ASTM A-453 Gr. 660

[QAFitz]

This Spec. calls out two different heat treatments, one for Grade A and one for Grade B. What heat treat process would need to be followed if I wanted to go from one to the other?

Both scenarios have shown up: we have inventoried Grade A and a customer wants Grade B, and, we have inventoried Grade B and a customer wants Grade A.

 

[metengr]

QAFitz;
Are these finished parts?

 

[QAFitz]

Sometimes bar stock and sometimes finished product. I can address bow/warp during the heat treat process, just looking to see what the heat treat process would be, and, is that spelled out any where.

 

[metengr]

QAFitz;
I reviewed ASTM A 453 and the reason for the two solution treatments is based on having fine versus coarse grained material. I also have quoted below an excerpt which addresses why there are two solution treatment temperatures, prior to aging, despite both Grades meeting the minimum mechanical and stress rupture proerty requirements;

The 1800 F solution
treatment results in a large grain size that provides
good creep-rupture life. The 1650 F solution
treatment results in a finer grain size material with
better short time tensile strength and ductility.

Based on the above information, I would not recommend re-heat treatment going from an original solution treatment temperature of 1800 deg F down to 1650 deg F because you will not achieve a fine grained structure.

Re-solution teatment from 1600 deg F original to 1800 deg F seems possible because you are going from a fine grained to a coarse grained structure with the higher solution treatment temperature, assuming all other ageing parameters are followed by specification.

The bottom line is the customer should be made aware of the effect on mechanical properties for end use as I indicated in the excerpt above. One can re-solution treat and age per the specification.

What I would do is to verify the above scenario by re-solution treatment/ageing several banks and have the mechanical property tests and stress rupture tests (100 hr minimum) per ASTM A 453 specification so you have all bases covered.

 

[metengr]

several banks

Sorry, this should be blanks or coupons, not banks.

 

[QAFitz]

Very good explanation with great detail. Thanks Metengr.