Precalentamiento 345S — H16, Lo, 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.

Entendiendo el Precalentamiento FC para M270M Gr.345S / M270 Gr.50S

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.

Dónde se Usa M270M Gr.345S / M270 Gr.50S

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.

Control de Hidrógeno H16 para 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.

Por qué el Precalentamiento Importa en 20–40 mm (3/4–1½ in)

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 en 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.

Mayor Precalentamiento con Designación H16

Los consumibles H16 permiten hasta 16 mL de hidrógeno difusible por 100g — el nivel más alto permitido para soldadura FC de puentes. En 20–40 mm (3/4–1½ in) con aporte térmico 1.2–2.0 kJ/mm, el precalentamiento de 200°F (100°C) compensa el mayor potencial de hidrógeno.

Otros Aceros de Puente en H16 1.2–2.0 kJ/mm · 20–40 mm (3/4–1½ in)

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

Prueba Diferentes Combinaciones

Usa la Calculadora de Precalentamiento D1.5 para Puentes para consultar cualquier acero AASHTO M270, nivel de hidrógeno y combinación de aporte térmico. También consulta la Calculadora de Precalentamiento D1.1 para acero estructural.

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