예열 M270M HPS345W — H4, Low HI, ≤ 20 mm: 100°F

M270M HPS345W / M270 HPS50W

AASHTO M270M HPS345W (M270 HPS50W) is a high-performance weathering bridge steel with enhanced weldability through controlled chemistry — 0.11% max carbon, 0.006% max sulfur with calcium treatment for inclusion shape control. Developed under FHWA-funded research to eliminate the lamellar tearing and inconsistent toughness problems of earlier weathering steel bridge designs. The lower carbon equivalent compared to conventional Gr.345W reduces cracking sensitivity at flange splices. NFC preheat per Table 6.3 Group 1; FC per Tables 12.6/12.7.

M270M HPS345W / M270 HPS50W의 FC 예열 이해

High-performance weathering 345 MPa steel with enhanced weldability. Under D1.5 fracture-critical requirements (Clause 12), the combination of H4 hydrogen designation and this heat input band requires 100°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 HPS345W / M270 HPS50W이 사용되는 곳

Preferred over conventional Gr.345W for new unpainted bridge construction. The HPS designation indicates FHWA-developed chemistry with 0.11% max carbon and controlled sulfur for enhanced weldability and lamellar tearing resistance. Flange splice CJP welds benefit from the lower carbon equivalent, reducing reject rates during cold-weather bridge fabrication. Material cost premium over standard Gr.345W is typically 15–25% per ton but eliminates weldability-related rework.

M270M HPS345W / M270 HPS50W의 H4 수소 제어

HPS345W (HPS50W) already has inherently low carbon equivalent due to HPS chemistry control. Combined with H4 consumables, the preheat requirement drops to the lowest tier in Tables 12.6/12.7 — frequently 20–30°F lower than conventional 345W, compounding the weldability advantage of HPS chemistry with optimized hydrogen control.

≤ 20 mm (3/4 in)에서 예열이 중요한 이유

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)에서의 M270M HPS345W / M270 HPS50W

HPS345W (HPS50W) at thin thickness is specified for stiffener attachments and connection details where the improved weldability and lamellar tearing resistance justify the 15–25% material cost premium over conventional 345W. The 0.11% max carbon provides significantly lower carbon equivalent than conventional weathering steel, reducing preheat sensitivity and reject rates during production welding.

FC 교량 용접용 H4 인증 용접재료

H4 보조 지정은 용접재료가 용착 금속 100g당 최대 4 mL의 확산성 수소를 방출함을 인증합니다. 파괴 임계 M270M HPS345W / M270 HPS50W에서 ≤ 20 mm (3/4 in) 두께, 1.2–2.0 kJ/mm 입열량 시 H4 용접재료는 FC 표에서 가장 낮은 예열 100°F (40°C)를 달성합니다.

H4 1.2–2.0 kJ/mm · ≤ 20 mm (3/4 in)에서의 다른 교량 강재

H4 1.2–2.0 kJ/mm에서의 M270M HPS345W / M270 HPS50W

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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