AK Steel ASTM A 1011, Grade 55 Hot Rolled Carbon Steel, Structural Steel (SS)

AK Steel ASTM A 1011, Grade 55 Hot Rolled Carbon Steel, Structural Steel (SS) Product Information -:- For detailed product information, please contact sales. -: AK Steel ASTM A 1011, Grade 55 Hot Rolled Carbon Steel, Structural Steel (SS) Synonyms -:- For detailed product information, please contact sales. -:

AK Steel ASTM A 1011, Grade 55 Hot Rolled Carbon Steel, Structural Steel (SS) Product Information -:- For detailed product information, please contact sales. -: **Product Name:** AK Steel ASTM A1011, Grade 55 Hot-Rolled Carbon Steel, Structural Steel (SS) --- ### **1. Overview** AK Steel's ASTM A1011 Grade 55 is a premium high-strength, low-alloy (HSLA) structural steel designed for the most demanding applications where exceptional strength, weight reduction, and structural efficiency are critical. With a minimum yield strength of 55 ksi (380 MPa), it occupies the upper tier of commonly available hot-rolled sheet and strip grades. This steel leverages advanced microalloying technology and controlled thermomechanical processing to achieve its high strength-to-weight ratio while maintaining superior weldability and toughness compared to traditional carbon steels of equivalent strength. It is the material of choice for engineers seeking to maximize payload, minimize dead weight, and ensure durability in heavy-duty structural frameworks. --- ### **2. International Standards** This product conforms to the following internationally recognized standard for high-strength hot-rolled 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. * This product meets the stringent requirements for **Grade 55**, specifically under the **High-Strength Low-Alloy Steel (HSLAS)** classification within the standard, denoting a fine-grained, microalloyed composition. --- ### **3. Chemical Composition (Typical, % by Weight)** Grade 55 is defined by a sophisticated, low-carbon microalloyed chemistry that prioritizes performance over simple carbon strengthening. | Element | Content (Maximum, unless specified) | Role & Implication | | :--- | :--- | :--- | | **Carbon (C)** | 0.15% max (typically 0.08-0.12%) | Kept very low to ensure excellent weldability and toughness. Primary strength comes from other elements. | | **Manganese (Mn)** | 1.20% - 1.60% | Major solid-solution strengthener; essential for achieving core strength and hardenability. | | **Phosphorus (P)** | 0.035% max | Residual; minimized. | | **Sulfur (S)** | 0.035% max | Residual; controlled for improved transverse properties and weldability. | | **Silicon (Si)** | 0.10% - 0.40% | Deoxidizer and strengthens ferrite. | | **Columbium (Cb/Nb)** | **0.02% - 0.06%** | **Critical Microalloy.** Primary agent for grain refinement and precipitation strengthening, enabling high strength with low carbon. | | **Vanadium (V)** | **0.03% - 0.08%** (often used with Nb) | **Key Microalloy.** Provides potent precipitation strengthening via vanadium carbonitrides. | | **Titanium (Ti)** | May be present in small amounts | Assists in grain refinement and sulfide shape control. | | **Aluminum (Al), Total** | 0.010% min | Grain refiner for fine austenite grain size. | | **Nitrogen (N)** | Controlled | Optimized to interact with microalloys. | **Key Distinction:** The strategic combination of **Niobium (Nb) and Vanadium (V)** is the hallmark of modern Grade 55 steel. This synergy allows for a very low carbon equivalent (CE), typically below 0.40, which is revolutionary for achieving 55 ksi yield strength with outstanding fabrication properties. --- ### **4. Physical & Mechanical Properties** Properties result from a precisely controlled hot-rolling schedule that induces fine grain size and precipitation hardening. | Property | Specification Minimum (ASTM A1011 for HSLAS Grade 55) | Typical Value / Description | | :--- | :--- | :--- | | **Yield Strength (min)** | 55 ksi (380 MPa) | Often consistently at or above 60 ksi. | | **Tensile Strength** | 70 ksi min (485 MPa) | Typically ranges from 70 - 90 ksi (485 - 620 MPa). | | **Yield-to-Tensile Ratio** | 0.78 - 0.85 | High ratio indicates efficient structural material, but requires attention in forming. | | **Elongation in 2" (min)** | 17% - 20% (varies with thickness) | Respectable ductility for its high strength level, enabled by fine grain structure. | | **Modulus of Elasticity** | 29,000 ksi (200 GPa) | | | **Notch Toughness** | **Exceptional.** The fine-grained, acicular ferrite/pearlite microstructure provides excellent Charpy V-Notch impact values, often suitable for low-temperature service. | A key advantage over quenched & tempered grades of similar strength. | | **Fatigue Strength** | High | Excellent resistance to cyclic loading due to clean microstructure and fine grain. | | **Surface Finish** | Standard hot-rolled mill finish. | | --- ### **5. Key Features & Advantages** * **Maximum Weight Reduction:** The 55 ksi yield strength allows for the thinnest possible gauges in structural design, leading to significant savings in material, freight, and energy costs over the lifecycle of a product. * **Outstanding Weldability:** Its very low carbon equivalent permits welding with minimal or no preheat in most thicknesses, drastically reducing fabrication complexity and cost compared to conventional high-strength steels. * **Superior Toughness & Impact Resistance:** The microalloyed, fine-grained structure offers best-in-class resistance to brittle fracture, making it ideal for dynamic, shock-loaded, or low-temperature environments. * **Excellent Cold Formability (for its strength):** Can be roll-formed, bent, and punched, though it requires significantly more force and larger bend radii (e.g., 3t - 4t) than lower-strength grades. * **Atmospheric Corrosion Resistance:** Often available as **Grade 55W** with added copper, phosphorus, and chromium, providing approximately 2x the corrosion resistance of plain carbon steel. --- ### **6. Product Applications** ASTM A1011 Grade 55 is specified for the most critical, weight-sensitive structural components across heavy industries. * **Heavy Transportation:** Main beams and side rails for ultra-high-capacity trailers, dump truck bodies, railcar center sills, and advanced military vehicle frames. * **Mobile Crane & Equipment:** Boom sections, outrigger pads, and main frames where strength-to-weight is paramount for performance and mobility. * **Mining & Logging:** Chassis and structural members for extreme-duty haul trucks, excavator arms, and logging equipment facing severe impact loads. * **Construction & Infrastructure:** Long-span building beams, bridge floor beams, and critical components in seismic-resistant structures. * **Energy & Utility:** Wind turbine tower flanges (non-welded), heavy-duty transmission poles, and offshore platform walkways. * **Material Handling:** Structural members for automated storage/retrieval systems (AS/RS) and heavy-duty industrial racks. --- ### **7. Fabrication & Processing Notes** * **Descaling:** Essential for welding and coating. Abrasive blasting is highly effective. * **Forming:** Requires powerful press brakes. Springback is significant and must be accounted for in tooling design. Heat-assisted forming may be used for very tight radii. * **Welding:** **Recommended for its excellent weldability.** Use low-hydrogen processes (GMAW with 90/10 Ar/CO₂, FCAW-G, SMAW with E7018). Preheat of 50-150°F (10-65°C) may be recommended only for very thick sections (>1.5") or highly restrained joints. Interpass temperature should be controlled. * **Thermal Cutting:** Plasma and laser cutting are ideal. Oxy-fuel cutting requires care due to higher alloy content; use appropriate fuel gases and procedures. * **Galvanizing:** Well-suited due to controlled, low-silicon chemistry. Consult the galvanizer for specific bath practices. --- **Disclaimer:** *This profile is a technical summary. AK Steel is now part of Cleveland-Cliffs Inc.* For all engineering and procurement, it is imperative to consult the latest **ASTM A1011** specification and the certified **Mill Test Report (MTR)** from the producer. Properties and chemistries, especially microalloy ratios (Nb/V), can vary. The MTR provides the exact data governing your material lot. Always qualify welding and forming procedures for the specific application. -:- For detailed product information, please contact sales. -: AK Steel ASTM A 1011, Grade 55 Hot Rolled Carbon Steel, Structural Steel (SS) Specification Dimensions Size： Diameter 20-1000 mm Length <4588 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, Grade 55 Hot Rolled Carbon Steel, Structural Steel (SS) Properties -:- For detailed product information, please contact sales. -:

Applications of AK Steel ASTM A 1011, Grade 55 Hot Rolled Carbon Steel, Structural Steel (SS) -:- For detailed product information, please contact sales. -: Chemical Identifiers AK Steel ASTM A 1011, Grade 55 Hot Rolled Carbon Steel, Structural Steel (SS) -:- For detailed product information, please contact sales. -:

Packing of AK Steel ASTM A 1011, Grade 55 Hot Rolled Carbon Steel, Structural Steel (SS) -:- 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 1059 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