The Committee on Welds of the Materials & Fabrication Division of the Pressure Vessel Research Council has been active for the past 20 years in the investigation of the effects of weld fabrication on the properties of Cr-Mo steels. The studies which have addressed the reheat and hydrogen cracking resistance and the elevated temperature performance of the full range of Cr-Mo materials from the traditional 1-1/4 Cr-1/2Mo, 2-1/4Cr-Mo to the 9Cr-1Mo steels. These programs have provided input for ASME Code considerations and defined the relative importance of the major and minor alloying elements on the primary characteristics of performance. The programs have also addressed filler metals for repair and for the improvement of elevated temperature performance while maintaining suitable weldability.
With the advent of the newer quenched and tempered tungsten modified vanadium-niobium Cr-Mo steels elevated temperature welded performance has suffered from reduced creep rupture performance, in comparison to the base material, in terms of preferential cavitation in the fine grained/intercritical region of the HAZ (the so-called Type IV phenomenon). To more thoroughly understand and define the metallurgical mechanisms responsible for the fine grained weld HAZ region cavitation and reduced creep rupture life, a 3 year program was undertaken to document the creep behavior of the various regions of the weld HAZ of the 9Cr vanadium-niobium modified (T/P91) and the 9Cr (T/P92) and 12Cr (T/P122) tungsten-vanadium-niobium modified materials. As the first step in this research program a survey of the literature was undertaken concerning the behavior of these newer steels and this Bulletin is the result of the literature review. The experimental work will be reported in detail upon the completion of the experimental study.
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| Number of Pages : | 46 |
| Published : | 2000 |
