Materials like 17-4PH H1150 might be used at -196°C but exhibit Charpy-V values less than 27J which corresponds to the impact energy at the DBTT.
I know people accepting value as low as 5J. Other say 5J is taking too big of a risk and require 10J. Other accept only above 15J.
Is really 15J safer...
I have a material data sheet for UNS S 17400 shows the following toughnesses at -196°C:
Condition H1150: 8.8J for test samples from 1" round bar
Condition H1150-M: 38J for test samples from 1" round bar
Condition H1150: 6.8J for test samples from 4" round bar
-Why is the toughness or thicker bar...
Metengr,
When you say that defect can grow due to quenching thermal stresses, do you mean that a crack can propagate or is there also a possibility for internal cavities to coalesce or become larger?
EdStainless,
There is no HT between casting and forging.
WKTaylor,
It's an open-die forging...
Actually the 01 heat treatment is done after forging.
So do you mean that any kind of heat treatment (01, T6 or other) don't generate defects? Only forging can be the origin of defects?
If so, could defects be acceptable for a class A ultrasonic testing done after forging and then become larger...
Dear all,
I have AA7075 aluminum forgings in O1 heat treatment. Then they get machined and hardened T6. The initial forging is US controlled after 01 ht but the part can't be US controlled after T6 because of its complex shape. Can defects develop or grow between 01 and T6 heat treatments...
