What are the physical properties of 4130 chrome-moly steel?

Written by andrew richard
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What are the physical properties of 4130 chrome-moly steel?
Steel alloy 4130 has physical properties that make it an excellent choice for aerospace applications. (Jupiterimages/Photos.com/Getty Images)

Steel alloy 4130 is a low-carbon steel material that contains chromium and molybdenum to provide superior strength and mechanical properties. The physical properties of 4130 steel rely upon its chemical composition and microstructure. The latter can be altered depending on the forming process. The superior physical properties of 4130 chrome-moly steel make it suitable for aerospace structural applications.

Chemical Composition

The physical properties of 4130 steel derive from its chemical composition. This grade of steel includes about 0.30 per cent carbon, making it a low-carbon alloy. The superior mechanical properties of the material derive from the addition of chromium and molybdenum ions. About 1.0 per cent chromium and 0.20 per cent molybdenum are used in standard 4130 steel materials. Other chemical ions such as manganese and silicon are present as well. Sulphur and phosphorous impurities must be kept to less than 0.04 per cent to avoid compromising the physical properties of 4130 steel.

Forming Techniques

Different forming methods can alter the physical properties of 4130 chrome-moly steel. Forming is typically conducted at elevated temperatures at which this alloy exhibits improved ductility. Machining is typically carried out prior to final heat treatments to avoid introducing unnecessary internal strains into the microstructure. Improper forming can lead to significant embrittlement of the material. The existence of internal strains lowers the strength, hardness and toughness of the material, reducing its scope of suitable applications.

Specific Property Values

The physical properties of 4130 steel can be broken down into three categories: mechanical properties, thermal properties and electrical properties. The density of 4130 steel is 7.7 kilograms per cubic meter. Its Poisson's ratio is approximately 0.28. Young's modulus for the steel is 190-210 gigapascals and its tensile strength is 560.5 megapascals. The steel's yield strength after annealing is 360.6 megapascals. The hardness of 4130 steel is 156. The thermal conductivity of this material is 42.7 Watts per meter Kelvin. The specific heat is 477 Joules per kilogram Kelvin. The electrical resistivity of 4130 steel is 223 nano-ohm meters.

Applications of 4130 Steel

Steel alloy 4130 is typically used for structural applications. This steel alloy finds many uses in the aviation industry due to its good strength, ductility and corrosion resistance. This steel also exhibits excellent toughness and elongation, which are useful in the fabrication of critical aerospace parts such as fuselage safety cages. Unlike those of other steel alloys, the physical properties of 4130 chrome-moly steel do not alter with time, a process known as ageing. A lack of ageing effect makes 4130 steel a natural choice for applications where dependability is essential, such as in the manufacture of aeroplane components.

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