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China Suppliers Factory for ASME B16.5 Class 150 Carbon Steel Lap Joint Flange (LJF) - Custom Sizes Available
Material Grade
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Carbon Steel
ASTM A105 / A105N
ASTM A350 LF2 / LF3
ASTM A694 F42 / 46 / 56 / 60 / 65
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Stainless Steel
ASTM A182 F304 / 304L / 304H, 316 / 316L, 310S, 317, 347, 904L
ASTM A182 F51, F53, F44
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Alloy Steel
ASTM A182 F11 / 12 / 5 / 9 / 91 / 92
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Sealing Face
RF | FF | FTJ
Frequently Asked Questions
Q
What is the difference between ASTM A105 and ASTM A105N?
ASTM A105 is a standard specification for carbon steel forgings used in piping applications. The "N" in A105N indicates that the material has been normalized — a heat treatment process that refines the grain structure, improving toughness and mechanical properties for higher-pressure or lower-temperature applications.
Q
When should I choose Stainless Steel over Carbon Steel for flanges?
Stainless steel flanges (such as ASTM A182 F304/316 series) are preferred in corrosive environments, high-temperature applications, or where hygiene is critical — such as in chemical, food processing, or marine industries. Carbon steel is more economical and suitable for general-purpose, non-corrosive service conditions.
Q
What are the main applications of ASTM A694 high-yield carbon steel flanges?
ASTM A694 flanges (F42 through F65) are designed for high-pressure gas and oil transmission pipelines. The grade number (e.g., F60, F65) represents the minimum yield strength in ksi, making them ideal for demanding pipeline projects that require both high strength and good weldability.
Q
What is the difference between RF, FF, and FTJ sealing face types?
RF (Raised Face) is the most common type, featuring a raised ring that concentrates bolt load on a smaller gasket area for a better seal. FF (Flat Face) has a flat sealing surface and is used when connecting to cast iron or other brittle flanges to avoid bending stress. FTJ (Female-Tongue & Groove / Face Tongue Joint) provides a more precise and leak-resistant seal, commonly used in high-pressure or hazardous fluid applications.
Q
What makes Alloy Steel (ASTM A182 F11/F12/F91/F92) suitable for high-temperature service?
Alloy steel grades such as F11, F12, F91, and F92 contain chromium and molybdenum additions that significantly improve creep resistance, oxidation resistance, and strength retention at elevated temperatures. These grades are commonly used in power generation, petrochemical, and refinery applications where service temperatures can exceed 500°C.
Q
Is 904L stainless steel better than 316L for corrosion resistance?
Yes. 904L (ASTM A182 F44) is a high-alloy austenitic stainless steel with higher nickel, chromium, molybdenum, and copper content compared to 316L. It offers superior resistance to pitting, crevice corrosion, and stress corrosion cracking, especially in sulfuric acid and chloride-rich environments. However, it comes at a significantly higher cost, so it is selected when standard 316L is insufficient.