ASTM B637 UNS N07718 in Compliance with NACE

[Aamir3354]

Gents,

Is it possible to produce ASTM B637 UNS N07718 with the hardness requirements of NACE ?

As per ASTM B637 the MIN hardness is 38 HRC and NACE calls for MAX hardness of 40 HRC. Thus, NONE of the manufacturer (including Special Metals who are the inventor themselves) are ready to supply in compliance to specification.

We have an alternate of using API 6A 718 but the API6A 718mYs (120KSI) is much lower than ASTM B637 mYs(150KSI) - Thus, end user are adamant of not accepting a deviation.

Can anybody recommend a manufacturer/stocking who can supply ASTM B637 718 in complince with NACE with max 40 HRC hardness??

Appreciate your advise

Regards,

Aamir Sayeed

 

[TVP]

If Special Metals won't certify to NACE/ISO 15156-3, then Rolled Alloys or NS Alloys are other options:

http://www.rolledalloys.com/alloys/nickel-alloys/718-nace/en/

http://www.nsalloys.com/products/nickel-alloy-bar/718inconel-nickel-alloy-bar

 

[EdStainless]

The short answer is no, you can't do it.
If you need to stay under 40RC then you cant use 718 in the age hardened (150ksi) condition.

That said I know that over the years some alternate aging treatments have been devised that result in lower strength (below 150ksi but above 120ksi).
I can't vouch for the usefulness of these.

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Plymouth Tube

 

[Aamir3354]

Thanks for your feedback guys !!

@ TVP - Refering to the datasheet Rolled Alloys & NSalloys , These are produced to API6A 718 which doesn't resolve the issue because of lower mYs in comparison to ASTMB637.

@ EdStainless - You are correct and I am failing to convince the end-user because many valve manufacturer claim to be in compliance with ASTM B637 & NACE , which I am certain their oversight on specification.

The heat treatment within API6A is only way forward to limit hardness below 40 HRC but deviates from ASTM standard.

Thus, It is possible to supply INCONEL alloy 718 to API6A and NACE MR0175 (40HRC max) with chemical composition only to ASTM B637.

Aamir Sayeed
Oliver Valves Ltd

http://www.Valves.co.uk

 

[EdStainless]

You are not allowed to only meet part of a spec., though it is done all of the time.
You could try to use the 718 raw material spec that does not require the heat treatment, and then use API6A to cover mechanicals.

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Plymouth Tube