Préchauffage M270M HPS485W — H8, Mid HI, 20–40 mm: 200°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.

Comprendre le Préchauffage FC pour 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 200°F minimum preheat at 20–40 mm (3/4–1½ 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 HPS485W / M270 HPS70W est Utilisé

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.

Contrôle d'Hydrogène H8 pour 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.

Pourquoi le Préchauffage est Important à 20–40 mm (3/4–1½ in)

Material from 20 to 40 mm (3/4 to 1-1/2 in) includes many girder web plates, splice plates, and bearing stiffener plates. Preheat increases to 20°C (70°F) for Group 1 and 50°C (125°F) for Group 2 under Table 6.3. The thicker section slows hydrogen diffusion, requiring higher preheat to maintain safe cooling rates.

M270M HPS485W / M270 HPS70W à 20–40 mm (3/4–1½ in)

At 20–40 mm, HPS485W (HPS70W) serves as the primary flange material for long-span bridge girders where weight reduction is the design driver. The 70 ksi yield enables 20–30% thinner flanges versus Gr.345 designs, reducing dead load and allowing shallower girder depths that save embankment costs. CJP flange splices at this thickness require precise heat input control to stay within the FC table parameters.

Autres Aciers de Pont à H8 2.0–2.8 kJ/mm · 20–40 mm (3/4–1½ in)

M270M HPS485W / M270 HPS70W à H8 2.0–2.8 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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