Heat Treating and material ductility
Heat Treating and material ductility
(OP)
Hello,
I have a small cylindrical adapter D=2" L=8".
For the strength needed, according to MIL-HDBK-5H table 2.3.0.2, I should use 4340 over 4140 since 4140 has a maximum diameter of 1" for quenching & tempering.
The question I have is especially regarding material ductility.
I can establish what strength I need, and specify a heat treatment accordingly.
As clearly shown in table 2.3.1.0(e), the higher the strength obtained from the Q&T, the more brittle the material is. I also remember this from my school textbooks.
However, in the real world, how do you determine that the resulting ductility will be acceptable, other than with tests?
For example, the reduction area here can vary between 43-55%.
Are there best practices when it comes to ductilty (such ensuring 45%min reduction area)...?
What is considered "brittle", quantitatively?
Thank you.
I have a small cylindrical adapter D=2" L=8".
For the strength needed, according to MIL-HDBK-5H table 2.3.0.2, I should use 4340 over 4140 since 4140 has a maximum diameter of 1" for quenching & tempering.
The question I have is especially regarding material ductility.
I can establish what strength I need, and specify a heat treatment accordingly.
As clearly shown in table 2.3.1.0(e), the higher the strength obtained from the Q&T, the more brittle the material is. I also remember this from my school textbooks.
However, in the real world, how do you determine that the resulting ductility will be acceptable, other than with tests?
For example, the reduction area here can vary between 43-55%.
Are there best practices when it comes to ductilty (such ensuring 45%min reduction area)...?
What is considered "brittle", quantitatively?
Thank you.





RE: Heat Treating and material ductility
The other criteria that might be of use is impact toughness.
Less ductile does not mean brittle. There are many applications where materials with 10% elongation are used all of the time. That is too low to low cold forming operations, but if the strength and design are correct it is perfectly serviceable.
Design is more critical with lower ductility. You need to avoid notches and sharp corners, you need to consider load path very carefully.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Heat Treating and material ductility
RE: Heat Treating and material ductility
Indeed I wanted to get opinions on what is considered safe for engineering/industrical applications. Like you said, 4340 Q&T to 260ksi tensile has approx 10% elongation (by the way, what does the '4D' refer to in elongation?). I also understand that stess concentrations should also be considered.
For this part in particular, the first third of the part is square, the second third of the part is cylindrical, and the last third is hexagonal.
There are filets for all transition faces. No threads, keyways, or any other features.
The part is an adapter for torque equipment. It will be loaded in torsion. Loading is a steady loading ramp (ie. not impact).
Without any impact loading, assuming I would need the 260ksi tensile (I don't) should the 10% elongation be worrisome?
RE: Heat Treating and material ductility
RE: Heat Treating and material ductility
RE: Heat Treating and material ductility
@weldstan it's cylindrical in shape, but it's a solid rod. (ie not a hollow cylinder).
RE: Heat Treating and material ductility