Pipe Design - 4130 Material Properties at design temperature 3

[Matt_SA_94]

Hi All

I am completing pipe design calculations using AISI4130 (75ksi yield) in an operating temperature range of -4F to 250F. I am trying to account for the shift in Young's modulus and yield strength at the elevated temperatures but need some advice.

ASME II Part D table Y-1 gives the temperature adjusted yield strength for a range of materials but unfortunately AISI 4130 is not on that list. Section 7-230 of ASME II states the guidelines for grade substitution (material composition needs to meet all the limits of the substituted material). The only material that meets the chemical composition requirement is L7M and B7 which is found in a bolting spec (ASTM A320 and ASTM A193).

In the bolting spec is states that 4130 can be substituted for L7M and B7 but I have never substituted a bolting spec material with a non-bolting spec material. Is it acceptable to use the adjusted yield for L7M (bolting) as per table Y-1 in my piping calculations which use AISI4130?

 

[EdStainless]

If the strength matched then the temp factors will match even for a different product form.
Just make sure that it is for the same strength level.
Over this small temp range you will not see much change.

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P.E. Metallurgy, consulting work welcomed

 

[jmec87]

Is this design per API 6A, ASME B31.3, a different code/standard, or no code/standard?

For API 6A designs, many designers/manufacturers assume that the room temperature properties are applicable up to 250°F and only account for reductions in strength above 250°F.

For ASME B31.3 and some other codes/standards, accounting for reduction in strength is required for any temperature above 100°F, but as you stated, 4130 is not listed ASME II Part D Table Y-1 (nor is it listed in ASME B31.3 allowable stress tables). Often other data can be relied upon to determine the appropriate reduction in strength. There are at least two options for this:

1. API TR6MET includes elevated temperature testing data at 300°F and higher along with suggested de-rating factors for 4130 (using the 300°F de-rating factor would be conservative for a design rated to 250°F). The de-rating factors from API TR6MET are also included in API 6A Annex G without the supporting test data.
2. The US DOT/FAA published "Metallic Materials Properties Development and Standardization(MMPDS)" includes graphs for effect of temperature on strength and Young's modulus on AISI low alloy steels (such as 4130). The most recent edition that I can find is the 2003 edition which is available for free online.