Help with heat treating drill rod

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EpicWill

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Hi guys, we just got a Paragon HT14D oven to heat treat some small tooling parts. I'm doing test with some oil hardening 1/4" drill rod (O-1 from what I can figure) which I have some small shafts I'll need to harden. I can't for the life of me get the small test parts to harden.

I've found a few different resources and they all seem to recommend 1450-1500F followed by a quench in 125-150F oil. The parts I'm testing with are about 2-3" long 1/4" diameter. I first tried going to 1200F for 30 minutes then to 1400F for 15 minutes. No go. Second attempt was 1200F for 30 then 1500F for 30. No go. I thought maybe they weren't heating properly as they were sitting on the bottom of the oven so I propped the last part up in the middle-ish of the oven (near the TC) on a piece of scrap steel tube and did 1200 for 30 and 1500 for 60. Nothing. The best result was with the 1200/30 - 1500/30 on the bottom of the oven, the 45HRC file doesn't cut but the 50 does.

The oil I'm using is Super Quenchfast high speed quenching oil.

From what I've seen these should be 63-65 post-quench and I'm clearly not getting that. I'm a complete noob for heat treating, what am I doing wrong? Thanks in advance.
 
Unless your furnace is supplied with a non oxidizing atmosphere, loss of carbon at the surface can cause low hardness, I use crushed coke in a covered metal box to act against decarb. When I worked in my apprentice shop, we used peach pit charcoal, when it became unavailable, they went to coke.
 
Two possible explanations for your observance. The steel is not O1 or you did not reach a hardening temperature. For the latter, it may be that the oven is out of calibration. Regarding the former, a spark test against a known good specimen is suggested.

A 1/4" rod shouldn't need a 30 minute soak. Test the heated rod with a magnet. If it doesn't stick, you should be at a hardening temperature. At the expense of increased grain size. try raising the temperature.

I will add, since you state you are a noob, when you quench, it should be done immediately upon removal from the oven and you need to agitate the piece in the quench oil. Tempering should be done as quickly as possible after quenching to prevent stress cracking.
 
Might not be O1. Oil hardening drill rod is my go-to for anything that needs to be hardened. I just heat it red hot with a torch and dunk it in motor oil. No thermometer, just my eyeballs. This tells me that the process is not very critical.
 
benmychree said:
My info says 1450 - 1500, temper 350 - 500 for Rc 62 - 57; Wondering if your material is mis identified.
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I don't think it is, it came as a bunch of rods in a bag from a reputable local supplier
benmychree said:
Unless your furnace is supplied with a non oxidizing atmosphere, loss of carbon at the surface can cause low hardness, I use crushed coke in a covered metal box to act against decarb. When I worked in my apprentice shop, we used peach pit charcoal, when it became unavailable, they went to coke.
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Ours has an option to add a gas regulator to inject Argon but we don't have it. I did buy some stainless heat treat bags from mcmaster to get around the oxidation thing but there was no scaling on the test rods after firing. Might have to try another piece in a bag and see how it goes.
RJSakowski said:
Two possible explanations for your observance. The steel is not O1 or you did not reach a hardening temperature. For the latter, it may be that the oven is out of calibration. Regarding the former, a spark test against a known good specimen is suggested.

A 1/4" rod shouldn't need a 30 minute soak. Test the heated rod with a magnet. If it doesn't stick, you should be at a hardening temperature. At the expense of increased grain size. try raising the temperature.

I will add, since you state you are a noob, when you quench, it should be done immediately upon removal from the oven and you need to agitate the piece in the quench oil. Tempering should be done as quickly as possible after quenching to prevent stress cracking.
Click to expand...
I did make sure to quench immediately after removing the parts. I also swirled them around in the oil and made sure to heat the oil first. My quench tank is just a piece of 3" steel tube welded to a 2x6 rectangle tube as a base. When you say check with a magnet I assume once it's cooled right? Couldn't the heat damage the magnet? I just went and checked the test parts and they're both magnetic still (but they're obviously cooled at this point). The parts were also a dull red, even after an hour long soak at 1500F. I was expecting them to be a little brighter but they weren't.
epanzella said:
Might not be O1. Oil hardening drill rod is my go-to for anything that needs to be hardened. I just heat it red hot with a torch and dunk it in motor oil. No thermometer, just my eyeballs. This tells me that the process is not very critical.
Click to expand...
It may have just not been hot enough. They were a dull red but not nearly as hot as I expected them to be. Maybe I'll try again at 1600F and see what they look like.

Thanks for everyone's suggestions. I'll play around with it some more today and tomorrow. I need to drill the firebrick where they added a see-through port in the front door so I can see the part color before opening the door.

Also do I need to soak at 1200F before bumping up to final temp? I also saw that it should be heated slowly but I don't see anything saying what "slowly" is. Is it 100F/hour? 400f/hour? For these test I let the kiln heat up as fast as possible - it reached 1200F in around 20-25 minutes I believe, maybe a little less. I know it was over 750 after 10.
 
Ok I just tried doing the torch method and it seemed to work pretty well when heated to a bright orange color. I checked one of the other pieces from yesterday and it seems to be between 55-60 HRC according to the hardness testing file set we bought. I think my interpretation of the instructions regarding "marking" the material were too vague as the 45 HRC file did mark it but it definitely skates across the surface compared to the 60 that for sure bites in.

I'm going to fire it up to 1500 again and take a picture when I open the kiln door so you guys can tell me if the color looks correct for that temp. I also have a thermal probe that a K type thermocouple so it'll go to 2300F so I'll see what it says the kiln is at when it saying it's at 1500F.
 
Magnet test is done using hot steel. Above the Curie point temperature the steel is no longer magnetic. A brief attempted touching of the magnet to the steel shouldn't harm either piece.

Using a separate thermocouple is a good idea. You can easily check it's calibration with some simple tests. Ice water and boiling water are two easy standards.
 
Ok I verified the TC was reading properly and stuck it in the sight hole in the front door. The display on the TC reader when to dashes after 1030F so that must be its max. I tested at 500F and 900F and the TC was reading 20-30F higher than the kiln controller was reading so at least the kiln isn't reading higher than it actually is.

I've got the kiln cooling off now and I'll toss a test part in once it's cooled.
 
EpicWill said:
Ok I verified the TC was reading properly and stuck it in the sight hole in the front door. The display on the TC reader when to dashes after 1030F so that must be its max. I tested at 500F and 900F and the TC was reading 20-30F higher than the kiln controller was reading so at least the kiln isn't reading higher than it actually is.

I've got the kiln cooling off now and I'll toss a test part in once it's cooled.
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Interesting the display on the reader is limited to about 1/2 the range of the TC material. High temp K probes are limited by the jacket and the choice of insulation on the wires, not the wire itself. Of course the reader could be limited as well.
 
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