Think of it as B7’s cold-weather cousin: the same strength, but toughened and tested to stay reliable in low-temperature service.
ASTM A320 Grade L7 is a low-temperature alloy stud bolt — the same heat-treated chromium-molybdenum steel as B7, but impact-tested for cold service. Where an ordinary stud could turn brittle in the cold, L7 is proven tough down to low temperatures, which is why it shows up on cryogenic, refrigerated, and outdoor cold-weather piping.
Low-temp alloy stud bolts
“L7” stamped on the end
Cold-service flanges & pressure piping
| Property | Detail |
|---|---|
| Tensile (min) | 125 ksi (≤2½″ dia) |
| Yield (min) | 105 ksi (≤2½″ dia) |
| Material | Cr-Mo alloy (AISI 4140/4142), quenched & tempered |
| Toughness | Charpy V-notch impact tested at −150°F |
| Marking | “L7” on the stud end |
L7 studs make up flanged joints on cold-service piping — the same role as B7, but where temperatures drop low enough that a standard stud could crack. That puts them in refrigeration, LNG and cryogenic lines, and cold-weather outdoor process piping. Count and size the studs from the flange stud & nut chart just like B7.
Look for “L7” on the stud end. The key difference from B7 is the nut: L7 pairs with low-temperature impact-tested nuts — ASTM A194 Grade 4 or Grade 7 heavy hex (not the standard 2H) — with F436 washers. Grade 7 is the usual match. Using a plain 2H nut on a cold-service joint defeats the purpose, so keep the set matched.
A320 L7 studs cut to your flange, with the matching Grade 4 or 7 nuts and washers. Tell us the flange size, class, and service temperature.
