4130 Stess relief 1

[nowings]

What temperature would a 4130N tube frame be stress relieved at? Is there a critical temperature to stay away from as to not change properties? This will be done in an oven.

 

[Carburize]

Typically the 4130 material will have been quenched and tempered to give the material its properties ( strength, hardness) - if the next heat treatment takes the material above the tempering temperature previously used then the hardness and strength will drop. A general rules-of-thumb is that the stress relieving temperature should be at least 100 degrees F below the tempering temperature to avoid softening.
Some codes however, such as NACE MR 01 75 specify minimum temperatures for stress relieving and then life can get complicated - so check that no specific codes apply to your weldment.