking for but couldn't seem to nail down. To the oven I go.

 

[mdubs]

Thank you all very much for the straight forward and simple answers.

The time required for a proper tempering is probably only one hour, buy most metallurgical procedures use two hours to assure complete transformation of any retained austenite and full tempering of the brittle martensite. This should be repeated to temper the new martensite formed by the converted austenite. A third temper does no good on anything but a very complex steel, like the super steels and high alloy stainless.

This was exactly the information I was looking for but couldn't seem to nail down. To the oven I go.