metalonis;
At 30,000 psi pressure this better be a code stamped pressure vessel. What are you going to do with 4340 alloy steel and this vessel? Is is being used for pressure boundary applications?
I've been working with high pressure vessels for 30+ years, so I'm well aware of the mechanical aspects of vessel design. This is an existing design, not yet put into service. Our customer now asks if it can be used in pure O2 service. What I'm unsure about are the corrosion and/or failure considerations of an oxygen/alloy steel interface.
My point to the above is not mchanical aspects of design it is material aspects of pressure vessel design and ASME B&PV Code does not approve the use of 4340 steel as pressure retaining material, regardless of environment. So, bottom line is this, you cannot use this material for Code-stamped pressure retaining applications.
For high pressure oxygen bottles, at ambient temperature high strength low alloy steel pressure vessel plate is acceptable.
Out of curiosity, why does the ASME B&PV code not allow 4340 steel for any PV apps? Does the provision for "high strength low alloy steel" specifically identify ferritic microstructures, or are tempered martensitic microstructures also allowed?
There are plenty of low alloy steels suitable for high pressure oxygen service in ASME Sect VIII, Div 3. Corrosion of low alloy steel at strengths necessary for 30ksi application is always an issue due to the possibility of HISCC. Some alloys are less susceptible than others, I will leave that to you to decide which is best. But, there are hundreds if not thousands of vessels made from SA508 or SA723 material in high pressure (> 30 ksi) applications containing hydrogen. As long as you design and fabricate the vessel to ASME Sect VIII. Div 3 requirements you should be OK
TVP;
For pressure vessel applications there are two uses; the first is pressure retaining function where the material is used under primary and secondary membrane stresses or as part of the pressure boundary (retaining). The second application deals with trim or non-pressure retaining function. It is under this application where any weldable grade of steel can be used.
Very simply, the reason 4340 steel is not specifically approved for use is because the carbon content exceeds 0.35% by mass. Material that is considered suitable for use must exhibit good weldability characteristics in addition to ease of fabrication and strength/ductility.
CoryPad;
Regardless, you would need to use one of the Code approved materials listed in Table 1A in Section II, Part D of the ASME B&PV Code if this is for pressure retaining service.
I was thinking the same thing as CoryPad, but didn't post the question. What if I were an enterprising young man and wanted to produce such a high strength cylindrical vessel, sans welding, using a steel such as 4340; could I work with the ASME B&PV Code gods to have a new provision written for non-welded applications, as long as the proper development was done, testing performed, high-quality presentation with real engineering data was given?
I was thinking the same thing as CoryPad, but didn't post the question. What if I were an enterprising young man and wanted to produce such a high strength cylindrical vessel, sans welding, using a steel such as 4340; could I work with the ASME B&PV Code gods to have a new provision written for non-welded applications, as long as the proper development was done, testing performed, high-quality presentation with real engineering data was given?
Yes. It would require a Code Case for submittal. The Code gods may lend some pitty on an enterprising young man in the name of safety first, and not just for business needs.
