Vorwärmung M270M HPS485W — H8, Low HI, ≤ 20 mm: 125°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 H8 hydrogen designation and this heat input band requires 125°F minimum preheat at ≤ 20 mm (3/4 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 H8 für M270M HPS485W / M270 HPS70W

HPS485W (HPS70W) at H8 represents a moderate preheat specification used when H4 consumables are not available in the required wire diameter or flux combination. For SAW on long girder flange welds, H8 wire-flux combinations are more readily available than H4 alternatives.

Warum Vorwärmung bei ≤ 20 mm (3/4 in) Wichtig ist

Material up to 20 mm (3/4 in) covers most cross-frame angles, stiffener clips, lateral bracing members, and light bridge plate. At this thickness, hydrogen diffusion is efficient and preheat requirements are the lowest in Table 6.3 — 10°C (50°F) for both groups. In FC service, this thickness tier also carries the lowest preheat in Tables 12.4–12.7, starting at 40°C (100°F) for H4 consumables.

M270M HPS485W / M270 HPS70W bei ≤ 20 mm (3/4 in)

HPS485W (HPS70W) under 20 mm is uncommon because its high-strength benefit is marginal at thin gauges where member capacity is governed by buckling rather than yield. When specified, it appears in compact tension flanges on short deep girders for interchange ramps. The Q&T microstructure makes welding procedure more sensitive to heat input than conventional grades — even at thin plate, interpass monitoring is essential.

Andere Brückenstähle bei H8 1.2–2.0 kJ/mm · ≤ 20 mm (3/4 in)

M270M HPS485W / M270 HPS70W bei H8 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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