Description
High-strength low-temperature AISI 4340-type bolting
ASTM A320 L43 Low Temperature Stud Bolts
ASTM A320 Grade L43 fully threaded alloy-steel stud bolts for demanding low-temperature pressure joints, supplied to the specified impact-test temperature, dimensions and inspection plan.
Quick answer
ASTM A320 Grade L43 is a high-strength low-temperature bolting grade associated with AISI 4340 nickel-chromium-molybdenum alloy steel. It is selected when the design specification requires L43 properties and impact performance; the required test temperature must be stated or confirmed for the order.
Product at a glance
What are ASTM A320 L43 stud bolts?
ASTM A320 L43 stud bolts use a high-hardenability nickel-chromium-molybdenum alloy-steel grade for low-temperature bolting. The current ASTM scope notes that achieving specified impact values at very low test temperatures may require tighter control of chemistry, including phosphorus and sulfur, than ordinary AISI 4340 supply.
L43 should therefore be purchased as certified ASTM A320 bolting rather than as generic 4340 threaded bar. Diameter, heat treatment, mechanical properties, impact-test temperature, specimen orientation, matching nuts and final machining all require coordinated manufacturing review.
ASTM A320 L43 stud bolt specifications
| Material | Nickel-chromium-molybdenum alloy steel associated with AISI 4340 |
|---|---|
| Grade requirement | Certified ASTM A320/A320M Grade L43 bolting, not generic 4340 bar |
| Low-temperature test | Charpy impact testing at the ordered temperature and acceptance criteria |
| Configuration | Fully threaded stud bolt; double-end studs by approved drawing |
| Threads | UNC, 8UN or project-specified series and class to ASME B1.1 |
| Dimensions | ASME B18.31.2, flange bolting schedule or approved drawing |
| Matching nuts | Compatible ASTM A194 grade with required low-temperature qualification |
| Documentation | MTC, chemistry, heat treatment, tensile, hardness, impact and dimensional results |
Final dimensions, tolerances, heat treatment, mechanical properties, impact or hardness requirements, coating and acceptance criteria follow the purchase order and the contractually specified standard edition.
Why specify this grade?
Select L43 only when the engineering design or material specification explicitly requires this high-strength low-temperature grade. It is valuable for demanding applications, but availability and achievable properties depend on diameter, melt chemistry, heat treatment and the required impact-test temperature.
Critical engineering note
AISI 4340 chemistry alone does not establish ASTM A320 L43 compliance. Do not publish or accept a generic minimum service temperature without checking the contract edition, impact test data, governing code and complete joint design.
Stud, nut and finish options
Typical applications
Quality, inspection and documentation
L43 orders receive material and manufacturing review before commitment because diameter, chemistry, heat treatment and impact-test temperature interact. The final certificate package records the evidence required by the approved inspection plan.
- EN 10204 3.1 material test certificate when ordered
- Heat-number and manufacturing-batch traceability
- Chemical composition and mechanical-property results
- Hardness testing at the frequency required by the ordered grade
- Charpy impact testing for low-temperature grades as specified
- Dimensional inspection and calibrated thread gauging
- Coating thickness or surface-condition inspection when applicable
- Third-party inspection, marking and export packing by agreement
Information required for quotation
- ASTM standard, grade and contractually required edition
- Stud diameter, overall length, thread series and thread class
- Quantity and whether two nuts per stud are required
- Matching nut specification, grade, style and finish
- Plain, coated or plated finish and the approved coating system
- Design temperature, impact-test temperature and sour-service requirements when relevant
- MTC, PMI, hardness, impact, coating and third-party inspection requirements
- Delivery destination, packing method and required schedule
Frequently asked questions
What material is ASTM A320 L43?
L43 is a low-temperature bolting grade associated with AISI 4340 nickel-chromium-molybdenum alloy steel and must meet ASTM A320/A320M requirements.
Is generic AISI 4340 threaded bar equivalent to L43?
No. L43 compliance also depends on heat treatment, mechanical properties, impact testing, dimensions, manufacturing controls and certification to the ordered ASTM A320 edition.
What is the minimum temperature for L43 stud bolts?
Do not use a universal product-page value. The purchase order must identify the required impact-test temperature and the designer must establish the allowable service temperature under the governing code.
Which nuts are used with L43 stud bolts?
Use the compatible ASTM A194 or project-specified nut grade required by the design, including any low-temperature impact testing, hardness and documentation requirements.
Related stud bolt products
Reference standards
Material requirements are controlled by ASTM A320/A320M. Matching heavy hex nut requirements are specified separately under ASTM A194/A194M when applicable. Thread form and stud dimensions may reference ASME B1.1 and ASME B18.31.2, subject to the purchase order. Always state the required edition instead of assuming the latest edition applies to an existing project.
Request a technical quotation
Send your flange bolting schedule, bill of materials, drawing or project specification. SASA FLANGE will review the grade, nuts, threads, dimensions, finish, documentation and delivery requirements before quotation.
