A913 Gr.70 SMAW (low-hydrogen) 예열 — over 2-1/2"

SMAW (Low-Hydrogen)

Low-hydrogen SMAW (E7018/E7016) uses basic-coated electrodes requiring rod oven storage, assigned to Category B in Table 5.11.

For high-strength shapes and plate, E7018 provides adequate tensile match for steels up to Category C. E8018-C3 or E9018-M may be required for higher-strength steels to meet weld metal strength matching requirements. Bead sequencing on thick TMCP flanges should follow qualified WPS parameters precisely to avoid overheating the refined microstructure.

A913 Gr.70

ASTM A913 Grade 70 (70 ksi yield, 90 ksi minimum tensile) is a TMCP structural shape used in heavily loaded columns and seismic applications requiring higher strength than Gr.50/60/65. It falls under Category C for standard low-hydrogen processes, with preheat requirements reflecting its higher strength level and CE-IIW of approximately 0.42-0.48. With H8-certified consumables, it qualifies for Category F — 32°F up to 2-1/2”, 150°F above. The TMCP QST microstructure provides inherent resistance to hydrogen cracking through its fine-grained bainitic structure, which is why H8 consumables unlock a reduced-preheat path not available for conventional Q&T steels at similar strength. A913 Gr.70 is primarily available in W14 sections ranging from W14x233 through W14x730, with limited W12 and W36 availability.

SMAW-LH를 사용한 A913 Gr.70의 이 예열 이유

TMCP 70 ksi shape with Category F reduced preheat using H8 consumables. The higher strength level of this steel places it in Category C of Table 5.11, which carries elevated preheat requirements compared to Category B grades. At 300°F minimum with SMAW-LH, the preheat ensures the cooling rate stays slow enough to prevent hydrogen-induced cracking in this higher-hardenability material. Category C steels demand careful attention to interpass temperature control throughout the weld sequence.

A913 Gr.70의 일반적인 용도

Used in heavily loaded interior columns of super-tall buildings, transfer truss compression chords, mega-brace members in outrigger systems, stadium roof cantilever supports, and seismic collectors in high-rise cores. A913 Gr.70 TMCP shapes enable smaller column sections, freeing usable floor space on every floor of the building. Column splice butt welds at upper stories and moment connection flange welds carry the highest inspection priority. The 70 ksi yield enables using W14x398 where conventional Gr.50 would require W14x550, saving 38% in material weight and 3-4 inches of floor space per column. Erection splices at every 2-3 stories use CJP groove welds with backing bars removed and back-gouged per seismic detailing requirements. The Category F path with H8 consumables (32°F up to 2-1/2", 150°F above) provides a practical alternative to full Category C preheat on these thick-flange column splices.

over 2-1/2"에서 예열이 중요한 이유

The heaviest sections demand the highest preheat in Table 5.11. Multi-pass sequences require maintaining interpass temperature throughout.

over 2-1/2"에서 SMAW (low-hydrogen)를 사용하는 다른 강재

A913 Gr.70, SMAW (low-hydrogen)

다양한 조합 시도

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A913 Gr.70 용접 가이드