ASTM A735 Low Alloy Steel Flange, Class 4

1,We Manufacturing processes are primarily classified into four types: 1:Forging, 2:Casting, 3:Cutting, 4:Rolling. 2,We can manufacture in accordance with these standards. Standards: GB Series (Chinese Standards), JB Series (Machinery Standards), HG Series (Chemical Industry Standards), ASME B16.5 (American Standards), BS4504 (British Standards), DIN (German Standards), and JIS (Japanese Standards). Internationally, there are two primary systems of pipe flange standards: the European system, represented by the German DIN standards (including those of the former Soviet Union), and the American system, represented by the US ANSI pipe flange standards. Other common standards include: the Chinese Ministry of Machinery Industry standards (JB series), the Ministry of Chemical Industry standards (HG series), the Chinese National Standard *GB/T 9112–9124-2010 Steel Pipe Flanges*, as well as US standards (ASME B16.5), British standards (BS4504), German standards (DIN), Japanese standards (JIS), and marine standards (CBM), among others. The nominal pressure ratings for the PN series are designated by "PN" and comprise the following nine levels: PN2.5, PN6, PN10, PN16, PN25, PN40, PN63, PN100, and PN160. The nominal pressure ratings for the Class series are designated by "Class" and comprise the following six levels: Class150, Class300, Class600, Class900, Class1500, and Class2500. Flange Classification 1. **According to Chemical Industry Standards:** Flanges are classified as follows: Plate Flat Welding Flange (PL), Necked Flat Welding Flange (SO), Necked Butt Welding Flange (WN), Integral Flange (IF), Socket Welding Flange (SW), Threaded Flange (Th), Butt Welding Ring Loose Flange (PJ/SE), Blind Flange (BL), Flat Welding Ring Loose Flange (PJ/PJ), and Lined Blind Flange (BL(s)). 2. **According to Petrochemical (SH) Industry Standards:** Flanges are classified as follows: Threaded Flange (PL), Butt Welding Flange (WN), Flat Welding Flange (SO), Socket Welding Flange (SW), Loose Flange (LJ), and Blind Flange (no specific designation). 3. **According to Machinery (JB) Industry Standards:** Flanges are classified as follows: Integral Flange, Butt Welding Flange, Plate Flat Welding Flange, Butt Welding Ring Plate Loose Flange, Flat Welding Ring Plate Loose Flange, Lap Joint Ring Plate Loose Flange, and Blind Flange. 4. **According to Connection Method/Type:** Flanges are classified as follows: Plate Flat Welding Flange, Necked Flat Welding Flange, Necked Butt Welding Flange, Socket Welding Flange, Threaded Flange, Blind Flange, Necked Butt Welding Ring Loose Flange, Flat Welding Ring Loose Flange, Ring-Type Joint (RTJ) Flange and Blind Flange, Large-Diameter Plate Flange, Large-Diameter High-Neck Flange, Figure-8 Blind Plate, Butt Welding Ring Loose Flange, etc. 5. **According to the Component Being Connected:** Flanges can be classified into Vessel Flanges and Pipe Flanges. 6. **According to Structural Type:** Flanges include Integral Flanges, Threaded Flanges, Flat Welding Flanges, Butt Welding Flanges, Lap Joint (Loose/Swivel) Flanges, and Blind Flanges. A flange—also referred to as a flange plate or rim—is a component used to connect shafts to one another, or, more commonly, to join the ends of pipes. Flanges are also utilized at the inlet and outlet ports of equipment to facilitate connections between two devices—for instance, the flange on a speed reducer. A "flange connection" or "flanged joint" refers to a detachable joint assembly comprising three interconnected elements—a flange, a gasket, and bolts—that together form a sealed structural unit. In the context of piping systems, a "pipe flange" specifically denotes a flange used for plumbing within the installation; when applied to equipment, it refers to the inlet or outlet flange of that specific device. Flanges feature a series of holes through which bolts are inserted to securely fasten the two flanges together, while a gasket placed between the flanges ensures a leak-proof seal. Flanges are broadly categorized into three types: threaded (screw-in) flanges, welded flanges, and clamp-type flanges. Flanges are invariably used in pairs; threaded flanges are suitable for low-pressure piping applications, whereas welded flanges are required for systems operating at pressures exceeding 4 kilograms per square centimeter. A sealing gasket is inserted between the two flange plates, which are then firmly secured using bolts. The thickness of a flange—as well as the specifications of the bolts used to fasten it—vary depending on the specific pressure rating required for the application. When connecting equipment such as water pumps or valves to piping systems, the corresponding connection points on these devices are often manufactured in the shape of a matching flange; this method of attachment is also referred to as a "flange connection." Generally, any connecting component that utilizes bolts to join and seal the perimeters of two flat surfaces—such as the joints in ventilation ducts—is termed a "flange"; such components may collectively be classified as "flange-type parts." However, since such a connection often constitutes merely a *portion* of a larger device—for instance, the interface between a flange and a water pump—it would be inappropriate to classify the entire water pump itself as a "flange-type part." Conversely, smaller components—such as valves—that feature such flanged interfaces may indeed be appropriately categorized as "flange-type parts." -:- For detailed product information, please contact sales. -: ASTM A735 Low Alloy Steel Flange, Class 4 Product Information -:- For detailed product information, please contact sales. -: ASTM A735 Low Alloy Steel Flange, Class 4 Synonyms -:- For detailed product information, please contact sales. -:

ASTM A735 Low Alloy Steel, Class 4 Product Information -:- For detailed product information, please contact sales. -: # **Product Introduction: ASTM A735/A735M Class 4 Low-Alloy Steel for High-Strength Cryogenic Applications** **ASTM A735/A735M Class 4** is a premium **low-carbon, nickel-molybdenum alloy steel** engineered for the most demanding **cryogenic pressure vessel applications**. This grade offers a superior combination of **high strength, exceptional toughness at extremely low temperatures, and excellent weldability**, making it a top-tier choice for critical containment systems. Supplied in the **normalized and tempered (N&T) or quenched and tempered (Q&T) condition**, Class 4 is specifically designed to withstand the severe thermal and mechanical stresses encountered in advanced cryogenic infrastructure, such as large-scale **liquefied natural gas (LNG) storage** and transportation. --- ## **International Standard & Key Specifications** * **Primary Standard:** **ASTM A735/A735M** - Standard Specification for Pressure Vessel Plates, Low-Carbon Manganese-Molybdenum-Columbium Alloy Steel, for Moderate and Lower Temperature Service, Normalized and Tempered. * **Clarification:** The specification includes multiple classes based on alloy content and properties. **Class 4 is a high-nickel, high-strength variant** designed for service at temperatures down to **-200°F (-130°C) or lower**, often competing with 9% nickel steel in performance. * **ASME Code Equivalent:** **SA-735/SA-735M** in ASME Boiler and Pressure Vessel Code, Section II, Part A. Mandatory for ASME-stamped cryogenic pressure equipment. * **Governing Standard:** **ASTM A20/A20M** - Standard Specification for General Requirements for Steel Plates for Pressure Vessels. * **Related Specifications:** Often evaluated against **ASTM A553 Type I (8% Ni)** for similar cryogenic applications. --- ## **Chemical Composition (Weight %, max unless range is specified)** The composition is precisely controlled to achieve high hardenability for strength and a robust nickel-molybdenum matrix for low-temperature toughness. | Element | Composition (%) | Role in Performance | | :--- | :--- | :--- | | **Carbon (C)** | 0.15 max | Very low to ensure outstanding weldability and maximize toughness. | | **Manganese (Mn)** | 0.80 - 1.40 | Provides solid solution strengthening and aids hardenability. | | **Phosphorus (P)** | 0.025 max | Kept at minimal levels for superior notch toughness. | | **Sulfur (S)** | 0.025 max | Tightly controlled to prevent hot cracking and ensure weld integrity. | | **Silicon (Si)** | 0.15 - 0.50 | Deoxidizer and solid solution strengthener. | | **Nickel (Ni)** | **4.50 - 5.50** | **Primary alloying element.** Imparts exceptional cryogenic toughness by stabilizing the austenite phase and lowering the ductile-to-brittle transition temperature. | | **Molybdenum (Mo)** | **0.20 - 0.35** | **Critical addition.** Enhances hardenability for high strength, improves toughness at cryogenic temperatures, and provides resistance to temper embrittlement. | | **Columbium (Cb/Nb)** | 0.05 max (optional) | Grain refiner for improved toughness. | | **Vanadium (V)** | 0.05 max (optional) | Grain refiner and precipitation strengthener. | | **Aluminum (Al)** | 0.06 max | Grain refining deoxidizer. | **Key Note:** The **Ni-Mo synergy** is the cornerstone of Class 4 performance, enabling high yield strength while maintaining ductility and fracture resistance in extreme cold. --- ## **Typical Physical & Mechanical Properties** Properties are typically achieved through a quenched and tempered process for optimal performance, though normalized and tempered may be specified. Mechanical properties are superior to lower classes. | Property | Value / Description | | :--- | :--- | | **Tensile Strength** | 690 - 860 MPa (100,000 - 125,000 psi) | | **Yield Strength (min)** | **585 MPa (85,000 psi)** | | **Elongation in 2-in (50 mm) (min)** | 20% | | **Modulus of Elasticity** | ~200 GPa (29 x 10⁶ psi) | | **Density** | ~7.85 g/cm³ (0.284 lb/in³) | | **Charpy V-Notch Impact Toughness** | **Test Temperature:** **-200°F (-130°C)**. **Minimum Avg. for 3 Specimens:** **25 ft·lbf (34 J)**. This stringent requirement qualifies it for full cryogenic (LNG) service. | | **Brinell Hardness (typical)** | 220 - 270 HBW | | **Maximum Allowable Stress (ASME Sec. VIII Div. 1)** | Among the highest for ferritic alloy steels, allowing for highly efficient, thin-walled vessel designs. | --- ## **Product Applications** ASTM A735 Class 4 is specified for the most critical cryogenic applications where failure is not an option, particularly in the burgeoning LNG and industrial gas sectors. **Primary Industries and Equipment:** 1. **LNG Infrastructure:** * **Primary and Secondary Containment Membranes** in onshore and offshore LNG storage tanks. * **Cargo Containment Systems** for LNG carriers (membrane and spherical tank designs). * **Process Vessels** within LNG liquefaction and regasification terminals. 2. **Ultra-Low Temperature Processing:** * **Storage Tanks** for liquefied ethylene, ethane, and other light hydrocarbons. * **Cold Boxes** and critical exchangers in air separation units (ASU) and petrochemical cracker plants. 3. **Industrial Gases & Energy:** * **Large-Scale Storage Tanks** for liquid oxygen, nitrogen, and argon. * **Vessels for Hydrogen Energy Storage and Transportation** (for liquid or cold compressed gas). * **Components** in superconducting magnet systems and advanced research facilities. --- ## **Advantages and Critical Fabrication Considerations** * **Advantages:** * **Unmatched Cryogenic Performance:** Combines 85+ ksi yield strength with guaranteed toughness at -200°F, meeting the requirements for LNG and other severe cryogenic services. * **High Design Efficiency:** High strength-to-weight ratio enables lighter, more cost-effective vessel designs with reduced material usage. * **Good Weldability (Relative to Strength):** Despite its high strength, the very low carbon content makes it more weldable than many lower-strength, higher-carbon alloys. * **Proven Reliability:** A well-established, code-approved material with a long history in critical cryogenic service. * **Critical Fabrication & Welding Considerations:** * **Stringent Welding Protocols:** **Mandatory use of ultra-low hydrogen processes and nickel-alloyed filler metals** (e.g., AWS A5.11 ENiCrMo-6, A5.14 ERNiCrMo-3/4). WPS qualification must include impact testing of weld and HAZ at the design temperature. * **Strict Preheat & Interpass Control:** Preheat of **250°F - 400°F (120°C - 205°C)** is typically mandatory to prevent hydrogen cracking and control cooling rates. * **Mandatory Post-Weld Heat Treatment (PWHT):** Required for all pressure vessel welds. Temperature must be carefully controlled (typically below 1150°F / 620°C) to avoid detrimental microstructural changes. * **Thermal Cutting & Forming:** Hot forming requires subsequent re-normalizing and tempering. Cold forming should be limited. Preheating is required for thermal cutting. * **Comprehensive NDT:** 100% radiographic (RT) and ultrasonic testing (UT) of all welds is standard. Advanced phased array UT (PAUT) is increasingly specified. **In summary, ASTM A735 Class 4 is a high-performance, nickel-molybdenum alloy steel representing the pinnacle of ferritic materials for cryogenic pressure vessels. Its combination of ultra-high strength and exceptional toughness at temperatures as low as -200°F makes it a cornerstone material for the safe and efficient containment of liquefied gases in the global energy and industrial gas supply chains, demanding and justifying the highest levels of fabrication expertise and quality control.** -:- For detailed product information, please contact sales. -: ASTM A735 Low Alloy Steel, Class 4 Specification Dimensions Size： Diameter 20-1000 mm Length <4526 mm Size:We can customized as required Standard： Per your request or drawing We can customized as required Properties（Theoretical） Chemical Composition -:- For detailed product information, please contact sales. -: ASTM A735 Low Alloy Steel, Class 4 Properties -:- For detailed product information, please contact sales. -:

Applications of ASTM A735 Low Alloy Steel Flange, Class 4 -:- For detailed product information, please contact sales. -: Chemical Identifiers ASTM A735 Low Alloy Steel Flange, Class 4 -:- For detailed product information, please contact sales. -:

Packing of ASTM A735 Low Alloy Steel Flange, Class 4 -:- For detailed product information, please contact sales. -: Standard Packing: -:- For detailed product information, please contact sales. -: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and Steel Flange drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 997 gallon liquid totes Special package is available on request. E FORUs’ is carefully handled to minimize damage during storage and transportation and to preserve the quality of our products in their original condition