M390 questions

Stang Bladeworks

Stang Bladeworks

Joined
Feb 19, 2018
Messages
660
Hi

I would like to start working with m390 but i have some questions first.

Does it tend to warp during any part of heat treating or cryo? For now my go to is cpm154 and I have never had it warp. I quench in plates then cryo then temper.

Do people typically follow the datasheets for heat treating. Does anyone have any recipes that work well?

I usually grind post HT. I imagine m390 will make this more challanging. Does anyone have any experience grinding m390 hard?

How is it in general to work with? Surface grinding, machining soft, drilling etc?

Thanks for reading. My apologies if this is a repeat question. I couldn't find all the answers I was after by searching around.
 
It's not too bad to work with compared to any other super steel. Its only quirk is its sensitivity to quench rate. It needs quenched pretty quick for an air quench.
 
Stang Bladeworks said:
Hi

I would like to start working with m390 but i have some questions first.

Does it tend to warp during any part of heat treating or cryo? For now my go to is cpm154 and I have never had it warp. I quench in plates then cryo then temper.

Do people typically follow the datasheets for heat treating. Does anyone have any recipes that work well?

I usually grind post HT. I imagine m390 will make this more challanging. Does anyone have any experience grinding m390 hard?

How is it in general to work with? Surface grinding, machining soft, drilling etc?

Thanks for reading. My apologies if this is a repeat question. I couldn't find all the answers I was after by searching around.
Click to expand...

Data sheets? Nobody follows data sheets. Who's been talking to you, man? Do you want to be talking about heat treatment data sheets or do you want to be talking about your own knife money-funded plane, baby! Data sheets...forget about data sheets, and let me ask you a question: Ferrari - red, or black?
 
Nathan the Machinist said:
It's not too bad to work with compared to any other super steel. Its only quirk is its sensitivity to quench rate. It needs quenched pretty quick for an air quench.
Click to expand...
Thanks,
Do you quench it in plates? Can you do multiple blades at once or are the plates typically too hot after one? I use 14" x 1" plates.
 
Mecha said:
Data sheets? Nobody follows data sheets. Who's been talking to you, man? Do you want to be talking about heat treatment data sheets or do you want to be talking about your own knife money-funded plane, baby! Data sheets...forget about data sheets, and let me ask you a question: Ferrari - red, or black?
Click to expand...
Black
 
Mecha said:
Data sheets? Nobody follows data sheets. Who's been talking to you, man? Do you want to be talking about heat treatment data sheets or do you want to be talking about your own knife money-funded plane, baby! Data sheets...forget about data sheets, and let me ask you a question: Ferrari - red, or black?
Click to expand...

M390 is a prime example of a steel whose data sheet, while not exactly wrong, is definitely wrong for knife makers. I think their numbers were developed from a slow atmosphere quench, which makes sense when you look at the data sheet and they're showing things like big ass extruder screws. These are things with high abrasive wear and corrosion resistance issues but no edge stability issues. Given a more rapid quench the heat treat response from M390 is much better and you will achieve substantially higher harnesses from a given austenization temperature.

A lot of M390 has so-so edge retention in normal use (without resorting to overly obtuse geometry) due to less than excellent edged stability. I think a lot of this is caused by issues with the structure due to a less than optimal heat treat for a knife application.

I think it is a good steel with good potential and lends itself well to custom knife makers because the optimal heat treat for the steel is difficult to scale up for a lot of manufacturers.
 
Nathan the Machinist said:
M390 is a prime example of a steel whose data sheet, while not exactly wrong, is definitely wrong for knife makers. I think their numbers were developed from a slow atmosphere quench, which makes sense when you look at the data sheet and they're showing things like big ass extruder screws. These are things with high abrasive wear and corrosion resistance issues but no edge stability issues. Given a more rapid quench the heat treat response from M390 is much better and you will achieve substantially higher harnesses from a given austenization temperature.

A lot of M390 has so-so edge retention in normal use (without resorting to overly obtuse geometry) due to less than excellent edged stability. I think a lot of this is caused by issues with the structure due to a less than optimal heat treat for a knife application.

I think it is a good steel with good potential and lends itself well to custom knife makers because the optimal heat treat for the steel is difficult to scale up for a lot of manufacturers.
Click to expand...

Great perspective, Nathan the Machinist. :thumbsup:
 
Nathan the Machinist said:
M390 is a prime example of a steel whose data sheet, while not exactly wrong, is definitely wrong for knife makers. I think their numbers were developed from a slow atmosphere quench, which makes sense when you look at the data sheet and they're showing things like big ass extruder screws. These are things with high abrasive wear and corrosion resistance issues but no edge stability issues. Given a more rapid quench the heat treat response from M390 is much better and you will achieve substantially higher harnesses from a given austenization temperature.

A lot of M390 has so-so edge retention in normal use (without resorting to overly obtuse geometry) due to less than excellent edged stability. I think a lot of this is caused by issues with the structure due to a less than optimal heat treat for a knife application.

I think it is a good steel with good potential and lends itself well to custom knife makers because the optimal heat treat for the steel is difficult to scale up for a lot of manufacturers.
Click to expand...
Thanks for the info. The data sheet seems to show a much lower max hardness. So far the most appealing recipe I have found is courtesy of Larrin showing a Rockwell of nearly 62HRC. I have yet to find anything that indicates it can be taken higher. I guess I will do some experimenting with scrap pieces and try to dial in some settings. I have heard a lot of talk lately about M390 in the 62 to 64 range and I was wondering if anyone had a recipe to get there. so far from my research I have found nothing. I will study the curves and play with things a bit to see what I can get.
 
Stang Bladeworks said:
Thanks for the info. The data sheet seems to show a much lower max hardness. So far the most appealing recipe I have found is courtesy of Larrin showing a Rockwell of nearly 62HRC. I have yet to find anything that indicates it can be taken higher. I guess I will do some experimenting with scrap pieces and try to dial in some settings. I have heard a lot of talk lately about M390 in the 62 to 64 range and I was wondering if anyone had a recipe to get there. so far from my research I have found nothing. I will study the curves and play with things a bit to see what I can get.
Click to expand...

Now you're talkin'! :thumbsup::D
 
If max hardness is what you're after then use 300F tempering. Test a range of austenitizing temperatures in 25 or 50F increments. And use cryo, of course, directly after the quench and before tempering.

Even when you're copying from a datasheet or from someone else I recommend the same procedure to see how the heat treatment matches up and if your batch of steel or furnace is different.
 
Larrin said:
If max hardness is what you're after then use 300F tempering. Test a range of austenitizing temperatures in 25 or 50F increments. And use cryo, of course, directly after the quench and before tempering.

Even when you're copying from a datasheet or from someone else I recommend the same procedure to see how the heat treatment matches up and if your batch of steel or furnace is different.
Click to expand...
Thanks for your reply. I will do some testing and try to determine the optimal numbers for my knives. I'm wondering in your opinion, is it advisable to attempt to go harder than 62? My application is a 3.5inch bladed framelock. I understand that everything is a trade off with heat treating I'm just looking for a good all around number to shoot for to start with. I plan to deviate slowly from that point and dial in an ideal hardness for my application. Edge retention is a priority for sure but not the only one. I don't want to sacrifice too much strength to the point where you have to baby the knife. I have been attempting to analyze charts as I find them, there just seems to be a huge range from one source to the next when compared to some other steels. Obviously some real world testing is needed on my end before I can say anything definitive. I will post up the results from my testing once it is completed in the hopes it may help someone else down the road.
 
Cultrotech knives are 63rc or so on their m390 and apparently it has incredible edge retention. There are some videos on YouTube but you have to enable English subtitles, in one the guy talks about their ht.
 
Whether it will work st the higher hardness will depend on the edge geometry and the end user. Some experimentation is necessary to see how much it can take, which will give you confidence in the knife' s capabilities.
 
Larrin said:
Whether it will work st the higher hardness will depend on the edge geometry and the end user. Some experimentation is necessary to see how much it can take, which will give you confidence in the knife' s capabilities.
Click to expand...
I read some article from Roman Landes some time ago.He says that if we compare two edge ,same steel and same hardness . One 0.10mm behind edge and one 0.2mm behind edge knife with 0.2mm behind ege is FOUR time stronger then other one with 0.10mm .
 
Stang Bladeworks said:
Thanks for the info. The data sheet seems to show a much lower max hardness. So far the most appealing recipe I have found is courtesy of Larrin showing a Rockwell of nearly 62HRC. I have yet to find anything that indicates it can be taken higher. I guess I will do some experimenting with scrap pieces and try to dial in some settings. I have heard a lot of talk lately about M390 in the 62 to 64 range and I was wondering if anyone had a recipe to get there. so far from my research I have found nothing. I will study the curves and play with things a bit to see what I can get.
Click to expand...

I found it to be a bit chippy at Rc62 with plate quench and cryo, low temper. It has plenty of wear resistance at Rc60/61. Not the best choice for a fine slicer, but if you are fine with geometry at 0.007-0.010” before sharpening, it is a fine performer.
 
Willie71 said:
I found it to be a bit chippy at Rc62 with plate quench and cryo, low temper. It has plenty of wear resistance at Rc60/61. Not the best choice for a fine slicer, but if you are fine with geometry at 0.007-0.010” before sharpening, it is a fine performer.
Click to expand...
Thanks for the info. I think I will start at 62ish and go from there.
 
Natlek said:
I read some article from Roman Landes some time ago.He says that if we compare two edge ,same steel and same hardness . One 0.10mm behind edge and one 0.2mm behind edge knife with 0.2mm behind ege is FOUR time stronger then other one with 0.10mm .
Click to expand...
And cuts 4 times worse :P
 
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