Compare two grades
How to put two steel grades side by side in Phases, on chemistry and under an identical process, and read the difference honestly.
You are choosing between two grades for a part, or a supplier has offered you a substitute, and you want to know what actually changes. Phases answers that in two separate ways, and it is worth knowing which is which before you start.
compare_materials puts two material definitions side by side. It compares chemistry and starting phase fractions. It does not run anything and it does not compare results.
To compare behavior, you run the same process on each grade and read the two runs. That is two requests, because Phases runs only the single simulator you named in your latest message and will not run an extra simulation on its own.
Step 1: load the first grade#
Load DP600.
This makes DP600 the active session material. Loading a built-in grade needs no confirmation — only a chemistry you supply yourself does. Once a material is active, every simulator uses it automatically unless you name a different one.
Step 2: compare the definitions#
Compare my active material with 22MnB5.
Phases calls compare_materials and returns:
| Field | What you get |
|---|---|
material_a | The active session material (DP600 here) |
material_b | The grade you named |
composition | One row per element: the value in A, the value in B, and the difference |
initial_phases | The same three columns for each starting phase fraction |
Only elements where at least one of the two grades is above zero appear in the table, so you get a short readable list rather than twenty mostly-zero rows. Element labels follow the material card, so boron appears as Bo.
If you name no second material at all, the tool compares the active material against its own base grade. That is the version you want after editing a chemistry:
Load DC04 with C = 0.15.
That first request hits the confirmation gate: Phases tells you which catalog grade the chemistry is closest to and creates nothing until you agree. Once you confirm, the modified material is active and you can ask:
Compare it with the base grade.
See Your own chemistry for what confirming does and does not do.
The second material for compare_materials must be either a built-in grade id or a material you already loaded in this session. It cannot reach into a run.
Step 3: run the same process on each#
Comparing chemistry tells you what is different on paper. Comparing runs tells you what it does. Ask twice, with the same conditions:
Run a heat treatment on DP600: hold at 860 °C for 5 seconds, then cool to 20 °C by 10 seconds.
Run the same heat treatment on 22MnB5.
When you state parameters like this, Phases normally answers with a Heat Treatment Configuration card carrying the material, a time step, and a read-only summary of the curve (0s → 860°C, 5s → 860°C, 10s → 20°C). Press Run Simulation on it. Every run gets its own run version in the session, numbered sequentially, so the two results stay distinct.
For transformation behavior instead of a single cycle, use the same pattern with a CCT sweep:
Generate a CCT diagram for DP600 at 0.1, 1, 10, 50 and 100 °C/s.
Now generate a CCT diagram for 22MnB5 at the same rates.
Step 4: read the difference#
Ask for the numbers rather than eyeballing two images:
List my runs.
What were the final phase fractions in each of those two heat treatments?
For heat treatment, the plots that come back are labeled Phase Fractions, Dilatation vs Time and Hardness (HV30). For CCT you get a single diagram per sweep, with a lower-left box listing the final phase percentages for each cooling rate.
Two cautions when you write the difference down:
- Predicted hardness is a bulk mixture value. It is not the hardness of an individual phase, and it is not a substitute for a measured coupon.
- Phases will not infer weld preheat requirements, toughness, quench-cracking risk or age-hardening response from composition or phase fractions. If you ask, it will say what additional calculation or test data would be needed.
Variations#
Compare a supplier chemistry against the grade it claims to be. Load the supplier analysis, confirm the gate, then compare against the base grade. The difference column is your incoming-inspection delta.
Compare a workspace material against a built-in. Load the saved workspace material by name, then compare with the built-in grade id. See Workspace materials.
Compare across simulators. The two grades must both be supported by the simulator you pick. Heat treatment and CCT run on catalog grades generally; resistance spot welding is restricted to a fixed list of 20 grades with validated bulk properties. Check Capability matrix before you plan a comparison around RSW.
Related#
- Material catalog — what you can name
- Heat treatment and CCT and TTT — the two simulators used above
- Reuse and share runs — getting both results back later
- Known limits