Vorwärmung M270M HPS345W — H4, High HI, 40–60 mm: 250°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.

Die FC-Vorwärmung für M270M HPS345W / M270 HPS50W Verstehen

High-performance weathering 345 MPa steel with enhanced weldability. Under D1.5 fracture-critical requirements (Clause 12), the combination of H4 hydrogen designation and this heat input band requires 250°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.

Wo M270M HPS345W / M270 HPS50W Eingesetzt Wird

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.

Wasserstoffkontrolle H4 für M270M HPS345W / M270 HPS50W

HPS345W (HPS50W) already has inherently low carbon equivalent due to HPS chemistry control. Combined with H4 consumables, the preheat requirement drops to the lowest tier in Tables 12.6/12.7 — frequently 20–30°F lower than conventional 345W, compounding the weldability advantage of HPS chemistry with optimized hydrogen control.

Warum Vorwärmung bei 40–60 mm (1½–2½ in) Wichtig ist

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 bei 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.

H4-Zertifizierte Zusatzwerkstoffe für FC-Brückenschweißen

Die Zusatzbezeichnung H4 zertifiziert, dass der Zusatzwerkstoff höchstens 4 mL diffusiblen Wasserstoff pro 100g abgeschiedenes Schweißgut abgibt. Für bruchkritischen M270M HPS345W / M270 HPS50W bei 40–60 mm (1½–2½ in) Dicke mit > 2.8 kJ/mm Wärmeeinbringung erreichen H4-Zusatzwerkstoffe die niedrigste Vorwärmung von 250°F (120°C) in den FC-Tabellen.

Andere Brückenstähle bei H4 > 2.8 kJ/mm · 40–60 mm (1½–2½ in)

M270M HPS345W / M270 HPS50W bei H4 > 2.8 kJ/mm

Verschiedene Kombinationen Ausprobieren

Verwenden Sie den D1.5 Brücken-Vorwärmrechner für jeden AASHTO M270 Stahl, Wasserstoffniveau und Wärmeeinbringungskombination. Siehe auch den D1.1 Vorwärmrechner für Baustahl.

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