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Certifications
- ISO 9001 - 2015 Certified
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- NACE MR0175/ISO 15156-2
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ASTM A320/A320M Grade L7B Chromium-Molybdenum Bolting
Quenched & Tempered Alloy Steel Fasteners - AISI 4137 Material
ASTM A320/A320M Grade L7B is a specialized chromium-molybdenum alloy steel bolting grade offering excellent strength-to-weight ratio for low temperature applications. Manufactured from AISI 4137 material and heat treated to achieve 125 ksi minimum tensile strength, L7B provides reliable performance in pressure vessels, valves, and flanges operating in sub-zero environments with mandatory Charpy impact testing at -150°F.
ASTM A320/A320M Grade L7B Stud Bolts Properties
ASTM A320/A320M Grade L7B Stud Bolts Chemical Requirements
Ferritic Steels
| Grade Symbol | Description | C | Mn | P, max | S, max | Si | Cr | Mo | |
|---|---|---|---|---|---|---|---|---|---|
| ASTM A320 L7B | Cr - Mo (AISI 4137) | Range,% | 0.35 - 0.40 | 0.70 - 0.90 | 0.035 | 0.04 | 0.15 - 0.35 | 080 - 110 | 0.15 - 0.25 |
| Product Variation, % Over or Under | 0.02 | 0.03 | 0.005 over | 0.005 over | 0.02 | 0.05 | 0.02 | ||
ASTM A320/A320M Grade L7B Stud Bolts Mechanical Requirements
Ferritic Steels
| Class and Grade, Diameter, in. [mm] | Heat Treatment | Minimum Tempering Temperature, °F [°C] | Tensile Strength, min, ksi [MPa] | Yield Strength, min, ksi [MPa] (0.2 % offset) | Elongation in 2 in. or 50 mm, min, % | Reduction of Area, min, % | Hardness, max |
|---|---|---|---|---|---|---|---|
| ASTM A320 L7B 21/2 [65] and underA | quenched and tempered | 1100 [593] | 125[860] | 105[725] | 16 | 50 | 321 HBW or 35 HRC |
ASTM A320/A320M Impact Test Requirements
| Grade | Test Temperature | CVN Specimen Section Size, mm | Min Average Impact Toughness of Three Test Specimens, ft-lbf [J] | Min Impact Value of a Single Specimen of Set of Three, ft-lbf [J] | |
|---|---|---|---|---|---|
| °F | °C | ||||
| ASTM A320 L7B | - 150 | - 101 | 10 × 7.5 | 16 [22] | 12 [16] |
| 10 × 10 | 40 [54] | 30 [41] | |||
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