LTCS A333 Gr 6 Smls Pipe
Dec 04, 2025
What is A 333 Gr 6 Material
A333 Gr.6 is a seamless steel pipe material specifically engineered for low-temperature environments, conforming to the ASTM/ASME standard system. This steel maintains excellent mechanical properties and toughness under extreme cryogenic conditions, making it a critical material for cryogenic engineering applications. The ASTM A333 standard covers seamless and welded steel pipes for low-temperature service, with Gr.6 being a grade specifically designed for defined temperature ranges.
The core performance of A333 Gr.6 is demonstrated in its Charpy V-notch impact test at -45°C, requiring:
Single specimen impact energy ≥18 J
Average impact energy ≥20 J (per ASTM A370)
This data confirms its superior resistance to brittle fracture in extreme cold, significantly outperforming conventional carbon steels (e.g., A106 Gr.B typically achieves <10 J at -29°C). In practical applications, heat treatment (normalizing or quenching + tempering) is essential to optimize the grain structure to meet these requirements.
Carbon Steel A333 Gr.6 Square Pipe Chemical Formula
| C(max) | Mn | P(max) | S(max) | Si | Ni | |
|---|---|---|---|---|---|---|
| Grade 1 | 0.03 | 0.40 – 1.06 | 0.025 | 0.025 | ||
| Grade 3 | 0.19 | 0.31 – 0.64 | 0.025 | 0.025 | 0.18 – 0.37 | 3.18 – 3.82 |
| Grade 6 | 0.3 | 0.29 – 1.06 | 0.025 | 0.025 | 0.10 (min) |
CS A333 Gr.6 Hollow Pipe Mechanical Analysis
| Grade | Yield strength, min, psi (MPa) | Tensile strength, min, psi (MPa) | Elongation (%) |
| A333 Gr.6 | 35 000 (240) | 60 000 (415) | 30 min |
Tolerance Chart of ASTM A333 Carbon Steel GR.6 Seamless Pipe and Welded Steel Pipe for Low-Temperature Service
| Outside Diameter, inch | Tolerance, % |
|---|---|
| 1/8≤OD≤2-1/2 | +20.0/-12.5 |
| 3≤OD≤18, WT/OD≤5% | +22.5/-12.5 |
| 3≤OD≤18, WT/OD>5% | +15.0/-12.5 |
| OD≥20, WT/OD≤5% | +22.5/-12.5 |
| OD≥20, WT/OD>5% | +15.0/-12.5 |
ASTM A333 Gr.6 vs Gr.3 Comparison Table
| Parameter | Gr.6 | Gr.3 |
|---|---|---|
| Core Alloy | 3.5% Ni Steel (Ni: 3.2–3.6%) | 3.5% Ni Steel (Ni: 3.2–3.6%) Same Composition |
| Temperature Range | -45°C (Min Design Temp) | -101°C (Min Design Temp) |
| Impact Test Temp | -45°C (Charpy V-notch) | -101°C (Charpy V-notch) |
| Impact Energy Req. | ≥18J (Single) / ≥20J (Avg) | ≥18J (Single) / ≥20J (Avg) |
| Microstructure | Ferrite + 5–15% Retained Austenite | Ferrite + 20–30% Retained Austenite (More Stable) |
| Cryo Toughness Mech. | Ni Suppresses Brittleness (Limited Austenite) | High Austenite Delays Ductile-Brittle Transition |
| Applications | • LNG Terminals (-45°C Zone) • Liquid Ammonia Tanks |
• Liquid Nitrogen Pipes (-196°C) • Ethylene Cold Boxes (-101°C) |
| Temp Strength Limit | Oxidation >200°C | Strength Drop >150°C |
| Welding Process | Preheat 95–150°C (Anti-Cracking) | Preheat 120–175°C (Stricter Requirement) |
| Cost Reference | Baseline | +15% (Stricter Element Control) |
Test and inspection
Packaging and shipping
