ASTM A736 Low Alloy Steel Seamless tube, Grade A, Class 2

ASTM A736 Low Alloy Steel Seamless tube, Grade A, Class 2 Product Information -:- For detailed product information, please contact sales. -: ASTM A736 Low Alloy Steel Seamless tube, Grade A, Class 2 Synonyms -:- For detailed product information, please contact sales. -:

ASTM A736 Low Alloy Steel, Grade A, Class 2 Product Information -:- For detailed product information, please contact sales. -: # **Product Introduction: ASTM A736/A736M Grade A, Class 2 Low-Alloy Steel for High-Strength Pressure Vessels** **ASTM A736/A736M Grade A, Class 2** is an advanced **precipitation-strengthened, high-strength low-alloy (HSLA) steel** specifically engineered for **welded pressure vessels requiring exceptional strength and toughness at elevated temperatures**. This grade represents a higher performance tier within the A736 specification, achieving its superior mechanical properties through a sophisticated **nickel-copper-chromium-molybdenum-columbium alloy system combined with precise heat treatment**. Supplied in the **normalized and tempered or quenched and tempered condition**, Class 2 is designed to maintain high yield strength while offering improved notch toughness and enhanced resistance to temper embrittlement compared to Class 1, making it suitable for more demanding service conditions. --- ## **International Standard & Key Specifications** * **Primary Standard:** **ASTM A736/A736M** - Standard Specification for Pressure Vessel Plates, Low-Carbon Age-Hardening Nickel-Copper-Chromium-Molybdenum-Columbium Alloy Steel. * **Key Distinction:** Class 2 typically indicates **specific, more stringent requirements for toughness and/or elevated temperature properties** within Grade A, often achieved through optimized chemistry and heat treatment control. * **ASME Code Equivalent:** **SA-736/SA-736M** in ASME Boiler and Pressure Vessel Code, Section II, Part A. Mandatory for ASME-stamped pressure equipment. * **Governing Standard:** **ASTM A20/A20M** - Standard Specification for General Requirements for Steel Plates for Pressure Vessels. * **Design Philosophy:** Provides one of the highest strength-to-weight ratios among ASME-approved pressure vessel steels while maintaining good fabricability. --- ## **Chemical Composition (Weight %, max unless range is specified)** The chemistry for Class 2 is tightly controlled with optimized alloy balances to achieve enhanced properties. Note that while Grade A composition ranges are specified, Class 2 typically represents material produced to the optimal middle or upper ranges of these limits for superior performance. | Element | Composition Range (%) | Role in Performance for Class 2 | | :--- | :--- | :--- | | **Carbon (C)** | 0.07 max | **Extremely low** - Maximizes weldability and base toughness; essential for the precipitation-hardening mechanism. | | **Manganese (Mn)** | 0.40 - 0.70 | Solid solution strengthener; typically controlled toward the upper end for optimal hardenability. | | **Phosphorus (P)** | 0.025 max | Impurity - kept at absolute minimum to prevent temper embrittlement. | | **Sulfur (S)** | 0.025 max | Impurity - tightly controlled for weldability and ductility. | | **Silicon (Si)** | 0.15 - 0.50 | Deoxidizer; controlled to avoid excessive strength in HAZ. | | **Nickel (Ni)** | 0.70 - 1.00 | Enhances toughness and hardenability; critical for microstructural stability. | | **Chromium (Cr)** | 0.40 - 0.65 | Improves hardenability and provides oxidation resistance; balanced with Ni for optimal properties. | | **Molybdenum (Mo)** | 0.20 - 0.30 | **Key element** - Provides solid solution strengthening, improves elevated temperature strength, and significantly reduces susceptibility to temper embrittlement. | | **Copper (Cu)** | 1.00 - 1.30 | **Primary precipitation-hardening element** - Forms coherent Cu-rich precipitates during aging/tempering; carefully balanced for optimal strengthening. | | **Columbium (Cb/Nb)** | 0.02 - 0.10 | **Critical microalloy** - Provides grain refinement and precipitation strengthening through Nb(CN) particles; essential for controlling the austenite grain size during heat treatment. | | **Vanadium (V)** | 0.03 - 0.08 | Secondary precipitation strengthener; complements Nb's effect. | | **Aluminum (Al)** | 0.06 max | Grain refining deoxidizer; controlled for consistent hardenability. | --- ## **Typical Physical & Mechanical Properties (Grade A, Class 2)** Properties represent material typically supplied in the quenched and tempered condition for optimal performance balance. | Property | Value / Description | Comparison to Class 1 | | :--- | :--- | :--- | | **Tensile Strength** | 690 - 860 MPa (100,000 - 125,000 psi) | Higher strength range | | **Yield Strength (min)** | **585 MPa (85,000 psi)** | **Higher minimum yield** | | **Elongation in 2-in (50 mm) (min)** | 18% | Similar | | **Reduction of Area (min)** | 45% | Typically higher | | **Modulus of Elasticity** | ~200 GPa (29 x 10⁶ psi) | Similar | | **Density** | ~7.85 g/cm³ (0.284 lb/in³) | Similar | | **Charpy V-Notch Impact Toughness** | **Test Temperature:** **-60°F (-50°C)**. **Minimum Avg.:** **35 ft·lbf (47 J)**. | **Higher toughness requirement** | | **Brinell Hardness** | 230 - 280 HBW | Higher due to increased strength | | **Elevated Temperature Yield Strength** | Maintains higher percentage of room temperature strength at 600°F (315°C) compared to conventional steels | **Key advantage over Class 1** | --- ## **Product Applications** ASTM A736 Grade A, Class 2 is specified for the most demanding pressure vessel applications where both exceptional strength and reliability under thermal cycling are critical. **Primary Industries and Equipment:** 1. **Power Generation (Fossil & Nuclear):** * **High-Pressure Feedwater Heaters** (especially for supercritical and ultra-supercritical plants) * **Steam Generators and Moisture Separator Reheaters (MSRs)** * **Nuclear Reactor Coolant System Components** (where approved by code) * **Hydrogen Coolers and High-Pressure Casing** 2. **Oil Refining & Petrochemical:** * **Hydrocracking and Hydrotreating Reactors** (for high-pressure hydrogen service) * **High-Pressure Heat Exchangers** in refinery and chemical processes * **Catalytic Reformer Reactors** 3. **Advanced Energy Systems:** * **Pressure Vessels for Hydrogen Storage and Transportation** * **Components in Carbon Capture and Storage (CCS) Systems** * **Geothermal Energy Systems** 4. **High-Performance Transportation:** * **Lightweight High-Pressure Vessels** for aerospace and defense applications * **Specialized Rail and Road Transport Tanks** for critical commodities --- ## **Advantages and Critical Fabrication Considerations** * **Advantages:** * **Exceptional Strength-Toughness Combination:** 85 ksi minimum yield strength with superior impact energy absorption * **Reduced Temper Embrittlement Susceptibility:** Optimized Mo content provides better resistance to long-term service embrittlement * **Good Elevated Temperature Properties:** Maintains strength better than conventional HSLA steels at moderate temperatures * **Excellent Strength-to-Weight Ratio:** Enables more efficient, thinner-walled designs for significant weight savings * **Critical Fabrication & Welding Considerations:** * **Precise Heat Treatment Control:** Properties are highly sensitive to tempering/aging parameters. Any deviation from specified heat treatment can significantly affect mechanical properties * **Advanced Welding Requirements:** **Mandatory use of ultra-low hydrogen processes** with strict controls on heat input. Welding consumables must be carefully selected to match both strength and toughness * **Comprehensive Procedure Qualification:** WPS qualification must include extensive mechanical testing, including impact tests at multiple locations (weld metal, HAZ, base metal) * **Strict Preheat/Interpass Control:** Typically 250°F-350°F (120°C-175°C) depending on thickness, with precise monitoring * **Post-Weld Heat Treatment (PWHT):** Essential but must be carefully controlled to avoid over-aging. PWHT parameters must be developed in consultation with material specialists * **Advanced NDT Requirements:** Typically requires 100% RT or UT of all welds plus additional examination of critical areas **In summary, ASTM A736 Grade A, Class 2 represents the premium tier of precipitation-hardened pressure vessel steels, offering an exceptional balance of ultra-high strength (85 ksi min yield), superior toughness, and enhanced resistance to service degradation. Its use enables breakthrough designs in weight-sensitive and high-performance applications across the energy sector, though it demands the highest levels of metallurgical expertise and fabrication control throughout the manufacturing process.** -:- For detailed product information, please contact sales. -: ASTM A736 Low Alloy Steel, Grade A, Class 2 Specification Dimensions Size： Diameter 20-1000 mm Length <4528 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 A736 Low Alloy Steel, Grade A, Class 2 Properties -:- For detailed product information, please contact sales. -:

Applications of ASTM A736 Low Alloy Steel Seamless tube, Grade A, Class 2 -:- For detailed product information, please contact sales. -: Chemical Identifiers ASTM A736 Low Alloy Steel Seamless tube, Grade A, Class 2 -:- For detailed product information, please contact sales. -:

Packing of ASTM A736 Low Alloy Steel Seamless tube, Grade A, Class 2 -:- 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 Seamless tube 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 999 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