01 re-heat treat?

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heatheninthehills

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Apr 14, 2009
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I've just started working with 01:( (will be the last for a while). my question is can this blade be re-heat treated? There was a problem with the quench and now only half of the blade is hard and there is a transition line that you can see. this piece is 17 inches in length and I would love to be able to save it. So would I just re anneal it and start my heat treat over? or are there special steps I need to take? Thanks in advance for any help.

Bennie
 
Normalize 2 or 3 times and then re-heat treat it. O-1 is forgiving like that.
 
heatheninthehills said:
I've just started working with 01:( (will be the last for a while). my question is can this blade be re-heat treated? There was a problem with the quench and now only half of the blade is hard and there is a transition line that you can see. this piece is 17 inches in length and I would love to be able to save it. So would I just re anneal it and start my heat treat over? or are there special steps I need to take? Thanks in advance for any help.

Bennie
Click to expand...

How was the steel dealt with? Like... Forged? Stock removal? Previously normalized? Full quenched or? What is your HT heat source? What is it you're figuring went wrong with the quench?

Not like TekSec is wrong or anything, I'm just curious...

Mike
 
My first guess would be the steel was not brought up and soaked at full temp then too slow to the quench. It probably went in tip first then cooled too much before getting the rest of the blade :D
 
Mike and Tecsek it was shipped to me annealed. stock removal profiled. the problem with quench( and the tub is maybe a foot from the forge) was a flairup that I was not expecting and I dropped the blade but its a thin tub and it fell to the side and took me a few seconds to scoop it up and finish quench( My real quench oil will be here by the weekend so I shouldn't have this problem again). my thermometer said that I was within 10 degrees thruout the 20 minutes I soaked it But maybe I didnt get the whole blade and thats why the line is like it is? As long as I can salvage it I will be happy. Not that I don't like 01 but I think I got in a little over my head so early in this. I plan on sticking with 1084 for awhile its much less of a headache :). Thanks for the replys


Bennie
 
Between 1084 and O1 I think it's a toss up for ease. O1 is a fairly simple steel to treat....but I can't really talk too much, I outsource my HTing :D What temp did you soak?
 
Tec the soak was anywhere from 1460 degrees faranheit to 1480 and i read that the soak should be around 1475 so I didnt think 5 degrees would make too much of a difference to burn it but the 15 degrees lower maybe hurt?
 
From what I've learned from others, including Peters' who does my stuff, you may have shot a little low. 1500 is the top end so maybe try for the 1475 to 1500 area, soak for 10 min at temp then quench.
 
Bennie,

O1 is a more difficult steel to maximize than 1084 is. It sounds like you have the temperature control needed to work with O1, though.

The grain size should have been equal in the steel when you got it and relatively small. Maybe it could have been normalized once as part of the HT process. The delay from soak to quench would have cooled the near-edge more than thicker areas. I guess it could have dropped enough to start forming perlite and create the line you see... differential hardening, upside down.

I've come across discussions on lower-than-normal-range austenitizing temperatures with longer soak times producing fully austenitized blades... mostly in connection with swords and water, and maybe keeping them from "tinking". I haven't understood what I've read about it well enough to describe it or apply it here.

Seems to me, the grain size is pretty well still equal but there is strain and it is unequal. A normalizing cycle would get rid of the strain, and make the structure the same thoughout. If I was going to worry about it (wanted to hedge my bets) a higher temp normalizing cycle to make sure all grain was the same size, then a lower temp normalizing cycle would refine the grain size. Some times I worry about things simply because I don't understand well enough to not worry...

Mike
 
tecSek thanks I'll try the higher temp and see how that works.

Mike maybe I'm not understanding the term but how exactly do I go about doing a normalize? I figured that the bar came ready to work then heat treat and would the stock removal not have acted as a normalization? Or is that one of the heats where you need to cool it real slow? thanks again guys for helping me on this.

Bennie
 
Bennie,

Normalizing in knifemaking is heating the steel above the critical range (A1 to A3/Acm) and air cooling in still or agitated air. Fully austenitized, in other words, then cooled relatively rapidly, but not quenched. If there is unequal grain size the normalizing equalizes it. If there is strain or different crystal structures, normalizing gets rid of the strain and makes all the crystals the same type. People who forge blades often normalize two or three times. The forging process, especially if forge welding damascus was part of the blade making, tends to cause large and unequal sized grain. Normalizing in this instance, 1x, makes the grain all of the same size, 2x, keeps grain equal sized but also makes them smaller, 3x, still equal but smaller yet. Small grain size in knife steel makes it tougher.

In your instance, normalizing after stock removal and before HT-ing isn't specifically necessary in that stock removal of tool steel doesn't change grain size. If machining was done in stock removal (wheel or belt grinding, milling, etc.), there will be some amount of strain in the steel. It can be removed with either normalizing or stress relieving. Stress relieving would be 1200F-1250F for an hour for O1 and a lot of similar knife steels.

So you know, temps above critical range can be high enough to cause grain growth. With your O1, the upper quench temp. of 1500F is a normalizing temp that will not grow grain size.

Mike
 
Mike

Thanks for the info. :) So If I have this right..... I need to take it up to about 1500 F and then let it cool say in front of a fan or just let it cool in the air x2 then start my heat treat over?

Bennie
 
Still air will do it, Bennie... I'm pretty sure agitated air needs to be strictly even flow.

Any temp up to 1600F (industry normalizing temp. for O1), then a lower temp for the second but not below the bottom end of O1 critical range... the low end quench temp of 1455F would be safe. Normalizing cycle temps are usually stepped down.

The idea of stepping down normalizing cycle temperatures is related to normalizing causing reduction of grain size, which causes lower hardenibility. I really don't understand it, though it sounds good... =] The idea is, as hardenibility lowers, the temperature at which grain growth starts also lowers. If 1600F is industry top end for normalizing O1 to make it happen quickly and avoid grain growth (generally a one time process in that world), further normalizing at 1600F, as the hardenibility is lowered, would/could/will/might have the steel in grain growth temps.

I don't know that normalizing O1 in the knife maker's world, say at 1525F/1500F/1475F, avoids grain growth any more than normalizing at 1525F 3x's.

Mike

Edit: Sorry Bennie... yes, to your question...
 
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Thanks Mike :thumbup: :) I'll get to it today and let ya know how it turns out.
I really should have gotten a smaller piece to break so I could see how the grain is after I'll definately have to get some more to test with.

Bennie
 
Kevin Cashen has discussed having test cupons of the same steel that are treated the same through all the HT steps as the blade. The cupon can have tests run on it with good certainty the results will be the same as if done on the blade.

If you have the ability to search BF, the specifics Kevin discussed should be findable.

Mike
 
Mike. Did the normalize yesterday. One at 1500f the other at around 1450f then reheat treated. So far everything is good :) Altho there was a small issue with a stress crack Just before the quench ( Its not a problem in the finished blade). Should I have held the normalize for a longer period? (I held them for about five minutes then let them cool).
As I said so far the file test turned out good and after sanding to 220 grit everything looks even. So thanks again for the advice.

Bennie
 
Mike. I did the Normalize yesterday. one at 1500 the other at 1450 then did the heat treat and so far everything looks good:thumbup:
I have the blade sanded to 220 so far and it all looks even. The file skates all across the blade so I know its hardened completely.
Thanks again To you and Tecsek for the help and advice. It wasn't as easy as I thought it would be to work with 01 but I guess I needed the experience with it. Oh yea and I will check for those posts you suggested. Thanks again

Bennie
 
Bennie,

Kevin has also posted on his methods of testing and the problems he has with using only file skating to verify hardness. In some ways, because the vast majority of knifemakers don't have Rockwell testers, immaculate attention to details of temperature and technique is all most have of "guaranteeing" correct hardness at points in the heat-treating process.

Wayne Goddard has a work-around for lack of Rockwell testing equipment and he has published articles in Blade Mag. on it... basically... having test cupons of known hardness (2 RHc apart) and comparing file action between blade and different hardness cupons until finding a match.

Because Kevin is not wrong about file testing for hardness having the problem of not telling true hardness in a number of common instances, for Wayne Goddard's method to work (and it does), a person has to have the mentioned "immacualte attention to details of temperature and technique"... known steel, proper method for the steel, proper method for HT processes.

Mike
 
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Mike Krall said:
Wayne Goddard has a work-around for lack of Rockwell testing equipment and he has published articles in Blade Mag. on it... basically... having test cupons of known hardness (2 RHc apart) and comparing file action between blade and different hardness cupons until finding a match.
Click to expand...
:thumbup: for that tip, Mike.
 
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