AWS D1.1 Table 3.2 Preheat — Now Table 5.11

Table 3.2 vs Table 5.11 — What Changed?

When D1.1 was reorganized in the 2015 edition, preheat requirements moved from Clause 3 to Clause 5. The old Table 3.2 became Table 5.11.

If you learned D1.1 from the 2010 or earlier editions, you may still think of this as "Table 3.2." It is the same table with the same logic — just renumbered and expanded. Any WPS that still references Table 3.2 was written to a pre-2015 edition and should be reviewed against the current code to confirm the preheat values still match. In most cases they will, and Categories E, F, and G apply only when the current table lists the exact steel specification and matching process/hydrogen condition.

The 7 Preheat Categories (A Through G)

Table 5.11 organizes listed steel specifications into Categories A through G, with applicable welding-process and electrode-hydrogen requirements plus thickness bands. Match all of those columns; a process, hydrogen suffix, or Table 5.6 group alone does not select a category.

Categories A and B apply to the vast majority of structural fabrication. Category A covers the listed steels welded by SMAW with other-than-low-hydrogen electrodes. Category B covers the listed steels welded by low-hydrogen SMAW, SAW, GMAW, or FCAW. Categories D through G apply only to the steel specifications and process/hydrogen conditions listed in their rows; tighter hydrogen control alone does not make an unlisted steel eligible.

How to Read Table 5.11

Read Table 5.11 in column order: locate the listed steel specification, select the row whose welding process and electrode hydrogen designation match, then apply the thickness band for the thickest part at the point of welding. The lookup is not by group.

In the matched Table 5.11 row, apply the thickness band for the thickest part at the point of welding. That row gives the minimum preheat and interpass temperature in °F and °C.

Understanding Thickness Bands

Table 5.11 Categories A–C code bands are 1/8 to 3/4 in. incl. (3 mm to 20 mm incl.); over 3/4 thru 1-1/2 in. incl. (over 20 mm thru 38 mm incl.); over 1-1/2 thru 2-1/2 in. incl. (over 38 mm thru 65 mm incl.); and over 2-1/2 in. (over 65 mm). Thicker material requires higher preheat because the greater mass acts as a larger heat sink, pulling heat away from the weld faster and increasing the cooling rate in the heat-affected zone.

For example, A36 with E7018 (Category B) requires 32°F for material up to 3/4 in thick, 50°F for over 3/4 through 1-1/2 in, 150°F for over 1-1/2 through 2-1/2 in, and 225°F for material over 2-1/2 in. When the base-metal temperature is below 32°F, footnote a requires at least 70°F and maintenance of that temperature during welding. The A36 Category A row also starts at 32°F, then requires 150°F, 225°F, and 300°F across the remaining bands.

Categories D through G use thickness bands and temperatures tied to each named steel specification and matching process/hydrogen condition. Read the exact row; no general lower-preheat progression can be inferred from the category letter or hydrogen suffix.

Hydrogen Designators (H4, H8, H16)

The hydrogen designator indicates the maximum diffusible hydrogen in the deposited weld metal, measured in milliliters per 100 grams of deposited metal. It is one Table 5.11 input and does not select a category by itself.

H16: 16 mL/100g maximum. This designator is one Table 5.11 input; it does not by itself select Category C. Match the listed steel specification, welding process, hydrogen condition, and thickness.

H8: 8 mL/100g maximum. Electrodes must be tested and classified to this level. Categories D, E, and F are limited to named steel specifications and matching table rows; the Table 5.6 group and H8 suffix are not a shortcut.

H4: 4 mL/100g maximum. The Category G row lists ASTM A913 Grade 80 with its process and thickness conditions; an H4 suffix on another steel does not make that steel Category G. Careful electrode storage and handling remain necessary to preserve the classification.

Which Category Applies to Your Weld?

The most common question fabricators have is: "I have A992 steel, E7018 electrodes, and 1 in plate — what category?" For this listed combination, use the A992 Category B row and its thickness band. Adding an H8 suffix does not move A992 to Category D because A992 is not listed there.

For a quick lookup of any steel, process, and thickness combination, use the preheat calculator. It covers all 464 combinations in Table 5.11 and shows the category, minimum preheat, and applicable footnotes.

CWI Exam Tip