A106 Gr.BのGMAW用予熱 — up to 3/4"

GMAW (Gas Metal Arc Welding)

GMAW (MIG) feeds continuous solid wire with shielding gas — an inherently low-hydrogen process assigned to Category B in Table 5.11.

GMAW on pipe requires specialized gun angles and travel speed control for circumferential joints. Pulsed GMAW is increasingly popular for pipe root passes as an alternative to SMAW. The absence of slag between passes eliminates inter-pass cleaning time, significantly improving productivity on multi-pass pipe joints.

A106 Gr.B

ASTM A106 Grade B covers seamless carbon steel pipe for high-temperature service up to about 750°F, with 35 ksi minimum yield and 60 ksi minimum tensile strength. Produced in sizes from 1/4" through 30" NPS, it is the standard pipe material for power plants, refineries, and process piping where elevated temperature and pressure coexist. Chemistry limits (0.30% max carbon, 0.29-1.06% manganese) give it a weldability profile that matches common structural grades with Category A and B preheat requirements. A106 is exclusively seamless, which eliminates the ERW seam concern present in A53. Grade C (40 ksi yield) exists but Grade B handles the vast majority of process piping service.

A106 Gr.BとGMAWでこの予熱が必要な理由

Seamless pipe rated for high-temperature service up to 750°F. With low-hydrogen GMAW, this combination falls under Category B rather than Category A, reflecting the lower hydrogen potential of the consumable. The 32°F minimum preheat is lower than what non-low-hydrogen SMAW would require at the same thickness. Low-hydrogen electrodes and inherently low-hydrogen wire processes reduce the driving force for hydrogen-induced cracking in the heat-affected zone.

A106 Gr.Bの代表的な適用例

Used in boiler steam headers, refinery piping racks, process plant branch connections, heat exchanger nozzle welds, power plant main steam lines, petrochemical reactor feed piping, and high-temperature manifolds. A106 Gr.B butt welds in process piping require joint preparation to B31.1 (power piping) or B31.3 (process piping) depending on service classification. Socket welds on small-bore A106 drain lines and instrument take-offs are common in utility stations, typically 1/2" to 2" NPS. Typical wall thicknesses range from Schedule 40 (0.237" wall on 2" NPS) to Schedule 160 (0.500" wall on 4" NPS) in critical high-energy service. Weld procedure qualification often includes side bend tests and tensile tests specific to the pipe diameter and wall thickness being joined. Field welds at pipe-to-flange connections and valve set-on joints require portable preheating equipment when wall thickness exceeds 1/2".

up to 3/4"で予熱が重要な理由

Thin material sheds heat quickly, allowing hydrogen to escape the HAZ readily — lowest preheat tier in Table 5.11.

GMAWとup to 3/4"における他の鋼材

A106 Gr.BとGMAW

別の組み合わせを試す

インタラクティブ予熱計算機を使用して、D1.1:2025 表5.11のあらゆる鋼材・プロセス・板厚の組み合わせを検索できます。

A106 Gr.B溶接ガイド