Welding Preheat Interpass: Cr_Mo
Minimum preheat and maximum interpass temperatures for welding per AWS D1.1, ASME BPVC, ASME B31.3, and EN 1011. Covers carbon steels (AWS categories A/B), HSLA (category C, HPS 70W/100W), quenched and tempered (category D), Cr-Mo alloys (P5/P11/P22/P91/P4/P5B), austenitic stainless (P8), duplex stainless (P10H), nickel alloys, aluminum, titanium, and copper. Each record includes base metal group, thickness range, carbon equivalent, preheat/interpass temperatures in both F and C, PWHT requirements, hydrogen control level, and welding process notes. 46 records.
| base metal group | AWS group number | PWHT required | PWHT temp range F | base metal examples | carbon equivalent CE max | hydrogen control | interpass max C (degC) | interpass max F (degF) | preheat min C (degC) | preheat min F (degF) | record key | thickness range in | thickness range mm | welding process notes |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cr_Mo | P11 | conditional | 1200_to_1375 | ASTM A387 Gr11 / A335 P11 / A182 F11 (1.25Cr-0.5Mo) | 0.65 | low_H2_required | 315 | 600 | 121 | 250 | P11#any | any | any | 250°F preheat for all thicknesses; PWHT required per B31.3 for t>0.75in; max interpass 600°F; bake-out at 300°F post-weld if PWHT deferred |
| Cr_Mo | P22 | yes | 1300_to_1425 | ASTM A387 Gr22 / A335 P22 / A182 F22 (2.25Cr-1Mo) | 0.7 | low_H2_required | 315 | 600 | 204 | 400 | P22#over_1/2 | over_1/2 | over_13 | Thicker sections raise preheat to 400°F; PWHT mandatory for pressure service; linear post-weld bake-out at 600°F before PWHT if deferred |
| Cr_Mo | P22 | conditional | 1300_to_1425 | ASTM A387 Gr22 / A335 P22 / A182 F22 (2.25Cr-1Mo) | 0.7 | low_H2_required | 315 | 600 | 149 | 300 | P22#up_to_1/2 | up_to_1/2 | up_to_13 | 300°F min preheat all thicknesses; PWHT typically required per B31.3 for t>0.375in; max interpass 600°F |
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