Call for Charpy toughness samples

[Willie71]

Warren, would you like a couple of little pieces of Admiral 9260? 1 x 1/4 hot rolled round edge flat bar.

I’d love it. I’ll send you my address.

 

[MBB]

Warren,

What's the point of the 175F tempers on N690 and 8670 in your chart? It seems a little low but maybe I just don't understand.

Mike

Here’s the database from batches 2 and 3:

41D7E3B0-48BC-4746-A02E-FCF24A62DC3A by Wjkrywko, on Flickr

D875BD58-4D39-4B18-ADEA-41DA4F5B3355 by Wjkrywko, on Flickr

Now it’s just batches one, and what’s currently in the works.

 

[Willie71]

Warren,

What's the point of the 175F tempers on N690 and 8670 in your chart? It seems a little low but maybe I just don't understand.

Mike

I’ve made a few. Kitchen knives in 8670 tempered that low, and they work great. The N690 was based on the chart from aks. Other steels were tested at Rc61/62, so I was aiming for the same range for the N690.

http://www.bohlerperu.com/media/n690.pdf

 

[mknife]

Warren,

What's the point of the 175F tempers on N690 and 8670 in your chart? It seems a little low but maybe I just don't understand.

Mike

I believe that for the N690 the 175° are not farenight but rather degrees centigrade. In this way I find myself perfectly with the times that I usually use and with which I reach hardness of 60HRc.

 

[Willie71]

I believe that for the N690 the 175° are not farenight but rather degrees centigrade. In this way I find myself perfectly with the times that I usually use and with which I reach hardness of 60HRc.

I have some more here and will make a few more samples.

You have to log in to see the heat treat info, but this chart shows Fahrenheit.

https://www.alphaknifesupply.com/shop/n690-stainless-steel That might be a mistake though.

 

[MBB]

I see. I'm going to guess that the AKS supplied heat treat for 8670 and N690 are industry standard rather than customized to max hardness, as I know 8670 can hit much higher numbers than shown with a hardening temperature of 1525F rather than the shown 1600F. Also, I had in my head that tempering below 300F did not do much. I guess the toughness testing will answer that question, though!

 

[cotdt]

I know a custom knifemaker who tempers 1095 with boiling water 212F and a second temper at 300F and his knives were reputed to perform very well in the kitchen. So I'm very curious how the 300F tempers perform.

 

[Willie71]

One of my questions is how low can we go, before tempering has little to no effect?

 

[MBB]

I think that sounds very interesting, although you'll likely need a lot of closely spaced tempering data points to pick up subtle transitions.

 

[Willie71]

I think that sounds very interesting, although you'll likely need a lot of closely spaced tempering data points to pick up subtle transitions.

Yup. And I’m going to guess each steel will haveits specific cut-off point.

 

[mknife]

I have some more here and will make a few more samples.

You have to log in to see the heat treat info, but this chart shows Fahrenheit.

https://www.alphaknifesupply.com/shop/n690-stainless-steel That might be a mistake though.

Warren is this the curve of which you write?

 

[Willie71]

Warren is this the curve of which you write?

Yes.

 

[cotdt]

There's also this graph in the CTS XHP datasheets showing that tempering at 200F hits a local maximum toughness point.

https://ibb.co/yyVQ2pF

I think it's worth looking into these really low tempering temperatures to get the best performance for knives. Even getting 1-2 extra hardness points out of stainless steels help.

 

[Willie71]

8670 and 80crv2 were heat treated tonight. 1525fx10 min. Quenched in DT-48. I’ll temper in 50f increments from 250f for 8670, and 300f for 80crv2, to 450f.

My foil is at the post office, but I was working too late tonight to pick it up. I’ll get it tomorrow afternoon, and start on the higher temp V4e/4v, and M4.

 

[Michael.Drinkwine]

Update on AEB-L test coupons.

Well, good news and bad news. The good...I have heat treated AEB-L coupons in 10 different conditions. Willie71 you will be happy to note the 300°f temper is included! My homemade jig is effective for grinding length and width within tolerances (.003", the thickness of a piece of copy paper).

The bad news. My jig WON'T hold .001" (the thickness of a thin cigarette paper) over 2 1/4 inches for the thickness tolerance. I have tried every thing I can think of, and a few things other people thought up. Close, but no cigar. Unfortunately, there is too much flex/lash in my disc grinder setup. Ahh, well. I have a Wuertz SGA-1 surface grinder arriving in the next week or so, and that will hopefully solve the problem. After I get the AEB-L done I will shift over to the A2 conditions.

Bonus good news is that I've learned more about machining in the last month than I ever thought possible!

Michael

 

[Larrin]

Learning is painful sometimes.

 

[moopahtroopa]

Will you be updating the chart at the top of the post as you get results?

 

[Larrin]

Will you be updating the chart at the top of the post as you get results?

That is the plan.

 

[Larrin]

I have one 52100 condition that is not listed in the table along with the N690, 8670, M2, and Z-Finit. Do you remember what the heat treatment was, Warren?

 

[Willie71]

I have one 52100 condition that is not listed in the table along with the N690, 8670, M2, and Z-Finit. Do you remember what the heat treatment was, Warren?

I’ll look through my notes again. If you know the hardness, I can extrapolate it too. They were all done using the Cashen normalize and thermal cycle protocol, heat treated at 1475, then tempered at different temperatures.

Edit: it’s not in my notes, but if there was only one sample, it was probably tempered at 300f, for Rc62.