440C/M2 mismatch

O

olivier coen

Joined
Sep 18, 2020
Messages
46
Dear god's of knowledge.
I made a mistake, at least I think I did.
My great masterplan was to make a San mai with M2 coresteel and 440c sides. The thinking being that 1' I have a lot of M2 and I absolutely love it as a knife steel and 2' I had easy access to 440c.
The high tempering for the M2 should give good toughness to the 440c at a low RC.
On paper I would get a beautiful, tough, high edge retention... Perfect knife 😅

But somehow I assumed M2 needed an aus temp of 1090°c which is to high for 440c but seemed acceptable since it wasn't the cutting edge in the first place.

But of course M2 needs 1150°c and at that temp I'm afraid I will totally ruin the 440c and get pebble sized grains.

What are your thoughts?
Thx already
 
olivier coen said:
Dear god's of knowledge.
I made a mistake, at least I think I did.
My great masterplan was to make a San mai with M2 coresteel and 440c sides. The thinking being that 1' I have a lot of M2 and I absolutely love it as a knife steel and 2' I had easy access to 440c.
The high tempering for the M2 should give good toughness to the 440c at a low RC.
On paper I would get a beautiful, tough, high edge retention... Perfect knife 😅

But somehow I assumed M2 needed an aus temp of 1090°c which is to high for 440c but seemed acceptable since it wasn't the cutting edge in the first place.

But of course M2 needs 1150°c and at that temp I'm afraid I will totally ruin the 440c and get pebble sized grains.

What are your thoughts?
Thx already
Click to expand...
I don't know anything about what you are doing but I love M2 and it sounds like an awesome project if it works. If it does let me know if it works. I would love to see it.
 
Storm W said:
I don't know anything about what you are doing but I love M2 and it sounds like an awesome project if it works. If it does let me know if it works. I would love to see it.
Click to expand...
If it is a reasonable idea I'll give it a go but if it's utter stupidity I'd rather put my time in another project, far to many of them anyway.

We'll see
 
I know nothing about M2, but since M2 is the core where you want fine grain, and the 440C is the outside where you don't care about the grain size I wouldn't worry about it. Normally for San Mai you HT for the core and don't worry about the outside layers. That's why wrought iron or mild steel can be used for San Mai.
 
Ken H> said:
I know nothing about M2, but since M2 is the core where you want fine grain, and the 440C is the outside where you don't care about the grain size I wouldn't worry about it. Normally for San Mai you HT for the core and don't worry about the outside layers. That's why wrought iron or mild steel can be used for San Mai.
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I agree for mild steel or wrought iron which don't harden in the first place.
But high alloy steel can become quite brittle if overheated if I am correct.
I'm starting with 3,2 millimetres for the sides and 2 for the centre so a lot of the work will have to be done by the 440c.
I'm ok with a hardness in the high 40's but I do want some toughness out of it.
Otherwise it's somewhat of a pointless experiment.

I made San Mai with 304 before and although beautiful I wasn't completely happy with the tendency to bend. That's one of the reasons I was going to give it a try with 440c
 
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I think, 440c harden at 1180c/2156F m2 aust would produce 30's rc due to massive RA. at this hardness it would be quite ductile, it has large plasticity range which occurs in intragranular mode hence super large grain brittleness doesn't applies inside this plasticity range, in other words - ductile huge grain is not a problem in san mai role.
 
Thanks everyone!

Mr Bluntcut, if I understand correctly I will probably end up with something similar to a San Mai with 304? Maybe marginally harder but not in any way 'springy'.

Don't know if there is benefits to using 440c in that case.

Or did I misunderstand? (Still slightly hopeful)

And thx Stacy but if I ignore the 440c where is the point of using it. Although not super expensive there's a lot of cheap stainless if I end up with ductile steel.
I kind of hoped to get somewhere in the high middle between ductile and hard... Basically spring steel territory.

Don't know an affordable stainless that benefits from the high temperatures for M2 so I guess I have to scrap the idea.

Thanks all for the knowledge!
 
olivier coen said:
Thanks everyone!

Mr Bluntcut, if I understand correctly I will probably end up with something similar to a San Mai with 304? Maybe marginally harder but not in any way 'springy'.

Don't know if there is benefits to using 440c in that case.

Or did I misunderstand? (Still slightly hopeful)

And thx Stacy but if I ignore the 440c where is the point of using it. Although not super expensive there's a lot of cheap stainless if I end up with ductile steel.
I kind of hoped to get somewhere in the high middle between ductile and hard... Basically spring steel territory.

Don't know an affordable stainless that benefits from the high temperatures for M2 so I guess I have to scrap the idea.

Thanks all for the knowledge!
Click to expand...
304 is very soft near bottom of HRB = doesn't even translate to 1 hrc. 30-ish hrc 440c is quite strong, maybe 70% of full spring elasticity range. So 440c/m2 san mai will be quite stiff and flexible rather than prone to permanent bend. You could use less expensive aebl instead of 440c, probably/guessing harden to 28-34rc.
 
bluntcut said:
304 is very soft near bottom of HRB = doesn't even translate to 1 hrc. 30-ish hrc 440c is quite strong, maybe 70% of full spring elasticity range. So 440c/m2 san mai will be quite stiff and flexible rather than prone to permanent bend. You could use less expensive aebl instead of 440c, probably/guessing harden to 28-34rc.
Click to expand...
Ok,
I misunderstood your other comment apparently.
Thanks for clarifying. My knowledge of metalurgy is still far to limited, need to address this.

Will give it a go and will let you know how it turned out.
Very grateful for the information.
 
Next time I come with an idea, can please someone tell me it's incredibly hard and not worth the trouble? 🙏,😅

After several failed attempts (to hot, to cold, to much power) I finally managed to make a decent billet today. Didn't want to forge out the blade completely as I failed to many times at just making the San Mai in itself, also wanted to keep the M2 cleanly in the middle of the piece.

Also rough heat-treated a piece of salvaged scrap from the failures.

I probably should have known since M2 is fairly rust resistant but I didn't manage to get the M2 etched dark once heat-treated... Before heat-treat it was all ok. I used ferrochloride by the way.

Anyone has an idea how to do this?

Thanks for the support!
 
Maybe try using different acids? Lemon juice, vinegar, muriatic...
 
A.McPherson said:
Maybe try using different acids? Lemon juice, vinegar, muriatic...
Click to expand...
Muriatic attacked the 440...
To be clear; it etched but didn't get black and more hazy than I expected, might be because of long soak times
Maybe the good old instant coffee will do the job.
 
so why not use a different stainless that requires a higher temperature for the sides ??
something like VG10/13c27/Elmax.. they require a 2000/2200 degree hold before hardening..
heat treated in molten salt could control the temp perfectly on both metals...
no compromise that way..
 
Pinoy Knife said:
so why not use a different stainless that requires a higher temperature for the sides ??
something like VG10/13c27/Elmax.. they require a 2000/2200 degree hold before hardening..
heat treated in molten salt could control the temp perfectly on both metals...
no compromise that way..
Click to expand...

The idea was to have a spring tempered stainless side steel (preferably not to expensive) and a hard carbon coresteel. I was basically looking for the 'compromise'

I don't know about 13c27 and not excessively about vg10 (I thought recommended tempering was at 200 °c/400F but I could be wrong) Elmax at 1150°c/2100F and tempered at 500°c/930F would give me high edge retention.... For a sidesteel. It's a tough steel but only compared to high edge retention steel.
Not even sure if it would be tougher than the M2 core.

Not saying it's a bad idea, just not what I had in mind.
And expensive to try to get it to work properly 😅
 
olivier coen said:
The idea was to have a spring tempered stainless side steel (preferably not to expensive) and a hard carbon coresteel. I was basically looking for the 'compromise'

I don't know about 13c27 and not excessively about vg10 (I thought recommended tempering was at 200 °c/400F but I could be wrong) Elmax at 1150°c/2100F and tempered at 500°c/930F would give me high edge retention.... For a sidesteel. It's a tough steel but only compared to high edge retention steel.
Not even sure if it would be tougher than the M2 core.

Not saying it's a bad idea, just not what I had in mind.
And expensive to try to get it to work properly 😅
Click to expand...
I have two pieces prepared for forge welding .Core is M35 and on sides 13C27 ,I'm waiting for spring to finish the project, it's too cold now in my shop .Dimensions are 23 cm. long, 4 cm wide. I will just weld them together and then shape knife from that , no draw no hammering .I will just heat them and gently set the weld .
You can look here how i done that in my first try to make san-mai

First san-mai weld

Well , few hours earlier I would not believe that it would turn out this way . The core is perfectly centered ,no sign of not welded part at all . Core is 1.5mm 1.2519 carbon steel and for side I use 1.2mm 304 stainless . 1.2519 was hardened /63-65 hrc/ before welding with 304 stainless .For...
bladeforums.com bladeforums.com
 
Natlek said:
I have two pieces prepared for forge welding .Core is M35 and on sides 13C27 ,I'm waiting for spring to finish the project, it's too cold now in my shop .Dimensions are 23 cm. long, 4 cm wide. I will just weld them together and then shape knife from that , no draw no hammering .I will just heat them and gently set the weld .
You can look here how i done that in my first try to make san-mai

First san-mai weld

Well , few hours earlier I would not believe that it would turn out this way . The core is perfectly centered ,no sign of not welded part at all . Core is 1.5mm 1.2519 carbon steel and for side I use 1.2mm 304 stainless . 1.2519 was hardened /63-65 hrc/ before welding with 304 stainless .For...
bladeforums.com bladeforums.com
Click to expand...
Hey Natlek, I don't know 13c27. Pinoy also mentioned it, is it another Sandvik steel?

I started with 2,2mm M2 so I had to draw it out.
Your 1200°c welding temp seems a little high, I went far lower, about 1050°c. And about 20min soak time

The challenge for me was to work hot enough to weld and not to hot to crack the steel. 1000°c +/-50°c seemed to be the sweet spot.

I welded 2 sacrificial pieces of steel to the sides to have more mass. This equalised the temp a bit and gave me the ability to work a little bit longer.

Also I used my hydraulic press... Think that helps but apparently light hammer blows do the job too.

Spring will be there soon 😋
 
olivier coen said:
Hey Natlek, I don't know 13c27. Pinoy also mentioned it, is it another Sandvik steel?

I started with 2,2mm M2 so I had to draw it out.
Your 1200°c welding temp seems a little high, I went far lower, about 1050°c. And about 20min soak time

The challenge for me was to work hot enough to weld and not to hot to crack the steel. 1000°c +/-50°c seemed to be the sweet spot.

I welded 2 sacrificial pieces of steel to the sides to have more mass. This equalised the temp a bit and gave me the ability to work a little bit longer.

Also I used my hydraulic press... Think that helps but apparently light hammer blows do the job too.

Spring will be there soon 😋
Click to expand...
It s typo , I mean on 12c27 .
Look in this thread about different steel from Sandvik .All of them are good for sandwich with M2

14c28n heat treatment

Hello everyone, I'm in to knifemaking since a few years and I mostley use O1. Recently I bought some 14c28n and I have some doubts about the heat treat. On sandvik page they say that the hardening temp is 1922F but do I ramp it to that temperature or I put it in the oven at that temperature...
bladeforums.com bladeforums.com
 
If the M2 is not etching then it is probably under-tempered. You will need to temper at or above 1000F to get the M2 to etch dark. The problem you have is the two materials are not metallurgically compatible at all. Heat treat, corrosion resistance is all on opposite spectrums.
 
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