Martensitic Steel Strength Property Model Settings

The default Evaluation temperature is room temperature. Otherwise, select the Evaluation temperature checkbox to evaluate the strength at a temperature other than room temperature. The value is taken from the Temperature defined under Condition Definitions.

Also:

1. If the Evaluation temperature is lower than the tempering temperature, then the model evaluates the intrinsic and solid solution strengthening at the selected temperature.
2. Alternatively, if the Evaluation temperature is higher than the tempering temperature, then in addition to (1), the model treats the evaluation temperature as the tempering temperature.

Enter an Annealing temperature, which is the temperature at which austenization or intercritical annealing is performed before the steel is quenched. The default is 1273.15.

Enter a Quench temperature, which is the end temperature for quench after austenization. The default is 298.15.

The Tempering temperature is the temperature at which tempering is performed. This is used to estimate martensite hardness after tempering. The default is 673.15.

Add a Tempering time [s]. The default is 3600 seconds. The time dependency is predicted using a machine learning model. If tempering time is set to a negative value, no tempering correction is applied to the total hardness.

Select the Suspend FCC, BCC, or cementite checkbox to choose to suspend one or more of these phases. All other phases can be deselected on the System Definer to exclude from the calculation as required.

Austenite (FCC_A1), ferrite (BCC_A2), and Cementite phases all need to be selected on the System Definer. However, for some alloys it might be necessary to suspend one or more of these from the tempering calculation.

Then from one or more of the FCC_A1, BCC_A2, or Cementite lists choose Entered or Suspended.

Select the More options checkbox to adjust settings for Grain size, the Parent phase Gibbs energy addition, and Constant strength addition.

This setting is available when More options is selected.

Enter the Grain size of the austenite in micrometers (μm). The default is 100 μm.

This setting is available when More options is selected.

In the Parent phase Gibbs energy addition [J/mol] field enter a value in J/mol to add a Gibbs energy offset to the parent austenite phase. This can be used, for example, to correct database offsets. The default is 0 J/mol.

This setting is available when More options is selected.

Enter a value for the Constant strength addition [MPa]. You can also enter expressions such as T*w(cr)+10 or similar.

Select a Flow stress mode:

• σ vs ϵ to calculate the stress at a total specified strain
• E, σ_y and σ_UTS to calculate engineering properties. This is generally referred to as the engineering properties mode in the theory section.

Available when σ vs ϵ is selected.

Enter a value for True strain [%] to evaluate the stress at a specified true strain (elastic plus plastic).

Enter a value for the Pre-straining [%] to specify the strain the material is exposed to before calculation. This is useful in cases where prior deformation needs to be accounted for, e.g., cold work, as it affects the calculated flow stress.

The value entered does not affect the calculated hardness

Select the User-defined flow stress parameters checkbox to define additional parameters related to the flow stress calculation.

When the checkbox is selected also define other settings such as the Flow stress model and Young's modulus. Then based on the Flow stress model, also define Strain hardening exponent(Ramberg-Osgood) or Saturation stress, and Hardening rate (Voce). In addition, a value for the Young's modulus needs to be given.

This is available when the User-defined flow stress parameters checkbox is selected.

Select a Flow stress model to use for the calculation: Ramberg-Osgood or Voce.

This is available when the User-defined flow stress parameters checkbox is selected.

Enter a value for the Young's modulus in GPa.

This is available when the User-defined flow stress parameters checkbox is selected and Ramberg-Osgood is the Flow stress model.

Enter a value for the Strain hardening exponent.

This is available when the User-defined flow stress parameters checkbox is selected and Voce is the Flow stress model.

Enter a Saturation stress, which is the stress value in MPa approached asymptotically with strain.

This is available when the User-defined flow stress parameters checkbox is selected and Voce is the Flow stress model.

Enter a Hardening rate, which is the rate at which strain hardening progresses according to the Voce model.

Select the Apply strain rate checkbox to account for the effect of strain rate on flow stress. If the checkbox is not selected (the default), flow stress is calculated for quasi-static conditions only.

When the checkbox is selected also define other settings such as Strain rate [1/s], Reference strain rate, and Strain rate sensitivity.

This is available when the Apply strain rate checkbox is selected.

Enter a value for the Strain rate in 1/s.

This is available when the Apply strain rate checkbox is selected.

Specify the Reference strain rate in 1/s. This should correspond to the strain rate at quasi-static conditions, i.e., in the range of 10^-4 to 10^-3

This is available when the Apply strain rate checkbox is selected.

Select the Apply user-defined strain rate sensitivity checkbox to enter a Strain rate sensitivity exponent. If the checkbox is not selected (the default), the strain rate sensitivity exponent is estimated by the model.

These plot quantities are available:

• Tempering temperature
• True stress
• Engineering strain
• Engineering stress
• Yield strength
• Yield strain
• Ultimate tensile strength
• Uniform elongation
• Fracture strength
• Elongation at fracture
• Young's modulus
• Constant strength addition
• Total martensite percentage: The percentage of martensite after quenching.
• Retained austenite percentage: The percentage of retained austenite after quenching.
• Precipitate fraction (Annealing): The fraction of any given phase present at the annealing temperature before quenching.
• Precipitate fraction (Tempering): The fraction of any given phase present after quenching and tempering (precipitates after temper are added to those at annealing, if any).
• Martensite hardening as-quenched
• Martensite hardening quenched and tempered
• Total solid solution hardening
• Solid solution hardening after temper
• Total hardness of the as-quenched steel
• Total hardness of the tempered steel