Engineered for the most demanding environments in high-pressure transmission lines, our A/SA694-F70 Welding Neck Flange offers superior integrity and durability. Designed specifically for the oil and gas industry, this flange combines high-yield strength carbon steel with a robust Ring Type Joint (RTJ) facing, ensuring a leak-proof seal even under the extreme stress of Class 900# applications.
Fully compliant with NACE MR0175 (ISO 15156), this product is certified for Sour Service, making it the primary choice for pipelines handling hydrogen sulfide (H2S) containing fluids where resistance to sulfide stress cracking is critical.
Key Features & Benefits
- High-Yield Material: Manufactured from A/SA694 Grade F70 carbon steel, offering a minimum yield strength of 70,000 psi. This allows for thinner wall thicknesses without compromising structural integrity in high-pressure piping systems.
- Welding Neck Design: The tapered hub reinforces the flange and transfers stress from the flange to the pipe. This design is crucial for applications involving high pressure, sub-zero or elevated temperatures, and line fluctuations.
- Ring Type Joint (RTJ) Facing: Designed for Class 900# and above, the RTJ face uses a metal ring gasket to create a metal-to-metal seal that tightens under pressure, virtually eliminating leaks.
- Sour Service Ready: The inclusion of NACE MR0175 compliance ensures the material has the necessary hardness controls and heat treatment to resist sulfide stress corrosion cracking (SSCC).
Technical Specification
ASTM 649 flange chemical composition:
| Element | F42 Content, % | F52 Content, % | F60 Content, % | F65 Content, % | F70 Content, % |
| Carbon (C) | 0.13~0.20 | 0.16~0.22 | 0.17~0.23 | 0.17~0.23 | 0.06~0.10 |
| Silicon (Si) | 0.20~0.40 | 0.15~0.40 | 0.15~0.40 | 0.15~0.40 | 0.20~0.40 |
| Manganese (Mn) | 1.20~1.60 | 1.10~1.40 | 1.20~1.50 | 1.30~1.60 | 1.10~1.40 |
| Phosphorous (P) | ≤ 0.030 | ≤ 0.025 | ≤ 0.020 | ≤ 0.025 | ≤ 0.020 |
| Sulfur (S) | ≤ 0.020 | ≤ 0.012 | ≤ 0.012 | ≤ 0.015 | ≤ 0.010 |
| Molybdenum (Mo) |
| 0.20~0.35 | 0.45~0.60 | 0.45~0.65 | 1.20~1.70 |
| Nickel (Ni) | ≤ 0.30 | ≤ 0.50 | 0.40~1.00 | ≤ 0.30 | 0.20~0.40 |
| Chromium (Cr) | ≤ 0.30 | ≤ 0.30 | ≤ 0.25 | ≤ 0.30 | ≤ 0.30 |
| Copper (Cu) | ≤ 0.25 | ≤ 0.25 | ≤ 0.25 | ≤ 0.25 | ≤ 0.25 |
ASTM 649 flange mechanical properties:
| STM A694 Grade | Yield Strength min. | Tensile Strength min. | Elongation min. |
| MPa | ksi | MPa | ksi | % |
| A694 F42 FLANGES | 290 | 42 | 415 | 65 | 20 |
| A694 F46 FLANGES | 315 | 46 | 415 | 60 | 20 |
| A694 F48 FLANGES | 330 | 48 | 425 | 62 | 20 |
| A694 F50 FLANGES | 345 | 50 | 440 | 64 | 20 |
| A694 F52 FLANGES | 360 | 52 | 455 | 66 | 20 |
| A694 F56 FLANGES | 385 | 56 | 470 | 68 | 20 |
| A694 F60 FLANGES | 415 | 60 | 515 | 75 | 20 |
| A694 F65 FLANGES | 450 | 65 | 530 | 77 | 20 |
| A694 F70 FLANGES | 485 | 70 | 565 | 82 | 18 |
Frequently Asked Questions (FAQ)
Q: What is the significance of the "F70" grade in A/SA694-F70?
A: The "F70" designates the minimum yield strength of the steel. In this case, 70,000 psi (485MPa). This high-yield strength is essential for high-pressure transmission pipelines and allows the flange to mate effectively with high-strength API 5L pipes.
Q: Why is NACE MR0175 compliance important for this flange?
A: NACE MR0175 compliance indicates that the material is suitable for "Sour Service" environments containing Hydrogen Sulfide (H2S). Without this standard, standard carbon steel flanges are prone to Sulfide Stress Cracking, which can lead to catastrophic failure in oil and gas lines.
Q: When should I use a Ring Type Joint (RTJ) over a Raised Face (RF)?
A: While Raised Face flanges are common, RTJ is specifically recommended for high-pressure ratings (Class 600 and above, such as this 900# flange) and high-temperature services. The metal gasket ring provides a more robust seal that adapts better to system stress.
Q: Is this flange compatible with API 5L X70 Pipe?
A: Yes, A/SA694-F70 flanges are specifically designed to match the mechanical properties of API 5L X70 line pipes, ensuring consistent strength across the pipeline weld joints.
Kasugai Group supply pipe fittings,steel pipes and flanges products for 100 years,If you want to know more about our piping products,please email us:zhangying@kasugai-group.co.jp
