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 420 (UNS S42000, DIN 1.4021, 1.4028) is similar to type 410, but with higher carbon content. This creates potential for higher strength, hardness and edge retention, but reduces weldability and formability. Its corrosion resistance and compatibility with machining is comparable. It contains 12-14% chromium (Cr), up to 1% silicon (Si), manganese (Mn) and nickel (Ni), and 0.15-0.36% carbon (C). It is used in applications that require high hardness and moderate resistance to corrosion, such as fasteners, cutlery, scissors, hand tools, surgical tools (blades) and valves.


Design properties
Cost usd/kg
4-8
Embodied energy MJ/kg
51-75
Carbon footprint kgCO2e/kg
4.7-6.8
Density kg/m3
7730
Tensile modulus GPa
200
Tensile strength MPa
585-1630
Hardness Mohs
5-6
Brinell hardness HB
201-495
Poissons ratio
0.28
Thermal expansion (µm/m)/ºC
10.3
Melt temperature ºC
1454-1510
Thermal conductivity W/mK
24.9
Temperature min-max °C
-40 to 500
Thermal
conductive
Electrical
conductor
Electrical resistivity µΩ⋅m
0.55