Material number S31603: 316L
S31603 is the Unified Numbering System designation for 316L, low-carbon austenitic chromium-nickel-molybdenum stainless steel specified in ASTM A240.
Reading S31603 digit by digit
A UNS designation (ASTM E527 / SAE J1086) is a letter followed by five digits. The letter S marks the alloy family — here stainless and heat-resisting steels — and the five digits 31603 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. S31603 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.
S31603 identity card
| Item | Value |
|---|---|
| UNS number (ASTM E527) | S31603 |
| Symbolic grade name | 316L |
| Steel group | S — stainless and heat-resisting steels |
| Sequential number in group | 31603 |
| Specified in | ASTM A240 |
| Steel family | Stainless steel |
| Also carries Werkstoff No. | 1.4404 |
| Yield, first condition in the table | ≥ 170 MPa (sheet/plate, annealed (ASTM A240)) |
| Tensile, same condition | ≥ 485 MPa |
| Cross-references held | 4 grades in 2 systems |
316L (1.4404, UNS S31603) is 316 with carbon capped at 0.030 %: the same molybdenum-bearing alloy, specified so welds do not sensitise.
Full data sheet for 316L → · Equivalent grades → · ASTM A240 →
UNS S — the neighbouring numbers
| UNS number | Grade | Type |
|---|---|---|
| S17400 | 17-4 PH | Martensitic precipitation-hardening stainless steel |
| S30400 | 304 | Austenitic chromium-nickel stainless steel |
| S30403 | 304L | Low-carbon austenitic chromium-nickel stainless steel |
| S31000 | 310 | Austenitic heat-resisting stainless steel (25 % Cr, 20 % Ni) |
| S31600 | 316 | Austenitic chromium-nickel-molybdenum stainless steel |
| S32100 | 321 | Austenitic Cr-Ni stainless steel, titanium-stabilized |
| S32205 | 2205 | Ferritic-austenitic (duplex) stainless steel |
| S41000 | 410 | Martensitic chromium stainless steel, hardenable |
| S43000 | 430 | Ferritic chromium stainless steel |
Same UNS letter, so the same alloy family. The digits generally carry an older AISI or SAE number.