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ASTM A320
Scope
Originally approved in 1948, the ASTM A320 specification covers alloy steel and stainless steel bolting materials for low temperature service. This standard covers rolled, forged, or strain hardened bars, bolts, screws, studs, and stud bolts used for pressure vessels, valves, flanges, and fittings. Like the ASTM A193 specification, unless otherwise specified, the 8UN thread series is specified on fastener larger than 1” in diameter.
Below is a basic summary of a few of the common grades within the ASTM A320 specification. A number of other less common grades of ASTM A320 exist, but not covered in the description below.
A320 Grades
| L7 Alloy steel | AISI 4140/4142 Quenched and tempered |
|---|---|
| L43 Alloy steel | AISI 4340 Quenched and tempered |
| B8 Class 1 Stainless steel | AISI 304, carbide solution treated |
| B8M Class 1 Stainless steel | AISI 316, carbide solution treated |
| B8 Class 2 Stainless steel | AISI 304, carbide solution treated, strain hardened |
| B8M Class 2 Stainless steel | AISI 316, carbide solution treated, strain hardened |
A320 Mechanical Properties
| Grade | Diameter | Tensile, ksi, min | Yield, ksi, min | Charpy Impact 20-ft-lbf @ temp | Elong, %, min | RA, %, min |
|---|---|---|---|---|---|---|
| L7 | Up to 21⁄2 | 125 | 105 | -150° F | 16 | 50 |
| L43 | Up to 4 | 125 | 105 | -150° F | 16 | 50 |
| B8 Class 1 | All | 75 | 30 | N/A | 30 | 50 |
| B8M Class 1 | All | 75 | 30 | N/A | 30 | 50 |
| B8 Class 2 | Up to 3⁄4 | 125 | 100 | N/A | 12 | 35 |
| 7⁄8 - 1 | 115 | 80 | N/A | 15 | 35 | |
| 11⁄8 - 11⁄4 | 105 | 65 | N/A | 20 | 35 | |
| 13⁄8 - 11⁄2 | 100 | 50 | N/A | 28 | 45 | |
| B8M Class 2 | Up to 3⁄4 | 110 | 95 | N/A | 15 | 45 |
| 7⁄8 - 1 | 100 | 80 | N/A | 20 | 45 | |
| 11⁄8 - 11⁄4 | 95 | 65 | N/A | 25 | 45 | |
| 13⁄8 - 11⁄2 | 90 | 50 | N/A | 30 | 45 |
A320 Chemical Properties
| Element | L7 (AISI 4140) | L43 (AISI 4340) | B8 (AISI 304) | B8M (AISI 316) |
|---|---|---|---|---|
| Carbon | 0.37 - 0.49% | 0.38 - 0.43% | 0.08% max | 0.08% max |
| Manganese | 0.65 - 1.10% | 0.75 - 1.00% | 2.00% max | 2.00% max |
| Phosphorus, max | 0.035% | 0.035% | 0.045% | 0.045% |
| Sulfur, max | 0.040% | 0.040% | 0.030% | 0.030% |
| Silicon | 0.15 - 0.35% | 0.15 - 0.35% | 1.00% max | 1.00% max |
| Chromium | 0.75 - 1.20% | 0.70 - 0.90% | 18.0 - 20.0% | 16.0 - 18.0% |
| Nickel | 1.65 - 2.00% | 8.0 - 11.0% | 10.0 - 14.0% | |
| Molybdenum | 0.15 - 0.25% | 0.20 - 0.30% | 2.00 - 3.00% |
A320 Recommended Hardware
| Grade | Nuts | Washers |
|---|---|---|
| L7 | A194 Grade 4 or 7 | F436 |
| L43 | A194 Grade 4 or 7 | F436 |
| B8 Class 1 | A194 Grade 8 | SS304 |
| B8M Class 1 | A194 Grade 8M | SS316 |
| B8 Class 2 | A194 Grade 8 | SS304 |
| B8M Class 2 | A194 Grade 8M | SS316 |
| Strain hardened nuts available as a supplementary requirement | ||
ASTM Specifications for Bolt Fasteners
| A193 | - Alloy steel and stainless steel bolting materials for high temperature or high pressure service. |
| A307 |
|
| A320 |
|
| A325 |
|
| A354 |
|
| A449 |
|
| A453 |
|
| A490 |
|
| F568 | - Standard for metric bolts, screws and studs that are used in general engineering applications |
| F593 |
|
| F1554 |
|
ASTM Specifications for Nuts
ASTM Specifications for Washers
| F436 | - Specification for Hardened Steel Washers , carbon steel, steel, washers, weathering steel, Hardened steel washers |
| F844 |
|
| F959 |
|
Astm A320 Alloy Stainless Steel Bolts Application Industries
Sunflex Metal Industries are engaged in manufacturing of robust quality of Astm A320 Alloy Stainless Steel Bolts. These Astm A320 Alloy Stainless Steel Bolts are widely used in the following industries:
Mining Industries Transport Industries- Rail and Road Construction Industries / Building Systems Manufacturing Industries Agriculture Industries Energy Industries Water Industries Automotive Industries Ship Building Industries Nuclear Power Plant Paper & Pulp Industries Sugar Industries Engineering Cement Industries Petro-Chemical Industries Food Industries Oil & Gas Industries Chemical & Pharmaceutical Industries
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