Thermo-Calc Applications to Welding and Joining with Bonus Scheil Example


Thermo-Calc software can
be used to calculate phase equilibria, phase transformation temperatures and thermodynamic properties for welding and joining applications using the step and map options in Thermo-Calc. DICTRA can be used to model the kinetics of diffusion controlled phase transformations as well. For non-equilibrium solidification, one can
use the Scheil Solidification Simulation Calculator to calculate the fraction solid curve as a
function of cooling, incipient melt temperature, latent heat during cooling and microsegregation
during solidification. In this video I’ll show you one such calculation, a Scheil Solidification Simulation based on
the austenitic stainless steel 18/8. You can follow along with this example by
downloading the free demo version of Thermo-Calc software. Simply click the link currently on the screen
or visit our website, then come back to this video once you have
installed the demo software. From the home screen of Thermo-Calc, click
on the Scheil Solidification Simulation template. All the nodes we need to complete the calculation
will appear in the project pane. Select the System Definer, where we will set
our database and elements. From the database dropdown menu, select the
FEDEMO database then select the elements: iron, chromium and
nickel. The actual austenitic stainless steel 18/8
also contains carbon and manganese, but the demo version of our software is restricted
to three elements because it is for demonstration purposes only. So we’ll be looking at a modified alloy. Next we’ll set the composition. Iron will be dependant, so we’ll let that
set automatically. From the top, chromium is 18 and nickel is
8. This sets iron to 74 mass percent. Our system is now defined, so select the Scheil
Calculator node where you configure the calculation. Here we can change, for instance, the temperature
and temperature units, we can choose to use Global minimization and
we can select which phase is identified as liquid. Notice that our composition auto populated
here as well. We’ll use the default values, so we don’t
need to change anything in this node. Our calculation is now set, so click Perform
Tree at the bottom centre of the program. Once the calculation is complete a plot will
appear in the Results pane. In this plot, the solid line shows you at
what temperature various phases form. If you zoom in, you can see the line more
clearly and the key will tell you which phases are
present in the colours currently on the screen. For instance, the red line shows us that between
approximately 1455 degrees and just below 1480 degrees BCC_A2 is forming. The dotted line represents equilibrium. We can see that below about 1475 degrees the
two lines diverge, which is due to microsegregation. The x-axis shows the total fraction of solids
from all phases at each temperature. For instance, the right most end of the graph
is entirely solid and the left most side of the graph is entirely
liquid. If you hover your mouse anywhere on the line
you will also see this information. For example, we can see that at about 1475
degrees the mole fraction of solid is approximately
.26 or about 26 percent. Starting with Thermo-Calc 2015b, the Scheil
module also allows you to view the results in the form of a table. Right click on the Scheil Calculator node, hover over Create New Successor and select
Table renderer. Then right click on the Table renderer node
and select Perform Now. Once the calculation is complete, your table
will appear in the Results pane alongside the plot. The table contains the same information as
the plot. For instance, if we look at approximately
1475 degrees, we see the same results we saw when we looked
at the plot – a mole fraction of solid of approximately
.26. We hope you found this video helpful. We’re constantly working to create new videos,
so check back regularly at www.thermocalc.com.

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