American Welding Society Forum
Can someone advise what is the main difference in composition between SS 304 and SS 304H materials.
For material certification, is there a possibility that the same batch of materials fall under both categories, ie dual certification?
What is the recommended welding fillers or electrodes for welding SS 304H plates.
Using SA240, here are the differences:
304: C (0.08 max), 304H; (0.04 - 0.10). All other listed elements are the same. 304 has N listed at 0.10 max (304H does not list it).
I've never seen it dual certified, but it looks like it could be.
I'll leave the filler metal selection to others.
If the difference is small and having same value for C (0.04 to 0.08 range), what would be the reason to state that 304H is for applications at higher temperature (above 500 degrees C)?
I was told that price for 304H is very much higher than for 304. The difference is large when working on project.
I don't know the full details of your project; however, B31.1 has a note related to the use of 304. It says: "The allowable stress values tabulated for temps over 1000F apply only if the carbon content of the material is 0.04% or higher." In other words, if the carbon is below 0.04%, the stress values at temperatures above 1000F are not valid. 304 may be used at the published stress values if the carbon content meets the minimum. Clearly the carbon has an impact on material stress values at elevated temperature (in the eyes of the ASME B31.1 Committee.
The matching filler metal for 304H is 308H.
Is filler metal 308L commonly used for welding 304H as well?
If you need the 304H material for its intended application (high temperature), the 308L will be undermatching and lead to early failure by creep if used at high temperatures.
The increased carbon content of the 304H does what carbon does best, it strengthens the alloy, thus higher allowable stresses at higher temperatures. Of course there are upper limits on the services temperature because the carbon can cause other problems in very high temperature applications.
Best regards - Al
Creep strength of H grade austenitic stainless steels is directly effected by carbon content.
I thought Molybdenum was the magic bullet for high temperature creep and resistance to sulfuric acids.
Best regards - Al
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