D2 grain size and toughness

N

Nico Cappelli

Joined
Apr 20, 2019
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27
Hello everybody.

https://it.scribd.com/document/4467...ss-and-Impact-Toughness-of-AISI-D2-Tool-Steel

Wandering around the web some time ago I came across this report on the mechanical characteristics of d2 subjected to various heat treatments(austenitize t range from 1800 to 1960 f). What is written in it is relatively simple and, among other things, remarks the interesting fact that the best toughness can be achieved by a 1070°C (1960°f)austenitize.
But, In short, say also:
increasing the austenitization temperature increases the grain size.
increasing the grain size decreases the impact resistance(toughness).

This leaves me very perplexed!
It seems to me that there are contradictions, but I could also be wrong in interpreting the graphs or can't understand some things ... For this I thank those who will have the patience to read and explain their point of view.
 
It’s an extremely poor study and very poorly written. The micrographs don’t even show grains. The paper keeps contradicting itself as to whether a higher austenitize made the grains smaller or bigger. It says that a 980C austenitize led to a 300% increase in UTS and doesn’t say what that percentage is compared to. The study claims an incredible 79% elongation in a tensile test. I wouldn’t even bother trying to make sense of this trash.
 
Larrin said:
It’s an extremely poor study and very poorly written. The micrographs don’t even show grains. The paper keeps contradicting itself as to whether a higher austenitize made the grains smaller or bigger. It says that a 980C austenitize led to a 300% increase in UTS and doesn’t say what that percentage is compared to. The study claims an incredible 79% elongation in a tensile test. I wouldn’t even bother trying to make sense of this trash.
Click to expand...
Thank you very much. I thought so too but since it seems written by 3 engineers, I am not allowed. However 300% in relation to the same steel but in annealed condition. This is specified
 
Nico Cappelli said:
Thank you very much. I thought so too but since it seems written by 3 engineers, I am not allowed. However 300% in relation to the same steel but in annealed condition. This is specified
Click to expand...
No you inferred that they were comparing to the annealed condition, it was not stated. You can figure out which they are referring to by comparing the values, of course, but that’s not how good writing is done. And why compare to the annealed condition anyway?
 
Nico Cappelli said:
Thank you very much. I thought so too but since it seems written by 3 engineers, I am not allowed. However 300% in relation to the same steel but in annealed condition. This is specified
Click to expand...

All the specimens are well under 60rc (~630 vickers hardness = 56-57rc at the hardest, 1070°C) there are doing a 550°C temper. Ridiculous

The Micrographs are bad, 400x and can't make out anything useful.

There is some confusion from the author, he says in the description above the micrographs that 1070°C created "14.8" um grain in the micrograph picture (d) Yet, shows in the "grain to austenitzing temperture graph" that 1070°C was over 20um, yet than states in the charpy test that the 1070C got the highest performance at 35j thanks to finer grains which they reiterate in the conclusion. Very confused article.

Useless.



Here is a good place to do some reading and research. There are links in the article that lead to other articles for more reading and information.
https://knifesteelnerds.com/2018/11/05/all-about-d2-steel-knives/
 
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