View Full Version : 0-1 heat treat problem
02-17-2007, 06:55 PM
I made a set of spotting buttons (six each of 1/4-5/8) out of 0-1. I machined them to have a ring around the point to make it easy to see the mark when transfered.
They were left in the oven too long (20 minutes) at 1475F. Quenched them in oil and checked the hardness which varied from 30 to 40RC. Wanted 56-58RC.
Is there anything that can be done to save these parts?
02-17-2007, 07:09 PM
Tool steel can be re-hardened. What you do next depends on why hardening failed in this case. I wouldn't have thought 20 min. would have been too long in the oven, but if parts have become decarburized, they can be carburized again to increase the carbon content in the surface.
If they were not up to temperature, or if they were cooled too slowly by maybe being in air too long before going into the oil, you can simply re-heat and re-quench them.
How much do you trust the temperature of your furnace?
What kind of oil were you using?
A couple of random guesses: they weren't quite hot enough or were allowed to cool too much before quenching, or the oil was too thick and didn't provide a fast enough quench.
I don't see why you couldn't try hardening them again.
02-17-2007, 07:39 PM
1. Are you sure about the temp?
2. Are you sure about the "O-1"?
3. Are you sure about the hardness test?
30-40RC is just slightly over mill hardness for O-1. Did the small ones test out to that too? It sounds like the temperature wasn't up to 1475 or as TG states, too much time before the quench. The larger pieces should be preheated then brought up to temp. The 20 minutes sounds about right but that time should be at temp--Not "in the oven time".
If you had your parts wrapped, you can just re-do them. If not, you might be better off doing a case hardening on them now.
02-17-2007, 09:56 PM
-Can't be 100% sure the oven is calibrated properly. They looked the same colour I use to heat treat 0-1 with the torch. They had a shell of carbon around them when I took them out, too hot maybe?
-I am absolutely sure the material is 0-1
-Pretty sure about the hardness test. I tried with a file to be sure.
The oven was pre-heated to 1200F, put the parts in and adjusted temperature to 1475F. Waited until it was up to 1475F, then 20 minutes later took parts out of the oven with no time to cool and quenched them in pre-warmed oil. Not sure what kind of oil it is, but it's there for heat treating and does work.
I took one part and tried to re-harden but it stayed unchanged.
02-18-2007, 12:32 AM
The oven was pre-heated to 1200F, put the parts in and adjusted temperature to 1475F.
That's one of the reasons I like W-1. It's not as sensitive to the hardening process. The larger pieces should be preheated to 1200 then brought up to 1475. Put the pieces in and bring the temp up to 1200. The parts need to be preheated as well as the oven. Hold the 1200 for about 10 minutes then bring the temp to 1475. Once at temp, hold for 20 minutes.
That's about the only thing I see different. The preheated oil is good too. I'd try and find a way to check your oven temp. The smaller pieces should have hardened past 40 with your process so I have doubts about the temps. The parts should have been a noticeable red coming out of the oven.
You might try checking with a magnet, if you can manage to do it before the pieces cool off too much -- they're pretty small. If they're hot enough, they shouldn't attract a magnet.
You could try quenching in water instead of oil.
02-18-2007, 11:22 AM
Iv had limited experience with hardening 0-1 but have built many of little bearing races with it for my bike cranks and they have turned out stellar,
some are very thin walled and I cant believe how stable the material is and im doing it the simplist posible way, build the race to where I want it --- heat it up cherry red with my little propane torch and dunk it and swirl in high sulfer cutting fluid, some of the races were press fit inserts and didnt shrink or deviate and I could not touch them with a high quality file, Iv been running ball bearings on them for hundreds of miles now and when i disassemble for inspection I cant believe how well these things are holding up...