SAE AISI 4135 Steel UNS G41350: Composition, Properties, and Uses
When it comes to the world of high-strength, versatile alloy steels, SAE AISI 4135 stands out as a remarkable choice…
When it comes to selecting the right material for high-stress applications, SAE AISI 1144 carbon steel, also known by its UNS designation G11440, stands out for its exceptional mechanical properties and versatility. Known for its superior machinability and high strength, this medium-carbon resulfurized steel is a favorite in industries ranging from automotive to general engineering. But what exactly makes SAE AISI 1144 so special? In this comprehensive guide, we’ll delve into the precise chemical composition that gives this steel its unique characteristics, explore its impressive mechanical, thermal, and electrical properties, and highlight the various applications where this robust material truly shines. Whether you’re an engineer, manufacturer, or researcher, understanding the full spectrum of SAE AISI 1144’s capabilities will help you make informed decisions for your next project. Let’s uncover the secrets behind this remarkable steel and see why it’s a go-to choice for demanding environments.
SAE AISI 1144 carbon steel, also known as UNS G11440, is a medium-carbon steel prized for its high strength and excellent machinability. This steel is specifically resulfurized to enhance its free-machining properties, making it ideal for producing complex and high-precision components.
AISI 1144 is notable for its strength and ease of machining. The added sulfur improves machinability without sacrificing strength and toughness. This makes it perfect for applications requiring extensive machining, such as complex components and high-precision parts.
This steel is widely used in automotive, construction, and engineering industries. Its ability to withstand high stress and perform reliably in demanding environments makes it versatile. Its robustness ensures it can handle significant loads and resist wear over time.
AISI 1144 is often used to make gears, shafts, spindles, and other critical parts requiring strength and precision. Its superior machinability lowers production costs and increases efficiency by reducing tool wear and allowing faster machining. Its consistent performance and reliability make it a trusted material for high-stakes applications.
Overall, SAE AISI 1144 carbon steel is highly valuable in many industrial applications. Its unique properties offer a balance of strength, machinability, and durability. This makes it an essential choice for engineers and manufacturers aiming for high-quality, efficient results.
The chemical makeup of SAE AISI 1144 carbon steel plays a vital role in its mechanical properties and uses. This medium-carbon steel is known for its high strength and excellent machinability, which are largely attributed to its specific elemental makeup.
SAE AISI 1144 carbon steel consists of the following primary elements:
Iron (Fe): 97.50 – 98.01%
Iron forms the main structure of the steel, giving it strength and durability.
Carbon (C): 0.40 – 0.48%
Carbon, making up 0.40 – 0.48% of the steel, is essential for its hardness and tensile strength.
Manganese (Mn): 1.35 – 1.65%
Manganese, present at 1.35 – 1.65%, improves toughness and hardness, and acts as a deoxidizer.
Sulfur (S): 0.24 – 0.33%
Sulfur, at 0.24 – 0.33%, improves machinability, making the steel easier to machine.
Phosphorus (P): Maximum 0.04%
Phosphorus, kept below 0.04%, enhances strength but must be controlled to prevent brittleness.
Trace amounts of other elements like silicon and aluminum may also be present:
The chemical composition of SAE AISI 1144 carbon steel balances strength, machinability, and toughness, making it ideal for automotive, construction, and general engineering applications.
Overall, the carefully balanced composition of SAE AISI 1144 carbon steel ensures it is strong, machinable, and tough, making it versatile for many industries.
SAE AISI 1144 carbon steel is known for its impressive tensile properties, making it ideal for high-stress mechanical applications. Its ultimate tensile strength typically ranges from 750 to 840 MPa (110,000 to 120,000 psi), with an average around 745 MPa (108,000 psi), indicating its ability to endure significant tensile loads before failure. The yield tensile strength usually falls between 420 and 690 MPa (61,000 to 100,000 psi), averaging about 620 MPa (89,900 psi), which shows the stress level where the steel starts to deform permanently.
The Brinell hardness of SAE AISI 1144 is generally between 220 and 230, averaging around 217, balancing strength and machinability. Converted, the Rockwell B hardness is about B95 and the Rockwell C hardness is around 17, indicating moderate hardness.
The elastic (Young’s) modulus is around 190 GPa (27 x 10^6 psi), reflecting the steel’s stiffness, with possible variations from 190 to 210 GPa (27,557-30,458 ksi) depending on processing. The shear modulus is typically 72 GPa (10 x 10^6 psi), with an average of 80 GPa (11,600 ksi), essential for torsional load applications. The shear strength ranges from 460 to 510 MPa (67,000 to 73,000 psi), usually around 73 ksi, indicating the material’s shear force resistance.
The elongation at break is between 11 and 17%, typically around 10%, showing the steel’s ductility before fracturing. The reduction in area ranges from 34 to 40%, commonly around 30%, indicating the material’s ability to withstand localized necking before rupture. The Poisson’s ratio is about 0.29, ranging from 0.27 to 0.30, describing the material’s tendency to expand perpendicularly under compression.
SAE AISI 1144 carbon steel has several key thermal properties that affect its performance in various applications.
The melting onset (solidus) for SAE AISI 1144 carbon steel occurs at approximately 1410°C (2580°F), and it completes melting (liquidus) around 1450°C (2650°F). This indicates the temperatures at which the steel begins and completes its transition from solid to liquid.
SAE AISI 1144 carbon steel can maintain its mechanical properties up to about 400°C (750°F). Beyond this temperature, the material may lose its structural integrity and mechanical strength, making it unsuitable for applications involving higher temperatures.
The specific heat capacity of this steel is roughly 470 J/kg-K (0.11 BTU/lb-°F), indicating how much heat is needed to raise the temperature of a given mass by one degree Kelvin.
With a thermal conductivity of 51 W/m-K (30 BTU/h-ft-°F), SAE AISI 1144 carbon steel efficiently conducts heat, making it ideal for applications requiring good heat dissipation.
The coefficient of thermal expansion, about 13 µm/m-K, shows how much the material expands with temperature changes, important for applications involving temperature variations.
SAE AISI 1144 carbon steel also has distinct electrical properties important for specific uses. Its electrical conductivity is around 7.2% of the International Annealed Copper Standard (IACS) by volume and 8.2% IACS by weight, compared to pure copper’s 100% conductivity.
These thermal and electrical characteristics make SAE AISI 1144 carbon steel suitable for various applications needing efficient thermal management and reliable electrical performance.
SAE AISI 1144 carbon steel has a density of about 7.85 g/cm³ (0.284 lb/in³), typical for medium-carbon steels. This density is crucial for calculating the weight of steel components in engineering applications.
The Poisson’s ratio for SAE AISI 1144 carbon steel is around 0.29, indicating how the material expands in directions perpendicular to compression. This property is key to understanding the material’s behavior under various loading conditions.
The elastic modulus, or Young’s modulus, of SAE AISI 1144 carbon steel is approximately 190 GPa (27 x 10^6 psi), reflecting the steel’s stiffness. It indicates how much the steel will deform under a given load, which is essential for designing components that must maintain their shape under mechanical stress.
The shear modulus of SAE AISI 1144 carbon steel is typically around 72 GPa (10 x 10^6 psi), with an average of 80 GPa (11,600 ksi). This property is critical for applications involving torsional loads or resisting shearing forces.
The coefficient of thermal expansion for SAE AISI 1144 carbon steel is about 13 µm/m-K, indicating how much the material expands or contracts with temperature changes. This is important for applications involving significant temperature fluctuations to ensure dimensional stability and structural integrity.
The specific heat capacity of this steel is around 470 J/kg-K (0.11 BTU/lb-°F), measuring the heat required to raise its temperature by one degree Kelvin. This property is crucial for thermal management in various applications.
SAE AISI 1144 carbon steel has a thermal conductivity of approximately 49.8 W/m-K (346 BTU-in/hr-ft²-°F), indicating its ability to conduct heat. This is crucial for applications needing efficient heat dissipation, such as in heat exchangers.
The electrical conductivity of this steel is about 7.2% of the International Annealed Copper Standard (IACS) by volume and 8.2% IACS by weight. This property is important for applications where electrical performance is a consideration, although steel is generally less conductive than materials like copper.
SAE AISI 1144 carbon steel is widely used in engineering and manufacturing because of its strength, durability, and ease of machining. This steel is ideal for producing machinery parts, gears, and mechanical components, and its enhanced machinability allows for efficient production of high-precision parts, reducing manufacturing time and costs.
In construction, SAE AISI 1144 carbon steel is used for strong, wear-resistant structural elements. Its ability to withstand significant loads and stress makes it suitable for critical structural applications, and in the transportation industry, it is used for high-stress, load-bearing parts like axles and shafts.
The automotive industry uses SAE AISI 1144 carbon steel for parts that need good mechanical properties and easy machining. Typical applications include engine components and transmission parts, where the steel’s high strength and machinability ensure reliable performance and longevity.
SAE AISI 1144 carbon steel is ideal for making valves, pumps, and related equipment because of its mechanical properties. Its strength and durability make it perfect for parts that face high pressures and continuous use, ensuring reliable and efficient performance in many industrial applications.
Besides these specific uses, SAE AISI 1144 carbon steel is widely used in general engineering. It is commonly used to produce bars, wire rods, plates, strips, sheets, and tubing, which are essential for making various strong and machinable products in multiple industrial sectors.
Stress relief is applied to SAE AISI 1144 carbon steel to reduce internal stresses from manufacturing. The steel is heated to 550-650°C (1022-1202°F) and then cooled slowly. This reduces residual stresses, preventing warping or distortion during machining or use.
Annealing softens SAE AISI 1144 steel, improves ductility, and relieves internal stresses. The steel is heated to about 790°C (1454°F) and slowly cooled in the furnace. This process refines the microstructure, enhancing tensile and yield strength. Post-annealing, the steel exhibits a tensile strength of around 584.7 MPa and a hardness of 167 HB.
Normalizing heats the steel to 870-900°C (1598-1652°F) before air cooling. This refines the grain structure, improving toughness and uniformity. Normalized SAE AISI 1144 carbon steel is often used in applications requiring improved strength and toughness.
To harden SAE AISI 1144 steel, heat it to 830-860°C (1526-1580°F) and quench in oil or water. Quenching can cause brittleness, so tempering usually follows. Tempering reduces brittleness but keeps the steel hard and strong. This is done by reheating the hardened steel to 150-200°C (302-392°F) and then cooling it.
SAE AISI 1144 carbon steel is highly machinable, thanks to its sulfur content. 1144 steel’s machinability is about 83% of the benchmark AISI 1212 steel. Use appropriate cutting fluids and HSS or carbide tools for better tool life and surface finish. The steel’s free-machining properties enable faster machining speeds, reducing production costs and time.
Welding SAE AISI 1144 steel is challenging because its sulfur content can cause cracking. Preheat the steel to 150-200°C (302-392°F) before welding to reduce cracking risk. Post-weld heat treatment (PWHT) helps relieve residual stresses and improve weld quality. Stress relief at temperatures between 550-650°C (1022-1202°F) can be effective. Using low-hydrogen welding electrodes can further reduce the risk of cracking.
Cold working strengthens and hardens the steel through strain hardening. This process is typically performed at room temperature, significantly enhancing the steel’s properties without changing its composition. Cold working processes include drawing, rolling, and bending. Excessive cold working can lead to brittleness, so it is often followed by a stress relief anneal to restore some ductility and reduce internal stresses.
These heat treatment and processing techniques enhance SAE AISI 1144 steel’s properties, machinability, and stability. By carefully selecting the appropriate treatment, manufacturers can tailor the steel’s properties to meet specific application requirements, ensuring optimal performance and longevity.
Below are answers to some frequently asked questions:
SAE AISI 1144 carbon steel, also known as UNS G11440, has the following chemical composition: Iron (Fe) ranges from 97.50% to 98.01%, Manganese (Mn) ranges from 1.35% to 1.65%, Carbon (C) ranges from 0.40% to 0.48%, Sulfur (S) ranges from 0.24% to 0.33%, and Phosphorus (P) is a maximum of 0.04%. This composition, particularly the higher sulfur content, enhances the machinability of AISI 1144, making it a preferred choice for applications requiring precise machining.
AISI 1144 steel, also known as Stressproof® Carbon Steel, exhibits several notable mechanical properties. It has an ultimate tensile strength of approximately 108,000 psi (745 MPa) and a yield tensile strength of around 89,900 psi (620 MPa). The steel typically shows a Brinell hardness ranging from 220 to 230, which converts to a Rockwell B hardness of approximately 95 and a Rockwell C hardness of around 17. It has a modulus of elasticity of about 29,700 ksi (or 190-210 GPa) and a shear modulus of 11,600 ksi (or 80.0 GPa). The elongation at break is 10%, with a reduction of area of 30%, indicating good ductility. These properties make AISI 1144 suitable for high-strength and high-wear applications, especially in automatic machine components, construction, and manufacturing.
The thermal and electrical properties of AISI 1144 steel are as follows:
Thermal properties:
Electrical properties:
These properties are critical for determining the suitability of AISI 1144 steel in various thermal and electrical applications within engineering and industrial contexts.
AISI 1144 steel is widely used in various industries due to its excellent machinability, high strength, and wear resistance. Typical applications include precision machine parts such as bearings, crankshafts, cams, and connecting rods in the automotive and aerospace industries. In the oil and gas industry, it is used for components that require high strength and resistance to wear and tear. In general manufacturing, it serves as an economical alternative to more costly quenched-and-tempered alloy grades and is used for fabricating fasteners, hydraulic fittings, machined bushings, shafts, axles, couplings, and gears. Additionally, it is recommended for high-production automatic machine components and parts in agricultural equipment that require high strength and excellent machinability.
AISI 1144 steel, also known as SAE-AISI 1144 or UNS G11440, is primarily heat-treated through a process known as "Stressproof," which relieves internal stresses created during manufacturing. This treatment enhances its dimensional stability, making it less prone to warping or distortion after machining. AISI 1144 steel has poor core hardening characteristics, meaning traditional heat treatments like water or oil quenching do not significantly improve its core hardness. As a result, additional heat treatment is generally not necessary for enhancing its mechanical properties.
In terms of processing, AISI 1144 is renowned for its excellent machinability, with a high machinability percentage of around 83%, making it ideal for producing high-quality, precise parts. It is primarily used in applications that require robustness and wear resistance, such as construction, transportation, and manufacturing of components like nuts, bolts, gears, shafts, and screws. The steel’s composition, which includes elements like manganese, carbon, and sulfur, contributes to its strength, stiffness, and resistance to stress and fatigue.
