01 pre soak

L

LRB

Joined
Feb 28, 2006
Messages
1,494
If one normalizes 01, is it necessary, or even desirable, to still give it a pre- soak at 1200o, before soaking at quench heat. This concerns blades done by stock removal.
 
LRB, if I remember correctly from what I was reading last evening, normalization is desireable after forging, after heavy machining, but before light machining. (if one is concerned with dimentional changes during heat treat.) The pre-soak at 1200 was what they called a "stress relief" prior to austenization. With stock removal method, I'm not so sure it would be as necessary as the soaking at austenetizing temp. I wish I could go verbatim from the book (ASM Handbook Heat Treating, Cleaning and Finishing Vol 2 1964) but I left it at work last night, so I'm left with my memory to work from. If I'm wrong, someone please correct my post. I hope at least some of this was correct and helped in some way. -Matt-
 
Greaseman, was what you were reading in regards to 01? 01 will air harden after being brought to red heat, so much that it will destroy common drill bits. I bring this up in reference to the book saying, "before light machining". It sounds like the book may be generalizing. Thanks for the input though.
 
Now you've got me thinking. I tell you what, I've got to go past work in a little while. I'll stop by and get the book and let you know what the book says. My memory isn't the best, so it is possible that I was mistaken. -It'll be a few hours before I get back. -Matt-
 
The 1200 F step is usually for large or complex sections to equalize temperature before hardening and minimize distortion. For a blade it's usually not necessary.
 
OK I got the book from work and I'll begin by quoting the section on Normalizing as it pertains to oil hardening cold work tool steels:

"Normalizing is desirable and sometimes necessary for parts that have been forged or heated previously to temperatures much higher than the proper austenetizing temperature, because it produces a more uniformly refined grain structure. Recommended normalizing temperatures are given in table 8. (Table 8 stated the temp is 1600f recommended) Work should be held at temperature for 15 minutes to 1 hour, depending on section size; prolonged soaking is not desirable. When tools are to be hardened after normalizing, precautions must be taken in order to avoid decarburization during normalizing. If tools are to be subsequently machined, annealing is recommended in preference to normalizing."

If you were just stock removing O-1 in it's annealed state from the factory, I would imagine that you could go right from grinding into the heat treat, since normalization isn't a necessary step and annealing had already been done for you. More to follow
 
Here is the section on Stress Relieving as it pertains to oil hardening cold work tool steels:

"IN most instances, stress relieving of finished tools prior to final hardening does not noticeably lessen distortion during hardening. If extreme dimesional accuracy after hardening is required, tools should be stress relieved after rough machining, but before final light machining. A recommended stress-relieving treatment consists of heating to 1200f to 1250f, holding at temperature for one hour per inch of thickness, and then air cooling."

It seems that I mixed it up in my original post, and I apologize for that. Mete's post is right in context (as usual, thanks Mete!) I also forgot to add that if you do normalize, you should follow it with an anneal or like you stated, it could wear out some tools! :eek:

LRB, I'd be more than happy to post info from other sections if you need them for anything, Preheating, Austenitizing, Quenching. Martempering, and Tempering.

Again, the book quoted is the ASM Metals Handbook, Vol 2, Heat treating Cleaning and Finishing, 8th Edition 1964. Yeah it's old, but the price was right! :D -Matt-

I hope I don't get sued for quoting from that book!
 
Greaseman, I have recently found that normalizing after grinding 01, seems to reduce warpage. I am still experimenting with this, but so far it has made a noticable difference. As far as I know, it can do no harm, but I was concerned that a 1200o pre-soak might undo the finer grain that normalizing produces, or allow carbon to precipitate into the grain boundaries, or both. I read most everything Kevin Cashen, or Mete' writes on heat treat, but often some of it gets over my head, or I cannot remember exactly what they said.
 
LRB said:
Greaseman, I have recently found that normalizing after grinding 01, seems to reduce warpage. I am still experimenting with this, but so far it has made a noticable difference. As far as I know, it can do no harm, but I was concerned that a 1200o pre-soak might undo the finer grain that normalizing produces, or allow carbon to precipitate into the grain boundaries, or both. I read most everything Kevin Cashen, or Mete' writes on heat treat, but often some of it gets over my head, or I cannot remember exactly what they said.
Click to expand...

Hey that's good news if you are getting a reduction in warpage! I may have to try that myself. I wouldn't think that a 1200f soak would undo any finer grain. The way I understand it, grain growth is a result of time and temperature at or above the critical temperature. Now I could be wrong here too, but for some reason that is pretty stuck in my head. As far as carbon precipitation into grain boundaries...perhaps someone could step in and help with that, because I'm still trying to wrap my head around that issue. -Matt-
 
Let's separate things ! Stress relief [as after machining , grinding] is usually done at 1200 F. Preheat is usually done at 1200 F also. After stress relief the part is cooled to room temperature. Preheat is just that 1200 F , hold, then raise to hardening temperature.
 
Mete', I did know that, but be aware that you are dealing here with someone who suffers from cranial hyperdensity, and a lack of higher academic exposure. What about carbon precipitation into the grain boundaries at the presoak temperature? we've established that the presoak is not really necessary with a knife blade, but if done, would it allow carbon precipitation, given that the time at temp could be twenty, or thirty minutes, or would it simply be an unnecessary, but harmless step, that should be eliminated for time sake?
 
Your not going to have any problems because grain growth, precipitation of carbides , decarb, scale, etc are next to nothing at 1200 F.
 
You can't grow grain and precipitate carbides until you get them into solution, which is above 1350F. Like mete said, it isn't a factor at 1200F.
Stacy
 
A short preheat at 1200 will not put much carbide in the grain boundaries, and the idea is to always have enough soak to reverse any segregation or spheroidizing that could have occurred on the way up. The heavy carbide laden grain boundaries require incompetence on a scale only bumbling bladesmiths can achieve by getting too creative with a process that was perfected long ago.

I would venture to guess that many times even the guys in industry get a little confused on which of the details they are going for and seeing (or we misinterpret what it is that they say). By this I refer to the idea of a preheat or presoak being a stress relief in the traditional sense, in that it removes any stored energy left from previous operations. There will be a reorganization of the matrix as soon as recrystalization temp is reached, for reducing distortion the more important factor is that you are holding at a lower temperature in order for the steel to thermally equalize before proceeding through Ac1 when the heating expansion will be reversed in a marked contraction as the steel shifts to the gamma iron phase. If this is not done evenly there could be distortion cause by some parts of the blade shifting before others. In this sense one can view the preheat much the same as the marquench in that you reduce distortion by equalizing before proceeding with an allotropic shift.

However as mete previously mentioned in blade cross sections the deviations in expansion/contraction rates are minimal compared to what industry has to deal with. We really don't appreciate how easy we have it by dealing with shapes as simple as flat stock with a bevel;).
 
You must log in or register to reply here.
Back
Top