Heat treating S35VN

[skillgannon]

I picked up some 1/8" S35VN from pops. It should be coming in today or tomorrow. Its said 1/8" followed by .140-.156 so I'm assuming it runs thick. I have LN now so I should be able to do a proper heat treatment. Does anyone have a suggestion about where to start? My big question is about quenching it. I assume that I will want to do a lot if work before heat treatment. If I do it will be a chef knife with a lot of distal taper. Am I going to get a fast enough quench with my plates like that?

 

[Willie71]

I prefer to grind knives under 1/8” thick post heat treat. As far as I know, S35VN is fine with air quenching, so putting it in the aluminum plates should be more than enough. Some steels need a bit more speed than air quenching to get optimum structures, but I don’t think s35vn is one of them.

1950f gives me Rc60, and 1975f gives me Rc61.

Good steel. I probably should use more of it.

 

[skillgannon]

I prefer to grind knives under 1/8” thick post heat treat. As far as I know, S35VN is fine with air quenching, so putting it in the aluminum plates should be more than enough. Some steels need a bit more speed than air quenching to get optimum structures, but I don’t think s35vn is one of them.

1950f gives me Rc60, and 1975f gives me Rc61.

Good steel. I probably should use more of it.

I grind my AEB-L post HT. I was worried that S35VN would be a problem. I assume you just belt finish it?

 

[Willie71]

I grind my AEB-L post HT. I was worried that S35VN would be a problem. I assume you just belt finish it?

I’ve hand sanded it in the past, but not any more. Kitchen knives can be belt finished lengthwise as there isn’t a plunge.

 

[skillgannon]

This is my first test knife..140 stock. I ended up going with 2000 degrees with a 15min soak followed by quench plates and then cooled off in the snow and 3 hours of LN and 3 2 hour tempers at 400 degrees.

I had to grind down the heal to get it into the ln dewar. I will fix the profile later. What disadvantage comes with the higher austenizing temp?

 

[Willie71]

This is my first test knife..140 stock. I ended up going with 2000 degrees with a 15min soak followed by quench plates and then cooled off in the snow and 3 hours of LN and 3 2 hour tempers at 400 degrees.

I had to grind down the heal to get it into the ln dewar. I will fix the profile later. What disadvantage comes with the higher austenizing temp?

Higher aust temp results in less toughness, and larger grain. Vanadium steels are pretty good at resisting grain growth though.

 

[skillgannon]

Higher suet temp results in less toughness, and larger grain. Vanadium steels are pretty good at resisting grain growth though.

I probably should have followed your recipe but there was no soak time. When I found the data sheet it was showing 2000 for 15 minutes for 61Rc. I don't know how much difference 25 degrees makes.
I gotta figure out what to do if I want to do a blade wider than 1 7/8"

 

[Willie71]

I probably should have followed your recipe but there was no soak time. When I found the data sheet it was showing 2000 for 15 minutes for 61Rc. I don't know how much difference 25 degrees makes.
I gotta figure out what to do if I want to do a blade wider than 1 7/8"

Get a flask and pour the LN in for the cryo, then return it to the dewar.

You can also temper lower to increase hardness. I’m going to send samples to larrin to compare 2000f 400f temper to something like 1950f 300f temper. Hardness should be similar, but toughness might be different. There’s likely a minimum temper temperature that needs to be met though.

 

[skillgannon]

Get a flask and pour the LN in for the cryo, then return it to the dewar.

You can also temper lower to increase hardness. I’m going to send samples to larrin to compare 2000f 400f temper to something like 1950f 300f temper. Hardness should be similar, but toughness might be different. There’s likely a minimum temper temperature that needs to be met though.

I thought part of the 300 vs 400 degree temper was to complete the last bit of RA and that was the increased toughness. Is that still a factor after cryo? Or is there another mechanism involved.

 

[Willie71]

I thought part of the 300 vs 400 degree temper was to complete the last bit of RA and that was the increased toughness. Is that still a factor after cryo? Or is there another mechanism involved.

There is a transition from untempered martensite to tempered martensite. There is a min temp required for each steel, to the best of my understanding. This is the part I’m trying to figure out right now. I need to do a lot more reading on this.

Cryo does a great job of completing the conversion from retained austentize to untempered martensite, up to a certain alloy level. Some steels require high temper regardless of cryo. Z-wear and V4e seem to do well with cryo, but once we get to M4 level alloying, is cryo enough?

 

[skillgannon]

There is a transition from untempered martensite to tempered martensite. There is a min temp required for each steel, to the best of my understanding. This is the part I’m trying to figure out right now. I need to do a lot more reading on this.

Cryo does a great job of completing the conversion from retained austentize to untempered martensite, up to a certain alloy level. Some steels require high temper regardless of cryo. Z-wear and V4e seem to do well with cryo, but once we get to M4 level alloying, is cryo enough?

How do we check. I have a 3"x3'x.140" M4 that I could get into if there are thing to be tried.

 

[Willie71]

How do we check. I have a 3"x3'x.140" M4 that I could get into if there are thing to be tried.

I’ve got some coming from chuck. 1st is are we getting max hardness, and second, are we losing toughness? Testing will tell.

Warren

 

[Robert Erickson]

I’ve got some coming from chuck. 1st is are we getting max hardness, and second, are we losing toughness? Testing will tell.

Warren

IIRC from another thread you'll be checking both low and high temperature tempering on the M4?

 

[Willie71]

IIRC from another thread you'll be checking both low and high temperature tempering on the M4?

Yes. M4 is in the mail right now. I got the first of two boxes, and m4 is in the second box.

Warren

 

[MotorCityMike]

I can only add how I HT S35vn

1575 for 15 minutes, 1975 for 25 minutes. Quench between aluminum plates with compressed air. I do a hardness test to be sure it's within crucible specs. I get HRC 63

Temper at 400 for 2.5 hrs x2

I end up with HRC 59-60 which I think is S35vn's sweet spot

I've done dry ice & acetone cryo but haven't seen any real difference/benefit. I think the DI doesn't get cold enough

I'll be adding LN cryo sometime in the future but for now I'm quite happy with the results I'm getting

 

[Willie71]

I can only add how I HT S35vn

1575 for 15 minutes, 1975 for 25 minutes. Quench between aluminum plates with compressed air. I do a hardness test to be sure it's within crucible specs. I get HRC 63

Temper at 400 for 2.5 hrs x2

I end up with HRC 59-60 which I think is S35vn's sweet spot

I've done dry ice & acetone cryo but haven't seen any real difference/benefit. I think the DI doesn't get cold enough

I'll be adding LN cryo sometime in the future but for now I'm quite happy with the results I'm getting

Just to add to your post. I get an extra Rc point with LN over subzero. I haven’t heat treated without subzero, so I have no reference point on that.