Temper Embrittlement of Pressure Vessel Steels BY R. A. SWIFT AND J. A. GULYA Pressure vessel steels and weld metals operating up to 1100 F vary in tendency to temper embrittlement depending on composition, structure, heat treatment and, in submerged arc welding, the choice of flux R. A. SWIFT is Research Engineer and J. A. GULYA is Supervisor, Alloy Research, Lukens Steel Company, Coatesvi/le, Pa. ABSTRACT. Temper embrittlement is a particularly important consideration for steels used in high pressure con- tainment vessels operating in the temperature range of 600 to 1100 F. On this basis, a comprehensive evaluation of commonly used pres- sure vessel steels and weld metals was undertaken. The steels investi- gated include C-Mo, Mn-Mo, Mn-Mo- Ni and Cr-Mo steels. Weld metals in- clude C-Mo, Mn-Mo and Cr-Mo com- positions. A total of 95 composition- treatment combinations, including 20 composition-treatment combinations of weld metal, have been evaluated. Of the materials tested, suscepti- bility to temper embrittlement varied with composition, structure, and heat treatment. The susceptibility was low- er for the C-Mo and Mn-Mo steels than for the Mn-Mo-Ni and Cr-Mo steels. The addition of Ni to Mn-Mo apparently increases susceptibility to embrittlement. Within the scope of the tests reported herein, no firm trends in the effects of As, Sb, P, and Sn on the susceptibility to temper em- brittlement are observed. The results of embrittlement tests on the weld metal were similar to those obtained for the corresponding plate steels. However, flux is a critical factor in determining susceptibility. It was shown that the susceptibility of weld metal is generally more severe than that of the base metal. Table 1—Specifications and Chemical Analysis of Materials Investigated Type C-Mo ASTM Specs (a) A204C Mn-Mo A302B A302B, A533A A302C, A533B 1 Cr-Mo A387B 2V4Cr-Mo A387D, A542 3Cr-Mo None None A387E Form Plate Weld™ Plate Weld ,b| Plate Plate Plate Plate Weld |b| Weld |b) Plate Plate Plate Weld |b) Weld ,b) Plate . Weld (b » Plate Plate Plate Plate Plate Heat Mn A2948 .36 .73 (RACO) .06 1.02 B5217 .19 1.34 (Linde) .07 1.32 A4069 .20 1.20 C4689 .21 1.27 C4694 .24 1.32 15756 .19 (RACO) .06 (L&R) .11 .13 12 .12 .13 .12 .12 B6730 A2766 A3588 (L&R-1) (L&R-2) C6669 (L&R-3) - (L-105) (C '11 A9367 .12 (L-104) (c) 13 B3683 .12 A2966 .14 .57 .80 .43 .46 48 .50 53 .44 .46 .47 .49 .39 .51 .40 .43 .023 .009 .023 .015 .023 .008 .016 .012 .018 .009 .016 .015 .024 .012 .022 .017 .018 .015 .012 .017 .024 .011 .020 .009 .025 .021 .011 .009 .014 .015 .010 .011 .017 .017 .015 .010 .020 .008 .008 .009 .010 .010 Cu 24 .29 .25 .12 .11 .12 .11 .22 .24 .20 .17 .18 ,16 .16 .15 .17 .16 .19 .15 .19 23 .15 .23 .45 26 .43 .24 .25 .15 .30 .57 .35 .21 .26 .26 .27 .22 .21 .20 .29 .24 .31 .26 .29 Ni .13 08 .13 .04 .08 .56 .56 .13 .19 .16 .17 ,18 .20 .17 .18 .48 Cr .07 .05 .10 .08 2.06 2.27 2.28 2.25 .17 .31 .22 30 .11 Mo .03 .54 ,14 .49 .05 .47 .07 .47 .60 .55 .21 1.11 .51 .14 1.34 .54 .20 1.34 .49 .96 .88 .95 .95 .96 .95 .92 .97 .98 .18 3.12 .48 .17 3.00 .89 .22 2.90 .93 Al .015 .013 .042 .008 .031 .014 .019 .023 .013 As Sb Sn .018 .016 .008 .007 .008 .005 .007 .009 .015 .027 .0026 .024 .0023 .0034 .024 .0032 .0029 .012 .0025 21.0 (l 18.6" .017 18.7 (( — 20.9 18.5 «J) .012 .00015 .00 9.3 .012 .011 .0001 .00 10.2 .023 .018 .0040 .015 19.8 .010 .025 .0025 .013 18.9 (a) Related plate specifications (b) Sub-arc welds (c) Laboratory melts (d) "X calculated assuming 0 015% Sn WELDING RESEARCH SUPPLEMENT! 57-s