AK Steel ASTM A 1011, Class 2 Formable, Grade 55K Hot Rolled Carbon Steel, Medium/High Strength Low Alloy Steel (HSLA)

AK Steel ASTM A 1011, Class 2 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 2 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 2 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 2 Formable, Grade 55K Hot-Rolled High-Strength Low-Alloy Steel (HSLA) --- ### **1. Overview** AK Steel's ASTM A1011 **Grade 55K, Class 2 Formable** is a premium, high-strength microalloyed steel engineered for structural applications demanding exceptional load-bearing capacity and weight efficiency. With a minimum yield strength of 55 ksi (380 MPa), it resides at the upper tier of commonly used structural HSLA grades. The **"Class 2 Formable"** designation indicates it meets the standard structural formability requirements, making it suitable for fabrication processes like bending, rolling, and welding, but not for severe drawing or complex stamping. This grade is the material of choice for critical, heavy-duty structural components where maximizing strength-to-weight ratio is paramount and forming operations are relatively straightforward. --- ### **2. International Standards** This product is manufactured to the stringent requirements of the following specification for high-strength structural steels: * **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 2 (Structural).** This classification defines the standard level of ductility and formability for high-strength structural applications, with property ranges optimized for reliable strength performance rather than enhanced forming. --- ### **3. Chemical Composition (Typical, % by Weight)** The chemistry is a sophisticated, low-carbon microalloyed system designed to achieve 55 ksi yield strength through advanced metallurgy. | Element | Content (Typical / Maximum) | Role & Implication | | :--- | :--- | :--- | | **Carbon (C)** | 0.08% - 0.14% max | Kept very low to ensure weldability and a degree of formability. Strength is primarily achieved through microalloying and controlled processing. | | **Manganese (Mn)** | 1.30% - 1.70% | Critical solid solution strengthener; essential for hardenability and supporting the high strength level. | | **Phosphorus (P)** | 0.025% max | Tightly controlled to preserve toughness. | | **Sulfur (S)** | 0.010% max (often calcium-treated) | Very low sulfur, often with calcium treatment, to ensure good through-thickness ductility (Z-direction properties) and enhanced weldability. | | **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%** | **Critical Microalloy.** Works synergistically with Nb to provide potent precipitation strengthening, enabling high strength with low carbon. | | **Titanium (Ti)** | May be present (~0.01%) | Assists in grain refinement and nitrogen control. | | **Aluminum (Al), Total** | 0.010% min | Grain refiner. | | **Key Characteristic:** | **Advanced Low Carbon Equivalent (CE).** Typically ~0.40-0.45. This represents a significant achievement, allowing this high-strength steel to be welded with established procedures, unlike quenched & tempered grades of similar strength. | | --- ### **4. Physical & Mechanical Properties** Properties reflect the high-strength, structural nature of Class 2 material. | Property | Specification Minimum (ASTM A1011, Grade 55K, Class 2) | Typical Value / Description | | :--- | :--- | :--- | | **Yield Strength (min)** | 55 ksi (380 MPa) | Often consistently exceeds minimum, typically 58-65 ksi. | | **Tensile Strength** | 70 ksi min (485 MPa) | Typically 70-85 ksi. **Class 2 allows for the full realization of high tensile strength**, resulting in a higher yield-to-tensile ratio suitable for structural design. | | **Yield-to-Tensile Ratio (Y/T)** | **Relatively High** | Typically 0.82 - 0.88. Characteristic of high-strength structural steels, indicating high elastic strain capacity but less uniform plastic deformation. | | **Elongation in 2" (min)** | **Standard for high-strength structural** (e.g., 16-18% min) | Provides sufficient ductility for structural integrity and standard fabrication (bending, welding), but not for severe forming. | | **Modulus of Elasticity** | 29,000 ksi (200 GPa) | | | **Notch Toughness** | **Excellent.** The fine-grained, often acicular ferrite microstructure provides outstanding impact resistance, suitable for low-temperature or dynamically loaded structures. | Often capable of meeting supplemental toughness requirements (e.g., -20°F / -30°C Charpy V-Notch). | | **Through-Thickness Ductility** | **Good (with Ca treatment)** | Improved resistance to lamellar tearing in thick welded sections compared to conventional steels. | --- ### **5. Key Features & Advantages** * **Maximum Structural Efficiency:** The 55 ksi minimum yield strength enables the greatest possible weight reduction in beams, columns, and plates, optimizing material use and reducing dead load. * **Superior Strength & Toughness Combination:** Offers an exceptional balance of high strength and excellent notch toughness, providing reliability under dynamic and impact loading. * **Good Weldability (for its strength class):** The advanced microalloyed, low-carbon chemistry makes it weldable with proper procedure, a key advantage over traditional means of achieving 55 ksi strength. * **Proven in Demanding Applications:** Established history in critical infrastructure, mining, and heavy equipment where performance is non-negotiable. * **Cost-Effective High-Performance:** Provides a more economical route to 55 ksi performance compared to heat-treated grades, especially in thicker sections. --- ### **6. Product Applications** ASTM A1011 Grade 55K Class 2 is specified for the most demanding structural applications across heavy industries. * **Heavy Construction & Infrastructure:** Primary beams and columns in high-rise buildings, long-span bridge girders, and offshore platform nodes. * **Mining & Heavy Equipment:** Chassis and structural frames for ultra-class haul trucks, excavator booms, shovel dippers, and crusher mainframes. * **Material Handling:** Gantry crane beams, heavy-duty stacker crane structures, and supports for extreme-capacity conveyor systems. * **Energy Sector:** Wind turbine tower flanges (for bolted connections), penstock supports, and heavy bases for power generation equipment. * **Transportation:** Main beams for extreme-capacity trailers, critical railcar underframe components, and heavy-duty vehicle chassis. --- ### **7. Fabrication & Processing Notes** * **Forming:** Suitable for **cold bending and roll-forming with caution**. **Requires large bend radii, typically ≥ 4x material thickness.** **Significant springback** must be compensated for in tooling design. **Not recommended for drawing or severe stretching.** Hot forming may be considered for complex shapes. * **Welding:** Requires **strict, qualified procedures**. Use **low-hydrogen processes exclusively** (FCAW-G, SAW, GMAW with 98/2 Ar/O₂). **Preheat (200-300°F / 95-150°C) is typically mandatory** for most thicknesses to prevent hydrogen cracking. Use high-toughness, matching-strength filler metals (e.g., E10018-D2, ER110S-G). Post-weld heat treatment is often recommended for thick sections to relieve stresses. * **Cutting:** **Plasma and laser cutting are strongly preferred.** Oxy-fuel cutting requires careful procedure and subsequent edge grinding for welding. * **Surface Preparation:** Complete removal of mill scale via abrasive blasting is essential prior to welding or painting. * **Design & Selection:** This is a high-performance structural material. **For applications involving any significant forming, Grade 55K, Class 1 Formable should be evaluated.** Class 2 is intended primarily for straight or simply curved structural members. --- **Disclaimer:** *This profile describes a high-performance structural steel. AK Steel is now part of Cleveland-Cliffs Inc.* Success with Grade 55K requires expertise. Always consult the latest **ASTM A1011** standard, the producer's **Technical Data Sheet**, and the certified **Mill Test Report (MTR)**. Procurement must specify **"ASTM A1011, Grade 55K, Class 2."** **Welding and forming procedures must be rigorously qualified** for the specific application. Collaboration with the steel producer's technical team during the design phase is highly recommended. -:- For detailed product information, please contact sales. -: AK Steel ASTM A 1011, Class 2 Formable, Grade 55K Hot Rolled Carbon Steel, Medium/High Strength Low Alloy Steel (HSLA) Specification Dimensions Size： Diameter 20-1000 mm Length <4600 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 2 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 2 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 2 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 2 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 1071 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