The mechanical properties of Carbon Steel can be predicted from its alloying elements and the heat treatment it has received, and this predictability will remain consistent as long as the alloying elements remain within acceptable limits. SAE and AISI have standardised the limiting chemical composition for a range of carbon steels containing up to 1% carbon that can be defined from its four-figure identification number.
As such, it is possible to estimate the chemical composition of any SAE/AISI graded carbon steel by its identification number and thereby predict its mechanical properties.
The dominant alloying element in plain and special carbon steels is their carbon content. However, this dominance is gradually displaced by other elements, such as nickel, chromium, vanadium, etc., in alloy carbon steels as their percentage content increases.
The carbon steel calculator has two calculation options 'Property to Grade' and 'Grade to Property', both of which calculate the mechanical properties of a given carbon steel based upon its chemical composition, but they use slightly different methods.
The database of grades in the carbon steel calculator includes the chemical compositions for all the SAE steel grades in our plain⁽¹⁾, special and alloy carbon steel web pages.
This calculation option requires the user to enter a desired hardness along with the percentage composition of all its non-trace elements except carbon. Carbon Steel will calculate the carbon content necessary to generate the entered hardness value in cold-rolled or normalised carbon steel with no additional heat treatment or work hardening.
Using the chemical composition entered, Carbon Steel will also generate an SAE/AISI grade that may or may not be extant. If your calculation generates an existing SAE grade, it will be repeated in the 'Grade List' text box. If your calculation generates a non-existent SAE grade, the nearest grade below your calculated grade will be displayed in the 'Grade List' text box.
The mechanical properties estimated in this calculation option will be for the chemical composition of cold-rolled (or normalised) steel. No heat treatment is considered in this calculation option.Plain and Special Carbon Steels
If you cannot achieve the desired hardness with manganese alone, you will need to add nickel, chrome, vanadium and/or molybdenum, in which case you will create an alloy carbon steel.Alloy Carbon Steels
Dependent upon the requirements for your alloy steel; corrosion resistance, hardenability, temperature resistance, etc., you will need to add acceptable levels of nickel, chrome, vanadium and/or molybdenum. An acceptable level of silicon will be required even though it has little effect on the mechanical properties of carbon steel because it is included in the CEV calculation.
Despite the fact that the SAE grade designation for alloy steels is not as well organised as those for plain and special carbon steels, Carbon Steel will attempt to generate a grade reference for alloy steels although they may not be as accurate.
This calculation option requires the user to enter an SAE/AISI grade designation of four characters.
If the first two numbers are '10' the calculation will be for plain carbon steel.
If the first number is '1' and the second number is between '1' and '9' the calculation will be for special carbon steel.
If the first number is between '2' and '9' the calculation will be for alloy carbon steel.
Or you can select an existing grade from the Grade List.
If the steel grade entered is not included in the 'Grade List', Carbon Steel will estimate the mechanical properties from the chemical composition of the carbon steel with an identification number immediately below the value entered (i.e. the grade listed in the 'Grade List').
If the steel grade entered is included in the Grade List, whether selected from the list or entered manually, Carbon Steel will know its chemistry.
Carbon Steel estimates the range of each mechanical property for the steel grade based upon all minimum and also all maximum alloying element percentage content. This will produce a greater range for each property than the specification for the material concerned as the specifications tend to limit the range of one alloying element dependent upon the percentage content of the other(s) in order to minimise the range of mechanical properties.
If a tempering temperature is entered (200°F<Ṯ<1200°F), Carbon Steel will also calculate the expected range of mechanical properties for the material when hardened and tempered at the entered temperature.
The carbon steel calculator uses a behaviour pattern to predict the properties of carbon steel with up to 1% carbon in normalised (cold-rolled) or hardened and tempered condition and this pattern is based upon the mechanical properties and the associated chemical compositions defined in the relevant SAE/AISI specifications.
Whilst the carbon steel calculator does not provide specified minimum and maximum properties according to the relevant SAE/AISI specifications, those calculated in the 'PROPERTY TO GRADE' calculation option are well within the property ranges identified in our Plain Carbon Steels web page and can be easily achieved by any competent forgemaster/supplier for the given chemical composition.
The 'GRADE TO PROPERTY' calculation option is similarly accurate but based upon the limiting chemical content of all the alloying elements occurring together, therefore the mechanical property range is significantly greater than that in the relevant specifications, which limit alloying elements dependent upon the measure of the others present. However these calculated properties can also be easily achieved by any competent forgemaster/supplier for the chemical composition concerned.
You will find further reading on this subject in reference publications(2, 3 & 44)