Toughness values of 10xx steels?

[Larrin]

in more or less plain carbon steels, do longer soak times lead to
lower MS/MF points..? and if so, increased benefits of sub-zero
treatment as a continuation of quenching...?

A longer soak time could lead to more destabilized retained austenite, but whether the point of diminishing return would be 10 seconds or 30 minutes I'm not sure. If you do cryo directly after the quench then it wouldn't matter.

 

[Juha Perttula]

The results of the toughness tests on those steels are not in the link you provided.

Yes, the link was about the effect of grain size on toughness.

I looked my toughness measurements and collected some data for unnotched Charpy specimens at 59-61 HRC. I have used specimens with different sizes, for that reason I scaled the results for square cm (cm2). Sorry, it was not S7, I have tested steel which was close to S5.

Unnotched Charpy toughness measurements at 59-61 HRC
10xx 10-100 J/cm2
80CrV2 ca 60-200 J/cm2
0.7%C-2%Si-0.5%Cr-0.7%Mo-0.2%V (ca. S5) 200-300 J/cm2
O1 60-200 J/cm2
52100 ca. 100 J/cm2
5260 ca. 150 J/cm2
Böhler K605 (3%Ni) ca. 200 J/cm2
Sandvik 15N2 (2%Ni) 200-300 J/cm2

I think the steel chemistry does not explain the different toughness values, it is the grain size and small variation in hardness. 10xx carbon steels had very large variation in toughness because they may have exceptional large variation in grain size depending on heat treatment and possible Al-addition.

 

[Larrin]

Yes, the link was about the effect of grain size on toughness.

I looked my toughness measurements and collected some data for unnotched Charpy specimens at 59-61 HRC. I have used specimens with different sizes, for that reason I scaled the results for square cm (cm2). Sorry, it was not S7, I have tested steel which was close to S5.

Unnotched Charpy toughness measurements at 59-61 HRC
10xx 10-100 J/cm2
80CrV2 ca 60-200 J/cm2
0.7%C-2%Si-0.5%Cr-0.7%Mo-0.2%V (ca. S5) 200-300 J/cm2
O1 60-200 J/cm2
52100 ca. 100 J/cm2
5260 ca. 150 J/cm2
Böhler K605 (3%Ni) ca. 200 J/cm2
Sandvik 15N2 (2%Ni) 200-300 J/cm2

I think the steel chemistry does not explain the different toughness values, it is the grain size and small variation in hardness. 10xx carbon steels had very large variation in toughness because they may have exceptional large variation in grain size depending on heat treatment and possible Al-addition.

Comparing samples of different sizes is not recommended, even when dividing by the cross-sectional area, because the relative size of the triaxial constraint region is smaller in subsize specimens with a larger percentage of biaxial stress state (shear lips): https://www.sfsa.org/publications/misc/ASTM A1-13 presentation.pdf

There are some papers or presentations like the one I linked above that provide methods for comparison but I don’t know how reliable they are.

 

[jdm61]

The one number that jumped out at me was the one for 15N20. But that should not be all that surprising. I would be interested to see the difference between 52100 done to "industry standard" say at 1550 and a sample done with the lower austenizing temp of 1475 that many knifemakers tend to use now.

Yes, the link was about the effect of grain size on toughness.

I looked my toughness measurements and collected some data for unnotched Charpy specimens at 59-61 HRC. I have used specimens with different sizes, for that reason I scaled the results for square cm (cm2). Sorry, it was not S7, I have tested steel which was close to S5.

Unnotched Charpy toughness measurements at 59-61 HRC
10xx 10-100 J/cm2
80CrV2 ca 60-200 J/cm2
0.7%C-2%Si-0.5%Cr-0.7%Mo-0.2%V (ca. S5) 200-300 J/cm2
O1 60-200 J/cm2
52100 ca. 100 J/cm2
5260 ca. 150 J/cm2
Böhler K605 (3%Ni) ca. 200 J/cm2
Sandvik 15N2 (2%Ni) 200-300 J/cm2

I think the steel chemistry does not explain the different toughness values, it is the grain size and small variation in hardness. 10xx carbon steels had very large variation in toughness because they may have exceptional large variation in grain size depending on heat treatment and possible Al-addition.

 

[JTknives]

The one number that jumped out at me was the one for 15N20. But that should not be all that surprising. I would be interested to see the difference between 52100 done to "industry standard" say at 1550 and a sample done with the lower austenizing temp of 1475 that many knifemakers tend to use now.

And then one that has been edge packed.

 

[jdm61]

Oh, hush!!!

And then one that has been edge packed.