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

M270M Gr.345S / M270 Gr.50S

AASHTO M270M Gr.345S (M270 Gr.50S) is the structural shape variant of Gr.345, intended for rolled W-shapes and channels used in bridge framing. The "S" suffix indicates the shape-specific chemistry and mechanical property requirements. Used in cross-frame angles, diaphragm members, and built-up sections where rolled shapes are specified rather than plate. Preheat requirements match Gr.345 — Table 6.3 Group 1 for NFC, Tables 12.4/12.5 for FC applications.

Comprendre le Préchauffage FC pour M270M Gr.345S / M270 Gr.50S

Shape-grade 345 MPa (50 ksi) steel for rolled bridge members. 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.345S / M270 Gr.50S est Utilisé

Used as rolled W-shapes and channels in bridge cross-frames, diaphragm members, and built-up sections. The "S" shape designation indicates procurement under AASHTO M270 with shape-specific chemistry and mandatory CVN testing. Common applications include WT sections for cross-frame members, MC channels for diaphragms, and W-shapes for floor beams on shorter spans. Weld details are primarily fillet welds at gusset connections and clip angles.

Contrôle d'Hydrogène H4 pour M270M Gr.345S / M270 Gr.50S

Shape-grade Gr.345S (50S) benefits from H4 at gusset-to-shape connections where access for torch preheat is limited by flanges and stiffeners. The lower preheat achievable with H4 reduces the thermal management complexity in tight spaces typical of cross-frame subassemblies.

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.345S / M270 Gr.50S à 40–60 mm (1½–2½ in)

Gr.345S (50S) shapes at 40–65 mm flange thickness are heavy built-up members — typically W14×426 or similar jumbo sections used as pier cap beams or transfer girders. The thick flanges of these shapes require full preheat per the heavy-section tier. Welding on thick rolled sections is complicated by residual stresses from rolling — preheat helps mitigate the cumulative effect of rolling residual stress plus welding shrinkage stress.

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.345S / M270 Gr.50S 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.345S / M270 Gr.50S 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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