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Glossary » Materials » Alloys » Steel » Alloy Steel » AISI 8640
AISI 8640 is a Standard grade Alloy Steel. It is commonly called AISI 8640 Nickel-chromium-molybdenum steel. It is composed of (in weight percentage) 0.38-0.43% Carbon (C), 0.75-1.00% Manganese (Mn), 0.035%(max) Phosphorus (P), 0.04%(max) Sulfur (S), 0.15-0.30% Silicon (Si), 0.40-0.60% Chromium (Cr), 0.40-0.70% Nickel (Ni), 0.15-0.25% Molybdenum (Mo), and the base metal Iron (Fe). Other designations of AISI 8640 alloy steel include UNS G86400 and AISI 8640.
Steel is the common name for a large family of iron alloys. Steels can either be cast directly to shape, or into ingots which are reheated and hot worked into a wrought shape by forging, extrusion, rolling, or other processes. Wrought steels are the most common engineering material used, and come in a variety of forms with different finishes and properties. Alloy steels are steels that exceed the element limits for Carbon steels. However, steels containing more than 3.99% chromium are classified differently as stainless and tool steels. Alloy steels also includes steels that contain elements not found in carbon steels such as nickel, chromium (up to 3.99%), cobalt, etc.

The typical elastic modulus of alloy steels at room temperature (25°C) ranges from 190 to 210 GPa. The typical density of alloy steels is about 7.85 g/cm3. The typical tensile strength varies between 758 and 1882 MPa. The wide range of ultimate tensile strength is largely due to different heat treatment conditions.

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