M270M HPS485W पूर्वतापन — H16, Low HI, 40–60 mm: 350°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 के लिए FC पूर्वतापन को समझना

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 350°F minimum preheat at 40–60 mm (1½–2½ 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.

M270M HPS485W / M270 HPS70W कहाँ उपयोग होता है

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 के लिए H16 हाइड्रोजन नियंत्रण

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.

40–60 mm (1½–2½ in) पर पूर्वतापन क्यों महत्वपूर्ण है

Material from 40 to 65 mm (1-1/2 to 2-1/2 in) covers heavy girder flanges, thick splice plates, and main member plate. This is the critical thickness range for bridge fabrication — preheat reaches 65°C (150°F) for Group 1 and 80°C (175°F) for Group 2. FC preheat at this thickness can exceed 200°C (400°F) depending on hydrogen level and heat input.

40–60 mm (1½–2½ in) पर M270M HPS485W / M270 HPS70W

HPS485W (HPS70W) at 40–65 mm represents the critical design case for long-span cable-stayed and continuous girder bridges. Flange plates this thick with 70 ksi yield can support spans exceeding 300 feet (90 m) with conventional plate girder construction. FC preheat at this thickness tier is substantially higher than Group 1 grades, and dual-readout temperature monitoring is mandatory to ensure compliance with both preheat minimum and interpass maximum.

H16 पदनाम पर अधिक पूर्वतापन

H16 उपभोज्य प्रति 100g में 16 mL तक विसरणशील हाइड्रोजन की अनुमति देते हैं — FC पुल वेल्डिंग के लिए अनुमत उच्चतम स्तर। 1.2–2.0 kJ/mm ऊष्मा इनपुट के साथ 40–60 mm (1½–2½ in) पर, 350°F (180°C) पूर्वतापन उच्च हाइड्रोजन क्षमता की भरपाई करता है। H8 या H4 उपभोज्य पर स्विच करने से इस जोड़ के लिए आवश्यक पूर्वतापन कम होगा।

H16 1.2–2.0 kJ/mm · 40–60 mm (1½–2½ in) पर अन्य पुल स्टील

H16 1.2–2.0 kJ/mm पर M270M HPS485W / M270 HPS70W

विभिन्न संयोजन आज़माएँ

किसी भी AASHTO M270 स्टील, हाइड्रोजन स्तर, और ऊष्मा इनपुट संयोजन को देखने के लिए D1.5 ब्रिज पूर्वतापन कैलकुलेटर का उपयोग करें। स्ट्रक्चरल स्टील के लिए D1.1 पूर्वतापन कैलकुलेटर भी देखें।

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