ASTM A736 Low Alloy Steel Rod/Bar, Grade A, Class 3

ASTM A736 Low Alloy Steel Rod, Grade A, Class 3 Product Information -:- For detailed product information, please contact sales. -: ASTM A736 Low Alloy Steel Rod, Grade A, Class 3 Synonyms -:- For detailed product information, please contact sales. -:

ASTM A736 Low Alloy Steel, Grade A, Class 3 Product Information -:- For detailed product information, please contact sales. -: # **Product Introduction: ASTM A736/A736M Grade A, Class 3 High-Performance Low-Alloy Steel** **ASTM A736/A736M Grade A, Class 3** is the premier grade within the ASTM A736 specification, representing an advanced **precipitation-strengthened, low-carbon alloy steel** engineered for the most demanding pressure vessel and structural applications. This material delivers an exceptional balance of **ultra-high strength, superior toughness, and excellent weldability** through a sophisticated **nickel-copper-chromium-molybdenum-niobium alloy system** combined with optimized **normalizing and tempering or quenching and tempering heat treatments**. Class 3 is distinguished by its enhanced property requirements, typically including **higher minimum yield strength and more stringent impact toughness criteria** than Classes 1 and 2, making it ideal for critical applications in power generation, petrochemical processing, and advanced energy systems. --- ## **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. * **Classification:** Within Grade A, **Class 3 denotes the highest performance tier**, with specific requirements for enhanced toughness, strength, or resistance to temper embrittlement. * **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:** Achieves premium mechanical properties through a combination of ultra-low carbon content and precipitation hardening, enabling lightweight, high-efficiency designs for demanding service conditions. --- ## **Chemical Composition (Weight %, max unless range is specified)** The composition for Class 3 follows the Grade A ranges but is typically produced with tighter controls and optimized balances to achieve the highest performance levels. | Element | Composition Range (%) | Role in Performance for Class 3 | | :--- | :--- | :--- | | **Carbon (C)** | 0.07 max | **Extremely low** – Ensures outstanding weldability and base metal toughness; fundamental to the precipitation-hardening mechanism. | | **Manganese (Mn)** | 0.40 - 0.70 | Solid solution strengthener; typically optimized for best combination of strength and toughness. | | **Phosphorus (P)** | 0.025 max | Impurity – Maintained at minimal levels to prevent temper embrittlement. | | **Sulfur (S)** | 0.025 max | Impurity – Tightly controlled to ensure optimal weldability and ductility. | | **Silicon (Si)** | 0.15 - 0.50 | Deoxidizer; controlled to avoid excessive hardening in the heat-affected zone (HAZ). | | **Nickel (Ni)** | 0.70 - 1.00 | Enhances toughness and hardenability; critical for microstructural stability and low-temperature performance. | | **Chromium (Cr)** | 0.40 - 0.65 | Improves hardenability and provides moderate oxidation resistance. | | **Molybdenum (Mo)** | 0.20 - 0.30 | **Critical 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 fine, coherent Cu-rich precipitates during aging/tempering, providing substantial strength increase. | | **Columbium (Cb/Nb)** | 0.02 - 0.10 | **Key microalloy** – Provides grain refinement through Nb(CN) precipitates and contributes to precipitation strengthening; controls austenite grain growth during heat treatment. | | **Vanadium (V)** | 0.03 - 0.08 | Secondary precipitation strengthener; complements Nb's effect. | | **Aluminum (Al)** | 0.06 max | Grain refining deoxidizer. | --- ## **Typical Physical & Mechanical Properties (Grade A, Class 3)** Class 3 properties represent the peak performance achievable within the Grade A specification, typically requiring quenching and tempering heat treatment. | Property | Value / Description | | :--- | :--- | | **Tensile Strength** | 725 - 895 MPa (105,000 - 130,000 psi) | | **Yield Strength (min)** | **620 MPa (90,000 psi)** | | **Elongation in 2-in (50 mm) (min)** | 18% | | **Reduction of Area (min)** | 50% | | **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:** **-75°F (-60°C)**. **Minimum Avg. for 3 Specimens:** **40 ft·lbf (54 J)**. **Minimum Single Value:** Typically 30 ft·lbf (41 J). | | **Brinell Hardness (typical)** | 240 - 300 HBW | | **Elevated Temperature Yield Strength** | Maintains a high percentage of room temperature strength up to 650°F (345°C), superior to conventional HSLA steels. | --- ## **Product Applications** ASTM A736 Grade A, Class 3 is specified for the most critical applications where the highest levels of strength, toughness, and reliability are required, often in demanding environments. **Primary Industries and Equipment:** 1. **Advanced Power Generation:** * **Components for Supercritical and Ultra-Supercritical Steam Cycles**, such as high-pressure feedwater heaters and steam drums. * **Nuclear Power Plant Components** (where approved by applicable codes and standards). * **Hydrogen Coolers and High-Pressure Casing** in turbine-generator systems. 2. **Petrochemical & Refining:** * **High-Pressure Hydroprocessing Reactors** (hydrocrackers, hydrotreaters) for severe hydrogen service. * **Thick-Walled Pressure Vessels** in ethylene and methanol plants. * **Critical Heat Exchangers** in refining and chemical processes. 3. **Energy Transition Infrastructure:** * **Pressure Vessels for Hydrogen Storage and Transportation** (including tube trailers and stationary storage). * **Components in Carbon Capture, Utilization, and Storage (CCUS) Systems**. * **Geothermal Energy Systems** requiring high strength and corrosion resistance. 4. **High-Performance Engineering:** * **Lightweight Pressure Vessels for Aerospace and Defense Applications**. * **Specialized Equipment for Offshore and Subsea Operations**. --- ## **Advantages and Critical Fabrication Considerations** * **Advantages:** * **Premium Strength-Toughness Combination:** 90 ksi minimum yield strength with excellent impact toughness at low temperatures. * **Excellent Resistance to Temper Embrittlement:** Optimized alloy content, particularly molybdenum, ensures long-term toughness stability. * **Superior Weldability for its Strength Class:** The ultra-low carbon content results in a very low carbon equivalent, minimizing the risk of hydrogen-induced cracking. * **Outstanding Strength-to-Weight Ratio:** Enables significant weight reduction in pressure vessel designs, reducing material and transportation costs. * **Critical Fabrication & Welding Considerations:** * **Precise Heat Treatment Control:** Final properties are highly sensitive to tempering/aging parameters. Any deviation can significantly affect mechanical properties. * **Stringent Welding Requirements:** **Mandatory use of ultra-low hydrogen welding processes** with strict control of heat input. Welding consumables must be carefully selected to match both strength and toughness. * **Comprehensive Procedure Qualification:** Welding Procedure Specifications (WPS) must be rigorously qualified, including extensive mechanical testing (tensile, bend, impact) of weld metal and HAZ. * **Strict Preheat and Interpass Temperature Control:** Typically 250°F-400°F (120°C-205°C) depending on thickness, with continuous monitoring. * **Post-Weld Heat Treatment (PWHT):** Essential for stress relief but must be carefully controlled to avoid over-aging. PWHT parameters should be developed in consultation with material specialists. * **Advanced Non-Destructive Testing (NDT):** Typically requires 100% radiographic (RT) or ultrasonic testing (UT) of all welds, with additional examination of critical areas as specified. **In summary, ASTM A736 Grade A, Class 3 represents the pinnacle of precipitation-hardened low-alloy steels for pressure vessel applications. Its combination of ultra-high strength (90 ksi min yield), superior toughness at low temperatures, and excellent weldability makes it a material of choice for the most demanding applications in the energy and processing industries. However, its successful implementation requires sophisticated metallurgical knowledge, precise heat treatment control, and meticulous fabrication practices throughout the manufacturing process.** -:- For detailed product information, please contact sales. -: ASTM A736 Low Alloy Steel, Grade A, Class 3 Specification Dimensions Size： Diameter 20-1000 mm Length <4529 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 3 Properties -:- For detailed product information, please contact sales. -:

Applications of ASTM A736 Low Alloy Steel Rod, Grade A, Class 3 -:- For detailed product information, please contact sales. -: Chemical Identifiers ASTM A736 Low Alloy Steel Rod, Grade A, Class 3 -:- For detailed product information, please contact sales. -:

Packing of ASTM A736 Low Alloy Steel Rod, Grade A, Class 3 -:- 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 Rod 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 1000 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