Help with heat treating drill rod

[piper184]

Did you test with a magnet before quenching?
Did you temper them after quenching?

If it were me, I would take a sample of the stock and heat up a couple of inches to a bright red and test with a magnet. If non- magnetic, quickly quench in oil until cool to the touch. Then, without tempering, put the piece in a vise at the mid-point of the area that was heated. Smack it with a hammer. It should break or at least be very hard to bend.
Do the same thing with another sample but quench in water, not oil. Is it harder or more brittle?
If it still doesn't get hard, you probably don't have stock that can be hardened.

I have had stock that was hard, then I annealed it and machined it then attempted to re-harden it. It didn't work well. Turned out it was originally case hardened and was really not a very high carbon steel to begin with.

Try the same testing techniques with some other materials. Try an old drill bit for example. You should be able to get it to snap off without too much trouble.

Have you done a spark test comparison of your stock to a known hard metal? Sometimes that will tell you a lot, sometimes it is hard to tell. I have some old broken taps that I keep near the grinder, just for comparison.

 

[WobblyHand]

If that picture is just as you opened the oven, those pieces don't look so hot. Sorry about that pun.

1500F should be bright red. Those look dull red. Here are some rough color temperatures: https://www.m4040.com/Knifemaking/Steel2.htm

Based on that picture you are below the correct temperature. Items in direct contact with the refractory will take longer to come to temperature. Think your oven setting isn't quite right, or it's lying to you, or you aren't waiting long enough. Or the parts cooled off while you were fiddling with the camera! That's the sort of thing that happens to me - I get fumble fingered.

If the part gets bright red to orange, it won't be magnetic at all.

It could be the material. Get some from a different source, maybe McMaster for a small piece, and see if it is different. It is worth a try - especially if nothing is working for you. But, honestly - those parts don't look hot enough. They are too dark.

 

[EpicWill]

Did you test with a magnet before quenching?
Did you temper them after quenching?

If it were me, I would take a sample of the stock and heat up a couple of inches to a bright red and test with a magnet. If non- magnetic, quickly quench in oil until cool to the touch. Then, without tempering, put the piece in a vise at the mid-point of the area that was heated. Smack it with a hammer. It should break or at least be very hard to bend.
Do the same thing with another sample but quench in water, not oil. Is it harder or more brittle?
If it still doesn't get hard, you probably don't have stock that can be hardened.

I have had stock that was hard, then I annealed it and machined it then attempted to re-harden it. It didn't work well. Turned out it was originally case hardened and was really not a very high carbon steel to begin with.

Try the same testing techniques with some other materials. Try an old drill bit for example. You should be able to get it to snap off without too much trouble.

Have you done a spark test comparison of your stock to a known hard metal? Sometimes that will tell you a lot, sometimes it is hard to tell. I have some old broken taps that I keep near the grinder, just for comparison.

I haven't done that yet but I'll give it a shot today. I have a piece of O1 on order, hasn't shown up yet. I tested with a small piece of 4140 yesterday though and it seemed to harden properly - between 50-55HRC. I'm starting to think the drill rod may not have been labeled correctly which would be a surprise.

I've tried doing a spark test but I don't have a known good piece of O1 here at the moment. I have some pulleys that we made from 4140 in the oven now for a cycle.

If that picture is just as you opened the oven, those pieces don't look so hot. Sorry about that pun.

1500F should be bright red. Those look dull red. Here are some rough color temperatures: https://www.m4040.com/Knifemaking/Steel2.htm

Based on that picture you are below the correct temperature. Items in direct contact with the refractory will take longer to come to temperature. Think your oven setting isn't quite right, or it's lying to you, or you aren't waiting long enough. Or the parts cooled off while you were fiddling with the camera! That's the sort of thing that happens to me - I get fumble fingered.

If the part gets bright red to orange, it won't be magnetic at all.

It could be the material. Get some from a different source, maybe McMaster for a small piece, and see if it is different. It is worth a try - especially if nothing is working for you. But, honestly - those parts don't look hot enough. They are too dark.

I think the picture is washed out due to how bright the elements were when I snapped the pic. The oven had been sitting at 1500 for about 20 minutes and I had the camera ready before I opened the door so it was only open for a second or two before the pic snapped. I didn't test them with a magnet but once the current parts are finished I'll toss a shaft back in and let it heat up and see what happens.

 

[WobblyHand]

Wouldn't surprise me if the material is mislabeled. I bought some "303" and it was horrible to machine, unlike the 303 I bought from McMaster, which was very nice to machine. Wish there was a way to inexpensively and accurately analyze materials (not a spark test).

Fortunately, I didn't buy a lot of the crap 303 from that suspect supplier. Need to mark that "303" as junk, before I forget!

 

[EpicWill]

Wouldn't surprise me if the material is mislabeled. I bought some "303" and it was horrible to machine, unlike the 303 I bought from McMaster, which was very nice to machine. Wish there was a way to inexpensively and accurately analyze materials (not a spark test).

Fortunately, I didn't buy a lot of the crap 303 from that suspect supplier. Need to mark that "303" as junk, before I forget!

So I just tested a piece from the bag and heated it about as hot as I could get it with two propane torches and quenched and it's HARD. The 60HRC file skates over and the 65 just barely bites it. So the material is good. Seems the furnace isn't getting hot enough.

I heated it with the torches to the same color as the parts that came out of the oven and it was just barely magnetic still so I think it's just not getting hot enough. That was with the oven set to 1500F. I also had the parts elevated on the left-to-right rods you see placed on the kiln floor. The parts I was treating were laid front-to-back on top of the left-to-right rods. I'll have to contact Paragon about it seemingly not getting hot enough. My only tester maxes out at 1000F so it won't read any higher. I do have a ton of industrial thermocouples and controllers but the TCs are only J type and max out at 900F (https://www.automationdirect.com/ad...ansmitters/temperature_sensors/thmj-d08l06-01). I'll order a type K and then test the oven.

I'm also going to throw a piece of drill rod in and bump the oven in 100º increments until the rod is orange and nonmagnetic.

 

[WobblyHand]

If you need some type K TC wire to have on hand (make your own) and you can afford to wait a couple weeks, I have ordered from this link and found the wire to be pretty good. The insulation is rated to 882C (1619F). Might be ok for occasional use. https://www.ebay.com/itm/165995550692?var=465499368008 Works pretty well with my PID controller. Just twist the wires together tightly (pliers) and you have a TC. Attach to a type K plug (yellow) and you would be good to go.

 

[EpicWill]

Ok so I found a KTC and a reader that'll read over 1000F. The oven is within 6F but the probe is slightly higher than the internal TC so that's to be expected. I also took a pic of the SS bag inside that's raised off the floor by 1/4"



You can see the built-in TC sticking out of the RH wall while the external probe is the thin wire sticking in through the door.

 

[ericc]

Spark test! O1 is pretty easy to identify. If you think your torch is not heating the material enough, cut an annular heat stop groove with a hacksaw with about 1/4" remaining. The torch will definitely get this hot enough. I would suspect the wrong material. A small piece is inexpensive on Ebay, and you can add it to your spark test keychain.

 

[G-ManBart]

So I just tested a piece from the bag and heated it about as hot as I could get it with two propane torches and quenched and it's HARD. The 60HRC file skates over and the 65 just barely bites it. So the material is good. Seems the furnace isn't getting hot enough.

I heated it with the torches to the same color as the parts that came out of the oven and it was just barely magnetic still so I think it's just not getting hot enough.

I'm also going to throw a piece of drill rod in and bump the oven in 100º increments until the rod is orange and nonmagnetic.

I've done a fair amount of heat treating and tempering in the blacksmithing realm and I've seen people have similar issues, often due to confusing terminology. People claim "heat it to cherry red then quench" and that is almost never hot enough. Maybe it depends on the variety of cherry, but to me cherry red is a fairly dark red...not hot enough. A bright red to orange is more like it but the magnet test and bumping the temps is a smart way to go.

Something to consider, if you haven't already, is that repeated heat cycling to really high temps can cause the grain size to increase leading to fractures under stress. So, if you've got parts that have been heated several times they might not be ideal for anything critical. There are ways to thermal cycle steel to reduce the grain size, but you'd need to research the proper process/temps for O1 as it varies with the steel type.

 

[pontiac428]

My two cents is you need to elevate the material you are treating into the center of the furnace. The furnace floor does not get the benefit of either radiant heat or convection, it just gets conducted heat, eventually. Put a furnace brick or two in there and get the work up to where the heat is.

You can learn a lot from a magnet. I honestly don't know why you've been putting that lesson off. Like, Eureka, dude.