Thread: Looking for the best heat treatment for O1

Hi All!

For some time now I make O1 steel razors, but I am not satisfied with the edges.The heat treatment is performed by a specialist, but now I bought a second hand HT Oven. I can practice a lot.

I honed quite a lot of razors(and knives), so the basis for comparison. My etalon is a Geneva Cutlery & Co. razor what I restored a couple of years ego.
The main problem is the edges of the knives made ​​by me are sensitive. I can hone them, but the fine edges soon corrupted. After some use or sometimes when in contact with the hone or strop. Form some glittering light on the edge.
Is there too large particle size? Poor HT? Does it have only these possibilities in these steel? Overhoning or bad sharpening?

A few more HT questions:

I use srp recepies, comments and Spazola video for my HT process. But I have a lot of questions.

I make normalizing 3 times. The first tempering cycle I put the steel to oven on room temperature. Is this ok, or I should preheat the razor?

I have a small oven (2kW) with thermo control. When I use my oven on higher temperature(1450-1500F) the stability is between +14C and -5C from adjusted value. Is this acceptable? On the tempering temperature this fluctuation is only +/- 2C.

I use 1 l canola oil for quenching. I'm not sure that an appropriate period of time inside the steel. I tried 5-10s and 30s periods. I tried to reach 400F before the air cool to room temperature. How can I monitor this process?

When I use HT-foil should I deep into the oil with foil or not? Because of the short time. And during the tempering process?

Sorry for my poor english.
Thank you for your help!

gregg

...I can hone them, but the fine edges soon corrupted. After some use or sometimes when in contact with the hone or strop. Form some glittering light on the edge. Is there too large particle size? Poor HT? Does it have only these possibilities in these steel? Overhoning or bad sharpening?

My first thought is that the grain/particle size is too large and yes, that is related to HT preparation. But help me refine my answers. Are you forging these to shape? If so this may be the problem. If stock removal it should be less of a problem, but the heat history of your bars is important. Did someone else forge the bars flat for you? I can't exclude the possibility of improper honing but it's not my area of strength.

....I use srp recepies, comments and Spazola video for my HT process. But I have a lot of questions.

Questions are good for everyone. The recipe on SRP is a standard process for O-1.

...I make normalizing 3 times. The first tempering cycle I put the steel to oven on room temperature. Is this ok, or I should preheat the razor?

Tell me more about your normalizing as this is intimately related to the final heat treatment and particle size. What are you using normalizing for? What temperature are you taking the blade to? Then you quench the blade, or allow it to cool to room temperature then repeat? Then complete the last hardening cycle? Tempering to me, is done after the heat treatment to harden the blade.

...I have a small oven (2kW) with thermo control. When I use my oven on higher temperature(1450-1500F) the stability is between +14C and -5C from adjusted value. Is this acceptable? On the tempering temperature this fluctuation is only +/- 2C.

This oven and controls should be adequate for O-1.

...I use 1 l canola oil for quenching. I'm not sure that an appropriate period of time inside the steel. I tried 5-10s and 30s periods. I tried to reach 400F before the air cool to room temperature. How can I monitor this process?

Hardening of the steel occurs at the speed of sound. I don't believe a human being could dip into the oil and withdraw fast enough to keep a blade from hardening. Monitoring temperature may require a thermocouple and thermometer. Follow this link: Thermocouple - Wikipedia, the free encyclopedia, and this one as a smith's shop will need a more durable thermocouple: Temp Sensor Notice the hard cladding and length. This allows for monitoring all sorts of high temperatures without getting your hand too near the heat. A K-type thermocouple will be accurate to 2300F and allow you to monitor your austenitizing temperatures as well.

...When I use HT-foil should I deep into the oil with foil or not? Because of the short time. And during the tempering process?

Foil is not an absolute requirement for HT of O-1. Its' more necessary when HT high alloy steels like stain resistant types. Leave the blade a little thicker, do not grind completely down to a finished thickness so you can remove some scale after the HT. There are brush on anti-scale coatings that are easier to work with than foil. O-1 needs to be quenched within 1-2 second from being removed from the heat and into the oil. Fumbling around with foil to remove it and the time is lost and your blade is soft. Quenching the foil wrapped blade won't cool the blade quickly enough and your blade will be softer than you want. You have to cool the foil, then the air inside the foil, then the blade inside the wrapper and too much time is lost.

I hope you can grasp my answers. Consider these and ask more questions. You are on the right path.

Mike, thank you for your rapid and detailed answer!

Originally Posted by Mike Blue

Are you forging these to shape? If so this may be the problem. If stock removal it should be less of a problem, but the heat history of your bars is important. Did someone else forge the bars flat for you? I can't exclude the possibility of improper honing but it's not my area of strength.

I bought the 1/4" thick rolled steel. I cut off the shape and grinding. Recently I have the shape cut with lazer. I leave it around 1/16-1/32" sometimes a bit less at the edge, but there is no difference in the result.

Originally Posted by Mike Blue

Tell me more about your normalizing as this is intimately related to the final heat treatment and particle size. What are you using normalizing for? What temperature are you taking the blade to? Then you quench the blade, or allow it to cool to room temperature then repeat? Then complete the last hardening cycle? Tempering to me, is done after the heat treatment to harden the blade.

I warm up my oven 1500F (or 1450F), then I put my razor into it around 3-5 minutes. Then I take out and then allowing it to cool slowly in
still air as long as it will not be all black(less then 1 min.). I do it two more times. Fourthly after heat up to 1500F (or 1450F) I put the blade into the
quench oil, preheated to 160F. Oh, no I think this is a problem. My oil is to hot, isnt it?

Originally Posted by Mike Blue

Foil is not an absolute requirement for HT of O-1. Its' more necessary when HT high alloy steels like stain resistant types. Leave the blade a little thicker, do not grind completely down to a finished thickness so you can remove some scale after the HT. There are brush on anti-scale coatings that are easier to work with than foil. O-1 needs to be quenched within 1-2 second from being removed from the heat and into the oil. Fumbling around with foil to remove it and the time is lost and your blade is soft. Quenching the foil wrapped blade won't cool the blade quickly enough and your blade will be softer than you want. You have to cool the foil, then the air inside the foil, then the blade inside the wrapper and too much time is lost.

The problem is I have some blade with to thin edge. This is the reason why I would like to use foil for these.

One more question: How many times can I HT a steel without significant loss?

Many thanks!

You say 1/6" steel?
How wide do you make your razor? The minimum ratio for thickness vs width is 1/4. Go below that and you will get problems with your edges.
For 1/6" steel, this means the maximum width of your razors should be 4/6" which is something like 5/8 and a bit.

Sorry, it was a typing mistake. Of course 1/4" (~6mm). Corrected.

Maybe thermal paints could be used to check for temperature, just an idea.

What does thermal paints mean?

Originally Posted by gregg71

What does thermal paints means?

These are used to check temperatures on metal pieces, used in experimental heat transfer studies. Different colors correspond to different temperatures.

http://www.thermalpaint.com/

I see, thanks!

Originally Posted by ferroburak

Maybe thermal paints could be used to check for temperature, just an idea.

I'm not sure the paints will be accurate enough. The range on the multi change paint is quite wide and the single change paints have odd set points that may not be good for heat treating steels. Even so, it looks like an inexpensive option but the price is unknown to me. I know some smiths who use clay pyrometric cones from the potter's shop to determine temperature.