NetLogo User Community Models
## WHAT IS IT?
This model’s goal is to simulate the effects on the microstructure of carbon steel while being exposed to varying temperatures. The idea is to simulate the **normalizing** and **hardening** processes and to observe the changes in the steel’s **grain structure** and its **mechanical properties**.
#### Grain structure
When looking at the initial grain structure of carbon steel it consists of different types of grains. **Ferrite** grains are made of pure iron determining mechanical properties like ductility inside the steel. Another type of grain, occurring more frequently the higher the carbon content is, is **Pearlite**. Pearlite consists of iron and carbon which is also called iron-carbide, giving the steel the properties of hardness and strength. In steel containing about 0.4% carbon, ferrite and pearlite grains are evenly distributed. The number of pearlite grains increases until 0.8% carbon, from where the steel consists of 100% pearlite grains.
## HOW IT WORKS
The model is setup with an adjustable amount of **initial grains**. Each grain consists of a multitude of **atoms**. The whole world area consists of one atom per patch. Each atom orientates itself to its nearest grain neighbor and inherits its properties (to distinguish between ferrite, pearlite etc.). Depending on the adjustable **carbon content**, ferrite grains exist beside the pearlite grains. Temperature can be applied to the material to simulate the processes of normalizing and hardening. The amount of heat in each atom determines its color by a **color-gradient**, roughly resembling the color real carbon steel would have at this temperature. If the material’s temperature is high enough, the atoms inside the grains will transform to **austenite**.
During normalizing the grains will reorganize themselves and grow in number if the correct amount of heat is applied. They will decrease in number if the average grain temperature exceeds the recommended normalizing temperature range.
If the material is quenched after having applied the correct amount of heat, the austenite will transform to martensite if the carbon content is at least 0.8%.
## HOW TO USE IT
**1.** Set the **state** dropdown to heat and click run.
At first nothing will change except the **Avg Grain Temp** monitor since heat is being applied from the outside and needs to spread through the material.
Observe the formation of austenite at a certain temperature.
**2.** When inside the normalizing temperature range, set the **state** to idle to keep applying the same amount of heat.
Observe how the number of grains grows over time. If the temperature is too high, the number of grains will decrease.
**3.** Set the **state** to cool to “air-cool” the steel.
Observe how the austenite forms back to ferrite and pearlite and color changes back to grey when cooled.
**4.** Compare the resulting **yield strength** with the original one after the setup.
Observe the same behavior as during normalizing.
**4.** Leave the **state** at heat until the maximum possible temperature is reached (observing the **Avg Grain Temp** monitor)
Observe how the material cools rapidly and the austenite forms back to pearlite and martensite.
**6.** Compare the resulting **hardness** with the original one.
**Avg Grain Temp**: The average grain temperature.
**Grains**: Number of grains over time (red). Average grain size over time (blue).
## THINGS TO NOTICE
In reality, new grains begin to form at the grain boundaries while normalizing. This model simulates this by simply hatching grains over time which will re-orientate along with the existing ones. Mechanical properties described in this model are simple indicators to show relations between the grain structure and composition. In reality, the mechanical properties of steel depend on many more factors which are not included in this model.
## THINGS TO TRY
Try to harden the material with less than 0.8% carbon. Is the hardening successful? Is there any transformation into martensite?
## EXTENDING THE MODEL
Obviously, the missing element in this model is the tempering process where the hardened steel is relieved of its brittleness.
## RELATED MODELS
## CREADITS AND REFERENCES
Made by Felix Rauchenwald in June 2019.
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