ASTM A320 Grades L71, L72, & L73 Sample MTC
Access a comprehensive, professionally formatted Material Test Certificate according to EN 10204-2004: 3.1 covering the specialized ASTM A320 Grades L71, L72, and L73. Review the rigorous documentation verifying specific alloy chemistries, high tensile strength, and mandatory Charpy V-Notch impact testing at -100°F (-73°C) for low-temperature service.
What's Inside This A320 L71/72/73 MTC Certificate
This master sample mill test certificate details the critical testing parameters required for ASTM A320 Grades L71, L72, and L73. These specific alloy steels—Carbon-Moly (AISI 4037), Chrome-Moly (AISI 4137), and Nickel-Chrome-Moly (AISI 8740)—are engineered for low-temperature fastening where a test threshold of -100°F (-73°C) is sufficient compared to the -150°F standard of L7A/B/C.
- Full Traceability: Certified with TC No.: S178/26-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 L73 for enhanced toughness and the specific Carbon/Molybdenum ranges for L71 and L72.
- 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 a required temperature of -100°F (-73°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 L71, L72, L73 MTC Data
Review the comparative chemical parameters and shared mechanical limits before downloading.
TC Number
S178/26-XX
TC Date
25.05.20XX
Material Spec
ASTM A320 L71 / L72 / L73
Bar Shape / Size
Round Bar / 1-1/2"
Dimensions / Item
Stud Bolt 1-1/2"-8UN x 12"
Quantity
80.00 NOS
Chemical Composition Specification Limits (%)
| Grade / Base Alloy | C | Mn | P (Max) | S (Max) | Si | Ni | Cr | Mo |
|---|---|---|---|---|---|---|---|---|
| L71 (AISI 4037) | 0.35 - 0.40 | 0.70 - 0.90 | 0.035 | 0.040 | 0.15 - 0.35 | - | - | 0.20 - 0.30 |
| L72 (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 |
| L73 (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 @ -100°F / -73°C |
|---|---|---|---|---|
| 130.4 | 112.5 | 19.0 | 285, 290, 288 | 45, 48, 42 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 -100°F (-73°C). Results meet minimum 20 ft-lbf requirement for L71, L72, L73. |
| 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 -100°F (-73°C)
- 100% visual inspection carried out
Technical FAQs — ASTM A320 Grades L71, L72, L73
How do L71, L72, and L73 differ from L7A, L7B, and L7C?
The base alloys are identical pairs: L71 is the same base chemistry as L7A (AISI 4037), L72 pairs with L7B (AISI 4137), and L73 pairs with L7C (AISI 8740). The critical difference is the **Charpy V-Notch test temperature requirement**. Grades L7A/B/C must pass impact testing at a severe -150°F (-101°C). Grades L71/72/73 only need to pass the same 20 ft-lbf energy threshold at a milder **-100°F (-73°C)**.
Why specify these grades if standard L7 is available?
While standard Grade L7 (AISI 4140) is highly versatile, engineers may specify L71, L72, or L73 to fine-tune the metallurgical properties of the fastener based on its diameter. For example, L73 (AISI 8740) contains added Nickel which allows for better hardenability and toughness in larger diameter studs without failing the -100°F impact requirement.
Are these grades suitable for pressure vessels?
Yes. All of these grades fall under the ASTM A320 specification which explicitly covers alloy steel bolting materials for pressure vessels, valves, flanges, and fittings intended for low-temperature service down to -100°F (-73°C).