Precalentamiento M270M Gr.345 — H4, Low HI, ≤ 20 mm: 100°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 H4 hydrogen designation and this heat input band requires 100°F minimum preheat at ≤ 20 mm (3/4 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 H4 para M270M Gr.345 / M270 Gr.50

Gr.345 (50) with H4 consumables achieves the lowest FC preheat requirements available for the workhorse bridge grade. On girder fabrication lines producing 50–100 meters of flange-to-web fillet weld per shift, the reduced preheat from H4 translates directly to faster welding speed and lower fuel costs for preheat maintenance.

Por qué el Precalentamiento Importa en ≤ 20 mm (3/4 in)

Material up to 20 mm (3/4 in) covers most cross-frame angles, stiffener clips, lateral bracing members, and light bridge plate. At this thickness, hydrogen diffusion is efficient and preheat requirements are the lowest in Table 6.3 — 10°C (50°F) for both groups. In FC service, this thickness tier also carries the lowest preheat in Tables 12.4–12.7, starting at 40°C (100°F) for H4 consumables.

M270M Gr.345 / M270 Gr.50 en ≤ 20 mm (3/4 in)

Gr.345 (50) under 20 mm covers web stiffeners, bearing stiffener clips, and cross-frame gusset plates — the highest-volume weld details in girder fabrication. These thin plates are fillet-welded to girder webs using semi-automatic FCAW with E71T-1 wire at 2–4 kg/hr deposition. Preheat is quick to achieve with a rosebud torch and verifiable with a temperature-indicating crayon. Joint fit-up at this thickness is critical because thin plate distortion from uncontrolled heat input causes cumulative girder sweep.

Consumibles Certificados H4 para Soldadura FC de Puentes

El designador suplementario H4 certifica que el consumible deposita no más de 4 mL de hidrógeno difusible por 100g de metal depositado. Para fractura crítica M270M Gr.345 / M270 Gr.50 en espesor ≤ 20 mm (3/4 in) con aporte térmico 1.2–2.0 kJ/mm, los consumibles H4 logran el menor precalentamiento de 100°F (40°C) en las tablas FC.

Otros Aceros de Puente en H4 1.2–2.0 kJ/mm · ≤ 20 mm (3/4 in)

M270M Gr.345 / M270 Gr.50 en H4 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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