17-4PH H1150 vs 17-4PH HH1150 or double aged 1

[mecoman]

Hello,

We are looking for the difference between the two materials with regard to internal stress after machining, hardness properties and corrosion properties.

We typically purchase the material in the H1150 and machine the part in the H1150 condition. We do the same with the H900 condition also.

Our supplier only offers the Annealed state, so they drop ship to a heat treatment facility that has proven to be unreliable to delivery...etc. So we have been search for an alternative supplier. We may have found one, but they double age the or HH1150 the material. Is there a benefit we are missing or a setback in the bushes?

We use the material in a wide variety of process industries. Many of which require design review for a material change if a replacement part is offered.

Any insight into the double aging of 17-4PH is appreciated.

Thank you in advance.
Paul

 

[tbuelna]

You need to look at the material and HT specs that you list on your PO. What standards do you use for material and HT when procuring this raw material? Is the added cost of double aged 17-4PH H1150 material acceptable for this application? I would be very hesitant to make a material change that requires a design review process or might require approval from existing customers using the product.

In the US, 17-4PH material is widely available, and heat treating it to H1150 condition is not complicated and there are dozens of competent vendors that can do this work. So I don't understand why you have a problem. The potential risk and liability from making a material change just to accommodate one particular material supplier does not seem justified in this particular situation.

 

[EdStainless]

A double H1150 should result in exactly the same mechanical properties and corrosion resistance as a the single age. It may be slightly better uniformity and it may have slightly lower residual stresses, though neither of these are guaranteed (may people believe so, but I have never seen quantitative proof).
You should be ordering the HT to a specification (perhaps use the AMS) and there should be no room for deviation from that. This isn't a difficult HT, finding a responsible vendor should be straight forward.

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P.E. Metallurgy, Plymouth Tube

 

[MagBen]

I doubt double aging is simply a repeat aging.
there is a status called H 1150M which is treated at 1400F/2hr, air cool, then 1150F/4hr air cool. This is for the best machinability with higher elongation and much higher impact strength, compared with single aging H1150.
It makes no sense aging the same twice.

 

[mecoman]

Hello All,

Thank you all for your insight into my query. All the comments are very helpful in explaining the obvious to the untrained mind and gaining some knowledge along the way.

May my next metals thread provide a little more comic relief and less, really?

Enjoy the spring!

MECOMAN