Kevin and Mete. please narrow it down

Sando

Sando

Knife Maker
Joined
Jul 4, 2002
Messages
1,148
After reading another triple quench thread (which I really enjoy!), I want to get serious about working with carbon steels. However no magic, no hearsay, .... I just want repeatable results.

I don't have all the years of a master like Kevin. So I'm just not going to be able to do all this work in the forge using colors and things and I can't make a salt pot for repeatable temps. Also, I don't have the education of Mete. So, could we please boil down a plan for me? Using what I have (or can get).

I really and truely want professional results from a metallurgist's perspective on reaching the finest grain and the most consisent process. I'm done with the magic home quench mixtures, magnets and colors, reducing flames, propane vs. coal. Etc. That's it!

I'm going to use an oven with precise temp control, commercial quenchant, and a blade coating. And I need your help.


Let me get specific:

Steel 1084
Forged blade
Computer Controlled oven
Turco Steel coating (so I don't have to worry about decarb)

--------------------------
Given all that, what's my plan to complete the blade (knife not sword)?

For example:

1. Turco coat the forged blade

2. Normalize
2.a Soak in Oven at 1550? 10? minutes
2.b Air Cool
2.c Soak in Oven at 1500? 10 minutes
2.d Air Cool
2.e Soak in Oven at 1475? 10 minutes
2.f Air Cool

3. Anneal
3.a Soak in oven at 1500? 10 minutes
3.b Oven Cool

4. Grind to final shape

5. re-Normalize
5.a Soak in Oven at 1500? 10 minutes
5.b air cool

6. Harden
6.a Soak in Oven at 1500? 10 minutes
6.b Quench in commerial fast-quench quenching oil at 140? degrees

7. Temper 3 times at 400 one hour each

Given all the states steel goes thru and the confusion I'm living in, could you review that sort of plan and tell me where to adjust it? Of course I'll try it out and tweak myself, but really I need a starting point.

Thanks so much. The guys on this forum are soo darned helpful, but you can understand how some of us week-end warriors get confused.

I'm not knocking the guys that can make a great knife with nothing more than a propane torch in a dark room and a bucket of pig's blood, but I just can't do that. I'm too much the engineer.

Steve
 
The normalize sounds ok. After you normalized 3 times I don't think the anneal is necessary.After grinding I wouldn't normalize ,just stress relieve at 1200F for 1 hour.Hardening is ok. Temper only 2 times , the third time won't do much.
 
"Steel 1084
Forged blade
Computer Controlled oven
Turco Steel coating (so I don't have to worry about decarb)"


Here is how I would do it if you took my salts away from me:

I would still prefer a coal forge for most of the operations, due to the ability to control the atmosphere, but I would like the oven for my anneal. I can always get a better heat treat out of a coal forge with an enclosed fire, than a gas forge due to the ability to localize and control the heat.

Specs sheets will give you a different temperature for each steel, but decalescence is what it is all about. Watch for the color the steel glows just as it is rebounding from the shadowy transformation range, this will be correct for what ever steel you are using since you are actually watching the transformation completing itself.

I would ALWAYS use a properly formulated quench oil, pigs blood and other fun mixes can be interesting to the general public but that is as far as I go with it.

1084 is so close to the eutectiod, that you need virtually no soak time at all at 1500F.. The magnet will tell you the Currie point of iron (around 1414F.) but will not tell you Acm (when complete austenite is achieved), and it will not be accurate at all on cooling, only on heating. Ar1 (transformation on cooling) is always much lower and is not where you want to quench from. Give it a try some time, heat a piece of steel to non-magnetic. As it cools see how long it takes for the magnet to stick. It will be almost black again before this happens.

I guess what I am saying is that you can make a fantastic knife with just a bit of practice and very simple tools like a forge, you just need to avoid the hocus pocus. Be aware that repeatable consistent results can be better had with more sophisticated equipment. The better your tools the more consistent the results. The single most powerful tool is KNOWLEDGE! Then the little things will add to your success. A proper quenchant design for your steel type will greatly increase your success without going as far as salt baths.

Keep the grain size small, keep the carbon in the steel, get things as hard as you can and then temper to the desired rockwell and you will do real well.

"1. Turco coat the forged blade"

Don't bother if you do this to the forging- it is all scaly anyhow. I never clean anything off my forgings before the anneal, if I have to decarburize something, let it be that black scaly mess on the outside that I will grind off anyhow.

"2. Normalize
2.a Soak in Oven at 1550? 10? minutes"

This is an eutectoid steel, it will come completely into solution at the lowest temp of any steel. Get it to 1550F and go right to cooling as evenly as possible. the grains will be a little larger that you want to end up with but they will be equally even in size.

" 2.b Air Cool
2.c Soak in Oven at 1500? 10 minutes
2.d Air Cool
2.e Soak in Oven at 1475? 10 minutes
2.f Air Cool"

A couple of heats at 1250F to 1325F will give you a very soft steel without the step 3 with 10XX steels. In 10xx steels above .80% carbon you will get spheroidal shaped carbide clusters. This makes for a very soft material but be aware that you will need to soak a little longer to pull that carbon back into solution when you heat treat. I often get phone calls from makers wondering what they did wrong with a hypereutectoid steel that has extra carbide forming elements. They get an odd damascus like pattern all over the blade. I tell them to soak longer or raise the temperature before the quench to dissolve those extra carbides and alloy banding and the problem will go away.

"3. Anneal
3.a Soak in oven at 1500? 10 minutes
3.b Oven Cool"

This will give you a traditional lamellar anneal (course pearlite) as opposed to the aforementioned spheroidal treatment. Be aware that this treatment will result in a courser grain, but it will be quite even and will recrystalize quite well on heating for the quench.

"4. Grind to final shape

5. re-Normalize
5.a Soak in Oven at 1500? 10 minutes
5.b air cool"

Quite honestly I would dispense with this normalizing step entirely. If you got things just how you want them before the grinding, don't mess with it any more. If you keep the thing cool while grinding you shouldn't have too many stress issues. There will be some strain energy from a course grinding belt but you can handle this, as well as getting things a little too warm with a stress relieving treatment (900F-1250F) without the radical treatment of another normalization.

"6. Harden
6.a Soak in Oven at 1500? 10 minutes
6.b Quench in commercial fast-quench quenching oil at 140? degrees"

I could not tell you how long to soak in an oven with the insulative affect of still air, but I can tell you that spheroidized 1084 requires only a 2 or 3 minute soak in salts to completely go into solution in blades type cross sections. O1 on the other hand requires at least 4 to 5 minutes to reach the mark in the same annealed state.

Make some small test samples and give them all the same anneal. Soak the first to 3 minutes and quench. Soak the next to four minutes and so on... out to perhaps 10 minutes. Do rockwell tests on each piece and you will notice a point of maximum hardness where longer soaks just don't matter. This will be your soak time in your oven. This would be a good place to use the anti scale compound if you are using and oven. It has been my experience that ovens and kilns are the most oxidizing of all methods of heating, with the exception of perhaps a torch.

The quench and its temperature sound good. Be sure to agitate! I drives me crazy to see smiths just hold the piece still in the oil and then complain that the oil isn't fast enough! In the words of Frederic Douglas "agitate, Agitate, AGITATE!" Don't swish the blade side to side in the oil, move it quickly tip to tang, to slice cleanly through the oil, if quenching horizontal; up and down or spine to edge, if vertical.


"7. Temper 3 times at 400 one hour each"

If you definitely know your results a single 2 hour temper will do the trick. I use 2 or 3 not because there is any magic associated with it, but this allows me to zero in on an exact HRC for each blade. After the first soak, I take a reading and then repeat with the temp bumped up a bit to increase the draw. I then take another reading and if it is where I want it, great! If it is not I go for a third. Industry also uses multiple tempers to cope with any retained austenite that may be present. The first tempering will convert it and make more martensite, so the second temper can zap the newly formed hard stuff.

The sooner you can get to the temper after the blade has reached Mf (THIS IS ROOM TEMP AT LEAST) the better off you will be. Not letting the blade completely cool to Mf will result in many problems, not the least of which would be the previously mentioned retained austenite.
 
Mr. Cashen should you let the steel completely cool in the quenchant or should you pull it out of quenchant once it goes to a black color and let cool in air, or how best to do it once it is in the quenchant before it goes into the preheated tempering oven?
 
Terry, alloy and carbon steels that are used for blades have a Mf temperature (the end of the martensite transformation) above the 140F of the oil.Thus there is no need to bring it down to room temperature. The most important thing is to drop the temperature to get past the pearlite nose so you get all martensite. This is especially critical for alloys like1095. Once you get past the nose you can slow the rate of cooling to reduce quenching stresses and reduce the possibility of cracking.
 
mete said:
Terry, alloy and carbon steels that are used for blades have a Mf temperature (the end of the martensite transformation) above the 140F of the oil.Thus there is no need to bring it down to room temperature. The most important thing is to drop the temperature to get past the pearlite nose so you get all martensite. This is especially critical for alloys like1095. Once you get past the nose you can slow the rate of cooling to reduce quenching stresses and reduce the possibility of cracking.
Click to expand...

Once again, what mete said. Except I would add that it is best to get the temp as close to Ms as possible before interrupting to get more complete martensite and avoid a high temperature spine bleeding heat to an edge that has cooled much faster and tempering your new martensite at 450F+. There are also some funny precipitation things that can occur if the cool is too slow from too high.
 
:D :D

This is just great! Thank you, thank you Kevin and Mete. You really don't know how much this information helps.

OK As recommended I'm trying to extend my knowledge. Did some more study on steel phases (if that's the right term). After reading and re-reading your post and looking up terms, I'm understanding better.

Goal of Normalize = smallest possible grain size, raise temp to just above Ac3 and cool

Goal of stress relief = relieve stress

Goal of Austentize = to get carbon into complete solution without destoying the fine grain, raise temp to just above Ac3

Goal of Quench = Lower Temp below Ms ASAP. Martensite transformation without destoying the fool thing

Goal of Temper = get the right hardness for application

1084 = Ac3 is something like 1400!? I think I can lower the temps?

I'm still worried about getting the edge over temp while trying to normalize/anneal and not getting the finest grain where it counts the most. Therefore I'm going to use the oven for everything. It's my belief that I can set the oven to the temp desired and 'soak' the steel long enough to get an even heat and good conversion.

To be honest, Kevin, on some of your answers I'm not sure if it is informational or something I need to change. For instance I'm not sure if I want a lamellar anneal or spheroidal prior to the hardening phase.

So given all that and what I understand of your guys advice, I'll revise the plan like this.

=====================================
1. Normalize
1.a Soak in Oven at 1475 10 minutes
1.b Air Cool
1.c Soak in Oven at 1475 10 minutes
1.d Air Cool

(Skipping the anneal)

2. Grind to shape

3. Coat in Turco

4. Stress Relieve
4.a Soak in Oven 1200 60 minutes
4.b Air Cool


5. Hardening
5.a Soak in Oven at 1500? 2-10 minutes (experiment)
5.b Quench in commerial fast-quench quenching oil at 140 degrees

7. Temper 2 times at 400 one hour each (adjust for proper hardness)

==========================================

OK Is that plan more in keeping with obtaining the optimal results?

Could I lower the Hardening heat to 1450 and soak for longer? Any advantage?

Steve
 
Many blade makers seem to be somewhat paranoid about grain growth. It is a time and temperature dependant process but more dependent on temperature.Keeping a reasonable hardening temperature with typical times will not cause a problem but when you start cutting time and temperature you get other problems . 1500F for 10 minutes will not cause problems....So do your thing Sando and do a destruction test to see exactly what you have.
 
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