Pré-aquecimento M270M Gr.345W — H16, Mid HI, 20–40 mm: 225°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.

Entendendo o Pré-aquecimento FC para M270M Gr.345W / M270 Gr.50W

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 225°F minimum preheat at 20–40 mm (3/4–1½ 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.

Onde M270M Gr.345W / M270 Gr.50W é Usado

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.

Controle de Hidrogênio H16 para 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.

Por que o Pré-aquecimento Importa em 20–40 mm (3/4–1½ in)

Material from 20 to 40 mm (3/4 to 1-1/2 in) includes many girder web plates, splice plates, and bearing stiffener plates. Preheat increases to 20°C (70°F) for Group 1 and 50°C (125°F) for Group 2 under Table 6.3. The thicker section slows hydrogen diffusion, requiring higher preheat to maintain safe cooling rates.

M270M Gr.345W / M270 Gr.50W em 20–40 mm (3/4–1½ in)

At 20–40 mm, Gr.345W (50W) serves as the primary plate for unpainted bridge girder webs and connection plates. Weathering steel butt splices require the same CJP quality as painted Gr.345 but with compositional matching of the filler metal. Improper filler selection leaves a cosmetically distinct weld face that does not develop the same protective oxide, creating a maintenance concern on exposed bridges.

Maior Pré-aquecimento com Designação H16

Os consumíveis H16 permitem até 16 mL de hidrogênio difusível por 100g — o nível mais alto permitido para soldagem FC de pontes. Em 20–40 mm (3/4–1½ in) com aporte de calor 2.0–2.8 kJ/mm, o pré-aquecimento de 225°F (110°C) compensa o maior potencial de hidrogênio.

Outros Aços de Ponte em H16 2.0–2.8 kJ/mm · 20–40 mm (3/4–1½ in)

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

Experimente Diferentes Combinações

Use a Calculadora de Pré-aquecimento D1.5 para Pontes para consultar qualquer aço AASHTO M270, nível de hidrogênio e combinação de aporte de calor. Veja também a Calculadora de Pré-aquecimento D1.1 para aço estrutural.

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