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ASTM A320 material was originally approved in 1948. This Standard is normally used in the petrol field and in chemical products applications. The ASTM Standard covers the steel and stainless steel alloys suitable for the fastening of low working temperature materials, it also includes the specifications of fastening devices to be used in pressure vessels, valves, flanges and fittings.
Here following is a basic summary of few common grades. ASTM A320 also
includes further standard specifications, not listed in this summary including B5, B6 and B16.
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
>> MECHANICAL PROPERTIES
| Grade | Size | 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 | sup a 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 |
>> RECOMMENDED NUTS and WASHERS | Grade | Nuts | Washers | | L7 | A194 Grade 4 o 7 | F436 | L43
| A194 Grade 4 o 7 | F436 | B8 Class 1
| A194 Grade 8 | SS304 | B8M Class 1
| A194 Grade 8M | SS316 | B8 Class 2
| A194 Grade 8 Grade 80
| SS304 | B8M Class 2
| A194 Grade 8M Grade 80
| SS316 |
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