Material number K03006: A106 Grade B
K03006 is the Unified Numbering System designation for A106 Grade B, seamless carbon steel pipe for high-temperature service specified in ASTM A106.
What K03006 means
UNS numbers (ASTM E527 / SAE J1086) use a letter for the alloy family and five digits: G = AISI/SAE carbon and alloy steels (G41400 = 4140), S = stainless and heat-resisting steels (S30400 = 304), K = miscellaneous steels (K02600 = A36), T = tool steels, N = nickel alloys. The UNS number identifies a composition, not a product form or property level, so K03006 appears in several ASTM specifications (plate, bar, pipe) with different mechanical requirements.
A106 Grade B at a glance
ASTM A106 Grade B (ASME SA-106 Gr B) is the seamless carbon steel pipe of refineries, power plants, chemical plants and process piping everywhere ASME B31.1/B31.3 apply: 240 MPa (35 ksi) minimum yield, 415 MPa (60 ksi) tensile, killed steel with a silicon minimum, intended for high-temperature service (ASME allowables run to 538 °C, practical use to about 425 °C). UNS K03006. Grade A is the softer version for bending and cold-forming, Grade C the stronger one (275/485 MPa) for higher pressure.
The specification is often confused with A53 Grade B, which has identical strength: the differences are that A106 is seamless only, must be fully killed (Si ≥ 0.10 %), has tighter chemistry with residual limits, and requires hydrostatic and NDE testing suited to pressure work. In practice most seamless pipe from NPS 1/2 to 24 is triple-stencilled A106 B / A53 B / API 5L B because it meets all three. Wall schedules follow ASME B36.10M (Sch 40, 80, 160, XXS…), and the pipe is supplied hot-finished (or cold-drawn in small sizes) with bevelled ends for butt welding.
For temperatures below −29 °C, A333 Grade 6 (same strength, Charpy-tested at −45 °C) replaces it; above 425 °C the Cr-Mo grades A335 P11/P22. European P235GH/P265GH (EN 10216-2), JIS STPG370/STPT410, GB 20/20G and GOST 20 are the near matches.
Full data sheet for A106 Grade B → · Equivalent grades →