quenched 1084 at to hot a temperature. now what

G

GMBlades

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Apr 27, 2014
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Today I started the HT of a 5/32" 1084 stock removal blade. Its 13.5" overall with blade length of 8.5 and 2" spine to edge.
It was the first time I used a recently acquired TC in my charcoal forge for a temperature monitoring method.:thumbdn: I have come to realize that as I have read many times before that it's not a great choice for a charcoal forge but I tried it anyways. Last knife I used salt (1475) and magnet (1414) and had decent results. I could hold the temp at 1480-1490 but probe placement inside the muffle was probably a bit off. When I pulled the blade out to quench (130* canola) it didn't appear to be red enough but I plunged it in regardless. There was no flash as I expected. This is where I made a bigger mistake. I didn't think this through clearly at this point, and decided to heat it back up and test with salt and re plunge in the oil. Bad move!:thumbdn: I reached temps of between 1475 - 1500 and plunged into not hot oil.It was at 230*F this time. I know this because while I was reheating the blade I thought of this so I tested the temp with my IR gun. I knew this was not good news it's just things happened so dam fast and I decided to plunge it anyway!! Flame for sure this time. Skate test under the decarb seemed ....well ok.
So I am assuming that it would not have been a fast enough quench. I cooled to 125* and carried on with temper in the kitchen oven. Only tempered at 425* for 1.25 hr.
Threw it back in my filing jig and I'm thinking it is not hardened where it needs to be. My first impression is that it really is not hardened.
What are my options here do you think?
Back to the charcoal forge for round 2 but with quenchant at proper temp??
 
If it didn't quench fast enough, it obviously won't be properly hard... My advice is if you question it, then start over. At this point, considering you didn't get the steel way above critical, another hardening with a proper quench won't hurt anything. Then temper from there. If you're really concerned do a normalizing cycle in there, but probably not a necessity.

Cheers
Eric
 
GM, glad the name change finally came through.

I told you previously that a TC will NOT WORK in a charcoal forge. I guess you didn't believe me and thought you knew more...OK, now you know.
The muffle is fine for putting the blade in to get a more even heat in a propane forge, but in a charcoal forge will still be a problem. Putting the TC in the muffle pipe might be a tad better, but likely will still read inaccurately.
In charcoal it is best to just keep the blade moving in the coals, watch the color, and check the temp with the magnet. .
An IR gun is good for checking the oil temp, but not for much more. Don't use it for checking austenitization.

I think I also previously said that using salt was a bad idea for determining temperature ( especially in a charcoal forge). You probably read it on the internet, but there is lots of bad ideas on the internet. Use a magnet in the manner I suggested.

The first temper follows full cooling to room temperature after quench. Cool in water between tempers to room temp.




You are in too much of a rush and not planning things completely before starting. Make a plan and follow it.

Now, re-do the HT following the parameters give to you before. Take your time and check that the forge is running low enough, the oil is at 120-130F, and all things needed are in place.
Good luck.
 
Thanks Eric. Within minutes of your post I was back at it.
Thanks Stacy.
By the time I read your post Stacy I was finished the HT the 2nd time around.. She'd be in the oven now.
I would never in a million years believe that I know more than 99.9% of the forum members here.
Yes you did however tell me that the TC would not work, however that was after my friend promised me one, so I figured I had nothing to loose by trying it. It was in the muffle and it was, yes, inaccurate. lol.
Being a newbie, I tend to read a lot on techniques and as you are well aware, there are many, many different opinions out there (even on BF). My problem is that I tend to use all the techniques at once...at least the ones that make sense to me. Like for instance, the salt. During the HT I had the PID, salt and magnet all in front of me. Salt was in case TC did not work then I would have a back up plan. I had things planned, actually fairly well, I usually do! I had a back up plan but failed to recognize that the oil would then be too hot.
On one of my prior posts a member suggested the muffle in charcoal (with chunk of hardwood inside) for a more even heat distribution and less decarb as well Stacy, why do you feel that this is not a good method in my case? And why is the salt not a great idea?

I have taken a ton of pics along the way on this project and when the knife is complete I plan on posting an new thread that shows my project from start to finish.


Thanks BTW for prompting Spark with regards to my name change.
If your doing nothing this evening, take a drive to Ontario and we will pop a few more in the forge. haha
 
I was sort of kidding, in an uncular way.

A muffle is primarily used to protect the blade from direct flame. It won't go too far to even out the heat. In a charcoal forge the difference in just a few inches can be a thousand degrees, especially if the blast is too high. The muffle will be hotter in the blast and cooler in the margins. It will be easier to just hold the blade in the tongs and move it back and forth through the hot zone ( with the blast reduced to very low) to evenly bring the entire blade up to the austenitic point. With some practice and skill, you can keep the blade on the edge of the hot zone and move it back and forth as needed to hold the blade at temp for a minute or two. Practicing on a plain bar of steel is a good way to learn how to control a charcoal forge.

I read all the time about adding a chunk of wood, charcoal, etc. in the muffle or in the HT oven. It probably won't hurt, but most likely won't do much to reduce the oxygen exposure, as the earth's atmosphere has plenty of oxygen to spare. The idea of a flaming piece of wood in my expensive HT oven or sitting on my blade in the muffle isn't appealing to me. This is one of those, "To each his own" things and not worth arguing about, but I don't do it. I have friends who do and we still drink beer together, so I guess it isn't a big enough deal to make a war over.

Salt will melt at around the temp of austenitization, but the salt is being exposed to the heat around the blade as well as the heat from the blade. Which one does the melting is not always clear.
The magnet is always working correctly and the blade is the only thing that it is acting on. Non-magnetic equals about 1400-1425F on blade steel....every time. Heating the blade a little hotter and quenching in warm canola or commercial quench oil equals a suitable HT....every time.
 
Slow down my friend !!! Make one plan and stick to it. Have all steps planed out. Don't fall for gimmicks . You should have no trouble heat treating 1084 . Sometimes when you are new you try to learn to much but end up learning nothing. Keep at and simplify .
 
Bladsmth:
For my own understanding, can you help me understand this statement because I will eventually be doing this very same thing.
"The first temper follows full cooling to room temperature after quench. Cool in water between tempers to room temp."
I think I understand cooling to room temp after quench, but are you putting it in water in between heat cycles immediately after it comes out of the oven?
 
Yes, j2dogs you can quench between tempers straight out of the oven.

GMB, both Eric and Stacy are far more versed than I, but 1 thing that stood out to me was if a single quench raised your quenchant temp by 100 degrees you likely need a larger volume of quenchant. How much oil did you use for that blade?

Chris
 
Salolan said:
Yes, j2dogs you can quench between tempers straight out of the oven.

GMB, both Eric and Stacy are far more versed than I, but 1 thing that stood out to me was if a single quench raised your quenchant temp by 100 degrees you likely need a larger volume of quenchant. How much oil did you use for that blade?

Chris
Click to expand...
I agree w/ salolan. Sounds like small volume. Didn't catch that when I read it personally...

Ah, GM, now I think I remember... been outta commish a bit. You're the chemist, no?

-Eric
 
jtwodogs said:
Bladsmth:
For my own understanding, can you help me understand this statement because I will eventually be doing this very same thing.
"The first temper follows full cooling to room temperature after quench. Cool in water between tempers to room temp."
I think I understand cooling to room temp after quench, but are you putting it in water in between heat cycles immediately after it comes out of the oven?[/QUOTE


Upon the quench the steel drops very rapidly to below 900F, and then more slowly to 400F and then slowly to below 200F. This is all determined by the type of quenchant and the volume. For 1084 a moderate speed quenchant is needed, and for all blades a minimum of one gallon of oil is needed. While Parks #50 would be great, canola will work. Many new makers use far too little oil, though. A quart of oil in a small can is not going to harden the blade properly. You want a volume of oil and a container sufficient to have 3" of space in all directions around the blade. That would be a minimum of 6". On smaller blades, you can get by with a 4" quench tank, but bigger is better in this case. ( Good catch, Chris. I missed that, too. )

To reach the finish of the martensite conversion (Mf) a 1084 blade needs to drop to room temperature ( stainless steels need a lower temperature). Thus you must take it out of the 120-130F oil and let it finish cooling. The blade can sit on the work table or anvil, or can be dunked in the slack bucket. Whatever you do, be gentle, as the blade is brittle martensite at this point....and will shatter if bumped/bent/dropped. Immediately after quench, I just take the blades to the sink and wash them off gently, but well, with dish soap and running water and then place in the pre-heated tempering oven.

Following the quench and being cooled to below 70-80F, the blade should be tempered as soon as possible. After the first temper, the blade should be cooled to 70-80F in water to drop the temperature fairly fast ( I stick it under the running tap), and then immediately tempered a second time....also followed by cooling in water.

Many people let the blade air cool slowly between tempers and after the last temper. While this won't ruin the blade, it is metallurgically better to cool the blade more quickly between and after the tempers to avoid undesired structures forming. If you do it slow, you are fine, but quicker is technically better.


I see/read a lot of new makers doing a third temper. On any steel but the most complex high alloy stainless steels, this is useless. Two one hour tempers are sufficient for 99% of all knives made.
Click to expand...
 
Thanks for the response and your super valuable knowledge. I do not have a teacher right here with me, but if not for you guys sharing your knowledge I would be totally lost. Thank-you for your generosity. I guess I need to ask one last question I am thinking oven temp should be 375 for 1084 does that sound right?
 
JTW shoot for between 400-450

No I'm no chemist, just work with 200 of them. I am a radiation safety officer.
Funny you mention that Salolan, following my incident I did a little more research and decided to increase the volume for my next. Started with a large coffee can full then went to a exhausted fire extinguisher for this blade. The extinguisher held just over a gallon. Might end up going for 3 gallons of Parks AAA for 1084.
Stacy, I see you reccomend Parks 50. I was originally going to go for that then saw that AAA was the better choice. So once again looking for advice on which quenchant to grab.
Have a good day everyone!
 
Last edited:
bladsmth said:
jtwodogs said:
Bladsmth:
For my own understanding, can you help me understand this statement because I will eventually be doing this very same thing.
"The first temper follows full cooling to room temperature after quench. Cool in water between tempers to room temp."
I think I understand cooling to room temp after quench, but are you putting it in water in between heat cycles immediately after it comes out of the oven?[/QUOTE


Upon the quench the steel drops very rapidly to below 900F, and then more slowly to 400F and then slowly to below 200F. This is all determined by the type of quenchant and the volume. For 1084 a moderate speed quenchant is needed, and for all blades a minimum of one gallon of oil is needed. While Parks #50 would be great, canola will work. Many new makers use far too little oil, though. A quart of oil in a small can is not going to harden the blade properly. You want a volume of oil and a container sufficient to have 3" of space in all directions around the blade. That would be a minimum of 6". On smaller blades, you can get by with a 4" quench tank, but bigger is better in this case. ( Good catch, Chris. I missed that, too. )

To reach the finish of the martensite conversion (Mf) a 1084 blade needs to drop to room temperature ( stainless steels need a lower temperature). Thus you must take it out of the 120-130F oil and let it finish cooling. The blade can sit on the work table or anvil, or can be dunked in the slack bucket. Whatever you do, be gentle, as the blade is brittle martensite at this point....and will shatter if bumped/bent/dropped. Immediately after quench, I just take the blades to the sink and wash them off gently, but well, with dish soap and running water and then place in the pre-heated tempering oven.

Following the quench and being cooled to below 70-80F, the blade should be tempered as soon as possible. After the first temper, the blade should be cooled to 70-80F in water to drop the temperature fairly fast ( I stick it under the running tap), and then immediately tempered a second time....also followed by cooling in water.

Many people let the blade air cool slowly between tempers and after the last temper. While this won't ruin the blade, it is metallurgically better to cool the blade more quickly between and after the tempers to avoid undesired structures forming. If you do it slow, you are fine, but quicker is technically better.


I see/read a lot of new makers doing a third temper. On any steel but the most complex high alloy stainless steels, this is useless. Two one hour tempers are sufficient for 99% of all knives made.
Click to expand...
Stacy, that's one of the better Cliff's Notes breakdowns I've read in a while. Good deal.

-Eric
Click to expand...
 
jtwodogs said:
Thanks for the response and your super valuable knowledge. I do not have a teacher right here with me, but if not for you guys sharing your knowledge I would be totally lost. Thank-you for your generosity. I guess I need to ask one last question I am thinking oven temp should be 375 for 1084 does that sound right?
Click to expand...

This is the guide I use for tempering 1084: http://www.cashenblades.com/steel/1084.html
 
AAA will work for medium quench speed steels. #50 is for faster quench steels. 1084 falls right on the border, depending on the alloy content. If you get a bucket of #50 you can do most carbon steels safely. With the AAA, you can't do the higher carbon ones like 1095, W-1/W-2,etc. and ones popular for hamon like 1060 and 1070. Steels like 5160/9260, O-1. and L-6 can all be done in canola, AAA. Using #50 is a bit fast for them, but usually does not have a problem.

In the best scenario, you have a 5 gallon tank of both.
 
Great thread - I am not making knives myself just yet but certainly gathering info!
Ever since I saw Nick Wheeler's WIP thread about the 1084 camp knife and his edge test with dried antler, I think I don't need anything better than 1084!

When I quench the 1084 steel in Parks 50 or AAA, how long should I leave the blade in the oil before taking it out for tempering?
 
bladsmth said:
Upon the quench the steel drops very rapidly to...

To reach the finish of the martensite conversion (Mf) a...


I see/read a lot of new makers doing a third temper. On any steel....
Click to expand...

You just made all that up, di-in't you?

One question... you said that after the quench, you often run the blades under water. Do you mean after the quench, once the blades are at the temperature of the oil(130F)? I was under the impression that the Ms to Mf phase shouldn't be sped up.

And for those using an IR pyrometer. Make sure the emissivity is set to whatever you are reading. I have a rather expensive unit and when compared to my surface probe and liquid TC, there is a huge difference(la couple hundred degrees in some cases)
 
Rick Marchand said:
You just made all that up, di-in't you?

One question... you said that after the quench, you often run the blades under water. Do you mean after the quench, once the blades are at the temperature of the oil(130F)? I was under the impression that the Ms to Mf phase shouldn't be sped up.

And for those using an IR pyrometer. Make sure the emissivity is set to whatever you are reading. I have a rather expensive unit and when compared to my surface probe and liquid TC, there is a huge difference(la couple hundred degrees in some cases)
Click to expand...

For simple carbon steels - the actual time needed for the quench to drop the steel from 1450F to below 900F is about one second. Then it can drop more slowly to 400F. During that time the blade is still austenite, and can be hand straightened ( with heavy gloves on) easily. Once it hits 400F all straightening must stop, as the blade will start converting to martensite and be brittle. The 400F to 200F range must be allowed to happen slowly and on its own. Sitting in the warm oil is the best place for that. Once below 200F the basic Mf has been reached, but the blade needs to drop to room temp before temper to assure minimum RA. The drop from the 120F oil to 80F can be fast or slow , as it doesn't matter at this point.
 
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