Q1: What are standard size ranges for Q235B welded pipe?
A1: Common diameters range from 1/2" to 24" (DN15-DN600) with wall thicknesses from 1.0mm to 12.7mm. Lengths typically come in random (5-12m) or fixed lengths (6m/12m). Larger diameters (up to 100") are available for specialized applications. Metric sizes follow GB standards while imperial sizes match ASTM specifications. Custom sizes can be produced with additional tooling.
Q2: What dimensional tolerances apply to OD and wall thickness?
A2: For GB/T 3091, OD tolerance is ±1.0% or ±0.5mm (whichever is greater). Wall thickness tolerance is ±10% for pipes ≤20mm wall, ±8% for thicker walls. ASTM A53 specifies ±0.8% OD tolerance and +20%/-12.5% wall variation. Tighter tolerances (±0.3mm) are available for precision applications at higher cost.
Q3: How straight must Q235B welded pipes be?
A3: Straightness tolerance is typically ≤1.5mm per meter length, with total bow ≤0.2% of total length. For 6m pipes, maximum deviation is 12mm. Critical applications (hydraulic systems) may require ≤0.5mm/m straightness achieved through additional straightening processes. Excessive curvature can cause installation issues in structural applications.
Q4: What are the acceptable surface finish requirements?
A4: Standard pipes allow minor imperfections (scratches, roll marks) ≤0.1mm deep. Seamless-appearance finish requires grinding weld beads smooth. Galvanized surfaces must be free of bare spots with zinc coating ≥80μm. Painted surfaces need proper pretreatment and uniform coating. Special finishes (polished, pickled) are available for aesthetic applications.
Q5: What are the ovality and eccentricity limits?
A5: Ovality (difference between max/min OD) is limited to 1.5% of nominal diameter. Eccentricity (wall thickness variation) must be ≤10% of nominal wall. These ensure proper fit-up in connections and uniform strength. Precision pipes for mechanical applications may specify ≤5% ovality and ≤5% eccentricity.
