AISI A514 Grade H Alloy Steel (UNS K11576): Composition, Properties, and Uses

In the realm of high-strength, quenched, and tempered alloy steels, AISI A514 Grade H stands out as a material of choice for demanding structural applications. Renowned for its impressive yield strength, toughness, and impact resistance, this alloy steel is engineered to perform under the most strenuous conditions. Whether you’re designing the next generation of construction equipment, fabricating robust transport trailers, or constructing towering crane booms, understanding the unique attributes of A514 Grade H is crucial.

This comprehensive guide delves into the intricate composition of AISI A514 Grade H, highlighting the specific chemical elements that contribute to its remarkable properties. We will explore its mechanical characteristics, including tensile strength, elongation, and Charpy V-notch impact toughness, which are critical for ensuring durability and reliability in high-impact environments. Additionally, we’ll provide insights into its formability and weldability, offering practical guidelines to optimize fabrication processes.

Join us as we uncover the multifaceted uses of A514 Grade H alloy steel, shedding light on its indispensable role in modern engineering and manufacturing. Discover how this alloy can elevate your projects, providing the strength and resilience needed to meet the highest industry standards.

Chemical Composition

Breakdown of Chemical Elements

AISI A514 Grade H alloy steel, also known as UNS K11576, features a carefully balanced chemical composition that gives it exceptional strength and toughness. The ASTM A514 standard specifies the exact ranges for each element in this alloy.

Carbon (C)

• Content Range: 0.12 – 0.21%
• Role: Carbon significantly influences the hardness, strength, and wear resistance of the steel. The specified range ensures a good balance between strength and flexibility.

Manganese (Mn)

• Content Range: 0.95 – 1.30%
• Role: Manganese enhances the steel’s hardenability and tensile strength. It also helps remove oxygen from the steel and improves its toughness.

Phosphorus (P) and Sulfur (S)

• Phosphorus Maximum Content: 0.025%
• Sulfur Maximum Content: 0.005%
• Role: Both phosphorus and sulfur are kept at low levels to prevent brittleness and maintain the steel’s toughness and ductility.

Silicon (Si)

• Content Range: 0.20 – 0.35%
• Role: Silicon improves strength and hardness, acts as a deoxidizer, and enhances the steel’s magnetic properties and resistance to oxidation.

Chromium (Cr)

• Content Range: 0.40 – 0.65%
• Role: Chromium increases the steel’s hardenability, strength, wear resistance, and corrosion resistance.

Molybdenum (Mo)

• Content Range: 0.20 – 0.30%
• Role: Molybdenum boosts the steel’s strength, toughness, and resistance to wear and corrosion, especially at high temperatures.

Nickel (Ni)

• Content Range: 0.30 – 0.70%
• Role: Nickel improves toughness, impact resistance, overall strength, and corrosion resistance.

Vanadium (V)

• Content Range: 0.03 – 0.08%
• Role: Vanadium increases strength, toughness, and wear resistance. It also refines the grain structure, enhancing the steel’s mechanical properties.

Boron (B)

• Content Range: 0.0005 – 0.005%
• Role: Boron, even in small amounts, significantly improves the steel’s hardenability, helping to achieve the desired mechanical properties with less alloying content.

Summary of Chemical Composition

In summary, the precise chemical composition of AISI A514 Grade H alloy steel ensures a balance of high strength, toughness, and other desirable properties, making it ideal for demanding applications.

Mechanical Properties

Mechanical Properties of AISI A514 Grade H Alloy Steel

AISI A514 Grade H alloy steel is known for its impressive mechanical properties, making it ideal for heavy-duty applications.

Yield Strength

For plates up to 2.5 inches thick, the yield strength is typically 100,000 psi (690 MPa). For plates 2.5 to 6 inches thick, it is 90,000 psi (621 MPa). This high yield strength ensures the steel can withstand significant loads without permanent deformation.

Tensile Strength

The ultimate tensile strength ranges from 110,000 to 130,000 psi (758 to 896 MPa) for plates up to 2.5 inches thick, and 90,000 to 130,000 psi (621 to 896 MPa) for thicker plates. This means the steel can endure substantial stretching or pulling forces without breaking, crucial for maintaining structural integrity under heavy loads.

Elongation

Elongation measures the steel’s ductility. For plates up to 2.5 inches thick, elongation is about 18% in 2 inches, and for thicker plates, it’s around 16%. These values demonstrate the steel’s ability to stretch before breaking, allowing it to absorb energy during deformation and reducing the risk of brittle failure.

Reduction of Area

Reduction of area indicates ductility and toughness by measuring the decrease in cross-sectional area at the fracture point. Higher values mean better toughness, which is essential for materials subjected to dynamic loads and impacts. Specific values for reduction of area are typically provided by the manufacturer and can vary based on composition and processing conditions.

Charpy V-Notch Impact Toughness

The Charpy V-notch test measures the steel’s ability to absorb energy during fractures at low temperatures. A514 Grade H maintains its toughness even in cold environments, ensuring reliable performance in demanding conditions.

Summary

Overall, AISI A514 Grade H alloy steel offers high yield strength, tensile strength, ductility, and impact toughness, making it suitable for demanding applications in various environments.

Formability and Fabrication

Cold Forming Guidelines

AISI A514 Grade H alloy steel is known for its good cold forming properties, but specific precautions are necessary to prevent cracking and maintain material integrity.

Preparation

Remove shear burrs and heat-affected zones from thermal cut edges by grinding to avoid cracks during forming.

Bend Radius and Die Width

For plates with a thickness of 1.25 to 2.0 inches:

• Perpendicular to Rolling Direction:
• Minimum inside bend radius: 4.5 times the plate thickness (4.5t)
• Die width: 12 times the plate thickness (12t)
• Parallel to Rolling Direction:
• Minimum inside bend radius: 6.75 times the plate thickness (6.75t)
• Die width: 16 times the plate thickness (16t)

Weldability

Welding AISI A514 Grade H alloy steel requires adherence to specific procedures to maintain the material’s properties and prevent defects.

Welding Procedures

• Use Low Hydrogen Electrodes: This helps to prevent hydrogen-induced cracking.
• Control Preheat and Interpass Temperatures: Manage these temperatures carefully based on material thickness and welding process.
• Post-Weld Heat Treatment: This may be necessary to relieve residual stresses. However, evaluate the risk of reheat cracking with a welding engineer.

Fabrication Practices

Proper techniques are essential to ensure quality and performance when working with AISI A514 Grade H alloy steel.

Cutting and Machining

Use standard techniques, paying attention to work hardening and thermal effects. Employing appropriate cutting fluids and tools can mitigate these issues.

Forming and Shaping

Follow the recommended bend radii and die widths to avoid cracking. Gradual bending and proper support are crucial.

Stress Relieving

Stress relieving may be necessary to reduce residual stresses. However, control the process carefully to avoid reheat cracking.

By adhering to these guidelines, AISI A514 Grade H alloy steel can be effectively formed and fabricated for a wide range of demanding applications.

Applications

Applications of AISI A514 Grade H Alloy Steel

AISI A514 Grade H alloy steel is renowned for its high yield strength and toughness, making it indispensable in various structural and industrial applications.

AISI A514 Grade H alloy steel is extensively used in structural applications due to its high yield strength and excellent toughness. This makes it ideal for constructing buildings, bridges, and heavy-duty construction equipment such as crane booms and mobile man-lifts. The robust properties of A514 Grade H alloy steel make it perfect for manufacturing construction equipment, ensuring reliable performance and durability in demanding environments.

This steel is also widely used in transport trailers and heavy vehicle frames, where its high yield strength and impact resistance are crucial for safety and longevity. A514 Grade H alloy steel’s high tensile strength and formability make it an excellent choice for crane booms and mobile man-lifts, providing the necessary strength and stability for these lifting devices.

In industries where equipment faces high impact and abrasion, A514 Grade H alloy steel is invaluable. Its hardness and toughness make it ideal for bucket parts, hauling devices, and other heavy machinery used in mining and construction. This steel is also used in agricultural machinery, such as plow blades and harvesting equipment, due to its strength and durability in harsh conditions.

The exceptional properties of AISI A514 Grade H alloy steel enhance the performance, safety, and longevity of equipment and structures across various industries.

Frequently Asked Questions

Below are answers to some frequently asked questions:

What is the chemical composition of AISI A514 Grade H alloy steel?

The chemical composition of AISI A514 Grade H alloy steel (UNS K11576) includes the following elements: Carbon (0.12% to 0.21%), Manganese (0.95% to 1.3%), Phosphorus (maximum 0.035%), Sulfur (maximum 0.035%), Silicon (0.20% to 0.35%), Chromium (0.40% to 0.65%), Molybdenum (0.50% to 0.67%), Nickel (0.30% to 0.70%), Vanadium (0.03% to 0.08%), and Boron (0.001% to 0.005%). This specific composition provides the steel with high strength, toughness, weldability, and corrosion resistance, making it suitable for various industrial applications.

What are the mechanical properties of A514 Grade H, such as yield strength and tensile strength?

The mechanical properties of A514 Grade H alloy steel are as follows:

• Yield Strength: The minimum yield strength is 100 ksi (690 MPa).
• Tensile Strength: The ultimate tensile strength ranges from 110 ksi to 130 ksi (758 MPa to 896 MPa).
• Elongation: The elongation at break is a minimum of 16% in a 2-inch (50 mm) specimen.
• Reduction of Area: The reduction of area for a 1.5-inch wide rectangular tension specimen is a minimum of 35%.
• Impact Toughness: Charpy V-notch impact toughness can be ordered as a supplementary requirement, indicating the material’s ability to absorb impact without fracturing, especially at low temperatures.

How does A514 Grade H perform in terms of formability and weldability?

A514 Grade H alloy steel exhibits good formability, especially in cold forming, provided that shear burrs, heat-affected zones, and sharp corners are properly prepared by grinding. Specific guidelines for the minimum inside bend radius and die width are recommended to ensure optimal results. In terms of weldability, A514 Grade H is weldable but requires careful control of preheat and interpass temperatures, low hydrogen filler metals, and controlled heat input to maintain its mechanical properties and avoid issues like hydrogen cracking and reheat cracking. Following proper welding codes and consulting with qualified welding engineers are essential for achieving successful welds.

What are the typical applications for A514 Grade H alloy steel?

A514 Grade H alloy steel is typically used in applications requiring high strength, toughness, and good formability. These applications include structural uses in construction equipment, transport trailers, crane booms, mobile man-lifts, and other heavy-duty machinery. The steel is also employed in high-impact and abrasion-resistant uses such as mining equipment and industrial applications. Its properties make it suitable for welded bridge structures and agricultural equipment, where its ability to withstand high stresses and impacts is beneficial.

What are the recommended welding procedures for A514 Grade H?

When welding AISI A514 Grade H alloy steel, it is essential to follow specific procedures to maintain its mechanical properties and prevent issues such as hydrogen cracking. Select filler metals with low hydrogen content, such as E11018M or E12018M for SMAW, ER 110S-1 or ER 120S-1 for GMAW, and E11XT1-K3C or E12XT5-K4C for FCAW. Preheat temperatures should generally range from 200°F to 400°F (90°C to 200°C), with interpass temperatures not exceeding 600°F (315°C). Control heat input to around 55,000 joules per inch (±20 percent). Use low hydrogen practices, avoid postweld heat treatment, and ensure compatibility with the specific application to maintain the material’s properties.