D1.4 Rebar Preheat Calculator
Look up the minimum preheat and interpass temperature for welding reinforcing steel bars per AWS D1.4/D1.4M:2018 Table 7.2. Enter the carbon equivalent (CE) and select the bar size.
Use AWS D1.4 Table 7.2 to look up reinforcing-bar preheat from carbon equivalent and bar size. The calculator keeps the D1.4 CE formulas separate from structural-steel IIW CE assumptions and flags cold-base-metal, natural-cooling, and structural-steel higher-preheat notes for shop checks before welding.
Built on AWS D1.4:2018 Table 7.2 — rebar preheat traced to the clause.
Preheat Lookup
Applies to SMAW with low-hydrogen electrodes, GMAW, FCAW, and GTAW. All processes share the same requirements.
Per AWS D1.4:2018
Clause 7.2.1: minimum preheat and interpass temperatures are in accordance withTable 7.2, using the highest CE fromClause 1.5.4.
D1.4 Table 7.2 — Complete Preheat Table
SMAW with low-hydrogen electrodes, GMAW, FCAW, or GTAW. When welding rebar to structural steel, also check D1.1 preheat requirements and use the higher value.
| Carbon Equivalent (CE) | Bar Size | °F | °C |
|---|---|---|---|
| Up to 0.40 | Up to #11 [#36] | None | None |
| Up to 0.40 | #14 and #18 [#43 and #57] | 50 | 10 |
| Over 0.40 to 0.45 inclusive | Up to #11 [#36] | None | None |
| Over 0.40 to 0.45 inclusive | #14 and #18 [#43 and #57] | 50 | 10 |
| Over 0.45 to 0.55 inclusive | Up to #6 [#19] | None | None |
| Over 0.45 to 0.55 inclusive | #7 to #11 [#22 to #36] | 50 | 10 |
| Over 0.45 to 0.55 inclusive | #14 to #18 [#43 to #57] | 200 | 90 |
| Over 0.55 to 0.65 inclusive | Up to #6 [#19] | 100 | 40 |
| Over 0.55 to 0.65 inclusive | #7 to #11 [#22 to #36] | 200 | 90 |
| Over 0.55 to 0.65 inclusive | #14 to #18 [#43 to #57] | 300 | 150 |
| Over 0.65 to 0.75 | Up to #6 [#19] | 300 | 150 |
| Over 0.65 to 0.75 | #7 to #18 [#22 to #57] | 400 | 200 |
| Over 0.75 | Up to #6 [#19] | 300 | 150 |
| Over 0.75 | #7 to #18 [#22 to #57] | 500 | 260 |
D1.4 Preheat Requirements
Rebar to structural steel: When steel reinforcing bars are welded to structural steel, the preheat requirements of D1.1 also apply. Use the higher preheat requirement of D1.4 Table 7.2 and D1.1 Table 5.11. Extreme caution is needed when welding rebar to quenched and tempered steels.
Cold weather: When the base metal is below 32°F (0°C), preheat to at least 70°F (20°C) and maintain during welding.
Cooling: After welding, bars must cool naturally to ambient temperature. Accelerated cooling is prohibited.
Carbon equivalent: For bars other than ASTM A706/A706M, use CE = C + Mn/6. For ASTM A706/A706M, use CE = C + Mn/6 + Cu/40 + Ni/20 + Cr/10 - Mo/50 - V/10. When chemical composition is not available, see D1.4 Clause 1.5.4. Use our Carbon Equivalent Calculator to compute CE from MTR data.
D1.4 Rebar Preheat FAQ
AWS D1.4:2018 Clause 1.5.4 uses two formulas, not the IIW formula. For bars other than ASTM A706/A706M, CE = C + Mn/6. For ASTM A706/A706M, CE = C + Mn/6 + Cu/40 + Ni/20 + Cr/10 - Mo/50 - V/10. Table 7.2 then maps CE and bar size to preheat.
Table 7.2 covers SMAW with low-hydrogen electrodes, GMAW, FCAW, and GTAW. All four processes share the same preheat requirements — unlike D1.1, D1.4 does not differentiate preheat by welding process. Non-low-hydrogen SMAW is not addressed in this table.
When reinforcing bars are welded to structural steel, both D1.4 Table 7.2 and D1.1 Table 5.11 apply. Use the higher preheat requirement of the two tables. If the structural steel requires a higher preheat than the rebar, that higher temperature governs. Extreme caution is needed when welding rebar to quenched and tempered steels.
When Table 7.2 shows 'none', no minimum preheat temperature is required for that combination. However, if the base metal temperature is below 32°F (0°C), you must still preheat to at least 70°F (20°C) and maintain that temperature during welding. After welding, bars must cool naturally — accelerated cooling is prohibited.