Welding Preheat Interpass: carbon steel
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 | 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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| carbon steel | B | no | A36/A529/A709 Gr36/A572/A588/A913/A992 and A53/A500/A501/A618 | 0.4 | low H2 required | 290 | 550 | 107 | 225 | B#over 2-1/2 | over 2-1/2 | over 64 | SMAW low-hydrogen electrodes FCAW GMAW SAW; Category B applies when low-H2 process used |
| carbon steel | B | no | A36/A529/A709 Gr36/A572/A588/A913/A992 and A53/A500/A501/A618 | 0.4 | low H2 required | 290 | 550 | 0 | 32 | B#up to 3/4 | up to 3/4 | up to 19 | SMAW low-hydrogen electrodes FCAW GMAW SAW; Category B applies when low-H2 process used |
| carbon steel | general | no | A36/A572/A992 general structural — carbon equivalent method | 0.43 | standard | 290 | 550 | 38 | 100 | general#1/2 to 1 | 1/2 to 1 | 13 to 25 | CE 0.41-0.43: 100°F preheat; mandatory low-H2 electrodes; FCAW, GMAW, SAW preferred |
| carbon steel | general | no | A36/A572/A992 general structural — carbon equivalent method | 0.4 | standard | 290 | 550 | 10 | 50 | general#1/4 to 1/2 | 1/4 to 1/2 | 6 to 13 | CE 0.36-0.40: 50°F preheat for sections 1/4 to 1/2 inch; low-H2 recommended |
| carbon steel | general | no | A36/A572/A992 general structural — carbon equivalent method | 0.45 | standard | 290 | 550 | 66 | 150 | general#1 to 2 | 1 to 2 | 25 to 50 | CE 0.44-0.45: 150°F preheat for 1-2 inch plate; strictly low-H2 process |
| carbon steel | general | no | A36/A572/A992 general structural — carbon equivalent method | 0.48 | standard | 290 | 550 | 93 | 200 | general#over 2 | over 2 | over 50 | CE >0.45 or plate >2in: 200°F minimum; consider 250°F for highly restrained joints |
| carbon steel | general | no | A36/A572/A992 general structural — carbon equivalent method | 0.35 | standard | 290 | 550 | 0 | 32 | general#up to 1/4 | up to 1/4 | up to 6 | CE<=0.35: no preheat required for thin sections; per IIW carbon equivalent formula CE=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15; verify CE from mill cert |
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