Vorwärmung M270M Gr.345S — H16, Low HI, 20–40 mm: 200°F

M270M Gr.345S / M270 Gr.50S

AASHTO M270M Gr.345S (M270 Gr.50S) is the structural shape variant of Gr.345, intended for rolled W-shapes and channels used in bridge framing. The "S" suffix indicates the shape-specific chemistry and mechanical property requirements. Used in cross-frame angles, diaphragm members, and built-up sections where rolled shapes are specified rather than plate. Preheat requirements match Gr.345 — Table 6.3 Group 1 for NFC, Tables 12.4/12.5 for FC applications.

Die FC-Vorwärmung für M270M Gr.345S / M270 Gr.50S Verstehen

Shape-grade 345 MPa (50 ksi) steel for rolled bridge members. Under D1.5 fracture-critical requirements (Clause 12), the combination of H16 hydrogen designation and this heat input band requires 200°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.

Wo M270M Gr.345S / M270 Gr.50S Eingesetzt Wird

Used as rolled W-shapes and channels in bridge cross-frames, diaphragm members, and built-up sections. The "S" shape designation indicates procurement under AASHTO M270 with shape-specific chemistry and mandatory CVN testing. Common applications include WT sections for cross-frame members, MC channels for diaphragms, and W-shapes for floor beams on shorter spans. Weld details are primarily fillet welds at gusset connections and clip angles.

Wasserstoffkontrolle H16 für M270M Gr.345S / M270 Gr.50S

Gr.345S (50S) at H16 applies primarily to field-erected cross-frame connections using self-shielded FCAW. The higher preheat requirement at H16 can be challenging to maintain on thin shape flanges that lose heat rapidly to the surrounding air — electric resistance heating pads help maintain uniform temperature.

Warum Vorwärmung bei 20–40 mm (3/4–1½ in) Wichtig ist

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.

M270M Gr.345S / M270 Gr.50S bei 20–40 mm (3/4–1½ in)

At 20–40 mm flange thickness, Gr.345S (50S) W-shapes serve as floor beams on shorter spans and as bracing members in steel box girders. Connection details include moment connections to girder webs requiring CJP flange welds with backing bars. Preheat is applied to the thicker element at the connection — when a 25 mm shape connects to a 50 mm plate, preheat must meet the requirement for the 50 mm thickness tier.

Höhere Vorwärmung bei H16-Bezeichnung

H16-Zusatzwerkstoffe erlauben bis zu 16 mL diffusiblen Wasserstoff pro 100g — das höchste zulässige Niveau für FC-Brückenschweißen. Bei 20–40 mm (3/4–1½ in) mit 1.2–2.0 kJ/mm Wärmeeinbringung kompensiert die Vorwärmung von 200°F (100°C) das höhere Wasserstoffpotential.

Andere Brückenstähle bei H16 1.2–2.0 kJ/mm · 20–40 mm (3/4–1½ in)

M270M Gr.345S / M270 Gr.50S bei H16 1.2–2.0 kJ/mm

Verschiedene Kombinationen Ausprobieren

Verwenden Sie den D1.5 Brücken-Vorwärmrechner für jeden AASHTO M270 Stahl, Wasserstoffniveau und Wärmeeinbringungskombination. Siehe auch den D1.1 Vorwärmrechner für Baustahl.

Verwandte Leitfäden