Stainless steel

4-20 usd/kg
Circularity potential
High
Strength
Very high
Production energy
High
Stiffness
Very high
Embodied CO2
High
Density
Extreme

Stainless steels have very good corrosion resistance compared to carbon steels, coupled with impressive mechanical properties. This combination is the result of the addition of a relatively high proportion of alloys, in particular chromium (Cr). They tend to be more expensive, and so reserved for applications that demand their superior properties.

Based on their crystalline structure, they are grouped in five families: ferritic, austenitic, martensitic, precipitation-hardening (PH) and duplex. Ferritic stainless steel is not seen much outside industrial applications, automotive and white goods, for which it is well suited. The lower alloy content makes it less expensive than the more common austenitic types.

Austenitic stainless steel, which includes the very popular 300 series, is a good all-rounder with high resistance to corrosion. It is non-magnetic (which makes it easy to distinguish from other steels), with excellent formability, machining properties and weldability.

Martensitic stainless steel has high hardness and strength, good for industrial applications, household appliances and some knife blades, with moderate resistance to corrosion. Its high hardness makes it relatively more difficult to form, cut and weld.

Duplex types are a modification on austenitic grades, designed to provide higher strength with comparable or improved corrosion resistance. PH stainless steels are a family of corrosion resistant alloys, which can be heat treated to tensile strength several times greater than austenitic types. They are used in very demanding applications in aerospace, off-shore and nuclear energy, for example.


Sustainability concerns
Non-renewable ingredients
Raw material generates polluting by-products


Type 410 (UNS S410000, DIN 1.4006) is a general-purpose martensitic alloy with good strength and reasonable resistance to corrosion. It has poor weldability and forming is difficult, but not impossible. It is commonly supplied in the hardened, but still machinable, condition. It contains 11.5-13.5% chromium (Cr), up to 1% silicon (Si), manganese (Mn) and nickel (Ni), and 0.09-0.15% carbon (C). It is classed as a low-carbon type and is stronger and more resistant to corrosion than high-carbon, high-hardness types.

Corrosion resistance is enhanced by processes including hardening, tempering and polishing. It has good hardness after heat treatment and as a result, is used in highly stressed parts. It is magnetic. It does not work harden to the same extent as the 300 series austenitic stainless steels. Applications include technical parts in valves and pumps, springs, bearings, kitchen utensils and fasteners, as well as brake disks, cutlery and general hardware. It is used in energy generation such as gas turbines, steam turbines and petroleum processing.


Design properties
Cost usd/kg
4-8
Embodied energy MJ/kg
51-75
Carbon footprint kgCO2e/kg
4.7-6.8
Density kg/m3
7800
Tensile modulus GPa
200
Tensile strength MPa
700-1300
Shear modulus GPa
73-83
Hardness Mohs
5-5.5
Brinell hardness HB
201-400
Poissons ratio
0.28
Thermal expansion (µm/m)/ºC
9.9
Melt temperature ºC
1400
Thermal conductivity W/mK
24.9
Temperature min-max °C
-40 to 500
Thermal
conductive
Electrical
conductor
Electrical resistivity µΩ⋅m
0.55