416SS San Mai HT'ing

[Ken H>]

Hello all, I'm looking for a bit of guidance on HT'ing a folder blade (slipjoint) that has been profiled, but no bevel. This has 416SS for cladding with a 1095 core. I've read 1095 can sometimes be quenched with 7% brine, but best of all Parks 50. All I've got available is heated canola oil or brine solution for quenching.

My thinking is the 416SS cladding will slow the quench a bit preventing the brine from being too fast, and will be hard pressed to get heated canola to be fast enough for 1095 that is sandwiched between two layers of 416SS.

The billet for this blade was allowed to cool in forge after drawing out. All the grinding and profiling was done and am now ready to HT. My thinking is to follow Stacy's instructions from July, 2012. Here is my summation of several posts on the thread below:

HT’ing 1095 blades per Stacy: https://bit.ly/2PmDy3y

Use 7% brine when HT’ing 1095. That is 2.5 pounds in 5 gallons of water. Just mix with room temp water and stir until it is dissolved. Any rock salt or table salt will work. The brine should be warm...about 80-100F...no more. For such a small blade, use one pound of salt and 2 gallons of water.

The blade edge should be about .040”-.050” for a brine quench. Coat blade really good with anti-scale product. Anti-scale might need to be reapplied between steps. (my blade is not beveled, profiled only)

Bring the oven to 1500F and stabilize, and place blade in oven. Allow the oven to return to 1500F and soak for 10 minutes. Remove and allow to air cool. This 1500F step causes the blade to form pearlite.

Stabilize oven to 1450⁰F, keeping the door shut. Place knife blade back in the oven when the temp reaches 1450°F. Let sit for ten minutes. Remove and quickly quench in oil (room temperature canola will be fine). This quenching in a medium fast oil forms martensite ...with some pearlite hanging around. The grain structure should be fine and even.

Stabilize oven to 1350⁰F, keeping the door shut. Place knife blade back in the oven when the temp reaches 1350°F. Let sit for ten minutes. Remove and air cool. This 1350F and air cool step will remove all stress from the blade and end with a fine grain pearlite blade. Straighten if any is needed.

Stabilize oven at 1450°F (1475°F?), place blade in oven. When oven returns to 1450°F, soak for 10 minutes and quench in the warm brine.

Temper at 450F for two hours twice. The blade should get into the tempering oven as soon as possible after the final quench. 1095 that has been water/brine quenched can crack just sitting there before tempering. Set the tempering oven to 450F and have it stabilized before doing the quench. After checking the blade from quench, and washing it off, immediately place it in the oven within minutes of the final quench.

I know the above is pretty long, but does it sound like I've got it correct? Comments are welcome.

Ken H>

 

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I won't get into the specifics of your HT, however I can offer some comments on the use of san mai laminated steel in a slipjoint.

"The blade edge should be about .040”-.050” for a brine quench."
did you grind the bevels already? You also said - "...been profiled, but no bevel. "
I would grind all after the HT.

question, you did alot of work already, why don't you just get the Park 50 quench oil?
Did you make the san mai on your own?
Have you done any tests with the bar of san mai? I'm assuming you have some material if you made this san mai.

Laminated steels work well in a straight water quench, I quench the laminated steel I use in straight warm water.

Did you already surface grind the blade? Did you drill undersized the pivot hole?

regards
Harbeer

 

[Ken H>]

did you grind the bevels already? You also said - "...been profiled, but no bevel. " I would grind all after the HT.

Yep, as I said grinding the bevels post HT is my idea also. About the only blades I do any bevel grinding on pre-HT is a thick blade over 1/8" at least.

question, you did alot of work already, why don't you just get the Park 50 quench oil? Did you make the san mai on your own? Have you done any tests with the bar of san mai? I'm assuming you have some material if you made this san mai.

Yes, I made the San Mai. It's pretty expensive to get Parks 50 just for a couple of folder blades. Since I work most everything is SS, so why spend the big bucks for P50 if it's not needed? What kind of test are you referring to?

Laminated steels work well in a straight water quench, I quench the laminated steel I use in straight warm water. Did you already surface grind the blade? Did you drill undersized the pivot hole?

That's what I was thinking, water/brine quench should be just fine because the low carbon cladding would slow quench and 1095 needs all the speed it can get. Because the cladding will slow quench, I wonder if 15N20 would be a better choice for the core?

Yes, I ground the billet on SGA after forging & drawing out to get sides smooth and core centered. Yep, the pivot hole is undersized for final reaming/polishing after HT'ing

 

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HT coupon test.

 

[Ken H>]

Hey, that's a good idea, and where most any HT questions should start. Do a HT, break coupon to check grain size of core. I'd got too focused on using Rc testing and can't Rc test a San Mai billet because of the cladding. Thanks for getting me back on track.