Looking for advice, high yield material with YS>180ksi 9

[canwestler]

Hi,

I'm new for this forum and looking for some advice regarding the materials. We designed the 2.125" shaft made of 17-4 H900 with 2" STUB ACME threads to withstand 400,000 lbf tensile load. The shaft has 47 HRc hardness, but it failed and broke off at 2" STUB ACME thread while pulling test at 255,000 lbf tensile load! The shaft is very brittle from what I found.

We are not familiar with the high strength materials with YS > 180 ksi and good ductility/toughness. Would anyone have some good advice and recommendations on what kind of materials are suitable for this application, I will appreciate?

Thank you.

Walt S.
Alberta, Canada

 

[metengr]

With limited information as to service, I would recommend a 4340 alloy steel that has been heat treated to your requirements. This alloy has deep hardening characteristics and excellent toughness. Work with a reputable heat treatment shop.

 

[canwestler]

Thank you for your advice. By the way, can EN30B or 4330 V+ heat treated be substituted for 4340 alloy steel? Our suppliers have those alloys in stock.

 

[metengr]

Not directly. The 4330V steel contains lower carbon in comparison to the 4340, which is where the strength level is achieved. The 4330V may reach the strength level you need with heat treatment. I would probably go with 300M, which is the modified 4340 rather than 4330V.

 

[canwestler]

Thank you again for the advice.

 

[monkeydog]

A star for metengr, straight forward help for the new "guy".

 

[SnTMan]

As usual

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[EdStainless]

I don't think that the failure is strictly related to your material selection,
I believe that you will get failures in the thread in any of the materials over 175kist UTS.
Are you rolling the threads? If they are machined are they peened after machining?
Do you need corrosion resistance? If so then you might consider 13-8PH H1000.
If you don't need corrosion resistance then 300M is one option but it is rarely used at strengths below 275ksi (575F temper).
4330, 4330V 4335V would all be good potions.
Remember that in order to get the best toughness you need to temper to the lowest strength that you need. Even for these alloys that would likely be a tempering temperature of 1000F.


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P.E. Metallurgy, Plymouth Tube

 

[canwestler]

They are machined threads and we need mild corrosion resistance for oilfield applications. It is not a permanent tool that stays in the oil well. I might need to redesign the threads.

Thank you for your advice.

 

[shu60]

EdStainless is right on the money! PH13-8Mo was developed for just such strenuous service requiring strength/toughness/some corrosion protection...the downside - higher cost due to its processing requirements. It is widely used in aircraft/space components. Sharp corners/notches can have a strong negative effect as Ed alludes to.

shu60

 

[EdStainless]

If I were making this from 13-8PH I would try to have the threads rolled prior to final aging.

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P.E. Metallurgy, Plymouth Tube

 

[WKTaylor]

A few questions...

I thought that 4330V steel at 220-to-240-KSI, was a common 'oil-field equipment' alloy/temper... but maybe by a different alloy designator.

Also, RE Acme stub threads... can they cold rolled?

Ceramic or vapor deposited TiN wear/corrosion coatings, over shot-peened surfaces, feasible?

Regards, Wil Taylor

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[canwestler]

Thank you for your advice.

 

[Metaldoctor]

4330 v mod is stocked by many oilfield distributors in bar form, at 150 ksi min yield strength. in some cases as high as 165 min yield.