Preheat M270M HPS485W — H8, Low HI, 40–60 mm: 325°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.

Memahami Preheat FC untuk M270M HPS485W / M270 HPS70W

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 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.

Di Mana M270M HPS485W / M270 HPS70W Digunakan

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.

Kontrol Hidrogen H8 untuk 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.

Mengapa Preheat Penting pada 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 HPS485W / M270 HPS70W pada 40–60 mm (1½–2½ in)

HPS485W (HPS70W) at 40–65 mm represents the critical design case for long-span cable-stayed and continuous girder bridges. Flange plates this thick with 70 ksi yield can support spans exceeding 300 feet (90 m) with conventional plate girder construction. FC preheat at this thickness tier is substantially higher than Group 1 grades, and dual-readout temperature monitoring is mandatory to ensure compliance with both preheat minimum and interpass maximum.

Baja Jembatan Lain pada H8 1.2–2.0 kJ/mm · 40–60 mm (1½–2½ in)

M270M HPS485W / M270 HPS70W pada H8 1.2–2.0 kJ/mm

Coba Kombinasi Berbeda

Gunakan Kalkulator Preheat Jembatan D1.5 untuk mencari baja AASHTO M270, tingkat hidrogen, dan kombinasi masukan panas. Lihat juga Kalkulator Preheat D1.1 untuk baja struktural.

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