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#1333 - 02/22/18 11:52 AM Shot peening non magnetic parts with steel shots
Mumu Offline
Member

Registered: 02/20/18
Posts: 5
Good morning,

We are having issues with some of our tubulars cracking in shot peened areas. We shot peen non-magnetic tubulars on the threaded sections (API Connections) with the objective to relieve machining stresses and mitigate galling. The material of the tubulars is 15-15 HS from Carpenter.

Could I have your opinion about the importance of shot peening these non-magnetic tubulars with non-magnetic media, benefits of doing so and risks of not using Stainless steel shot.

I am trying to understand the pro and cons of shot peening with carbon steel media vs stainless steel media. Would both media improve the corrosion and oxidation resistance of our tubular the same amount?
What would the risks of shot peening nonmagnetic tubulars with carbon steel media?

If we were to shot peen our nonmagnetic tubulars with regular carbon steel shot, would we have a greater risk for stress corrosion cracking? Would it make them more prone to develop oxidation and corrosion?

Thank you.

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#1334 - 02/22/18 12:06 PM Re: Shot peening non magnetic parts with steel shots [Re: Mumu]
Walter Online   content



Registered: 05/03/99
Posts: 167
Loc: East Hartford, CT, USA
Cast steel shot will leave a ferrous residue on the surface that will eventually rust. I assume these parts are for the oil drilling industry, there very well may be an issue with magnetization if cast steel shot is used. Sensors used to guide the drill head can be negatively effected. In my experience peening API threads was done with SS Conditioned cut wire shot then followed up by peening with glass bead at a significantly lower intensity. This would clean the part and improve the surface finish. This additional step also could lead to increased fatigue life.

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#1335 - 02/22/18 01:08 PM Re: Shot peening non magnetic parts with steel shots [Re: Mumu]
Mumu Offline
Member

Registered: 02/20/18
Posts: 5
Thanks a lot Walter! This helps a lot!

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#1336 - 02/22/18 08:05 PM Re: Shot peening non magnetic parts with steel shots [Re: Mumu]
Jack Champaigne Offline


Registered: 04/20/99
Posts: 325
Loc: Mishawaka, IN, USA
What is the issue about peening with non-magnetic media? Is there a fear of imparting magnetism to the part?
Stainless steel cut wire media can retain high magnetism.
New high density ceramic bead from St Gobain could be used for full range of "A" peening intensities.

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#1337 - 02/26/18 03:27 PM Re: Shot peening non magnetic parts with steel shots [Re: Mumu]
Mumu Offline
Member

Registered: 02/20/18
Posts: 5
Thank you Jack. We are not worried about magnetism here at this point. We are just trying to understand why it is cracking axially and radially on our shot peened areas. Shot peening might be the cause but we are not sure.

I will make sure we use SS shot in the future.

Walter, as you said, these parts are for oil drilling industry. What do do you think about the following requirements:
* S-110 SS shots at 8-10 "A" intensity, 200% coverage
* S-100 Glass beads at 8-10 "N" intensity, 200% coverage

Thanks in advance,

Muriel

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#1338 - 02/26/18 03:34 PM Re: Shot peening non magnetic parts with steel shots [Re: Mumu]
Walter Online   content



Registered: 05/03/99
Posts: 167
Loc: East Hartford, CT, USA
I would limit the S-110 intensity to .009A Max. especially if you a using regular hardness media ASR 45-52rc and not ASH 55-52rc.
Peening intensities too high with too small of media becomes abusive to the part surface.

I'm not familiar with S-100 Glass bead. Unfortunately glass bead has numerous designations for size. I'm am familiar with the AMS designations such as AGB or the US Military size designation. If you can convert S-100 to one of those perhaps I can be of more assistance.

It seems like you are on the correct track to finding a proper call out for your project.

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#1339 - 02/26/18 04:32 PM Re: Shot peening non magnetic parts with steel shots [Re: Mumu]
Mumu Offline
Member

Registered: 02/20/18
Posts: 5
Sorry, not sure what happened here, I did not edit the size properly.
I meant 60-80 (#7) Glass Bead. I know we have used that size for other parts but I have no idea what intensity I should run it at.

Thank you for precising about the intensity of the S-110. I wasn't aware of that.

Thanks a lot for all your help!

Muriel

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#1341 - 02/28/18 01:35 PM Re: Shot peening non magnetic parts with steel shots [Re: Mumu]
Mumu Offline
Member

Registered: 02/20/18
Posts: 5
Hello, this is me again smile

I am having a real hard time to find charts or standards on what requirements I need for this process. How do you determine the size, hardness and intensity of the media? Is there some charts or document somewhere that gives recommendations for each type of material and each media combination?

Any help would be appreciated. Thank you.

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#1342 - 02/28/18 02:47 PM Re: Shot peening non magnetic parts with steel shots [Re: Mumu]
Walter Online   content



Registered: 05/03/99
Posts: 167
Loc: East Hartford, CT, USA
This maybe of some help.
AEROSPACE RECOMMENDED PRACTICE
ARP7488 Peening Design and Process Control Guidelines

You have to purchase it from SAE.org

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