ASTM A320 L43 — Chemical Composition & Mechanical Properties
ASTM A320 L43 is a bolting & nut grades grade for stud bolts / bolting (UNS G43400, EN / W.Nr ≈ 1.6565). It is also known as AISI 4340. This sheet summarises its chemical composition limits, minimum mechanical properties, heat treatment and typical service. Teshi Group manufactures stud bolts and nuts in this grade.
ASTM A320 L43 at a glance
| Specification | ASTM A320 L43 |
|---|---|
| Material family | Bolting & nut grades |
| Product form | Stud bolts / bolting |
| UNS number | G43400 |
| EN / W.Nr equivalent | ≈ 1.6565 |
| Also known as | AISI 4340 |
| Document | TG-MG-125 · Rev. 1 · October 2026 |
Typical service
Heavy-section bolting for −101 °C service
Heat treatment
Quenched and tempered 595 °C min
Chemical composition of ASTM A320 L43 (weight %)
Single values are maximums unless shown as a range or “min”.
Mechanical properties
| Tensile strength, min | 860 MPa |
|---|---|
| Yield strength (0.2 % offset), min | 725 MPa |
| Elongation, min | 16 % |
| Charpy V-notch test temperature | −101 °C (27 J avg) |
| Hardness | Not specified |
About bolting & nut grades
Flange bolting is specified as a stud-bolt grade plus a nut grade. ASTM A193 covers high-temperature bolting (B7, B7M, B16, B8, B8M), A320 covers low-temperature bolting (L7, L7M, L43, B8 classes), A453 covers high-strength austenitic bolting (Grade 660), and A194 covers the nuts (2H, 2HM, 4, 7, 8, 8M).
Reference information compiled from the published standard for convenience. It does not replace the current edition of the governing standard, which takes precedence. Verify critical dimensions and properties before design, purchase or fabrication. Teshi Engineers & Sales Promoters (P) Ltd accepts no liability for errors or omissions.
International equivalents of ASTM A320 L43
All equivalents| Standard system | Nearest equivalent grade |
|---|---|
| USA — ASTM / ASME | ASTM A320 L43 · ASME SA-320 L43 |
| USA — UNS | G43400 |
| Europe — EN designation | 34CrNiMo6 |
| Europe — W.Nr | 1.6582 |
| Japan — JIS | SNCM439 |
| China — GB / NB | 40CrNiMoA (GB/T 3077) |
| China — old GB designation | 40CrNiMoA |
| India — IS | 40Ni2Cr1Mo28 (IS 1570) |
| UK — BS (withdrawn) | BS 970 817M40 |
Equivalents are the nearest commonly cited grades. Chemistry, mechanical properties and testing differ between standards — compare them before substituting one for another.
Standards for ASTM A320 L43
All material standardsFAQ
ASTM A320 L43: common questions
What is the minimum yield strength of ASTM A320 L43?
725 MPa, with a minimum tensile strength of 860 MPa.
What is the carbon content of ASTM A320 L43?
0.38–0.43 %.
What is the UNS number and EN equivalent of ASTM A320 L43?
UNS G43400; the nearest European designation is W.Nr ≈ 1.6565. Equivalents are close but not identical — check the specification if substituting.
How is ASTM A320 L43 heat treated?
Quenched and tempered 595 °C min.
What is the Chinese (GB) equivalent of ASTM A320 L43?
The nearest Chinese equivalent is 40CrNiMoA (GB/T 3077), formerly 40CrNiMoA. Equivalents are close but not identical — compare chemistry and properties before substituting.
What is the JIS equivalent of ASTM A320 L43?
The nearest Japanese (JIS) equivalent is SNCM439.
Does Teshi Group supply ASTM A320 L43?
Teshi Group manufactures stud bolts and nuts in this grade. Send your size, rating and quantity to info@teshigroup.com for a quotation with EN 10204 3.1 certificates.
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