SAE-AISI 4815 Alloy Steel: Composition, Properties, and Uses
Imagine a material that combines strength, versatility, and durability, becoming a cornerstone in industries ranging from automotive to aerospace. SAE-AISI…
In the realm of advanced materials, the quest for precision and reliability drives innovation. Alloy 48, also known by its designation UNS K94800, stands out as a quintessential controlled expansion alloy that has carved a niche in various high-tech industries. Composed primarily of nickel and iron, this alloy offers a remarkable balance of mechanical and physical properties, making it indispensable in applications where thermal stability is crucial. From ensuring the integrity of glass-to-metal seals in electronic devices to maintaining the accuracy of industrial thermostats, Alloy 48’s unique attributes make it a material of choice for engineers and manufacturers alike. In this article, we will delve into the intricate composition of Alloy 48, explore its impressive properties, and highlight its diverse uses, shedding light on why it remains a cornerstone in the world of specialized alloys.
Alloy 48, known by trade names like Nilo 48 and Pernifer 48, is a nickel-iron alloy prized for its low and consistent thermal expansion. This property makes it ideal for applications requiring precise dimensional stability over varying temperatures.
The creation of Alloy 48 began with early attempts to develop materials with predictable thermal expansion. Metallurgists fine-tuned the nickel and iron content to produce an alloy that expands and contracts minimally with temperature changes. This achievement met the demands of various specialized applications, particularly those requiring materials that maintain dimensional stability under thermal stress.
Alloy 48 is incredibly important in modern industry. It is extensively used in manufacturing glass-to-metal seals for electronic devices, radio valves, and electric lamps, where matching the expansion rate of glass is crucial to prevent cracks or leaks.
Alloy 48 is also used in making industrial thermostats. These thermostats benefit from the alloy’s stable thermal expansion, ensuring reliable operation across a wide temperature range. The material’s stability and durability make it ideal for components that must withstand thermal cycling without performance degradation.
Alloy 48 is characterized by its balanced composition of nickel and iron, with specific additions of elements like manganese, silicon, and chromium to enhance its properties. The alloy’s mechanical and physical properties, including its tensile strength, yield strength, and density, contribute to its robustness and versatility. Its thermal conductivity and electrical resistivity further extend its suitability for various engineering applications.
Overall, Alloy 48 is a versatile, reliable material crucial for applications needing precise thermal expansion matching. Its development and continued use underscore its importance in advancing technology and industrial processes.
Nickel makes up about 48% of Alloy 48, playing a crucial role in its thermal expansion properties. This high nickel content ensures minimal dimensional changes with temperature variations, meeting specific thermal expansion requirements for various applications.
Iron forms the remaining part of Alloy 48, providing structural strength and stability. It complements nickel to achieve the desired mechanical and thermal properties.
Manganese is present in Alloy 48 at up to 0.80%, acting as a deoxidizer and improving toughness and wear resistance. It also enhances the alloy’s hardenability and tensile strength, contributing to its durability.
Silicon, present at up to 0.30%, improves the alloy’s strength and hardness. As a deoxidizing agent, silicon removes oxygen during production, preventing the formation of unwanted oxides that could weaken the material.
The carbon content is kept below 0.05% to maintain the alloy’s ductility and toughness. Excessive carbon can form carbides, negatively affecting the alloy’s properties in high-temperature environments.
Chromium, included up to 0.25%, enhances corrosion resistance and durability. It also adds hardness and strength, making the alloy suitable for demanding applications.
Phosphorus is kept below 0.025% to improve machinability and hardness without causing brittleness.
Sulfur, present at up to 0.025%, enhances machinability while maintaining toughness and ductility.
Aluminum is included up to 0.10%, acting as a deoxidizer and improving strength and hardness. It also refines the grain structure, enhancing the alloy’s mechanical properties and stability.
Cobalt is an incidental element, not intentionally added but present in small amounts due to raw materials. Cobalt can affect the alloy’s magnetic properties and thermal stability.
Alloy 48 has an ultimate tensile strength of about 75,000 psi (520 MPa). This high tensile strength means the alloy can endure significant stretching or pulling forces before breaking, making it ideal for demanding applications.
Alloy 48’s yield strength, at 0.2% offset, is around 38,000 psi (260 MPa). This ensures the material maintains its shape under moderate stress without permanent deformation.
Alloy 48 has an impressive elongation rate of 43% in 2 inches, showing its excellent flexibility. This property allows the material to stretch significantly before breaking, making it ideal for applications requiring flexibility and the ability to withstand thermal cycling.
Alloy 48 has a hardness of up to 80 on the Rockwell B scale (HRB). This provides a good balance between toughness and machinability, ensuring the material can be shaped and finished without excessive wear on tools.
Alloy 48 has a density of 8.2 g/cm³ (0.298 lb/cu in). This relatively high density is typical for nickel-iron alloys and contributes to the material’s strength and stability.
The melting point of Alloy 48 is approximately 1450 °C (2640 °F). This high melting point allows the alloy to perform well in high-temperature environments, making it suitable for applications involving significant heat exposure.
Alloy 48 has a thermal conductivity of 16.7 W/m°C at 20°C (116 BTU-in/sq. ft-hr-°F at 68°F). This ensures efficient heat dissipation, which is important for applications like electronic components that generate heat.
Alloy 48 is designed to have a low and controlled thermal expansion coefficient, closely matching soft lead and soda-lime glasses. The thermal expansion coefficients are 8.5 µm/m°C (20-100°C), 8.3 to 9.3 µm/m°C (20-300°C), 8.3 to 9.3 µm/m°C (20-400°C), and up to 13.9 µm/m°C (20-1000°C). These values ensure that Alloy 48 expands and contracts minimally with temperature changes, preventing stress and potential failure in composite materials, such as glass-to-metal seals.
Alloy 48’s electrical resistivity is 47 microhms-cm at 20°C (283 ohm-cir mil/ft at 68°F). This higher resistivity makes it suitable for applications needing electrical insulation or controlled electrical properties.
The Curie temperature of Alloy 48 is 471°C (880°F). At this temperature, the material loses its ferromagnetic properties and becomes paramagnetic, which is crucial for applications involving magnetic fields.
Alloy 48 is widely used in industrial thermostats due to its stable thermal expansion properties. These thermostats often operate in environments with significant temperature fluctuations, so materials that maintain dimensional stability are essential for accurate temperature control. Thermostats made from Alloy 48 can reliably function at temperatures up to 450°C (840°F), making them suitable for various industrial applications like manufacturing processes, heating systems, and climate control equipment.
One of Alloy 48’s key uses is in creating glass-to-metal seals. The alloy’s thermal expansion coefficient closely matches that of soft lead and soda-lime glasses, preventing stress and potential breakage where glass and metal meet. Alloy 48 is extensively used in making glass-to-metal seals for radio valves and electric lamps, which must withstand thermal cycling without failure. In addition to radio valves and electric lamps, Alloy 48 is used in other devices requiring reliable glass-to-metal bonds, such as vacuum tubes and certain electronic components.
Alloy 48 is ideal for numerous electronic applications due to its stability and thermal properties. In electronics, Alloy 48 ensures components remain stable and reliable despite temperature changes, making it perfect for connectors, relays, and other precision parts. The alloy’s electrical resistivity and thermal conductivity also enhance its performance in electronic applications, ensuring devices are efficient and long-lasting.
The ASTM F30 standard outlines the requirements for Alloy 48 in various forms such as sheets, strips, rods, bars, tubing, and wires. This standard ensures consistent quality and performance, making it suitable for critical applications.
Under the Unified Numbering System (UNS), Alloy 48 is designated as K94800. This standardized naming convention helps identify and procure the alloy across different industries, ensuring uniformity and compatibility.
In Germany, Alloy 48 is recognized under the DIN 17745 standard, which covers the alloy’s composition and properties. This ensures the alloy meets stringent requirements for various industrial applications, identified by Werkstoff numbers 1.3922, 1.3926, and 1.3927.
The MIL-1-23011 CL 3 military specification defines the requirements for Alloy 48 in military applications. This ensures the alloy can withstand the demanding conditions in defense environments, providing reliability and durability.
The Aerospace Material Specification (AMS) 1-23011 CL 3 is crucial for Alloy 48 in aerospace applications. This specification ensures the material meets high-performance criteria for aircraft and spacecraft components.
In France, Alloy 48 is regulated by the AFNOR NF A54-301 standard. This ensures the material meets French industrial requirements for chemical composition, mechanical properties, and performance.
Alloy 48’s properties, such as tensile strength, yield strength, elongation, and thermal expansion coefficient, are consistently defined across these standards, though slight variations may exist due to different testing conditions or specific application requirements. These standards collectively ensure Alloy 48’s high quality and reliability in various industries.
When selecting Alloy 48 for a specific application, refer to the relevant standard to ensure it meets the necessary requirements. Understanding these specifications helps make informed decisions, ensuring the alloy performs optimally in its intended use.
Below are answers to some frequently asked questions:
The chemical composition of Alloy 48 (UNS K94800) includes the following elements: Nickel (48.0% nominal), Manganese (maximum 0.80%), Silicon (maximum 0.30%), Carbon (maximum 0.05%), Chromium (maximum 0.25%), Cobalt (present as an incidental element), Phosphorus (maximum 0.025%), Sulfur (maximum 0.025%), Aluminum (maximum 0.10%), and Iron (balance). This composition is carefully controlled to ensure the alloy’s thermal expansion properties match those of soft lead and soda-lime glasses, making it ideal for applications such as glass-to-metal seals.
Alloy 48, also known as Nilo 48, exhibits specific mechanical and physical properties that make it suitable for various applications. Its mechanical properties include an ultimate tensile strength of 75,000 psi (520 MPa), a yield strength (0.2%) of 38,000 psi (260 MPa), an elongation of 43% in 2 inches, and a maximum Rockwell hardness (HRB) of 80 when annealed. The modulus of elasticity is 23.2 x 10^6 psi (160 GPa).
Regarding its physical properties, Alloy 48 has a density of 0.298 lb/cu in or 8.2 g/cm³ and a specific gravity of 8.25. The melting point is 2640°F (1450°C), and the Curie temperature is 880°F (471°C). It has an electrical resistivity of 47 microhms-cm at 20°C and a thermal conductivity of 116 BTU-in/sq. ft-hr-°F at 68°F (16.7 W/m °C at 20°C).
The coefficient of thermal expansion for Alloy 48 varies with temperature: from 30 to 300°C, it is 8.8 µm/m °C; from 30 to 400°C, it ranges between 8.2 to 9.2 µm/m °C; and from 30 to 500°C, it is 9.4 µm/m °C. Additionally, from 68-212°F, it is 4.7 x 10^-6 in/in °F, from 20-100°C, it is 8.5 µm/m °C, and from 20-400°C, it ranges between 8.3 to 9.3 µm/m °C. These properties contribute to its effectiveness in applications requiring precise thermal expansion control, such as glass-to-metal seals and industrial thermostats.
The thermal expansion coefficient of Alloy 48 is specifically designed to be low and controlled, making it ideal for applications requiring precise dimensional stability. For the temperature range of 30 to 300°C, the coefficient is approximately 8.8 µm/m•°C, and for 30 to 500°C, it is about 9.4 µm/m•°C. This controlled thermal expansion is particularly matched to soft lead and soda-lime glasses, which makes Alloy 48 highly suitable for glass-to-metal seals in devices such as radio valves and electric lamps. In comparison, other materials like Kovar (UNS 4J29) have a lower thermal expansion coefficient of around 5 ppm/°C, tailored for hard glass seals. General metals like steel and aluminum have significantly higher coefficients, typically ranging from 10-20 x 10^-6 /°C, making Alloy 48 unique for applications where low thermal expansion is critical, such as industrial thermostats and precision instruments.
Alloy 48 is typically used in several critical applications due to its controlled thermal expansion properties. These applications include:
Glass-to-Metal Seals: Alloy 48 is extensively used in creating reliable seals between glass and metal, especially with soft lead and soda-lime glasses. This makes it ideal for use in electronic tubes and hermetic devices where a matching coefficient of thermal expansion is crucial.
Industrial Thermostats: The alloy is employed in industrial thermostat rods that need to operate efficiently at high temperatures, up to 450°C (840°F). This ensures precise temperature control in various industrial processes.
Electronic Components: It finds application in various electronic devices such as radio valves and electric lamps, where its specific thermal expansion properties help maintain the integrity and performance of the components.
Alloy 48 is used in industrial thermostats due to its stable thermal expansion characteristics and high-temperature operation capabilities. It can function reliably at temperatures up to 450°C (840°F), making it ideal for high-temperature environments. The alloy’s mechanical properties, such as tensile and yield strength, contribute to its durability and long service life, ensuring consistent performance in thermostat applications.
In glass-to-metal seals, Alloy 48 is chosen for its coefficient of thermal expansion, which closely matches that of soft lead and soda-lime glasses. This compatibility is crucial for creating hermetic and reliable seals, essential in applications like radio valves, electric lamps, and various electronic components. The alloy’s ability to be hot or cold worked, machined, and formed further facilitates its use in manufacturing these seals.
