예열 M270M HPS485W — H4, High HI, 20–40 mm: 150°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 HPS70W의 FC 예열 이해

High-performance 485 MPa (70 ksi) weathering bridge steel. Under D1.5 fracture-critical requirements (Clause 12), the combination of H4 hydrogen designation and this heat input band requires 150°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 HPS70W이 사용되는 곳

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 HPS70W의 H4 수소 제어

For HPS485W (HPS70W), specifying H4 consumables is a strategic choice that significantly reduces preheat costs on thick flange splices. At 40+ mm flange thickness, every 25°F reduction in required preheat saves approximately 15–20 minutes per splice in heating time, directly impacting the critical-path schedule of bridge girder fabrication.

20–40 mm (3/4–1½ in)에서 예열이 중요한 이유

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)에서의 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.

FC 교량 용접용 H4 인증 용접재료

H4 보조 지정은 용접재료가 용착 금속 100g당 최대 4 mL의 확산성 수소를 방출함을 인증합니다. 파괴 임계 M270M HPS485W / M270 HPS70W에서 20–40 mm (3/4–1½ in) 두께, > 2.8 kJ/mm 입열량 시 H4 용접재료는 FC 표에서 가장 낮은 예열 150°F (70°C)를 달성합니다.

H4 > 2.8 kJ/mm · 20–40 mm (3/4–1½ in)에서의 다른 교량 강재

H4 > 2.8 kJ/mm에서의 M270M HPS485W / M270 HPS70W

다양한 조합 시도

D1.5 교량 예열 계산기를 사용하여 AASHTO M270 강재, 수소 수준 및 입열량 조합을 조회하세요. D1.1 예열 계산기도 참조하세요.

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