AWS D1.1:2025 · Table 5.11

Preheat Calculator for Welding

Free online tool for welders and fabricators — look up minimum preheat and interpass temperature from AWS D1.1:2025 Table 5.11. Select steel specification, welding process, and thickness.

For the Annex B chemistry-based alternative, use our carbon equivalent calculator.

Built on AWS D1.1:2025 Table 5.11 — every value traced to the clause.

Method Selector

Which calculator should you use?

Use this tool when you need the prequalified D1.1 prescriptive lookup from Table 5.11. If you are running the chemistry-based Annex B path, switch to the carbon equivalent calculator first, then continue with Annex B calculations.

Steel Specification Welding Process

Electrode/flux is H8-certified (≤8 mL/100g per AWS A4.3)

Thickness of the thickest part at the point of welding

For Table 5.11, use the thickness of the thickest part at the point of welding.

Reference

Prequalified Minimum Preheat — `Table 5.11` Summary

Cat	Process Column	≤3/4"	>3/4–1½"	>1½–2½"	>2½"
A	SMAW non-LH	32/0	150/65	225/110	300/150
B	LH / SAW / GMAW / FCAW	32/0	50/10	150/65	225/110
C	LH / SAW / GMAW / FCAW	50/10	150/65	225/110	300/150
D	H8 (any process)	32/0 — all thicknesses over 1/8"
E	H8 (any process)	≤1": 50/10 \| >1": 120/50
F	H8 (any process)	≤2½": 32/0 \| >2½": 150/65
G	H4 (any process)	32/0	50/10	150/65	225/110

Temperatures: °F / °C. All values per AWS D1.1:2025 Table 5.11, §5.7.

Per AWS D1.1:2025 Clause 5.7.1: “Table 5.11 shall be used to determine the minimum preheat and interpass temperatures for steels listed in the code.”

D1.1 Preheat Methods

Two Methods for D1.1 Preheat

D1.1 Table 5.11 is the default prescriptive method for determining preheat. The table defines 7 material categories (A through G) across 4 thickness ranges for 4 welding processes, producing the minimum preheat and interpass temperature for any prequalified combination.

This calculator uses Table 5.11. Select your steel grade, welding process, and material thickness to look up the value. No chemistry data is needed. Table 5.11 applies to all prequalified WPS per Clause 5.7.

D1.1 Annex B provides an alternative analytical method using carbon equivalent from your steel chemistry. CE(IIW) drives the HAZ hardness control method for fillet welds. Pcm drives the hydrogen control method for all joint types. Use our carbon equivalent calculator to compute CE and Pcm from mill test report values.

Table 5.11 is the preheat source for prequalified WPSs (Clause 5.7.1). Per Clause B1, Annex B may indicate whether Table 5.11 is overly conservative or, in some cases, not sufficiently demanding for your steel. Annex B does not qualify an unlisted steel: only base metals listed in Table 5.6 may be used in prequalified WPSs (Clause 5.3), except unlisted auxiliary-attachment material within a listed steel's chemical composition range, which may be used in a prequalified WPS when approved by the Engineer, with Table 5.7 filler metal and Clause 5.7 preheat (Clause 5.3.1). Any other unlisted base metal needs a WPS qualified under Clause 6 (Clause 6.8.3). A prequalified WPS must include the base metal preheat category (Table 5.5, item 4). For a WPS qualified by testing, the minimum preheat is established by a Clause 6.8.4.1 method, and the WPS values come from the procedure qualification record (PQR) (Clause 6.7).

In using Annex B as an alternative to Table 5.11, Clause B1 requires careful consideration of the assumptions made, the values selected, and past experience; under Clause 6.8.4.1(2), an Annex B preheat lower than Table 5.11 may be used for WPS qualification. See our carbon equivalent explained page for the full Annex B zone classification and decision flow. For fillet weld symbol callouts on your drawings, preheat applies equally to fillet and groove welds per Table 5.11.

Preheat is an essential variable in ASME Section IX (QW-406) and a prequalified requirement in D1.1 (Table 5.11). Different codes, different rules — always verify against your governing code.

Once your preheat is set, throughput planning typically pairs with the deposition rate calculator to translate your wire feed speed into pounds of weld metal per hour at the same voltage and amperage you'll run on the hot plate.

"The single most common cause of hydrogen cracking in structural steel is inadequate preheat — not the steel, not the electrode, but the temperature of the base metal when the arc strikes."
— Common CWI training principle, reinforced by D1.1:2025 Commentary C-5.7

Common Questions

FAQ

What is the minimum preheat for A36 steel?

A36 is a Group I steel in D1.1:2025 Table 5.6 and falls into preheat Category A or B depending on your welding process per Table 5.11. With non-low-hydrogen SMAW electrodes like E6010 or E6011 (Category A), minimum preheat is 32°F (0°C) for material up to 3/4 in, 150°F (65°C) for 3/4 to 1-1/2 in, 225°F (110°C) for 1-1/2 to 2-1/2 in, and 300°F (150°C) over 2-1/2 in. With low-hydrogen processes — E7018 SMAW, SAW, GMAW, or FCAW (Category B) — preheat requirements are lower: 32°F up to 3/4 in, 50°F (10°C) for 3/4 to 1-1/2 in, 150°F for 1-1/2 to 2-1/2 in, and 225°F over 2-1/2 in. Preheat temperature shall be checked just prior to initiating the arc for each pass, per Clause 7.6.4.

Does GMAW require preheat for structural steel?

Yes. GMAW falls under Category B in D1.1 Table 5.11, grouped with low-hydrogen SMAW, SAW, and FCAW. For common structural steels like A36, A572 Gr.50, and A992, minimum preheat with GMAW is 32°F (0°C) up to 3/4" thickness, 50°F (10°C) for 3/4"–1-1/2", 150°F (65°C) for 1-1/2"–2-1/2", and 225°F (110°C) over 2-1/2". The 32°F minimum for thin plate means no active preheat is needed above freezing — ambient shop temperature satisfies the requirement. GMAW qualifies for Category B because solid wire electrodes like ER70S-6 inherently produce low diffusible hydrogen levels, typically well below the H8 threshold of 8 mL per 100g of deposited weld metal. This low hydrogen characteristic is why GMAW receives the same favorable preheat treatment as low-hydrogen SMAW electrodes like E7018. However, GMAW is never listed under Category A because non-low-hydrogen classification does not apply to the gas metal arc welding process.

What is Category B in D1.1 preheat?

Category B in D1.1 Table 5.11 covers steels welded with low-hydrogen electrodes (E7018, E7016, etc.), submerged arc welding (SAW), gas metal arc welding (GMAW), or flux-cored arc welding (FCAW). It applies to the most commonly used structural steels in building and bridge construction: A36, A572 Gr.50, A992, A588, A709 Gr.36, A709 Gr.50, A500 Gr.B/C, A53 Gr.B, and A106 Gr.B. Category B has lower preheat requirements than Category A because these processes and electrodes produce significantly less diffusible hydrogen in the weld deposit, which reduces the risk of hydrogen-induced cracking (also called cold cracking or delayed cracking). The preheat values for Category B are: 32°F (0°C) up to 3/4", 50°F (10°C) for 3/4"–1-1/2", 150°F (65°C) for 1-1/2"–2-1/2", and 225°F (110°C) over 2-1/2". In practice, Category B is the most frequently used preheat category because most structural steel fabrication uses low-hydrogen processes.

What is the difference between preheat and interpass temperature?

In D1.1, the minimum preheat temperature is the base metal temperature required before the first arc is struck. The minimum interpass temperature is the lowest temperature the weld zone may cool to between successive passes in a multi-pass weld. Table 5.11 sets both to the same value — the listed temperature applies to both initial preheat and between-pass cooling. You cannot let the weld area cool below the listed temperature during multi-pass welding. For example, if Table 5.11 specifies 150°F for your steel and thickness, you must preheat to at least 150°F before welding and maintain at least 150°F between every pass. Preheat temperature shall be checked just prior to initiating the arc for each pass per Clause 7.6.4. Some higher-strength steels also have a maximum interpass temperature limit to prevent grain coarsening — check the WPS for any upper bound.

Do I need preheat for plate under 3/4 inch?

No single preheat value applies to every plate under 3/4 in. In Table 5.11, locate the specific listed steel specification, match the welding process and electrode hydrogen designation, and then read the applicable thickness band. For example, the A36 rows in Categories A and B both give 32°F (0°C) for 1/8 through 3/4 in. Per Table 5.11 footnote (a), when the base metal is below 32°F, preheat it to at least 70°F (20°C) and maintain the minimum interpass temperature during welding. Table 5.6 separately groups approved base metals for filler-metal matching; its group is not the Table 5.11 lookup key.

What does D1.1 Table 5.11 cover?

D1.1 Table 5.11 specifies minimum preheat and interpass temperatures for prequalified welding procedure specifications (WPS). Read it in column order: locate the exact listed steel specification, match the welding process and electrode hydrogen designation in that row, then apply that row’s thickness band. The number and range of thickness bands vary by row. Table 5.6 separately groups approved base metals; its group is not the Table 5.11 lookup key. Table 5.11 applies to prequalified WPSs under Clause 5. For a WPS qualified by testing under Clause 6, Clause 6.8.4.1 establishes the minimum preheat by one of three methods: the Table 5.11 or Table 6.10 value, an Annex B value (a lower Annex B value may be used for WPS qualification), or a value qualified by the WPS qualification test.

What is the difference between H4 and H8 electrodes?

H4 and H8 are diffusible hydrogen designations defined by AWS A4.3 testing methods. H8 means the electrode, wire, or flux combination deposits no more than 8 mL of diffusible hydrogen per 100 g of deposited weld metal. H4 is stricter — no more than 4 mL per 100 g. These designations matter for Table 5.11 because higher-strength steels are more susceptible to hydrogen-induced cracking and require tighter hydrogen control. For example, A913 Gr.50, 60, and 65 steels in Table 5.11 qualify for Category D preheat when welded with H8 consumables. A913 Gr.80 requires H4 consumables — the most restrictive classification — reflecting its higher yield strength and greater cracking sensitivity. Common H8 consumables include E7018-H8 SMAW electrodes and most GMAW solid wires like ER70S-6. H4 consumables typically require special handling and storage procedures to maintain their low-hydrogen rating.

What is the Annex B alternative to Table 5.11?

D1.1 Annex B provides two analytical methods for determining preheat using actual steel chemistry instead of specification-based categories. The HAZ hardness control method uses CE = C + (Mn+Si)/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 for fillet welds. The hydrogen control method uses Pcm = C + Si/30 + Mn/20 + Cu/20 + Ni/60 + Cr/20 + Mo/15 + V/10 + 5B for all joint types. Annex B considers the actual chemistry from your mill test report, the hydrogen level of your consumables, and the restraint of your joint — three variables that Table 5.11 does not account for. Table 5.11 is the default for prequalified WPS. Annex B is the alternative when Table 5.11 appears overly conservative or not sufficiently demanding for your specific steel chemistry. Clause B1 requires careful consideration of the assumptions made, the values selected, and past experience when Annex B is used as an alternative to Table 5.11, and Clause 6.8.4.1(2) permits a lower Annex B preheat for WPS qualification. Source note: both formulas are not legible at the source resolution we verify against (AWS D1.1:2025 Annex B prints them as low-resolution images); both match AWS D1.1:2020 (2020 OCR witness, unchanged passage); check the published standard.

Calculate your CE and Pcm with our carbon equivalent calculator.

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Common Steel & Process Preheat Pages

A36 + SMAW3/4"–1-1/2" — 150°F A36 + GMAW≤3/4" — 32°F A572 Gr.50 + GMAW3/4"–1-1/2" — 50°F A992 + FCAW1-1/2"–2-1/2" — 150°F A516 Gr.70 + SMAW-LH>2-1/2" — 225°F A588 + SMAW-LH3/4"–1-1/2" — 50°F A709 Gr.50 + SAW>2-1/2" — 225°F A106 Gr.B + SMAW3/4"–1-1/2" — 150°F

AWS D1.1/D1.1M:2025 (current edition)