Préchauffage M270M Gr.345 — H4, High HI, 40–60 mm: 150°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.

Comprendre le Préchauffage FC pour 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 150°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.

Où M270M Gr.345 / M270 Gr.50 est Utilisé

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.

Contrôle d'Hydrogène H4 pour 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.

Pourquoi le Préchauffage est Important à 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 à 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.

Consommables Certifiés H4 pour Soudage FC de Ponts

Le désignateur supplémentaire H4 certifie que le consommable dépose au maximum 4 mL d'hydrogène diffusible par 100g de métal déposé. Pour fracture critique M270M Gr.345 / M270 Gr.50 à 40–60 mm (1½–2½ in) d'épaisseur avec apport de chaleur > 2.8 kJ/mm, les consommables H4 atteignent le préchauffage le plus bas de 150°F (70°C) dans les tableaux FC.

Autres Aciers de Pont à H4 > 2.8 kJ/mm · 40–60 mm (1½–2½ in)

M270M Gr.345 / M270 Gr.50 à H4 > 2.8 kJ/mm

Essayez Différentes Combinaisons

Utilisez le Calculateur de Préchauffage D1.5 pour Ponts pour consulter tout acier AASHTO M270, niveau d'hydrogène et combinaison d'apport de chaleur. Voir aussi le Calculateur de Préchauffage D1.1 pour l'acier de construction.

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