M270M HPS485W予熱 — H16、Mid 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.

M270M HPS485W / M270 HPS70WのFC予熱を理解する

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 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.

M270M HPS485W / M270 HPS70Wの使用箇所

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.

M270M HPS485W / M270 HPS70WにおけるH16水素管理

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.

≤ 20 mm (3/4 in)で予熱が重要な理由

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.

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

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.

H16指定での高い予熱

H16溶接材料は100gあたり最大16mLの拡散性水素を許容します — 橋梁FC溶接で許可される最高レベルです。2.0–2.8 kJ/mm入熱での≤ 20 mm (3/4 in)では、125°F (50°C)予熱が高い水素ポテンシャルを補います。この継手にH8またはH4溶接材料に切り替えると必要な予熱が低下します。

H16 2.0–2.8 kJ/mm · ≤ 20 mm (3/4 in)における他の橋梁鋼材

H16 2.0–2.8 kJ/mmでのM270M HPS485W / M270 HPS70W

別の組み合わせを試す

D1.5橋梁予熱計算機を使用して、AASHTO M270鋼材の水素レベルと入熱の任意の組み合わせを検索できます。構造用鋼にはD1.1予熱計算機もご覧ください。

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