Can a2 support a fine edge?

[noob93]

A2 does fine for edge stability (probably better than 3V), but consider your use of cryo and the effect that RA plays on edge stability. There is more RA than we used to believe.

I saw this the other day. From "Heat Treating, Including Steel Heat Treating in the New Millennium" (ASM Heat Treating Society) 2000.

A2 oil quenched from 1775°F had RA 16-18% (as quenched), 64-65HRC.
A single 400°F temper had no change on RA, but reduced hardness to ~60HRC.
A single 1000°F temper reduced RA to levels below X-Ray diffraction detection (<2%), lowering hardness to 56-57HRC.

A2 oil quenched from 1775°F
A -100°F cold treatment was applied to as-quenched sample, reducing A2 RA to 9% raising hardness to 65-66HRC.
A single 400°F temper drop RA in A2 to 4%, hardness 61-62HRC.

A2 oil quenched from 1775°F
immersed in LN for 3 hours, result was RA <2%, 66.5HRC

The problem with RA and possibly converted RA is weakness on a small scale and possibly reduced cohesion with surrounding matrix of converted structures. This is important for fine edge stability. This is low hanging fruit.

So, A2 does pretty well with edge stability, but not "out of the box", you have to process it for edge stability. Cryo is an important part of the equation, as is starting with quality A2. :thumbup:

Awesome right up from you there thank you. I watched the experiment Aaron Gough did and it seemed to prove what you just said to be very true. I'm not a metallurgist but find science in general very interesting. It's cool to see people pushing the boundaries of ht and your certainly one of them. Thanks for the read even if I only understood not quite a third of it haha.

 

[kuraki]

Nathan, thanks for posting that. I think I'll buy that book.

 

[JTknives]

A2 does fine for edge stability (probably better than 3V), but consider your use of cryo and the effect that RA plays on edge stability. There is more RA than we used to believe.

I saw this the other day. From "Heat Treating, Including Steel Heat Treating in the New Millennium" (ASM Heat Treating Society) 2000.

A2 oil quenched from 1775°F had RA 16-18% (as quenched), 64-65HRC.
A single 400°F temper had no change on RA, but reduced hardness to ~60HRC.
A single 1000°F temper reduced RA to levels below X-Ray diffraction detection (<2%), lowering hardness to 56-57HRC.

A2 oil quenched from 1775°F
A -100°F cold treatment was applied to as-quenched sample, reducing A2 RA to 9% raising hardness to 65-66HRC.
A single 400°F temper drop RA in A2 to 4%, hardness 61-62HRC.

A2 oil quenched from 1775°F
immersed in LN for 3 hours, result was RA <2%, 66.5HRC

The problem with RA and possibly converted RA is weakness on a small scale and possibly reduced cohesion with surrounding matrix of converted structures. This is important for fine edge stability. This is low hanging fruit.

So, A2 does pretty well with edge stability, but not "out of the box", you have to process it for edge stability. Cryo is an important part of the equation, as is starting with quality A2. :thumbup:

I just experanced this first hand on a customers blade I am heat treating.
A2: 1775°F X 30-45min soak (I place blade in oven and start the clock and give it 45min). Blade hits temp in around 5min or so and I get a good 30-40min soak. I then plate quench between 2 large aluminium plates. Next it goes straight into the liquid nitrogen and I soaked it for 24hrs. I did a hardness test after the cryo and it was sitting right at 66.5rc. After a 2hr 400° temper it was at 64hc which normally would have been 60rc. So the cryo is defently helping somewhere and the bump in hardness is quite shocking.

 

[jdm61]

Looking at the numbers, it appears that the austenizing temps for A2 and 410/416ss are very close. Do you think that would be a good combination for stainless clad san mai as long as you kept the tempering temps below 425F and did the LN treatment??