rwl-34 lost magnetism after heat treat and temper

Q

Quinn406

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Nov 6, 2021
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Is this normal? I saw another post about this but there was no clear answer. Before heat treat my mag chuck would grab it no problem. I did a foil wrap and 25 minutes at 1950F, then plate quench. Came out looking great, almost no discoloration. It seems maybe a tad low on hardness but not really sure. The 60hrc file bites pretty easy, even the 55 kinda scratches but i never know if im using those quite right. This was before temper which should have been easily over 60. Im done with one temper and no change to magnetism, doing second temper now, both at 450 for 2 hours each.
Is it normal to lose magnetism with rwl34/cpm154 or did something go wrong in my heat treat? This is a homemade oven with inkbird controller. I have some orton cones on the way so i can check if my temps are right.
 
It should be magnetic at room temp after HT.
Austenite is non-magnetic, martensite and ferrite are magnetic. There may be a very high RA in your blades. What temperature did you do the HT at and how long a hold?
 
Stacy E. Apelt - Bladesmith said:
It should be magnetic at room temp after HT.
Austenite is non-magnetic, martensite and ferrite are magnetic. There may be a very high RA in your blades. What temperature did you do the HT at and how long a hold?
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1950f for 30 minutes, plate quench. Pretty common recipe for this steel. Im guessing the temp must be off. Does it sound like I was over or under? I ordered Orton cones to confirm my temp.
 
DevinT said:
Retemper at 975’f for 2 hrs and see if improves.

Hoss
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Did the 975 temper, still won't stick to a magnet. I'm thinking it must have gone way over temp. I built a really small oven, only 4x4.5x9 inside. The elements are in the side walls on either side and the thermocouple up along the top. The blade sits up on edge right between the 2 elements only 2 inches away so maybe it's getting much hotter than the thermocouple. I have Orton cones coming to test it. Would a big overheat explain this issue?

I checked again this morning and I will say the 975 temper made a slight difference. It slightly pulls on the mag chuck now, definitely not enough to surface grind it but there is a difference.
 
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https://imgur.com/a/OhXgDZF
Here's a pic of the inside of my oven. The chamber is only 4x4.5x9, plenty large enough for the folder blades I'm doing. The blade in foil sits on edge in the notch of the angle iron, thermocouple is up at the top. Is this configuration likely to cause issues because of the elements facing directly at the faces of the blade? I'm warming it up now for a salt test. I'll try 1350 first and slowly bring it up until it melts, then I'll try copper. I'm sure the Orton cones will be much more accurate but those are a week out. I just don't know what else could have gone wrong here. I feel like my quench was really good. I had oven sitting right next to my machining vise with aluminum plates bolted to jaws. I was maybe 5 seconds from oven to fully clamped in jaws and then air blast.

salt melt was pretty much right on, just slightly over temp. left at 1460 for a good 10 minutes with no melting, bumped it up to 1470 and it melted, so maybe like 5-10 degrees over. ill try copper now to test closer to hardening temp but its looking like temp is not my issue.
 
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ran the heat treat again, this time a bit lower and faster. I copied john grimsmos recipe since its the same steel. brought oven to 1925, put the blade in and brought back up to 1925 which took about 5 minutes, then a 15 minute soak, then plate quench. Same results as before. Hardness is low, maybe 55 before temper and almost completely non magnetic at room temp. after temper it gains a very slight amount of magnetism (ability to stick to a magnet), still almost none. After doing the salt melt test im pretty confident that my oven could not be far off enough to cause an issue like this. I really have no idea what could be going on here other than being sent the wrong steel but it seems unlikely. Came from jantz and has an rwl-34 sticker right on it
 
Hmmm, that seems like it should be right.
I wonder if the powder metallurgy makes it different than mono-steel.
 
Stacy E. Apelt - Bladesmith said:
Hmmm, that seems like it should be right.
I wonder if the powder metallurgy makes it different than mono-steel.
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yeah the recipe is definitely fine for the steel, im looking at some charts and anywhere a low as 1850f and as high as 2050F should be giving me minimum 60hrc before temper and i dont even know what to make of the loss in magnetism. I emailed jantz about it to see if its possible i was given the wrong steel.
 
Following. This is indeed weird … I would not expect the powdered metallurgy process to have such a profound effect on magnetic properties.

Larrin likely has an idea … but I am curious what happens if you anneal the material … do you recover the same behavior as the original stock? Maybe you could do some playing with a coupon from the remains of the bar…
 
Cushing H. said:
Following. This is indeed weird … I would not expect the powdered metallurgy process to have such a profound effect on magnetic properties.

Larrin likely has an idea … but I am curious what happens if you anneal the material … do you recover the same behavior as the original stock? Maybe you could do some playing with a coupon from the remains of the bar…
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I'll try annealing and see what happens. I'll cut the second blade out of the bar and cut a few small pieces from the remainder.

John grimsmo is using this exact steel and exact heat treat for the Norseman and he gets very consistent results. I'm pretty certain he is doing surface grinding on mag chuck after heat treat. I guess the one difference is he's doing cryo and I'm not. I suppose I can't say 100% that it isn't normal for the steel to lose its magnetism but what I do know for sure is that I am way under target for hardness. Before any cryo or temper, I should be around 62hrc and I'm not even hitting 55. The target of low 60's pre temper is based on multiple sources of documentation for rwl-34/cpm154 (same steel), as well as what I know grimsmo is hitting. He has his whole process shown pretty clearly on his YouTube channel.

Based on those things, I see only 2 possibilities. Either this chunk of steel I have isn't actually rwl-34, or the steel is not hitting the temps I think it is. Based on the salt melt test and copper melt test, it looks to me like my oven is pretty dang accurate, But I guess there's still the possibility that having the blade standing up between elements facing directly at it only 2 inches away is giving unexpected results. Theres 2 other things I'm going to try. First of all I'm gonna try sheilding the blade from the elements. I don't have much room in there to do that, but I'll figure something out. Second thing to try is laying a test piece on the bottom of the oven on just some small rods rather than standing up between elements. I suppose I could also try raising and lowering the temp by 100 degrees or so to see what happens. Ill have this figured out eventually, there's only a couple possibilities For what could be happening. This recipe with this steel is proven to work, so either the steel is wrong, or the temps are wrong.
 
You can build baffles for the coils by utilizing a few ceramic tile firing racks and a couple ceramic tiles along each side.
 
I don't think it is the distance from the elements. My furnace is only slightly wider than yours, but I have put two blades side by side so that they are about as far away from the elements as in your setup. A simple experiment that might shed some light on what's going on might be to put two coupons in a foil packet, one from the RWL-34 you're having problems with and a second one from a different steel that you know will harden. I think a piece of AEB-L should work well at that temperature, but I'm not sure how the long soak time would affect it. My guess is that it will be fine. At any rate, if the second coupon hardens but your steel doesn't, I think it's most likely that the steel is something other than RWL-34. If you want to try that and don't have any material on hand, I'd be happy to ship you some AEB-L coupons you can use for testing, just let me know what size you need and where to send them.
 
Hubert S. said:
I don't think it is the distance from the elements. My furnace is only slightly wider than yours, but I have put two blades side by side so that they are about as far away from the elements as in your setup. A simple experiment that might shed some light on what's going on might be to put two coupons in a foil packet, one from the RWL-34 you're having problems with and a second one from a different steel that you know will harden. I think a piece of AEB-L should work well at that temperature, but I'm not sure how the long soak time would affect it. My guess is that it will be fine. At any rate, if the second coupon hardens but your steel doesn't, I think it's most likely that the steel is something other than RWL-34. If you want to try that and don't have any material on hand, I'd be happy to ship you some AEB-L coupons you can use for testing, just let me know what size you need and where to send them.
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Appreciate the offer, I did get some more steel coming to test on. I bought that rwl-34 back when I first started designing my folder thinking it would be a good compromise of workability and a pretty decent steel. Back then I was planning on doing a fair amount of hard milling but I have a better method now that will rely on mostly machine grinding post HT so I decided to try some s45vn. Pretty much a surface grinding operation but with some tricky fixturing to deal with the nonplaner surface of my bevel.
 
Wanted to give an update here. Yesterday i received my orton cones as well as my chunk of s45vn. Once again confirmed the oven is accurate, at least with in 10 or 15 degrees. Cut a couple small test pieces off the s45vn for heat treat. Pretty much same recipe as ive been trying on the rwl-34 that was failing. The s45vn behaved exactly as expected, easily over 60hrc right after quench, the 65 file barely grabs, i would say 63-64, right as it should be. Tempering now and should drop to 60 or so. Also it sticks to a magnet, image that.

At this point i dont know for sure if its safe to conclude they sent me the wrong steel, but the evidence is stacking up. I tried probably 6 or 7 times to treat that rwl-34 along a pretty wide range and the result was always the same, under 55hrc right out of quench and non magnetic. I emailed jantz about the results i was having and basically they responded with, "heat treating takes skill and youre obviously doing it wrong, we arent replacing your steel". I mean i get it, im sure theres plenty of guys doing heat treat wrong and wanting their steel replaced. First of all, i never asked them to replace the steel, i just explained my results to them and wanted to know if it was possible the wrong steel was sent. Whatever, im just glad to be getting results now. Would have been nice to not waste a week trying to figure out what i was doing wrong, but im back on track now. Thanks for the suggestions everyone.
 
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