Help with 1084 heat treat.....

I may have missed something, so i want to be sure.
Normalization won't leave small grain, it is not supposed to. Hopefully it will give even size grains (quite large) where to start from, plus small evenly dispersed carbides. Then you have to follow up, running the pieces through a series of heats at progressive lower temperatures intervalled by air cooling or quenching to black (to where the magnet sticks again). This will give you a fine, homogeneous grain.

The grain in the pictures looks like very large, even if your control is reading the correct temp you need to place the piece in the electric kiln only when it has stabilized at the intended temperature... or it is likely that it will overshoot before equalizing.
 
stezann said:
I may have missed something, so i want to be sure.
Normalization won't leave small grain, it is not supposed to. Hopefully it will give even size grains (quite large) where to start from, plus small evenly dispersed carbides. Then you have to follow up, running the pieces through a series of heats at progressive lower temperatures intervalled by air cooling or quenching to black (to where the magnet sticks again). This will give you a fine, homogeneous grain.

The grain in the pictures looks like very large, even if your control is reading the correct temp you need to place the piece in the electric kiln only when it has stabilized at the intended temperature... or it is likely that it will overshoot before equalizing.
Click to expand...

Yes, my mistake I just called it 'normalization'! I understand the need for additional cycling for grain size. This last test wasn't normalized or cycled. Here is my current regime from samuraistuart....

For example, with his 1084 this is my procedure: Normalize to dissolve carbides...1600°F for 10 minutes, allow to cool in still air. Carbides taken care of...check. Grain growth...maybe. Let's thermal cycle to nucleate new aus grains. 1550°F, air cool. 1500°F air cool. 1450°F, air cool.
Click to expand...

Possibly I'm doing this all wrong? I always put the coupon in the oven, then ramp to temperature and then soak for the specified time. Should I be ramping to temperature, then inserting the coupon for the soak? How could/would I know when the coupon has equalized before starting the soak time?

Thanks stezann!
 
DING DING DING DING DING!!!!! Bells just went off!!!! So you are putting the coupon in the oven cold, and THEN ramping the heat up???? Oh my goodness, this is a major variable. Yeah....grain growth would be possible. This 1084 has a touch of Vanadium to help keep grain growth in check....but not much at all. I'm no metallurgist, but it with the lower alloy stuff we are working with it is always best to place the knife/coupon in an oven that is ALREADY at aus temp. As a matter of fact, I always wait 15-20 minutes AFTER my readout reaches my target temp. The thermocouple may be 1500, but the atmosphere may not be quite that hot yet!!!! I've always heard that placing the knife in cold, then ramping, can cause grain growth, especially if your oven is like mine, 110V, and takes a while to get to 1500 (a little over an hour). Too much time spent above Ac1.

When do you know the coupon has equalized? I use a simple formula.....when the digital readout has rebounded, I start my soak time. That means, ramp the oven up to 1500. Wait 15 minutes, just in case. Insert blade, watch the readout drop because of the mass of the cold knife. Usually only takes a minute, then start soak time. I don't know EXACTLY when the blade is EXACTLY the temperature I want, but it is within a couple minutes of inserting it. That's good enough. Sometimes, depending on the mood I'm in, I'll add a minute or two to my soak time, just to be sure the piece is at target temp when I start soak time.

I know we are running you around all over the place, but I for one would like to see better RC numbers and grain size with your samples. You may try this, normalize 1600F, soak 10 minutes, air cool. Thermal cycle 2 times 1475, 5 minute soak air cool, then one time 1425, 5 minute soak, air cool. This is just a variation of thermal cycling...not all that different/more important than the one I gave earlier.

My STRONG recommendation is to get that kiln up to temp FIRST, then insert your coupons, wait for the temp re-bound, add a minute if you want, start your soak of 5 minutes, 10 most.
 
samuraistuart said:
DING DING DING DING DING!!!!! Bells just went off!!!! So you are putting the coupon in the oven cold, and THEN ramping the heat up???? Oh my goodness, this is a major variable. Yeah....grain growth would be possible. This 1084 has a touch of Vanadium to help keep grain growth in check....but not much at all. I'm no metallurgist, but it with the lower alloy stuff we are working with it is always best to place the knife/coupon in an oven that is ALREADY at aus temp. As a matter of fact, I always wait 15-20 minutes AFTER my readout reaches my target temp. The thermocouple may be 1500, but the atmosphere may not be quite that hot yet!!!! I've always heard that placing the knife in cold, then ramping, can cause grain growth, especially if your oven is like mine, 110V, and takes a while to get to 1500 (a little over an hour). Too much time spent above Ac1.

When do you know the coupon has equalized? I use a simple formula.....when the digital readout has rebounded, I start my soak time. That means, ramp the oven up to 1500. Wait 15 minutes, just in case. Insert blade, watch the readout drop because of the mass of the cold knife. Usually only takes a minute, then start soak time. I don't know EXACTLY when the blade is EXACTLY the temperature I want, but it is within a couple minutes of inserting it. That's good enough. Sometimes, depending on the mood I'm in, I'll add a minute or two to my soak time, just to be sure the piece is at target temp when I start soak time.

I know we are running you around all over the place, but I for one would like to see better RC numbers and grain size with your samples. You may try this, normalize 1600F, soak 10 minutes, air cool. Thermal cycle 2 times 1475, 5 minute soak air cool, then one time 1425, 5 minute soak, air cool. This is just a variation of thermal cycling...not all that different/more important than the one I gave earlier.

My STRONG recommendation is to get that kiln up to temp FIRST, then insert your coupons, wait for the temp re-bound, add a minute if you want, start your soak of 5 minutes, 10 most.
Click to expand...


Actually this is good, I'm learning! And I'm good with the running about, education has a price.

I will DEFINITELY accept your recommendation and give it a try tonight!
 
Woo hoo best test yet! Please note that I did post up my 'procedures' in my very first post in this thread, but after nobody commented specifically on them I assumed they were OK, bad move on my part!

After today's revelations I prepped up 2 coupons tonight. 1st test pure heat treat, 2nd test normalization, grain refinement and then heat treat. I'm doing the 1st test because that's what I started with and I wanted to see the results. Both tests will be inserting the coupons into the oven after the ramp!

I got the 1st test through heat treat and quench and Rockwell testing, results below. The 2nd test I only processed through normalization, life got in the way, but I will finish it up tomorrow.

1st test rockwell results


1st test breaks


These are undeniably the best HRc results I've had period! Probably within the accuracy of my skill at measurement. The breaks aren't great but then it wasn't normalized or heat cycled. That test will be tomorrow.

Thank you stezann and samuraistuart, I can't tell you how much I appreciate your knowledge and help!

Joe
 
Nicely done guys.
I was using one of Stuart's knives last night in the kitchen. :60:
Dozier (not Bob)
 
So I got through the normalization and the grain refinement and the heat treat process for the 2nd sample.

HRc


breaks


The Rockwell tests are good but not as good as the last test. Not sure why? I think the break grains look a bit better but I'm not sure they are good enough? Note that for all cycles the coupon was inserted at temperature and allowed to equilibrate before starting soak time. Your feedback please!?

Note also that there was only one heat treat operation, I just listed it twice!

Thanks!
 
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Just to be sure... you are NOT tempering these coupons before you break them, right? The Rc numbers are looking decent but the grain size still isn't where I would think it should be.
 
Hey there Mr Dozier!

Agreed with John. RC numbers could be a little better, grain should look finer. I wonder, are we using the same coupons to test and re-test? Also, is the Parks 50 at optimal temp of just above room temp, no hotter than 100F? Also....are you agitating the coupon in the quench? As for grain size, to help get smaller grain, I wonder if shorter soak time might be better. 1084 is just above eutectoid....barely....so no REAL soak time is needed. You might try a 5 minute soak. You can even try a 3 or 4 minute soak. I've seen pics of Aldo's 1084 grain tests posted by others, and they were way worse than this.

I noticed that the spot on the coupon with the highest RC number looks to be the corner farthest from the tongs, probably the corner that went into the quench first. The areas tested with lower RC numbers are those closest to the tongs. Depending on the mass of the tongs, especially near the tips, this can suck heat out of that coupon as soon as you grab it.

I am just saying this for the sake of saying it..... but 0.2" is no thin piece of steel, and 1084 is pretty shallow hardening with a PN of about 1 second. Make sure you agitate in the quench (not side to side but back and forth...we usually say that because thin cross sections like knives with bevels cut already will warp in the quench if moved side to side instead of back and forth...may not be an issue with .2" thick coupons...still.....). It would be cool to have a cross section of a beveled blade as a coupon to do these tests with. Like a 1/8" thick spine, 1.5" tall, down to a .030" edge. I always prefer to have bevels cut pre HT, especially on shallow hardening steels. Less mass for the quench that needs to be FAST.

Keep it coming, Jaxxas
 
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No tempering as of yet, I'm trying to tackle one issue at a time. Though I think I may have my tempering setup ready to go once I have nailed the hardening.

I am using new coupons each time, lately I have been breaking each test to see the grain.

Parks 50 is right at 84-86 degrees, ambient in my shop this time of year! Yes, I have been agitating the coupon in the Parks 50, back and forth as well as vertically. (no left to right)

You are probably correct about the about the higher HRc corner submerging in the quench first. I haven't been noting which part goes in first as I just try to get it into the quench as fast as possible. As was suggested (thank you wdtorque!) earlier in this thread I could drill the hole in the sample again and then use a wire loop through the hole and hopefully eliminate any tong effect. I like this idea because probably all knives in the future would have a hole or two in the handle.

And I could make the coupon into a cross section of a blade shape but then how would I test it? As I 'understand' it the test must be flat on both sides in order for the Rockwell test to be accurate? Also I recently read 'somewhere' that maybe I should be using the the smaller platen on the Rockwell tester as it's more rigid, I have been using the larger one on all of my tests to date. I will change out the platen and retest some of old test coupon pieces.

I will make up some more coupons to test shorter soak times. Maybe 3, 5 and 7 minute tests.

Thank guys for all your help!

Joe
 
Just for kicks you could bump the austenitizing temp down to 1475 F. and try that too. Don't temper the pieces if you're going to break them to look at the grain. Or for getting initial hardness for that matter either. You want full hard coupons for both. They need to be flat to accurately test so knife shaped cross sections are out.

For what it's worth, I use my parks 50 at around 110-120 F.
 
J. Doyle said:
Just for kicks you could bump the austenitizing temp down to 1475 F. and try that too. Don't temper the pieces if you're going to break them to look at the grain. Or for getting initial hardness for that matter either. You want full hard coupons for both. They need to be flat to accurately test so knife shaped cross sections are out.

For what it's worth, I use my parks 50 at around 110-120 F.
Click to expand...


Great idea John, I hadn't even considered going with less heat! Also that's what I thought I had read about Rockwell testing and flatness. Thanks! As I posted earlier though maybe not so clearly I haven't even attempted any tempering on any 1084 steel as of yet.

Today was a bit of not a lot done on what I wanted to do but on doing what needed to be done, I managed to re-wheel my welding cart. Cheap Harbor Freight casters had froze up so I had ordered 2 new casters from Caster City about 10 days ago and as I received them yesterday I really need to get them installed. I have a small shop, everything is on wheels. And if can't move it, it's in the way! Took me about 3 hours to re-caster my welding cart including a few mods I had been wanting to make.

I was able to process 4 new coupons through the normalization process at 1600 F. I went with holes in the corner beside the ID notches to attach a wire loop to hopefully remove any tong effect. Yet another variable. I was processing the normalized coupons by removing the entire ceramic caddy and letting them air cool on a steel bench in the ceramic kiln caddy. With the wire loop I remove the entire caddy and then hang each individual coupon in still air until cool. Hopefully this should help with hardening tong effect too. I guess we shall see. I will definitely test 1 coupon at 1475 and the other 3 spaced out over the range!

I thought I read on the Parks 50 info that came with my Parks shipment that 120 F was the max temp to quench at? Not that I'm opposed to trying it at that temp. Lately I have been thinking about fabricating a re-circulating pump through a filter and a PC radiator to keep my quenchant cool, just so I could quench more than a single blade before the Parks got too hot!? This may absolutely necessary here in Arizona when the ambient temps in my shop hit 105 F.

Thank John!
 
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When I received the P50 it said the same thing.....do not use above 120F. It is best in that room temp range up to around 120F max. Temp in the garage is around 85, I take it out in the sun for an hour to bring it up to 95-97. Probably no difference, really, but I do it anyway.

Wire loop thru hole instead of tongs....excellent.
Hang in still air rather than leaving on the ceramic cart.....most excellent.
The recommendation of 1475F (instead of 1500)....may indeed give better results.

I, for one, would like to see constant 65, maybe 66, and a gray velvet surface. We will get there, come hell or high water. See you down in Arizona Bay!
 
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My next test results.....Worked late getting them done but here they are.

Note all 4 of these coupons were normalized at 1600 F, and air cooled.

Thermal cycling - all 4 coupons went through the same thermal cycling heats
1500 F, 10 min soak, air cooled to black, quenched
1475 F, 10 min soak, air cooled to black, quenched
1425 F, 10 min soak, air cooled to black, quenched


All coupons were handled via a wire loop through all heats!


#1




#2




#3




#4





First note that I tried using the smaller platen on my Rockwell tester but the results were way different than the large platen. Not sure why, maybe I'm not flat enough on my coupons? ( I swear my grinding is getting much better!) Maybe I would have to re-calibrate the tester with the small platen? I think I like the large platen! The X's denotes small platen testing and the O's designates the large platen testing. All secondary tests were at least 3 mm from any previous test. Also when I check the calibration on my tester I am usually a half to 1 point low. So maybe a 65 should be considered a 66?

Tried to monitor the quench temps, they really were trying to climb. I kept a fan on the tank and frequently agitated the oil vigorously to keep the temps down for 4 quenches in a relatively short time.

I have no idea what I did wrong to test 3, the results are bad, maybe just an anomaly? Still scratching my head on this one.

Overall the other 3 tests aren't bad. #1 is a little low and inconsistent. #2 is just a bit off in one corner, and #4 is pretty nice and fairly consistent. Overall I think the grain looks a bit better!? I think it could be better though, should I be normalizing at 1650 as has been suggested?

I would also note that all of these samples broke hard, I had to really lay into them with a 3 lb baby sledge.

Thanks for all your help guys, I really appreciate you sticking through this with me!
 
I agree I think that the numbers and the grain looks a lot better. I take it that there was no temperature cycling done on any of the coupons. You could try thermal cycling starting at 1600°-1650° and then walk it back down to about 1400° in steps and then harden from 1500° with a 6 minute soak to see what that did for hardness and grain size.

Doug
 
1500 F, 10 min soak, air cooled to black, quenched
1475 F, 10 min soak, air cooled to black, quenched
1425 F, 10 min soak, air cooled to black, quenched
Click to expand...

I just noted teh "air cooled to black", quenched statement. Are you saying the coupon was removed from oven at 1475, held in the air until it cooled to black, then put in quench? I think the idea is to removed from oven and get into quench as fast a possible.

Maybe I'm not understanding what your "air cooled to black" statement is.

Ken H>
 
Doug Lester said:
I agree I think that the numbers and the grain looks a lot better. I take it that there was no temperature cycling done on any of the coupons. You could try thermal cycling starting at 1600°-1650° and then walk it back down to about 1400° in steps and then harden from 1500° with a 6 minute soak to see what that did for hardness and grain size.

Doug
Click to expand...

Yes I thermal cycled these coupons with the following program...


Note all 4 of these coupons were normalized at 1600 F, and air cooled.

Thermal cycling - all 4 coupons went through the same thermal cycling heats
1500 F, 10 min soak, air cooled to black, quenched
1475 F, 10 min soak, air cooled to black, quenched
1425 F, 10 min soak, air cooled to black, quenched

I'm thinking I want to try 1650 F next time for better grain refinement.

Thanks Doug!
 
KenH said:
I just noted teh "air cooled to black", quenched statement. Are you saying the coupon was removed from oven at 1475, held in the air until it cooled to black, then put in quench? I think the idea is to removed from oven and get into quench as fast a possible.

Maybe I'm not understanding what your "air cooled to black" statement is.

Ken H>
Click to expand...


Yes this was just during the thermal cycling. The coupons were cooled in still air until 'black' or magnetic again and then I quenched them to reprocess to the next stage.

Thanks Ken
 
Joe, let me confirm, when you quenched for hardness, you went direct from oven at 1500ºF (or the appropriate temperature) direct to quench with no pause between oven and quench? What temperature did you go direct from oven to quench?

Ken H>
 
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