ASTM A320 Grades L7A, L7B, & L7C Sample MTC
Access a comprehensive, professionally formatted Material Test Certificate according to EN 10204-2004: 3.1 covering the specialized ASTM A320 Grades L7A, L7B, and L7C. Review the rigorous documentation verifying specific alloy chemistries, high tensile strength, and mandatory Charpy V-Notch impact testing at -150°F (-101°C) for extreme low-temperature service.
What's Inside This A320 L7A/B/C MTC Certificate
This master sample mill test certificate details the critical testing parameters required for ASTM A320 Grades L7A, L7B, and L7C. These specific alloy steels—Carbon-Moly (AISI 4037), Chrome-Moly (AISI 4137), and Nickel-Chrome-Moly (AISI 8740)—are engineered as specialized alternatives to standard L7 for low-temperature fastening in pressure vessels and valves.
- Full Traceability: Certified with TC No.: S142/26-XX and fully mapped to ASTM A320 low-temperature alloy steel specifications.
- Specialized Alloy Chemistry: Explicitly details the chemical composition limits for all three grades, highlighting the Nickel addition in L7C for enhanced toughness and the specific Carbon/Molybdenum ranges for L7A and L7B.
- Charpy V-Notch Impact Testing: All three grades mandate stringent impact testing. The certificate logs passing impact test energy values (min 20 ft-lbf / 27 J) at the extreme temperature of -150°F (-101°C).
- Controlled Tempering: Verification that the material was quenched and tempered at a minimum of 1100°F (593°C) to relieve residual stress and lock in ductility.
- Shared Mechanical Performance: Detailed logs conforming to the shared mechanical requirements: Tensile Strength (125 ksi min), Yield Strength (105 ksi min), and Hardness limits (Max 321 HBW).
Live Preview: ASTM A320 Grade L7A, L7B, L7C MTC Data
Review the comparative chemical parameters and shared mechanical limits before downloading.
TC Number
S142/26-XX
TC Date
28.02.20XX
Material Spec
ASTM A320 L7A / L7B / L7C
Bar Shape / Size
Round Bar / 1-1/8"
Dimensions / Item
Stud Bolt 1-1/8"-8UN x 8"
Quantity
120.00 NOS
Chemical Composition Specification Limits (%)
| Grade / Base Alloy | C | Mn | P (Max) | S (Max) | Si | Ni | Cr | Mo |
|---|---|---|---|---|---|---|---|---|
| L7A (AISI 4037) | 0.38 - 0.48 | 0.70 - 0.90 | 0.035 | 0.040 | 0.15 - 0.35 | - | - | 0.20 - 0.30 |
| L7B (AISI 4137) | 0.35 - 0.40 | 0.70 - 0.90 | 0.035 | 0.040 | 0.15 - 0.35 | - | 0.80 - 1.10 | 0.15 - 0.25 |
| L7C (AISI 8740) | 0.38 - 0.43 | 0.75 - 1.00 | 0.035 | 0.040 | 0.15 - 0.35 | 0.40 - 0.70 | 0.40 - 0.60 | 0.20 - 0.30 |
Shared Mechanical & Impact Properties
| TENSILE STRENGTH (ksi) | YIELD STRENGTH 0.2% Offset (ksi) | % ELONGATION (GL-2in) | HARDNESS (HBW) | IMPACT ENERGY @ -150°F / -101°C |
|---|---|---|---|---|
| 132.5 | 114.2 | 18.5 | 295, 292, 298 | 32, 35, 30 ft-lbf |
| Min: 125 ksi (860 MPa) | Min: 105 ksi (725 MPa) | Min: 16% | Max: 321 HBW | Min: 20 ft-lbf (27 J) |
Standard References & Compliance
Our MTC certificates comprehensively align with the demanding specifications of the low-temperature industrial sector. The test reports confirm exact compliance with ASME/ASTM A320 / A320M with respect to the specific heat and lot tested.
| Standard / Requirement | Confirmation on Certificate |
|---|---|
| Visual Inspection | 100% visual inspection carried out & found free from defects. |
| Charpy V-Notch Impact Test | Tested at -150°F (-101°C). Results meet minimum 20 ft-lbf requirement for L7A, L7B, L7C. |
| Safety Requirements | Material is free from radioactive contamination and mercury. |
| Dimensional Accuracy | All Dimensions are as per PO Specification / ASME B18.2.1 / ASME B18.31.2. |
Certification Details
We confirm that the above mentioned items were Manufactured, Sampled, Tested, and Inspected in accordance with the subjected Customer's Purchase Order and applicable Drawings, Material Specifications, Codes & Standards.
Documentation Standard
- EN 10204-2004: 3.1 Standard
- Free from radioactive contamination
- Certified ISO 9001: 2015 Company
Heat Treatments
- Quenched & Tempered
- Min Tempering Temp: 1100°F (593°C)
Testing Conditions
- Charpy Impact Test carried out at -150°F (-101°C)
- 100% visual inspection carried out
Technical FAQs — ASTM A320 Grades L7A, L7B, L7C
How do L7A, L7B, and L7C differ from standard Grade L7?
While standard Grade L7 is typically made from AISI 4140 (Chromium-Molybdenum), Grades L7A, L7B, and L7C allow for different base alloys to achieve the same mechanical and impact properties. L7A utilizes AISI 4037 (Carbon-Moly), L7B utilizes AISI 4137 (a lower-carbon Chrome-Moly), and L7C utilizes AISI 8740 (Nickel-Chrome-Moly). These grades provide engineers with options to optimize hardenability and toughness based on the specific diameter and application of the fastener.
Why is Nickel added to Grade L7C?
Grade L7C (AISI 8740) includes 0.40 - 0.70% Nickel. The addition of Nickel in alloy steels significantly enhances low-temperature toughness and deep hardenability. This makes L7C an excellent choice for larger diameter fasteners that still need to pass the strict -150°F (-101°C) Charpy impact tests.
Do all three grades require the same Charpy impact test?
Yes. The ASTM A320 specification groups L7, L7A, L7B, and L7C together regarding impact testing. All of these grades must absorb a minimum of 20 ft-lbf (27 Joules) of impact energy when tested at an extreme low temperature of -150°F (-101°C) to prevent brittle failure in service.