17-4 PH

[metalonis]

We had a 15+" diameter bar of condition A, ASTM A705, 17-4 PH double aged to condition H1150. The hardness came out around 37 HRC. NACE requires the hardness to be 33 HRC max.

1. Any ideas as to what went wrong?
2. Would there be any bebefit to repeating the double aging process?

 

[unclesyd]

If you go back to the original data from Armco on 17/4 Ph S/S you will find that they give you a range of hardness for each condition, though this seems high for an 1150, 1150 treatment..
If the H1150,H1150 was done correctly you will not get the hardness down by redoing it.
Let me do some checking as you might use the overaging treatment to lower the hardness.

That is rather a large bar how did you take the hardness?

 

[fritzcoinc]

What hold time did you use?
You will need to hold at 1125 D.F. for at least 13.5 hours then set the temp. up to 115 D.F. for 4 hours at heat. Repeat for Double 115O NACE condition.

 

[unclesyd]

I'm still looking for my literature.
What is the actual physical dimension of your part?

 

[metalonis]

We've decided to go ahead and re-treat the bar in an attempt to draw back the hardness. Thanks all for your input.