M270M HPS485W予熱 — H8、Low HI、20–40 mm: 225°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 H8 hydrogen designation and this heat input band requires 225°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.

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H8水素管理

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.

20–40 mm (3/4–1½ in)で予熱が重要な理由

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.

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

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.

H8 1.2–2.0 kJ/mm · 20–40 mm (3/4–1½ in)における他の橋梁鋼材

H8 1.2–2.0 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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