Alloy steel

1-20 usd/kg
Circularity potential
High
Strength
Very high
Production energy
Medium
Stiffness
Very high
Embodied CO2
Medium
Density
Extreme

The properties of steel are transformed with the addition of alloys – such as chromium (Cr), manganese (Mn) and silicon (Si) – and tempering (controlled heating and cooling cycles in manufacture). While adding no more than 0.05% alloy to a plain carbon steel can almost double its strength, the cost is raised only very slightly. Other alloys, such as copper (Cu) and Cr, are added to improve corrosion resistance and yield materials that can tolerate extremely corrosive environments, or be left outdoors unpainted for more than a century.

Steel is relatively low cost and grades have been developed to suit almost every imaginable application. Its properties are highly tailorable and as a result, it is used in packaging (coated mild steel or naked stainless), automotive (steels with tensile strength of more than 550 MPa are known as advanced high-strength steel, AHSS), furniture, construction, buildings, bridges, heavy duty equipment, manufacturing equipment, laboratory environments and shipbuilding. Its tolerance to low and high temperatures in service depends on the grade, with some tool steels able to withstand extreme loads and shocks, and maintain incredible hardness (equivalent to granite and concrete) at over 500 degC.

Heat treatment (tempering) is a critical step in the production of many high performance steels. It is as important as the ingredients for the mechanical properties of the final part. Typically carried out once forming and welding have been completed, a steel item may be worth many more times the initial cost of the base metal by this point. Therefore, processes have been developed to reduce the risk of distortion, cracking and other defects. It has evolved into a sophisticate and critical step in the production of many types of steel.


Sustainability concerns
Non-renewable ingredients
Potential conflict commodity (3TG)
Raw material generates polluting by-products


High speed steel (HSS), is a tool steel based on high carbon content (0.7-1.6% C) with alloys – tungsten (W), molybdenum (Mo), chromium (Cr), vanadium (V) and for specific application cobalt (Co) – that boost the steels capacity for retaining a high level of hardness while cutting metal at high speed and elevated temperatures. They are used for high speed cutting operations, such as cutting tools, mills, taps, drills, saw blades and mill rolls. The three main groups are:
– T-series, tungsten is the principal alloy. T1-8 and T15. These are limited, and more expensive, due to the supply of tungsten.
– M-series, molybdenum is the principal alloy. M1-10 and M30-36. They are comparable to T-series, but less expensive and more readily available.
– M-series, super high speed tools steels, where a mix of alloys, such as Co and V, is used to provide exceptional hardness. M41-52 and M62.


Design properties
Cost usd/kg
8-20
Embodied energy MJ/kg
75
Carbon footprint kgCO2e/kg
6.8
Density kg/m3
7860-8160
Tensile modulus GPa
200
Tensile strength MPa
1200
Compressive strength MPa
3250
Hardness Mohs
5.5-6.5
Brinell hardness HB
400-730
Poissons ratio
0.29
Thermal expansion (µm/m)/ºC
10
Melt temperature ºC
1430
Thermal conductivity W/mK
41
Temperature min-max °C
-40 to 500
Thermal
conductive
Electrical
conductor
Electrical resistivity µΩ⋅m
0.2