Material number G43400: 4340
G43400 is the Unified Numbering System designation for 4340, nickel-chromium-molybdenum low-alloy steel, deep hardening specified in ASTM A29.
Reading G43400 digit by digit
A UNS designation (ASTM E527 / SAE J1086) is a letter followed by five digits. The letter G marks the alloy family — here AISI and SAE carbon and alloy steels — and the five digits 43400 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. G43400 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.
G43400 identity card
| Item | Value |
|---|---|
| UNS number (ASTM E527) | G43400 |
| Symbolic grade name | 4340 |
| Steel group | G — AISI and SAE carbon and alloy steels |
| Sequential number in group | 43400 |
| Specified in | ASTM A29 |
| Steel family | Quenched & tempered steel |
| Yield, first condition in the table | ≈ 470 MPa (Annealed (810 °C, furnace cool) — typical) |
| Tensile, same condition | ≈ 745 MPa |
| Cross-references held | 9 grades in 6 systems |
4340 steel (AISI/SAE 4340, UNS G43400): 0.40 % C, 1.8 % Ni, 0.8 % Cr, 0.25 % Mo. Q&T to 1000–1900 MPa with high toughness; through-hardens to 100+ mm. Composition, heat treatment, hardness by temper, 4340 vs 4140, 34CrNiMo6/SNCM439/EN24 equivalents.
Full data sheet for 4340 → · Equivalent grades → · ASTM A29 →
UNS G — the neighbouring numbers
| UNS number | Grade | Type |
|---|---|---|
| G10100 | SAE 1010 | Low-carbon steel for cold forming, welding and case hardening |
| G10180 | 1018 | Low-carbon steel, cold-finished bar (case-hardenable) |
| G10450 | 1045 | Medium-carbon steel, hardenable |
| G10950 | 1095 | High-carbon steel (spring / knife / blade steel) |
| G41300 | 4130 | Chromium-molybdenum low-alloy steel, weldable (chromoly) |
| G41400 | 4140 | Chromium-molybdenum low-alloy steel (chromoly) |
| G52986 | 52100 | High-carbon chromium bearing steel |
| G86200 | 8620 | Nickel-chromium-molybdenum case-hardening steel |
Same UNS letter, so the same alloy family. The digits generally carry an older AISI or SAE number.