Vorwärmung M270M HPS485W — H4, Low HI, > 60 mm: 350°F

M270M HPS485W / M270 HPS70W

AASHTO M270M HPS485W (M270 HPS70W) is a high-performance weathering steel with 485 MPa (70 ksi) yield, used in long-span bridge girder flanges and heavily loaded members where weight reduction is critical. Produced as quenched-and-tempered plate up to 100 mm (4 in) thick. The high strength level places it in NFC Group 2 (Table 6.3) with higher minimum preheat than Group 1. FC preheat follows Tables 12.6/12.7 alongside the 345W grades but at higher temperatures reflecting the increased hardenability. Maximum interpass per Table 6.4 is 230°C (450°F) to protect the Q&T microstructure.

Die FC-Vorwärmung für M270M HPS485W / M270 HPS70W Verstehen

High-performance 485 MPa (70 ksi) weathering bridge steel. Under D1.5 fracture-critical requirements (Clause 12), the combination of H4 hydrogen designation and this heat input band requires 350°F minimum preheat at > 60 mm (> 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 HPS485W / M270 HPS70W Eingesetzt Wird

Used in long-span bridge main girder flanges, cable-stayed bridge edge girders, and heavily loaded interchange ramp girders where weight reduction is critical. Enables 20–30% weight savings versus Gr.345 designs, allowing shallower girder sections that reduce embankment costs. Flange thickness often exceeds 50 mm (2 in), making preheat and interpass control critical at every CJP splice. Fabricators must use dual-readout temperature monitoring to ensure joints stay within the qualified range between minimum preheat and maximum interpass.

Wasserstoffkontrolle H4 für M270M HPS485W / M270 HPS70W

For HPS485W (HPS70W), specifying H4 consumables is a strategic choice that significantly reduces preheat costs on thick flange splices. At 40+ mm flange thickness, every 25°F reduction in required preheat saves approximately 15–20 minutes per splice in heating time, directly impacting the critical-path schedule of bridge girder fabrication.

Warum Vorwärmung bei > 60 mm (> 2½ in) Wichtig ist

Material over 65 mm (2-1/2 in) includes the heaviest bridge girder flanges and box-section walls. Table 6.3 requires 110°C (225°F) for both groups at this thickness. Extended preheat soak time is necessary to achieve uniform through-thickness temperature. FC preheat for the heaviest sections reaches 180–200°C (350–400°F) at the H16 hydrogen level.

M270M HPS485W / M270 HPS70W bei > 60 mm (> 2½ in)

HPS485W (HPS70W) above 65 mm is the heaviest plate used in high-performance bridge construction. Flange widths reach 750–900 mm (30–36 in), with splice welds requiring 100+ passes over multiple shifts. Temperature management becomes the dominant production variable — too cold risks cracking, too hot risks softening the Q&T microstructure. Fabricators invest in automated temperature monitoring systems with data logging for FC traceability.

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 HPS485W / M270 HPS70W bei > 60 mm (> 2½ in) Dicke mit 1.2–2.0 kJ/mm Wärmeeinbringung erreichen H4-Zusatzwerkstoffe die niedrigste Vorwärmung von 350°F (180°C) in den FC-Tabellen.

Andere Brückenstähle bei H4 1.2–2.0 kJ/mm · > 60 mm (> 2½ in)

M270M HPS485W / M270 HPS70W bei H4 1.2–2.0 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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