Vorwärmung M270M Gr.345W — H16, Mid HI, > 60 mm: 375°F

M270M Gr.345W / M270 Gr.50W

AASHTO M270M Gr.345W (M270 Gr.50W) is a weathering bridge steel with 345 MPa (50 ksi) yield that forms a protective oxide patina for unpainted bridge service. The copper-chromium-nickel alloying provides atmospheric corrosion resistance, eliminating lifetime repainting costs estimated at $15–25 per square foot per cycle. Weld filler must match the weathering composition (E8018-W2 or equivalent) for exposed joints. NFC preheat per Table 6.3 Group 1; FC per Tables 12.6/12.7 which carry higher preheat than the non-weathering grades.

Die FC-Vorwärmung für M270M Gr.345W / M270 Gr.50W Verstehen

Weathering 345 MPa (50 ksi) bridge steel for unpainted service. Under D1.5 fracture-critical requirements (Clause 12), the combination of H16 hydrogen designation and this heat input band requires 375°F minimum preheat at > 60 mm (> 2½ in). Lower hydrogen levels (H4 < H8 < H16) allow lower preheat because less hydrogen enters the weld deposit. Similarly, higher heat input reduces preheat requirements because slower cooling rates give hydrogen more time to diffuse out.

Wo M270M Gr.345W / M270 Gr.50W Eingesetzt Wird

Deployed in unpainted bridge plate girders across humid, coastal, and high-maintenance-cost environments. The weathering patina eliminates lifetime repainting cycles estimated at $15–25/sq ft per cycle. Weld filler must match the weathering composition (E8018-W2 or ER80S-G-W) for exposed joints to ensure the weld face develops the same protective oxide as the base metal. Conventional Gr.345W is being replaced by HPS345W in new designs due to superior weldability.

Wasserstoffkontrolle H16 für M270M Gr.345W / M270 Gr.50W

Weathering Gr.345W (50W) at H16 is used for field splices when self-shielded FCAW is the only practical process due to wind exposure on elevated bridge erection. The significantly higher preheat at H16 — often 40–60°F above H4 — makes weather-window scheduling critical for winter field splice operations.

Warum Vorwärmung bei > 60 mm (> 2½ in) Wichtig ist

Material over 65 mm (2-1/2 in) includes the heaviest bridge girder flanges and box-section walls. Table 6.3 requires 110°C (225°F) for both groups at this thickness. Extended preheat soak time is necessary to achieve uniform through-thickness temperature. FC preheat for the heaviest sections reaches 180–200°C (350–400°F) at the H16 hydrogen level.

M270M Gr.345W / M270 Gr.50W bei > 60 mm (> 2½ in)

Gr.345W (50W) above 65 mm is increasingly rare as HPS345W replaces it in new designs. The conventional weathering composition at this thickness has elevated lamellar tearing risk from sulfide inclusion elongation — the problem that drove development of the HPS grades with calcium-treated, inclusion-shape-controlled steel. Existing bridges with thick 345W flanges require careful Z-direction tension checks during rehabilitation welding.

Höhere Vorwärmung bei H16-Bezeichnung

H16-Zusatzwerkstoffe erlauben bis zu 16 mL diffusiblen Wasserstoff pro 100g — das höchste zulässige Niveau für FC-Brückenschweißen. Bei > 60 mm (> 2½ in) mit 2.0–2.8 kJ/mm Wärmeeinbringung kompensiert die Vorwärmung von 375°F (190°C) das höhere Wasserstoffpotential.

Andere Brückenstähle bei H16 2.0–2.8 kJ/mm · > 60 mm (> 2½ in)

M270M Gr.345W / M270 Gr.50W bei H16 2.0–2.8 kJ/mm

Verschiedene Kombinationen Ausprobieren

Verwenden Sie den D1.5 Brücken-Vorwärmrechner für jeden AASHTO M270 Stahl, Wasserstoffniveau und Wärmeeinbringungskombination. Siehe auch den D1.1 Vorwärmrechner für Baustahl.

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