Low alloy steel

The material. Addition of manganese (Mn), nickel (Ni), molybdenum (Mo), or chromium (Cr) to steel lowers the critical quench rate and comes to cre­ate martensite, allowing thick sections to be hardened and then tempered. Adding some vanadium, V, as well creates a dispersion of carbides, giving strength while retaining toughness and ductility. Chrome-molybdenum steels such as AIS 4140 are used for aircraft tubing and other high-strength parts. Chrome-vanadium steels are used for crank and propeller shafts and high-quality tools. Steels alloyed for this purpose are called low alloy steels, and the property they have is called hardenability.

Composition

Fe/ < 1.0 C/ < 2.5 Cr/ < 2.5 Ni/ < 2.5 Mo/ < 2.5 V/

General properties

Density Price

Mechanical properties

Young’s modulus Yield strength (elastic limit)

Tensile strength Elongation Hardness—Vickers Fatigue strength at 107 cycles Fracture toughness

Thermal properties

Melting point

Maximum service temperature Thermal conductor or insulator?

Thermal conductivity Specific heat capacity Thermal expansion coefficient

Electrical properties

Electrical conductor or insulator?

Electrical resistivity

Low alloy chrome-molybdenum and chrome-vanadium steels are used for high-quality tools, bike frames, and automobile engine and transmission components.

Ecoproperties: processing

Casting energy Casting CO2 footprint Deformation processing energy Deformation processing CO2 footprint

Recycling

Embodied energy, recycling CO2 footprint, recycling Recycle fraction in current supply

Typical uses. Springs, tools, ball bearings, rollers; crankshafts, gears, con­necting rods, knives and scissors, pressure vessels.