Material number K02303: A572 Grade 50
K02303 is the Unified Numbering System designation for A572 Grade 50, high-strength low-alloy (HSLA) columbium-vanadium structural steel specified in ASTM A572.
Reading K02303 digit by digit
A UNS designation (ASTM E527 / SAE J1086) is a letter followed by five digits. The letter K marks the alloy family — here miscellaneous steels and ferrous alloys — and the five digits 02303 place the composition inside it, usually by carrying an older AISI or SAE number forward.
What a UNS number does not carry is the product form or the property level. K02303 therefore appears in several ASTM specifications — plate, bar, pipe, forging — each with its own mechanical requirements, and the number alone is not a complete purchase specification.
K02303 identity card
| Item | Value |
|---|---|
| UNS number (ASTM E527) | K02303 |
| Symbolic grade name | A572 Grade 50 |
| Steel group | K — miscellaneous steels and ferrous alloys |
| Sequential number in group | 02303 |
| Specified in | ASTM A572 |
| Steel family | Structural steel |
| Yield, first condition in the table | 290 MPa (Grade 42 (290 MPa) — plate ≤ 150 mm, all shapes) |
| Tensile, same condition | ≥ 415 MPa |
| Cross-references held | 10 grades in 6 systems |
ASTM A572 Grade 50 (UNS K02303): HSLA structural steel with 345 MPa (50 ksi) minimum yield and 450 MPa (65 ksi) tensile, micro-alloyed with Nb/V. All five grades (42–65), thickness limits, A572 vs A36 / A992 / S355, Q355/SM490 equivalents.
Full data sheet for A572 Grade 50 → · Equivalent grades → · ASTM A572 →
UNS K — the neighbouring numbers
| UNS number | Grade | Type |
|---|---|---|
| K02600 | A36 | Carbon structural steel |
| K02700 | A516 Grade 70 | Carbon steel plate for pressure vessels, moderate and lower temperature |
| K03005 | A53 Grade B | Pipe steel for general and structural service, welded or seamless |
| K03006 | A106 Grade B | Seamless carbon steel pipe for high-temperature service |
| K03006 | A333 Grade 6 | Carbon steel pipe for low-temperature service, impact tested at −45 °C |
Same UNS letter, so the same alloy family. The digits generally carry an older AISI or SAE number.