ASTM A320 is used in low temperature application, these are available in various types, like stud bolts, heavy hex bolts,
hex bolts which are forged or not forged. The main application and areas where this is used is in pipe lines, valves, and pipe fittings and flange joints in piping application. These are generally manufactured similar to A 193
and are available in 8UN threads from 1" diameter and above.
Below we have mentioned the grades that fall under A320.
A320 Typical Grades
| L7 |
AISI 4140/4142 Quenched and tempered |
| L7M |
Chromium, Molybdenum, Alloy Steel Quenched and tempered |
| L43 |
AISI 4340 Quenched and tempered |
A320 Mechanical Requirements
| Grade |
Size |
Tensile ksi, min |
Yield ksi, min |
Elong %, min |
RA % min |
HBW |
Rockwell |
| L7 |
Up to 2-1/2 |
125 |
105 |
16 |
50 |
321 Max |
35 Max |
| L7M |
Up to 2-1/2 |
100 |
105 |
16 |
50 |
321 Max |
35 Max |
| L43 |
Up to 4 |
125 |
105 |
16 |
50 |
321 Max |
35 Max |
A320 Chemical Properties
| Element |
L7 (AISI 4140) |
L7M |
L43 (AISI 4340) |
| Carbon |
0.38 - 0.48% |
0.38 - 0.48% |
0.38 - 0.48% |
| Manganese |
0.75 - 1.00% |
0.75 - 1.00% |
0.75 - 1.00% |
| Phosphorus, max |
0.035% max |
0.035% max |
0.035% max |
| Sulfur, max |
0.04% max |
0.04% max |
0.04% max |
| Silicon |
0.15 - 0.35% |
0.15 - 0.35% |
0.15 - 0.35% |
| Chromium |
0.80 - 1.10% |
0.80 - 1.10% |
0.70 - 1.10% |
| Nickel |
- |
- |
1.65 - 2.00% |
| Molybdenum |
0.15 - 0.25% |
0.15 - 0.25% |
0.20 - 0.30% |
A320 Compatible Nuts & Washers
| Bolt Grade |
Nut |
Washers |
| L7 |
A194 Grade 4 or 7 |
F436 |
| L7M |
A194 Grade 7M |
F436 |
| L43 |
A194 Grade 4 or 7 |
F436 |
