ary.” Compositions within this grey shaded boundary area may or may not be martensitic and may or may not fail a bend test — there is a degree of uncertainty when compositions lie inside this boundary area. However, weld metal composition corresponding to 60% dilution lies to the left of an extrapolation of the light green dashed boundary that separates primary austenite solidification mode (region labeled “AF” in Fig. 1) from primary ferrite solidification mode (region labeled “FA” in Fig. 1). This means that, even if the 60% dilution composition does not form martensite, it is likely to be susceptible to solidification cracking. Solidification cracking is usually longitudinal to the welding direction. Note that the inquirer also reported occasional longitudinal cracks. The composition labeled “40% Dilution” in Table 1 lies 40% of the distance along the second tie-line from the ER309/309L filler metal to the point labeled “Mix of Base Metals.” This is almost exactly at the point where the second tie-line crosses the light green dashed boundary between the AF and FA regions. The 40% dilution composition will not form martensite and may or may not be susceptible to solidification cracking. Any composition of less than 40% dilution will lie in the FA region and therefore not be susceptible to solidification cracking and not form martensite. Such compositions should be considered to be in the highly desirable “sweet spot.” Of course, somewhat different compositions for the base metals and filler metal illustrated in the examples of Table 1 would shift the “sweet spot” slightly, but the general trend will be the same. The 20% dilution composition in Table 1 would be found at 20% of the distance along the second tie-line proceeding from the ER309/309L composition towards the point labeled “Mix of Base Metals.” This lies comfortably above the martensite boundary and comfortably within the region of compositions that solidify as primary ferrite. It is well within the “sweet spot.” So the remedy for the problem described by the inquirer is to ensure that the weld metal composition will lie in the “sweet spot” of less than 40% dilution. That can be accomplished by expanding the root opening — the inquirer indicated a root opening of 1⁄16 JULY 2016 / WELDING JOURNAL 19 Fig. 1 — WRC1992 diagram including typical compositions of carbon steel, 304 stainless steel, and ER309/309L stainless steel filler metal. Fig. 2 — Joint type 1 from AWS B2.11/ 8010: 2015. For info, go to aws.org/adindex
Welding Journal | July 2016
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