temperature limitation for use of low-carbon stainless steel
temperature limitation for use of low-carbon stainless steel
(OP)
Can someone please explain to me the rationale behind the disparity in maximum allowable temperature between low-carbon austenitic stainless steel such as 304L and 316L, and the "regular" carbon grades (304, 316)? 304L and 316L are limited to 850F for Sec. VIII Div. 1 use, whereas 304 and 316 are allowed up to 1500F. Everything I've found indicates that the strength vs. temperature drops off at about the same rate - so is it due to creep resistance? I realize that the advantage of using low-carbon grades - increased resistance to sensitization - is no longer an advantage when the material sees those temperature over a prolonged period of time, but that does not explain to me why its use is precluded above 850F.
Anyone know?
Best Regards,
Jeroen Valensa, P.E.
Anyone know?
Best Regards,
Jeroen Valensa, P.E.





RE: temperature limitation for use of low-carbon stainless steel
To obfuscate the issue, I have seen special B&PV Sec.VIII code cases approved for use of 304L up to 1600F. Now we have "dual spec" TP304/304L that has 304 mechanicals and 304L metallurgy. Go figure.
RE: temperature limitation for use of low-carbon stainless steel
RE: temperature limitation for use of low-carbon stainless steel
All the 304 SS used by our site is purchased to a restricted Carbon (0.015% max) along with restriction on S, P, and Si. The latter 3 can be waived depending on the end use, but the carbon spec. is never waived.
The problem arises in that nearly all the pipe and plate comes on site with the dual specification of 304/304L. based on evidently on tensile and yield strength at RT. The carbon meets our specification of 0.015% max. There is no way we would used this material at the higher temperature for the reasons put forward by [/]metengr[/b]. The design review has always caught this but everyone is waiting for some to get by. I seen it come close to getting into service.
Another problem has cropped up with pipe from a well know pipe manufacturer. Not only is the pipe dual certified it is dual standard in every way except the MTR.
1 3/4" x 0.083 A/SA213 A269 304/304L A&P Ht #
The problem arises when the MTR only covers ASTM A213 only. Same Ht #
As I posted concerning fasteners, the majority of the people handling these materials have no clue to relevance and meaning of the markings.
RE: temperature limitation for use of low-carbon stainless steel
304 can be provided in a range of carbon spanning from L grade to H grade (low carbon to high carbon grades).
If you have type 304 stainless steel, there is a footnote to the allowable stress table that requires a minimum carbon content (0.04% min) to use the allowable stresses at temperatures above 1000F. If the material you have does not satisfy that min carbon content, you need to use the allowable stresses at temperatures above 1000F for the low carbon grade of the material, 304L. The difference in allowable stresses has to do with differences in creep properties, at these higher temperatures.
If you have dual stamped material, the metalurgy has been tweeked to provide the required room temperature strength of the straight grade, while complying with the low carbon content requirement for the L grade. Thus, it meets both specifications. For this material, you would use the allowable stresses for the straight grade to 1000F, and the allowable stresses for the L grade at temperatures above 1000F.
RE: temperature limitation for use of low-carbon stainless steel
you can not mix its properties,
gb
RE: temperature limitation for use of low-carbon stainless steel