Patriot Bolt machines ASTM A320 Grade L7 fasteners for low-temperature service. L7 uses the same quenched and tempered chrome-moly steel as B7, with Charpy V-notch impact testing at −150 °F on every lot.
This page brings together the L7 fasteners we make, the L7 property and impact requirements, and how L7 compares with other alloy steel bolting grades.
A320 L7 at a Glance
- Specification
- ASTM A320 / ASME SA320 Grade L7
- Material
- AISI 4140 / 4142, UNS G41400
- Strength
- 125 ksi min tensile, 105 ksi min yield (2-1/2 in and under)
- Impact test
- Charpy V-notch at −150 °F
- Matching nut
- A194 Grade 7L
- Products
- Stud bolts, heavy hex bolts, nuts
A320 L7 Fasteners We Machine
Choose a product to see its standards and options. Every order ships with mill test reports traceable to the heat.
A320 L7 Stud BoltsFull L7 page
A194 Grade 7 Heavy Hex NutsMatching nut (7L)
L7 Heavy Hex BoltsMade in L7A320 L7 Mechanical Properties
| Diameter | Tensile, min | Yield (0.2%), min | Charpy at −150 °F |
|---|---|---|---|
| 2-1/2 in and under | 125 ksi | 105 ksi | 20 ft-lb avg / 15 ft-lb single |
Full chemistry is on the A320 L7 stud bolts page. For diameters over 2-1/2 in, see A320 L43.
L7 vs. Other Alloy Steel Bolting Grades
| Grade | Strength (to 2-1/2 in) | Typical use |
|---|---|---|
| A320 L7 | 125 ksi / 105 ksi, impact tested at −150 °F | Low-temperature flanges to 2-1/2 in |
| A320 L43 | 125 ksi / 105 ksi to 4 in, impact tested at −150 °F | Large-diameter low-temperature flanges |
| A193 B7 | 125 ksi tensile / 105 ksi yield | General flange bolting to about 800 °F |
Compare all grades in the Fastener Materials Matrix.
A320 L7 Fastener FAQ
What is the difference between L7 and B7?
Same steel, heat treatment and strength. L7 adds a required Charpy impact test at −150 °F.
Which L7 fasteners does Patriot Bolt make?
We machine L7 stud bolts, heavy hex bolts and nuts, as well as custom parts made to your drawing.
Do the nuts need impact testing too?
Yes. A320 requires nut material to be impact tested. A194 Grade 7 nuts tested this way are marked 7L.
Do L7 fasteners come with certifications?
Yes. Patriot Bolt is ISO 9001:2015 certified, and every L7 order includes mill test reports traceable to the heat and a certificate of conformance to your purchase order.
Request a Quote
Send us the product, size, specification and quantity, or upload your drawing. Call (281) 581-0176 or request a quote.