Precalentamiento M270M Gr.345 — H8, Low HI, 20–40 mm: 175°F

M270M Gr.345 / M270 Gr.50

AASHTO M270M Gr.345 (M270 Gr.50) is the standard bridge plate and shape grade with 345 MPa (50 ksi) minimum yield, corresponding to ASTM A709 Gr.50. It is the baseline strength for modern highway bridge design per AASHTO LRFD. Used for plate girder flanges, webs, floor beams, cross-frames, and splice plates. Flanges on large plate girders routinely reach 50–75 mm (2–3 in) thick, making preheat compliance at upper thickness tiers a significant production consideration. NFC preheat per Table 6.3 Group 1; FC per Tables 12.4/12.5.

Entendiendo el Precalentamiento FC para M270M Gr.345 / M270 Gr.50

Standard 345 MPa (50 ksi) bridge plate for girders and floor beams. Under D1.5 fracture-critical requirements (Clause 12), the combination of H8 hydrogen designation and this heat input band requires 175°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.

Dónde se Usa M270M Gr.345 / M270 Gr.50

Standard for highway bridge plate girder flanges, box girder webs, cross-frame angles, bearing sole plates, and splice plates in bolted-welded connections. Gr.345 (50) is the baseline strength for modern AASHTO LRFD bridge design. Flange butt splices, web-to-flange continuous fillet welds, and bearing stiffener clips are the dominant weld types in girder fabrication. Girder flanges typically range from 20 to 75 mm (3/4 to 3 in) thick with widths from 300 to 750 mm (12 to 30 in), requiring extended preheat soak times on thicker flange splices.

Control de Hidrógeno H8 para M270M Gr.345 / M270 Gr.50

Gr.345 (50) with H8 is the standard specification for most bridge fabrication shops. H8 consumables are more widely stocked than H4, providing procurement flexibility without significantly increasing preheat requirements. The preheat increase from H4 to H8 is typically 10–25°F depending on thickness tier.

Por qué el Precalentamiento Importa en 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.345 / M270 Gr.50 en 20–40 mm (3/4–1½ in)

At 20–40 mm, Gr.345 (50) serves splice plates, web plates, and bearing sole plates in standard highway bridge girders. CJP butt welds at flange splices are the most critical joint at this thickness — full-penetration ultrasonically-inspected joints that must pass D1.5 acceptance criteria. Preheat compliance is production-critical: 70°F minimum means heated fabrication bays in northern climates during winter bridge contracts.

Otros Aceros de Puente en H8 1.2–2.0 kJ/mm · 20–40 mm (3/4–1½ in)

M270M Gr.345 / M270 Gr.50 en H8 1.2–2.0 kJ/mm

Prueba Diferentes Combinaciones

Usa la Calculadora de Precalentamiento D1.5 para Puentes para consultar cualquier acero AASHTO M270, nivel de hidrógeno y combinación de aporte térmico. También consulta la Calculadora de Precalentamiento D1.1 para acero estructural.

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