Recommendation? Tempering, Explain this to me please.

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Way-Barney

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I have 2 steels

Steel A - Hardness after austenitization 66 - temper to 62 - toughness is 10 ftlb
Steel B - Hardness after austenitization 65 - temper to 62 - toughness is 30 ftlb

If I am happy with toughness of 10 ftlb can I just leave steel B untempered and still get roughly same toughness as steel A but at HRC 65, why should I bother tempering steel B?
 
Way-Barney said:
I have 2 steels

Steel A - Hardness after austenitization 66 - temper to 62 - toughness is 10 ftlb
Steel B - Hardness after austenitization 65 - temper to 62 - toughness is 30 ftlb

If I am happy with toughness of 10 ftlb can I just leave steel B untempered and still get roughly same toughness as steel A but at HRC 65, why should I bother tempering steel B?
Click to expand...
Tempering temperature for A and B ? A and B are same steel ?
 
No. Tempering is required after hardening to increase toughness. But, not tempering at all leaves it too brittle. You would use the charts or tests to find the actual temperature you want.

I assume the numbers you posted are from charts in a book. They are guides but not necessarily real end results. Those were attained in labs/shops with good equipment and expensive test machines. The bst most of us can do is use them as a guide and do our own tests to find where we came out. Toughness testing in most shops is cutting tests. Hardness can be measured witha Rockwell tester, so if you have one of those you can pick a hardness that will yield approx. the toughness desired.

Best system for a hobbyist is to use the charts and test the hardness after quench. Do two temper cycles at the lower end, say 350°F, and test the blade for hardness and toughness. If it is chippy, temper a third time at 375°, and test. Continue up to your target hardness or when the toughness indicates suitable use. Noting down these numbers and test results will give you a chart that you can use in your shop with your equipment to get consistent results.
 
Its largely theoretical, lets say 200 c, 400f
to Natlek
 
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Stacy, after Austenitization is toughness zero and we temper to achieve toughness?
 
No, toughness is whatever it is. 1084 is not the same toughness as-tempered than CPM-3V.

The "theoretical" recommended hardness and toughness results in charts and books are steel specific, and determined by "best use testing" .
It would be false to think that merely raising or lowering one parameter would not change more than one other thing.
If steel A is recommended with a temper of 400°F yielding 10ftlb toughness, then most likely that was where it was the best.
Comparing two different steels as if they were the same in all ways will lead you to madness.
 
Stacy E. Apelt - Bladesmith said:
No, toughness is whatever it is. 1084 is not the same toughness as-tempered than CPM-3V.

The "theoretical" recommended hardness and toughness results in charts and books are steel specific, and determined by "best use testing" .
It would be false to think that merely raising or lowering one parameter would not change more than one other thing.
If steel A is recommended with a temper of 400°F yielding 10ftlb toughness, then most likely that was where it was the best.
Comparing two different steels as if they were the same in all ways will lead you to madness.
Click to expand...
ha ha,
I am thinking about as hardened, not tempered.
is 3v tougher as hardened than 1084 or will both snap if dropped on the floor
 
Consider an extreme example and you will answer your own question:
Steel A is 1030. Steel B is 1095. As hardened, will they be the same toughness or brittleness? No.
 
Last year someone mentioned that a maker water quenches AEB-L in foil packet and does not temper. This is a practice I would never think about doing but I was curuios so I tried it out.

Hardenss was right at 62 Rc. For basic cuts no issues but when I started carving on a softer knot free wood I was able to pop chips. The edge was to brittle.
 
Way-Barney said:
ha ha,
I am thinking about as hardened, not tempered.
is 3v tougher as hardened than 1084 or will both snap if dropped on the floor
Click to expand...
Way-Barney said:
Stacy, after Austenitization is toughness zero and we temper to achieve toughness?
Click to expand...

Best way to answer your own questions is to leave the world of theory behind and join the world of practice.

At a certain point, there is no way to theory your way to understanding at the higher levels of complexity. Things are working beyond our intuition and require testing and data to understand what is happening not "What seems right" or "what feels right"

If you have specific questions that can be measured and tested one of the easiest ways to get some solid data is to make some "rectangles" and find out.

Here are the perimeters below to make your own conditions.

"The cure for boredom is curiosity and for curiosity there is no cure."
-Dorothy Parker

Screenshot_20240106-082423.png
 
Thank you for all your replies, I am going to throw a shovel of soil into this rabbit hole.
I have ended up down the hobby within a hobby within a hobby on a previous occasion,
In my home brew days, I became so interested in the yeast (function and process) that I set up a small lab, and of course the microscopes were never quite good enough so chased that around for a while, eventually I started to to capture wild yeast and isolated several strains that were good for brewing beer, My whole hobby changed from brewing a nice IPA or traditional Bitter to be used on a relaxing evening to wild yeast bottle bombs and historical sour beers to be entered in competitions. LOL
 
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