This WPS covers GMAW-S (short-circuit transfer MIG) on 4" Schedule 40 A106 Gr B carbon steel pipe in the 45° inclined fixed position. Short-circuit GMAW is commonly used for utility and process piping where GTAW root quality is not required. The procedure specifies ER70S-6 filler with a 75/25 Ar/CO2 gas mix and pulsed parameters for the fill and cap passes to improve bead profile on the overhead quadrant. IronKit generated this WPS for a mechanical contractor who needed a single procedure for all routine carbon steel pipe work. The key detail is the short-circuit root with pulsed spray fill — a two-mode approach that many shops use but rarely document properly.
Frequently Asked Questions
What is GMAW-S (short-circuit MIG)?
GMAW-S uses low voltage and wire feed speed to create a short-circuit transfer mode — the wire touches the puddle and shorts out repeatedly, depositing small amounts of metal with each short. It produces low heat input, making it ideal for root passes on thin-wall pipe where burn-through is a risk.
Why switch from short-circuit to pulsed spray for fill passes?
Short-circuit has limited deposition rate and penetration. Pulsed spray delivers higher heat input and faster fill rates while maintaining good bead profile. The combination gives the best of both — a clean root with fast fill.
Does this WPS work for 6" pipe too?
The qualified thickness range (0.118" to 0.474") does not cover 6" Sch 40 (0.280" wall — it does fit). For 6" Sch 80 or heavier, a separate qualification may be needed depending on the specific thickness.