التسخين المسبق لـ A913 Gr.70 مع SMAW (low-hydrogen) — 3/4" to 1-1/2"

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.

SMAW-LH Tips for High-Strength and TMCP Steels

For A913 Gr.70 TMCP shapes, E7018 at 120-150 A (1/8" rod) gives the lowest heat input manual option for column splice CJP welds on heavy W14 flanges. Stringer beads limit heat input to 25-35 kJ/in, well within safe range for QST properties. Consider E7018-1 for seismic applications requiring CVN at -20°F per AISC 341. With H8-certified E7018, qualifies for Category F.

Typical values for reference — always verify against your approved WPS and electrode manufacturer data.

Filler Metal for SMAW-LH

Electrode: E7018 (AWS A5.1) — the universal low-hydrogen structural rod. Diameter: 1/8" (general/out-of-position), 5/32" (production), 3/16" (heavy plate flat only). Storage: 250°F rod oven minimum per D1.1 §7.3.2.1. Exposure limit: 4 hours out of oven per Table 7.1, then re-bake at 500-800°F for minimum 2 hours per §7.3.2.4 (A5.1 classification).

Typical values for reference — always verify against your approved WPS and electrode manufacturer data.

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.

لماذا هذا التسخين المسبق لـ A913 Gr.70 مع SMAW-LH

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 150°F minimum with SMAW-LH, E7018 low-hydrogen electrodes produce typically 4-8 mL/100g diffusible hydrogen under proper rod oven conditions, but the preheat must still ensure the cooling rate stays slow enough to prevent hydrogen-induced cracking in this higher-hardenability material.

التطبيقات النموذجية لـ A913 Gr.70

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.

لماذا يهم التسخين المسبق عند 3/4" to 1-1/2"

Preheat climbs at this range as thicker material slows heat dissipation, trapping hydrogen at crack-susceptible grain boundaries.

التسخين المسبق الفئة C لـ A913 Gr.70

الفئة C في الجدول 5.11 تنطبق على الفولاذ عالي المقاومة حيث يتطلب مزيج قابلية التصلب والإجهاد المتبقي تسخيناً مسبقاً مرتفعاً. لـ A913 Gr.70 عند 3/4" to 1-1/2"، التسخين المسبق الأدنى 150°F يبطئ معدل تبريد اللحام لمنع تشكل المارتنسيت القابل للتشقق في المنطقة المتأثرة بالحرارة.

أنواع فولاذ أخرى مع SMAW (low-hydrogen) عند 3/4" to 1-1/2"

A913 Gr.70 مع SMAW (low-hydrogen)

جرّب تركيبات مختلفة

استخدم حاسبة التسخين المسبق التفاعلية للبحث عن أي تركيبة من الفولاذ والعملية والسماكة من D1.1:2025 الجدول 5.11.

أدلة لحام A913 Gr.70