Préchauffage M270M HPS345W — H8, Low HI, 40–60 mm: 325°F

M270M HPS345W / M270 HPS50W

AASHTO M270M HPS345W (M270 HPS50W) is a high-performance weathering bridge steel with enhanced weldability through controlled chemistry — 0.11% max carbon, 0.006% max sulfur with calcium treatment for inclusion shape control. Developed under FHWA-funded research to eliminate the lamellar tearing and inconsistent toughness problems of earlier weathering steel bridge designs. The lower carbon equivalent compared to conventional Gr.345W reduces cracking sensitivity at flange splices. NFC preheat per Table 6.3 Group 1; FC per Tables 12.6/12.7.

Comprendre le Préchauffage FC pour M270M HPS345W / M270 HPS50W

High-performance weathering 345 MPa steel with enhanced weldability. Under D1.5 fracture-critical requirements (Clause 12), the combination of H8 hydrogen designation and this heat input band requires 325°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 HPS345W / M270 HPS50W est Utilisé

Preferred over conventional Gr.345W for new unpainted bridge construction. The HPS designation indicates FHWA-developed chemistry with 0.11% max carbon and controlled sulfur for enhanced weldability and lamellar tearing resistance. Flange splice CJP welds benefit from the lower carbon equivalent, reducing reject rates during cold-weather bridge fabrication. Material cost premium over standard Gr.345W is typically 15–25% per ton but eliminates weldability-related rework.

Contrôle d'Hydrogène H8 pour M270M HPS345W / M270 HPS50W

HPS345W (HPS50W) with H8 is common practice where the HPS weldability advantage partially compensates for the higher hydrogen level. The controlled chemistry means HPS345W at H8 often has lower total cracking susceptibility than conventional 345W at H4 — illustrating how base metal chemistry and hydrogen control interact.

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 HPS345W / M270 HPS50W à 40–60 mm (1½–2½ in)

HPS345W (HPS50W) at 40–65 mm covers main flange plates on new unpainted highway bridges. The controlled chemistry gives better CVN toughness transition behavior than conventional 345W — 20–30 J higher at -29°C (−20°F) — which improves the fracture resistance of thick flange splices in cold-climate service. Fabricators report 30–40% fewer repair rates on HPS flange splice welds compared to conventional 345W at the same thickness.

Autres Aciers de Pont à H8 1.2–2.0 kJ/mm · 40–60 mm (1½–2½ in)

M270M HPS345W / M270 HPS50W à H8 1.2–2.0 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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