AK Steel ASTM A 1011, Class 1 Formable, Grade 55K Hot Rolled Carbon Steel, Medium/High Strength Low Alloy Steel (HSLA)

AK Steel ASTM A 1011, Class 1 Formable, Grade 55K Hot Rolled Carbon Steel, Medium/High Strength Low Alloy Steel (HSLA) Product Information -:- For detailed product information, please contact sales. -: AK Steel ASTM A 1011, Class 1 Formable, Grade 55K Hot Rolled Carbon Steel, Medium/High Strength Low Alloy Steel (HSLA) Synonyms -:- For detailed product information, please contact sales. -:

AK Steel ASTM A 1011, Class 1 Formable, Grade 55K Hot Rolled Carbon Steel, Medium/High Strength Low Alloy Steel (HSLA) Product Information -:- For detailed product information, please contact sales. -: **Product Name:** AK Steel ASTM A1011, Class 1 Formable, Grade 55K Hot-Rolled Medium/High Strength Low-Alloy Steel (HSLA) --- ### **1. Overview** AK Steel's ASTM A1011 **Grade 55K, Class 1 Formable** represents the pinnacle of formable high-strength low-alloy (HSLA) steel technology in the hot-rolled sheet market. Delivering a formidable **minimum yield strength of 55 ksi (380 MPa)** while simultaneously meeting the most stringent ductility requirements (Class 1 Formable), this grade achieves a previously difficult balance of extreme strength and exceptional cold formability. The **"K" suffix** denotes advanced microalloying with Columbium (Niobium) and Vanadium, and the **Class 1** designation guarantees superior elongation and controlled tensile properties. It is engineered for the most demanding applications where maximum weight reduction via down-gauging must be coupled with the ability to manufacture highly complex, deeply drawn, or severely stretched components. --- ### **2. International Standards** This product is manufactured to the exacting requirements of the following standard, specifically meeting its highest formability class for this strength level: * **ASTM A1011 / A1011M:** Standard Specification for Steel, Sheet and Strip, Hot-Rolled, Carbon, Structural, High-Strength Low-Alloy and High-Strength Low-Alloy with Improved Formability. * **Grade:** 55K (Microalloyed HSLA Steel) * **Formability Class:** **Class 1 (Formable).** This classification mandates the highest level of ductility within the specification for this strength grade, imposing strict upper limits on tensile strength and guaranteeing superior minimum elongation values. --- ### **3. Chemical Composition (Typical, % by Weight)** The chemistry is an advanced, ultra-low carbon microalloyed design, pushing the boundaries of metallurgy to decouple strength from poor formability. | Element | Content (Typical / Maximum) | Role & Implication | | :--- | :--- | :--- | | **Carbon (C)** | 0.06% - 0.12% max | Extremely low for a 55 ksi steel. This is the foundational element enabling its formability and weldability, with strength derived almost entirely from microalloying and processing. | | **Manganese (Mn)** | 1.30% - 1.70% | Critical for solid solution strengthening and hardenability, working in synergy with microalloys. | | **Phosphorus (P)** | 0.025% max | Very tightly controlled to maximize ductility and toughness. | | **Sulfur (S)** | 0.010% max (often calcium-treated) | Very low, often with calcium treatment for sulfide shape control, drastically improving transverse ductility and through-thickness toughness (Z-direction properties). | | **Silicon (Si)** | 0.10% - 0.40% | Deoxidizer. | | **Columbium (Cb/Nb)** | **0.03% - 0.07%** | **Critical Microalloy.** Primary agent for grain refinement and precipitation strengthening. | | **Vanadium (V)** | **0.04% - 0.10%** (Typically used with Nb) | **Critical Microalloy.** Provides potent precipitation strengthening; the Nb-V combination is key to achieving 55 ksi with low carbon. | | **Titanium (Ti)** | May be present in small amounts | Assists in grain refinement and fixes nitrogen. | | **Aluminum (Al), Total** | 0.010% min | Grain refiner. | | **Nitrogen (N)** | Tightly Controlled | Precisely managed to optimize microalloy carbonitride precipitation. | | **Key Characteristic:** | **Ultra-Low Carbon Equivalent (CE).** Typically ≤ 0.40. This is a revolutionary achievement for 55 ksi yield strength and is the core reason for its exceptional formability and weldability. | | --- ### **4. Physical & Mechanical Properties** Properties are optimized for severe forming operations, a rare feat for this strength level. | Property | Specification Minimum (ASTM A1011, Grade 55K, Class 1) | Typical Value / Description | | :--- | :--- | :--- | | **Yield Strength (min)** | 55 ksi (380 MPa) | Often consistently at or above 60 ksi. | | **Tensile Strength** | **70 ksi min, with a strictly controlled *maximum*** | **Critical Class 1 Feature.** A tightly enforced upper limit (e.g., 80-85 ksi max) ensures a favorable, lower yield-to-tensile ratio (Y/T) essential for formability. Typically 70-80 ksi. | | **Yield-to-Tensile Ratio (Y/T)** | **Optimized to be as low as possible** | Typically 0.78 - 0.85. The lower end of this range is a key target for Class 1, promoting uniform strain distribution. | | **Elongation in 2" (min)** | **Highest for this strength grade** (e.g., 18-22% min, thickness dependent) | **Defining Class 1 Feature.** This high minimum elongation is what enables severe forming without failure. | | **Modulus of Elasticity** | 29,000 ksi (200 GPa) | | | **Notch Toughness** | **Exceptional.** The fine-grained, often acicular ferrite microstructure provides outstanding Charpy V-Notch impact values, suitable for low-temperature or dynamic loading applications. | | | **Through-Thickness Ductility (Z-direction)** | **Excellent** (when specified with sulfide shape control) | Critical for preventing lamellar tearing in welded joints of thick, restrained parts. | | **Surface Finish** | High-quality hot-rolled finish, suitable for demanding applications. | | --- ### **5. Key Features & Advantages** * **Unprecedented Combination:** Delivers the highest commonly available HSLA sheet strength (55 ksi min yield) with Class 1 formability, enabling revolutionary lightweight designs with complex geometries. * **Superlative Weldability:** The ultra-low carbon equivalent allows welding with minimal preheat, reducing fabrication cost and complexity. Excellent heat-affected zone (HAZ) toughness. * **Maximum Weight Reduction:** Enables the most aggressive down-gauging strategies, maximizing payload capacity and fuel efficiency in transportation and mobile equipment. * **Exceptional Toughness:** Provides best-in-class resistance to brittle fracture and fatigue, ensuring durability and safety in critical components. * **Design Freedom:** Allows engineers to design parts with deeper draws, tighter bends, and more complex shapes than ever before possible with 55 ksi material. --- ### **6. Product Applications** This steel is specified for the most advanced, weight-critical, and structurally demanding formed components. * **Automotive & Heavy Truck:** A-pillars, B-pillars, rocker panels, front rails, and other critical safety structural components requiring both ultra-high strength for crashworthiness and complex formability for packaging. * **Mobile Crane & Aerial Work Platforms:** Boom sections, outrigger pads, and complex structural members where every pound saved increases lift capacity or platform reach. * **Mining & Logging Equipment:** Cab structures, loader arms, and highly stressed formed components on equipment where weight directly impacts productivity and fuel consumption. * **Defense & Military Vehicles:** Armored vehicle hull components, structural members, and blast panels where weight savings and complex shapes are paramount. * **Energy Sector:** Formed sections for wind turbine hubs, specialized brackets, and mobile power generation equipment. * **High-Performance Transportation:** Chassis and structural components for buses, motorhomes, and specialty trailers. --- ### **7. Fabrication & Processing Notes** * **Forming:** Capable of **severe cold forming**, including deep drawing, stretch forming, and bending. Requires powerful press brakes and well-designed tooling. **Springback is significant** and must be accurately compensated for in tool and die design. Minimum bend radii are typically **3t to 4t**. The use of high-quality forming lubricants is essential. * **Welding:** **Excellent weldability for its strength.** Use low-hydrogen processes (GMAW with 90/10 Ar/CO₂, FCAW). Preheating of 50-200°F (10-95°C) is recommended for thicknesses over 1" or in highly restrained joints. Use matching or slightly undermatching filler metals (e.g., 70-80 ksi tensile) for optimal performance. * **Cutting:** Plasma and laser cutting are preferred for clean edges. Oxy-fuel cutting requires careful procedure due to alloy content. * **Surface Preparation:** Mill scale removal via abrasive blasting or pickling is required for painting or coating. * **Handling:** Material is high strength; proper handling equipment is required to prevent damage. --- **Disclaimer:** *This profile is a technical summary. AK Steel is now part of Cleveland-Cliffs Inc.* This is a premium, highly engineered product. For all engineering and procurement, it is **imperative** to consult the latest official **ASTM A1011** specification, the producer's **Technical Data Sheet**, and the certified **Mill Test Report (MTR)**. Procurement must explicitly state **"ASTM A1011, Grade 55K, Class 1 Formable"**. Close collaboration with the steel producer's technical team is strongly recommended during part and process design to fully leverage this material's advanced capabilities. -:- For detailed product information, please contact sales. -: AK Steel ASTM A 1011, Class 1 Formable, Grade 55K Hot Rolled Carbon Steel, Medium/High Strength Low Alloy Steel (HSLA) Specification Dimensions Size： Diameter 20-1000 mm Length <4596 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. -: AK Steel ASTM A 1011, Class 1 Formable, Grade 55K Hot Rolled Carbon Steel, Medium/High Strength Low Alloy Steel (HSLA) Properties -:- For detailed product information, please contact sales. -:

Applications of AK Steel ASTM A 1011, Class 1 Formable, Grade 55K Hot Rolled Carbon Steel, Medium/High Strength Low Alloy Steel (HSLA) -:- For detailed product information, please contact sales. -: Chemical Identifiers AK Steel ASTM A 1011, Class 1 Formable, Grade 55K Hot Rolled Carbon Steel, Medium/High Strength Low Alloy Steel (HSLA) -:- For detailed product information, please contact sales. -:

Packing of AK Steel ASTM A 1011, Class 1 Formable, Grade 55K Hot Rolled Carbon Steel, Medium/High Strength Low Alloy Steel (HSLA) -:- 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 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 1067 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