A516 Gr.55/60のSMAW (non-low-hydrogen)用予熱 — up to 3/4"
A516 Gr.55/60をSMAW (non-low-hydrogen)で板厚up to 3/4"で溶接する場合の最低予熱およびパス間温度。AWS D1.1:2025 表5.11に基づく。
AWS D1.1:2025 表5.11に基づく — すべての値は条項に追跡可能。
非低水素SMAWプロセス
SMAW (Non-Low-Hydrogen)
Non-low-hydrogen SMAW (E6010/E6011) uses cellulosic electrodes with higher hydrogen potential, assigned to Category A in Table 5.11.
For pressure vessel plate, non-low-hydrogen SMAW is typically limited to non-pressure attachments and temporary fit-up clips. Code requirements per ASME Section VIII often mandate low-hydrogen processes for pressure-retaining welds. Any E6010 tack welds on pressure boundaries must be completely removed before final low-hydrogen welding.
A516 Gr.55/60
ASTM A516 Grades 55 and 60 are carbon steel plates designed for moderate and lower temperature pressure vessel service. Grade 55 (55 ksi tensile, 30 ksi yield) and Grade 60 (60 ksi tensile, 32 ksi yield) are widely used in storage tanks, heat exchangers, and process drums. Chemistry limits (0.24% max carbon for Gr.55, 0.27% max carbon for Gr.60 on thicker plate) and typical carbon equivalent of 0.38-0.44 qualify them for both Category A (non-low-hydrogen) and Category B preheat in Table 5.11. A516 is produced in plate thicknesses from 1/4" through 12". Grades 55 and 60 may be ordered as-rolled, normalized, or stress-relieved depending on the ASME Code requirements for the specific vessel design temperature and thickness.
A516 Gr.55/60とSMAWでこの予熱が必要な理由
Pressure vessel plate for storage tanks and heat exchangers at moderate strength. At this thickness, SMAW with non-low-hydrogen electrodes places the joint in Category A of Table 5.11. The minimum preheat of 32°F compensates for the higher diffusible hydrogen from cellulosic electrode coatings. The thicker the material, the longer hydrogen takes to escape the heat-affected zone, which is why preheat rises with thickness even for this common grade.
A516 Gr.55/60の代表的な適用例
Specified for atmospheric storage tank shells per API 650, heat exchanger tube sheets, air receiver vessels, condensate drums, deaerator shells, and low-pressure separator vessels. A516 Gr.60 is the workhorse for ASME VIII Division 1 vessels under 650°F design temperature. Shell-to-head circumferential seams and nozzle reinforcement pads are the primary weld details. Plate thicknesses for API 650 tank shells typically range from 5/16" at the top course to 1" or more at the bottom course depending on tank diameter and liquid specific gravity. Vertical seam welds carry the full hydrostatic head and require complete joint penetration with radiographic examination. Tank diameters range from 15 feet for small day tanks to over 300 feet for crude oil terminal storage. Shop-welded vessel shells are rolled from flat plate with longitudinal seams welded first, then circumferential seams joining shell courses together on the vessel rotator.
up to 3/4"で予熱が重要な理由
Thin material sheds heat quickly, allowing hydrogen to escape the HAZ readily — lowest preheat tier in Table 5.11.
A516 Gr.55/60に32°Fが適用される理由
最低予熱32°F（0°C）は、氷点以上の条件では積極的な予熱が不要であることを意味します。表5.11 カテゴリーAは、A516 Gr.55/60を非低水素SMAWで溶接する場合、この板厚では延性が十分で炭素当量が低いため水素割れのリスクが最小限であるとして、周囲温度を最低値として設定しています。脚注(a)により、32°F未満で作業する場合は、継手を少なくとも70°F（20°C）まで予熱し、溶接中も維持すること。
A516 Gr.55/60とSMAW (non-low-hydrogen)
A516 Gr.55/60溶接ガイド
D1.1:2025参考データ。AWSとの提携なし。