ASTM A320 L43 specification for stud bolt
ASTM A320 Grade L43 is a standard material specification for alloy steel bolting materials for pressure vessels, valves, flanges, and fittings for low temperature services. ASTM A320 Grade L43 is heat treated chromium molybdenum alloy steel (AISI 4140/AISI 4140H) with notch toughness properties. We would like to introduce the chemical composition, mechanical properties, impact test requirement, and reference standards for product dimensions, threads, coatings and recommended nuts and washers.
| Grade | A320 L7M |
|---|---|
| Corresponding Standard | ASTM A320/A320M Alloy-steel and stainless steel bolting for low-temperature service |
| Classification | Alloy Steel |
A320 L43 Chemical Element Composition Content (%)
| Component | C | Si | Mn | P | S | Cr | Ni | Mo |
|---|---|---|---|---|---|---|---|---|
| Minimum Value | 0.38 | 0.15 | 0.6 | – | – | 0.7 | 1.65 | 0.2 |
| Maximum Value | 0.43 | 0.35 | 0.85 | 0.035 | 0.04 | 0.9 | 2 | 0.3 |
A320 L43 Mechanical Properties
| Heat Treatment or Condition | Tensile Strength σb Mpa |
Yield Point σs Mpa |
Elongation or Extension Rate δ % |
Reduction of Area ψ % |
Hardness HBW |
|---|---|---|---|---|---|
| Quenching and Tempering, Minimum Tempering Temperature 593℃ | ≥860 | ≥725 | ≥16 | ≥50 | ≤321 |
ASTM A320 Impact Test Requirements (Notch Toughness)
| Size of Specimen, mm | Test Temperature | Minimum impact value required for average of each set of three specimens, ft-lbf [J] | Minimum impact value permitted for one specimen only of a set, ft-lbf [J] | |
|---|---|---|---|---|
| °F | °C | |||
| 10 X 10 | -150 | -101 | 20 [27] | 15 [20] |
| 10 X 7.5 | 16 [22] | 12 [16] | ||
ASTM A320 L43 Stud bolt is normally applied for the stud bolt size over than 2 1/2″,which is used for low temperature applications.ASTM A320 Grade L43 is a standard material specification for alloy steel bolting materials for pressure vessels, valves, flanges, and fittings for low temperature services.
ASTM A320 L43 Stud Bolt – Specification & FAQ
1. What is ASTM A320 L43?
ASTM A320 L43 stud bolts are high-strength, low-temperature fasteners made from Nickel-Chromium-Molybdenum (Ni-Cr-Mo) alloy steel, specifically AISI 4340 or equivalent. These bolts are designed for use in cryogenic and sub-zero temperature environments, such as LNG plants, offshore structures, and pressure vessels.
Common Applications:
Cryogenic & Low-Temperature Services (Down to -150°F / -101°C)
Oil & Gas Industry (Offshore drilling, refineries, pipelines)
Aerospace & Power Plants
Difference between A320 L7/L7M and ASTM A320 L43 ?
| Property | A320 L7 (4140/4142) | A320 L7M (4140/4142) | A320 L43 (4340) |
|---|---|---|---|
| Tensile Strength | 125 ksi min | 100 ksi min | 125 ksi min |
| Yield Strength | 105 ksi min | 65 ksi min | 105 ksi min |
| Hardness | 321 HB max | 235 HB max | 321 HB max |
| Impact Toughness | Moderate | High (Hydrogen resistance) | Superior |
| Best For | Standard low-temp use | Sour gas (H₂S) service | Extreme low-temp & high-stress applications |
3.What coatings are available for ASTM A320 L43 Stud Bolts?
Hot-Dip Galvanizing (HDG) – Best for corrosion resistance
Zinc Plating – Provides a moderate protective layer
PTFE (Teflon) Coating – Excellent chemical resistance
Cadmium Plating – Used in offshore & aerospace applications
4. What are the standard sizes for ASTM A320 L43 Stud Bolts?
Diameter Range: 2 1/2” to 4”
Thread Type: UNC, UNF, 8UN, Metric
