Precalentamiento M270M Gr.345 — H8, Low HI, 40–60 mm: 225°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 225°F minimum preheat at 40–60 mm (1½–2½ 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.

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 40–60 mm (1½–2½ in)

Material from 40 to 65 mm (1-1/2 to 2-1/2 in) covers heavy girder flanges, thick splice plates, and main member plate. This is the critical thickness range for bridge fabrication — preheat reaches 65°C (150°F) for Group 1 and 80°C (175°F) for Group 2. FC preheat at this thickness can exceed 200°C (400°F) depending on hydrogen level and heat input.

M270M Gr.345 / M270 Gr.50 en 40–60 mm (1½–2½ in)

Gr.345 (50) at 40–65 mm includes the main flange plates on medium-span highway bridges. Flange width typically runs 400–600 mm (16–24 in), requiring multi-pass CJP butt splices that accumulate 40–60 passes. Interpass temperature must stay above preheat minimum between passes and below the Table 6.4 maximum — this dual constraint makes temperature monitoring continuous during flange splice welding. Magnetic particle examination of each completed splice adds to the production schedule.

Otros Aceros de Puente en H8 1.2–2.0 kJ/mm · 40–60 mm (1½–2½ 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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