As regards your spherodizing in #6 above, I'm not quite sure what you are trying to do with a 2 minute soak 3 times?

The spherodizing of the carbides does not occur simply because you brought it up to 1300 degrees, it results by soaking it at length for even distribution, and then the key is the SLOW COOL from that temp.

It's the SLOW COOL that creates the spherodized structure.

You need the long soak to get all the alloy evenly distributed prior to the slow cool.

By the way, you are correct to do it after creating martensite, at least in hyper-eutechtoid steel.

|quoted:

Hello all.

As with most I expect, the more I learn about steel and heat treating the more questions I have, LOL.

In considering which steel to use for a performance test blade I'm leaning towards 1084 from Aldo Bruno for some personal testing and evaluation. My main reasons for choosing this steel over 5160 is 1. I plan to use this steel in the future and probably not so much 5160 and 2. known quality of Aldo's steel (ie- known chemical composition for consistant and re-peatable results).

Since attending the Intro course I've been thinking- If using the 1084 how should I go about heat treating it to pass the perfomance test ?

This is my game plan based on some things I "THINK" I know- (reserving the right to be totally wrong and please let me know if I am ! )

1. The best state to have the blade in to pass the BEND part of the test is- Fine grained, Speroidized, martinsite (????)

To accomplish this-

1. forge to shape

2. Normalize @ 1600

3. Rough grind

4. Normalize @ 1550

5. Heat to 1500 and fully quench tang and all to form martinsite.

6. Spheroidize @ 1300 x3 (2 minute soak each time as opposed to a 1 hour soak with the goal of keeping as fine grain structure as possible)

Now the entire blade should be Sheroidized, fine grained, martinsite (????) and on to hardening and tempering the edge of the blade

1. Torch heat the (edge only) to a little past non-magnetic and quench.

2. Temper immediately 2 hours 2 times cooling to room temp in between. Thinking intially temper @ 375 degrees and test performance but probably 400 maybe sufficent

I "THINK" following this procedure will result in a blade that's soft and tough all the way down to the portion of the blade hardedned with the torch. Aside from the possibility of overheating the edge and getting grain growth that would result in a chippy edge the cutting edge should be hardened and tempered to perform the cutting and chopping portions of the test as well as the next blade.

Assuming that that I'm correct in my thinking up to this point-

I see no benefit from doing multiple edge quenches as I should already have a very fine structure with two normalizations and two quenches. (????)

Also no need to draw the spine and body of the blade at all and if anything may risk overheating and redistributing the spheroidized carbon. (????)

I've been thinking about this ALOT, but also thinking why re-invent the wheel just order some 5160 and use heat treat methods that have been proven to pass the performance test.

Of course affirming or debunking of my thinking and any and all other advice will be GREATLY appreciated.

If you've read this far Thanks Alot !

-Josh

Josh, I guess I wouldn't do it that way.

I'm not sure the quality of the steel is going to make or break this... given U.S. steel (and that of many other countries) is going to be very good. Kelly Cupples (for one) has 1080 and he will have the chemistry for it. I'd tend to hypoeutectoid carbon level for the specific use, rather than eutectoid or hypereutectoid, for the simple reason less carbon at the same RHc will be tougher. It's like wood saw steel... most of it is in the 0.70% to 0.75% carbon range. For a wood saw, that is about the most carbon it can contain and still be tough enough to do the job. I understand wanting to work with your steel of choice. The reality is there is little difference in heat-treating process from 1055 through 1084... minor temperature differences is what it amounts to.

Industry normalizes 1055 at 1650F, 1060-1070+ at 1625F, 1078-1084 at 1600F. That is to equalize the grain size using a temperature that does not cause rapid grain growth and results in a steel with a grain size perfectly adequate for the use. Many knife makers normalize three times, with some folks quenching in fast oil on the third cycle, then high-temp tempering (spheoroidize anneal). Normalizing two more times reduces the grain size with each following cycle. All else being equal, smaller grain size makes the steel tougher... an advantage for thin section tools. For hypoeutectoid and eutectoid steel, three normalizing cycles will leave the steel plenty soft enough to grind, drill, etc. Quenching on the third normalizing cycle and high-temp tempering at 1200F to 1250F will make the steel softer yet, among some other advantages, but it is not necessary to build this blade.

If I was using 1084 with it's heat-to quench temp of 1500F I'd normalize at 1600/1565/1530, and I'd be soaking a minimum of 5 minutes before hardening quench.

I would not heat the edge with a torch but heat the entire blade and edge quench instead, for the simple reason I feel I cannot heat an edge as evenly as I can heat an entire blade, no matter the heat source. There is so much about the end product that has to do directly with the evenness of heating/cooling, I'd want the margin of error reduced. There is going to be a significant area in the blade that is a mixture of perlite and martensite (full martensite grading to full perlite). All that in as even a band as possible is what looks best to me. That has something to do with the grind, also.

Cooling to "hand warm" (around 125F) and tempering as you say...

If a person uses 1084 and hits the quench correctly, the martensite will be appoximately 65 HRc. Charts show 375F - 400F RHc in the 61+ to 62+ range. The range for 60RHc to 58+RHc is 500F to 550F. There is a disparity between ASM Heat Treaters Guide tempering charts and what a person hears most knife makers are using for tempering temperatures. There are a lot of makers using 375F and 400F for the common forging steels and finding (or figuring) the RHc at 61-59. I understand a tempering curve is percentage relative... that an ideal as-quenched hardness will drop a percentage between, say, 375F and 425F, and if the as quenched hardness is 62HRc instead of 65HRc the same percentage drop will be found between those two temperatures. In the end, if 1084 blades actually are 60HRc from 2x's 2hr., 400F, temper cycles, the only guess I have is the as-quenched hardness was lower than possible.

I think there is an advantage to fully hardening a blade and drawing back the spine if it needs to flex radically. Full martensite blades are very strong and spring tempered martensite has that advantage and is not at all brittle. I don't know that learning the technique solves the test blade problem better enough to mean anything in the required testing, though. Flexing radically without failure has a lot to do with cross section... thinner cross sections flex without failure more readily than same profile/hardness with thicker cross section.

Mike

Karl-

Thanks for posting your question ! I remeber ALOT of info read on the forums but sometimes doing some digging to find and re-read things is of great benefit as what I recall is slightly different that what was actually said. In this case I "THOUGHT" I remembered reading that you could spheroidize using multiple sub-critical heats without a long soak. What was actually said was that this method would be better than nothing but wouldn't result in the softest state possible due to exactly what you mentioned- the size and even distribution of the spheres of carbides. So you've certainly corrected me on that point and the typical method of a 1 hour soak @ 1300 and a slow cool would definately be the way to go.

Mike-

I'm approaching my thinking about the test blade almost as if it were 2 blades in one. The edge "blade" and the tang, spine, body, "blade". I could be wrong in my thinking on this point but I think pretty much all the commonly used blade steels will easily pass the cutting portions of the test if a few conditions are met. Those being full martinsite conversion (on the edge) fine grain structure, and a suitable temper for the chosen steel (of course proper geometry and being sharp are also needed but I'm focusing mainly on the heat treating aspect). Again I could be wrong about this but I think these conditions have to be met reguardless of the steel type so I'm thinking that most likely the biggest risk to failure is the bend part of the test.

Now for the rest of the blade other than the edge I want the steel in the condition that is least likely to break so my goal is to have a shereiod annealed blade with a hardened edge. To accomplish this I need to avoid bringing the whole blade up to austinizing temp and edge quenching so I don't end up with pearlite on the parts of the blade that weren't quenched.

I agree with you about the lack of precision with the torch temps but it seems the surest way to get a hardened edge while protecting the sphereoidized structure in the rest of the blade. Another option may be to use satanite to insulate the body of the blade from the heat. I don't know if that would keep the temp low enough to keep from redistributing the sphereoidized carbides (????). I'm thinking that I read this will begin to happen around 900 degrees (????) If it would work I'd definately prefer it to using a torch. I do remember hearing that converting from martinsite to austinite will happen almost insantly with zero soak so it very well may work to use the clay as an insulator.

I do understand what you're saying about tempering temps(I think). Supposing one smith gets full hardness of 65 he may require a temper of 500 to get to the final desried hardness while another smith who gets a hardness of 63 out of the quench will require a lower tempering temp to achieve the same end goal.

Thanks ALOT for your replies Guys. It is appreciated !

-Josh

A person can spheroidize with multiple short heats to temps near, but below austenitizing temps (AC1). It works really well if the blade has been quenched out of the third (or second) normalizing heat. I did it this way when forge & toaster oven were my only heat sources. Heating short times made it easier to keep from going over temp into austenitizing range (magnet and color for control), and doing it a number of times, little by little, spheroidizes most of the carbon. A person does have to soak at quench temp. for some amount of time to diffuse the carbon again before quenching.

If I'd gotten all of your first post HT process before I started yapping I'd have been better off. I'd be fully quenching, tempering the whole blade to get the edge hardness I wanted, then differentially tempering the spine (edge in water) to spring hardness. Primarily, I'm saying that because I've got a clearer picture of the process and outcome in my head... never have learned or thought about edge heating with a torch. Seems to me the process you describe is going to create some amount of perlite between the harder edge martensite and the spheroidized martensite. That wouldn't happen doing a differential temper.

Mike