FAQ

DANTE can model most case hardening, thermal, and quench hardening processes. Some case hardening processes include low pressure and gas carburization, gas nitriding, induction, flame, and laser hardening. Quench hardening processes such as immersion into oil, water, or polymer, high pressure gas quenching, press/fixture quenching, and spray quenching. Some other processes that can be modeled include cryogenic treatment, tempering, precipitation hardening, martempering, austempering, normalizing, and annealing. This is not an exhaustive list, so if you have a process that is not listed, contact us. We love to model new and interesting process.

No. Analytical phase transformation models are applied in DANTE instead of TTT/CCT phase diagrams because the application of the TTT/CCT phase diagrams are limited. TTT/CCT diagrams can only describe the transformation timing, whereas the transformation timing and transformation strains are required to properly model the stress state of the part.  Strengths of the DANTE phase transformation models are listed below:

• Phase transformation types for austenitization cover slow transformation during furnace heating, as well as high rate of transformation for processes such as induction heating, laser heating, flame heating, etc.
• Phase transformations for cooling include the formation of ferrite, pearlite, bainite and martensite. The formation of bainite includes upper bainite and lower bainite because the two phases have significant differences in mechanical properties.
• Formation of tempered martensite can be considered for tempering processes or for slower cooling or self-tempering processes.
• The phase transformation model robustly models carbon effects to combine the carburization process in the models.
• Effect of phase transformation to one phase on other phases can be accurately described.

One strength in DANTE is its multiple phase mechanical model. The internal state variable (ISV) mechanical model is implemented in DANTE instead of a traditional constitutive model based on effective strain. 

The heat treatment process includes stress reversals due to thermal gradients and phase transformations, and these strain reversals make the traditional constitutive model ineffective. The temperature of the part continually changes during the heat treatment process, and the strain generated in the material at one temperature has a significant effect on stress at another temperature, which also makes the traditional constitutive model ineffective. 

To have a proper heat treatment simulation model, material properties spanning several phenomena are needed.

• Diffusion Properties: This includes carburizing and nitriding, or a combination of the two. Diffusion of the element(s) (carbon and/or nitrogen) is needed, as well as the formation and dissolution rates of the carbides and/or nitrides. All properties must be functions of temperature and element concentration. The effects of grain size on the diffusion properties can also be incorporated into the model if necessary.
• Phase Transformation Properties: Of all the material properties needed for heat treatment simulation modeling, the phase transformation kinetics are probably the most important. The transformation timing, transformation rate, and the transformation strains are the key properties. They must be functions of temperature, time, and carbon content. DANTE Solutions has developed a tool used to aid in fitting experimental data to DANTE’s phase transformation model.
• Thermal Properties: The thermal material properties required are thermal conductivity, specific heat, and coefficient of thermal expansion. All of these properties must be functions of phase and temperature.
• Mechanical Properties: Both elastic and plastic properties need to be determined. They must be fit to the internal state variable model used in DANTE. DANTE Solutions has developed a tool used to aid in fitting experimental data to DANTE’s mechanical model. The mechanical properties must be functions of phase, temperature, strain, and strain rate.

A standard material database is included with the DANTE software package. The database includes most standard U.S. steel grades. 

• The database includes properties for the phase transformation kinetics for pearlite, ferrite, upper and lower bainite, martensite, and tempered martensite to austenite and vise versa. The phase transformation kinetics are functions of carbon concentration where applicable. 
• The database includes mechanical properties for all relevant phases as a function of temperature, phase, strain, and strain rate.
• The database includes thermal properties for all relevant phases as a function of phase and temperature.
• The database includes diffusivity data, as a function of chemical concentration and temperature, for applicable materials.

The database includes materials such as 10XX, 40XX, 41XX, 43XX, 48XX, 51XX, 86XX, 93XX, 52100, 304SS, and many more. The “XX” in the grades indicate there are properties for multiple carbon levels, allowing for the modeling of a carburized component.
DANTE also includes a user material database where users can add additional materials to suit their needs. DANTE Solutions has developed utility programs to facilitate the fitting of experimental data to the DANTE heat treatment simulation models. 

Yes. Experiments will be needed to characterize the phase transformation kinetics, mechanical properties, and thermal properties for heat treatment simulation. The extent of the experiments will be determined by several factors:

1. The chemistry of the new alloy. The closer the chemistry is to an alloy already in the DANTE material database, the fewer the experiments. Most minor changes to chemistry have minor effects on the mechanical and thermal properties. Therefore only the phase transformation timing and strains will need to be determined.
2. The hardenability of the alloy. The more hardenable the alloy, the fewer the experiments needed. For example, an air hardenable steel will only need to examine the martensitic transformation. A high alloy/carbon steel may require only martensite and bainite characterization; and a low alloy/carbon steel will need to characterize martensite, bainite, ferrite, and pearlite.
3. Intended use of the alloy. If the alloy is to be carburized or nitrided, the diffusivity of these elements, including carbide/nitride formation and dissolution, need to be determined. If the processing of the alloy will never produce a particular phase, then that phase can be ignored in the phase transformation characterization. If this is the case, the user must be aware of the modeling limitations imposed by this decision.

Several different types of experiments are required to properly and fully characterize a material for heat treatment simulation. DANTE Solutions has characterized many materials over the years, and can help you design the experiments, as well as the necessary coupons, to characterize your material for the DANTE material database. Below is a quick description of the types of experiments and coupons utilized for particular parameters:

• Diffusivity: A special coupon designed by DANTE Solutions is used in conjunction with specially designed diffusion recipes. The recipes are designed such that the diffusion coefficient, as well as carbide/nitride formation and dissolution, can be determined. The recipes designed for this type of fitting are not representative of production schedules and are designed solely to make diffusivity characterization possible. This is especially true of low pressure carburizing, where the carbon during the boost steps can exceed the saturation limit in austenite.
• Phase Transformations: Dilatometry experiments are preferred. These experiments must be done as a function of carbon content, heating rates, and cooling rates. The carbon, heating rates, and cooling rates should be representative of actual processing conditions to limit the number of experiments. Standard dilatometry coupons are normally utilized, although special coupons have been designed and used in certain circumstances.
• Thermal Properties: The coefficient of thermal expansion can be determined from the data gathered during the phase transformation dilatometry experiments. This data needs to be a function of phase and temperature. Specific heat and thermal conductivity are also required and are functions of phase and temperature.
• Mechanical Properties: Tension and compression tests are used. The experiments must be done as functions of phase, temperature, strain, and strain rate. These tests can usually be performed on the same machine as the dilatometry experiments, using a slightly modified coupon design.

Yes. The format is determined by either ANSYS or ABAQUS, depending on which solver you are using in conjunction with DANTE. We have used Joule heating as a function of time from several different electromagnetic modeling software packages and stress profiles from forming and casting softwares. 

DANTE results can also be used as inputs or initial conditions to other models. Most common is the use of the residual stress from heat treatment as an initial condition to loading or fatigue models. The format again is determined by the FE solver being used for the loading or fatigue models. The version of DANTE linking to ANSYS includes a convenient post processing tool that allows for the generation of a file that writes the residual stress tensor as a function of Cartesian coordinates to a text file, which is then read back into ANSYS Mechanical for loading models. 

Yes. There are several methods which can be used to model induction hardening with the DANTE Heat Treatment Simulation software. 

1. Model the electromagnetic phenomenon using a third party software. The Joule heating as a a function of time is then mapped into the DANTE thermal model. The stress analysis is then carried out like any other DANTE stress model. This method requires knowledge of the inductor design and process parameters for troubleshooting a current process. 
2. Mimic the skin effect of induction heating by assigning body flux to discrete layers of elements in the DANTE thermal model. The stress analysis is then carried out like any other DANTE stress model. This method requires knowledge of the hardness profile to determine the depth of the hardened case for troubleshooting a current process.

Yes. The phase transformation models can properly account for the transition of martensite to tempered martensite. The mechanical model can account for the mechanical property differences between martensite and tempered martensite. The mechanical model can also account for the relaxation of residual stress as carbides precipitate out of the martensite matrix.

High temperature tempering is now also available in DANTE. This model works well for secondary hardening steels, as well as a model for the fast heating rate, short time induction tempering process. These models also account for volume shrinkage seen at tempering temperatures above 300 degrees Celsius.