Préchauffage M270M HPS485W — H16, Low HI, > 60 mm: 400°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 H16 hydrogen designation and this heat input band requires 400°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.

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 H16 pour M270M HPS485W / M270 HPS70W

HPS485W (HPS70W) at H16 represents the highest-risk FC scenario for this grade — the combination of high strength, high hardenability, and high hydrogen demands the maximum preheat in Tables 12.6/12.7. Production scheduling must account for extended preheat soak times at every joint. Many fabricators refuse H16 on HPS485W, requiring H4 or H8 in their shop standards.

Pourquoi le Préchauffage est Important à > 60 mm (> 2½ in)

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 à > 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.

Préchauffage Plus Élevé avec Désignation H16

Les consommables H16 permettent jusqu'à 16 mL d'hydrogène diffusible par 100g — le niveau le plus élevé autorisé pour le soudage FC de ponts. À > 60 mm (> 2½ in) avec apport de chaleur 1.2–2.0 kJ/mm, le préchauffage de 400°F (200°C) compense le potentiel d'hydrogène plus élevé.

Autres Aciers de Pont à H16 1.2–2.0 kJ/mm · > 60 mm (> 2½ in)

M270M HPS485W / M270 HPS70W à H16 1.2–2.0 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.

Guides Associés