By -
Date 04-20-2005 20:04
Charles,
Since this material is used in high heat applications, and is very recognizable for creep strength, I am quite sure the Boron is added as an enhancement for the creep strength at elevated temperatures over a long period of time. The allowable range being 0.001-0.006 tells me that it is useful up to the maximum range, but higher can have detrimental affects, like possible cracking problems over a period of time. Maybe a comparative example might be Bismuth. When added to a flux core composition, Bismuth is allowed for easier slag removal, but just slightly higher, it is prone to contribute to hot cracking. Both would be, in my opinion, what we consider trace elements.
Chuck
By -
Date 04-20-2005 21:50
Charles,
Yes it is strange that W (tungsten) is listed as one of the "other elements". The data sheet that I have lists every element, there is no "other elements" listing. NF616, produced by Nippon Steel [A213 T92/A335 P92] gives the complete alloy listing. In this P92, tungsten plays a mojor part in improving creep strength values, so it is odd it is not given more credit. Comparing the P91 to the P92, there are various min/max rangers concerning the carbon, Si, P, Cr, Mo (which yu pointed out), W ( a big difference here), Ni, V, Nb, Al, and B ( which we idscussed). The differences are slight except for the tungsten.
Chuck