DEFORM 2D V91 HeatTreatWizard Lab 2

DEFORM™-Heat Treatment Wizard Lab

TWO STAGE TEMPERING HEAT TREATMENT : LAB 2

1. Starting a new problem 1

2. Initialization 2

3. Import geometry 2

4. Generate mesh 2

5. Material definition 3

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6. Workpiece initialization

7. Medium definition

8. Schedule definition

9. Simulation control

10. Submit simulation

11. Post processing

DEFORM™-Heat Treatment Wizard Labs

Problem Summary: This lab will demonstrate how to simulate a complex tempering heat treatment problem of a steel part. This lab can also help users understand the capabilities and limitations of DEFORM-HT's phase transformation calculation scheme. In this lab, the problem is set up using the Heat Treatment Wizard, as multiple stages are involved in the heat treatment. Theoretically, this type of problem can also be set up in the regular Pre-Processor, but with less convenience and greater flexibility.

1. Starting a new problem

Start a new Heat Treatment Wizard problem with problem ID "Tempering". You can do so by clicking the “New problem” button and choose “Heat treatment”(See Figure 1). Alternatively, you can right click on the directory tree to create an empty directory and click “Heat treatment” on the right side of the main window.

Figure 1: GUI-MAIN Window

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2. Initialization

In the "Initialization" dialog, set the "Unit System" to SI, and set "Geometry Type" to Axisymmetric. Turn on "Deformation", "Diffusion", and "Phase Transformation" (See Figure 2). Click "Next".

Figure 2: GUI-PRE with Initialization Window

3. Import geometry

In page “Geometry”, choose “import from a geometry, KEY, or DB file” and click “Next”. Go to directory Labs/HeatTreat, and load geometry file “TemperingPart.GEO”. Click "Next".

4. Generate mesh

In page “Mesh Generation”, use 300 for unstructured mesh. Use 2 layers of structured surface layer, set "Thickness mode" to be "ratio to object overall dimension", and 0.005 and 0.01 for thickness of layer 1 and 2, respectively (See Figure 3). Click “Next”. (The structured surface mesh helps provide better thermal solution accuracy with less computing time.)

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Figure 2: Mesh Generation Window

5. Material definition

In page “Material”, choose “Import from .DB and .KEY” (See Figure 3)and click “Next”. Import material "Demo_Temper_Steel.KEY" from directory “Lab/Heat Treat”.

You can click button "Advance" to view and edit the material and transformation data (See Figure 4).

Note that this is a complex mixture material with eight constituents (phases), including Austenite (A), Pearlit+Banite (PB), Martensite (B), Ferrite (F), Low-carbon Martensite (LM), Temper Banite (TB), Temper Ferrite+Cementite (TFC). The transformation kinetics between the phases include A->F, A->PB, A->TB, A->M, PB->A, M->LM, M->A, LM->TFC, TB->A, and TFC->A. Among these kinetics, A->F, A->PB, A->TB, M->LM, and LM->TFC are diffusion-controlled defined by TTT curves. A->M uses Martensitic transformation model, and PB->A, M->A, TB->A, and TFC->A use simplified diffusion model. In addition, A->F has an equilibrium volume fraction that depends on carbon contents.

We are going to use the default values for this lab, hence close the “Phase Transformation window by clicking on “Close” button and then Click “Next”.

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Figure 3: Material Window

Figure 4: GUI-PRE with Phase Transformation Window

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6. Workpiece initialization

In page "Workpiece initialization", for "Temperature", choose "Uniform" and set 20 C. For "Atom", choose "Uniform" and input 0.2. For "Phase volume fraction", choose "Uniform" and set 1.0 for "Pearlite + Banite", and zero for the rest (See Figure 5). Click 'Next'.

Figure 5: Work Piece Initialization Window

7. Medium definition

In page “Media details”, you will define various media and heat transfer zones associated with them (See Figure 6).

1) Rename the first media to “Furnace” and set the “default” heat transfer coefficient (HTC) to constant 0.1.

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Figure 6: Media details Window

2) Add a media “Polymer Solution”. For its "default" zone, define the HTC as a function of temperature as follows:

Temperature HTC 20 3.5 400 8.5 700 15 900 5.2

3) Add a heat transfer zone to the media “Polymer Solution”. Click on the workpiece boundary to specify this zone using the "start-and-end-point" selection mode. The zone should be on the bottom of the workpiece as shown in the Figure 7. Define HTC as a function of temperature as follows:

Temperature HTC 20 3.5 200 4.5 400 8.8 700 3.5 900 2.8

4) For media “Polymer Solution”, deactivate "Radiation". Specify the "Diffusion Surface Reaction Rate" as a function of temperature as follows:

Temperature HTC 20 0.1 500 0.2 1000 0.6

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5) Add one more media “Air”. Input 0.02 for the default HTC (See Figure 8). Turn on Radiation. Click 'Next'.

Figure 7: Showing zone#1 Selection

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Figure 8: Media Details Window showing a addition of Air as a Media

8. Schedule definition In “Schedule” page, click on 'Add' button and input a five-stage schedule as explained below (See Figure 9)

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Figure 9: Schedule Window

1) One hour (3600 s) of furnace heating. The temperature of the furnace is specified as a function of time. This function can be input by clicking the corresponding "Define" cell in the "Advance" column (See Figure 10).

Figure 10: Advanced Process set-up Window

Here, the furnace temperature function is as follows:

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Time (s) Temperature 0 20 600 600 1200 880 3600 880

2) 10 minutes (600 s) of quenching in the polymer solution. Specify the "Atom" content to be 0.8 at 30C

3) 30 minutes (1800 s) of tempering at 250C.

4) 30 minutes (1800 s) of tempering at 350C.

5) One hour (3600 s) of cooling in the air at 20C)

click 'Next'

9. Simulation control

In "Step Definition", change "Temp. change per step" to 2. Accept other default settings (See Figure 11)_.

In this simulation, elasto-plastic deformation will be computed. Thus, additional boundary conditions need to be specified here. To do so, you need to select a boundary condition item and then assign it to appropriate boundary nodes or edges by picking the start and end points. Alternatively, you can let the program generate boundary conditions for you by clicking "Auto" buttons. Make sure to double-check the boundary conditions before you proceed. Here, we will accept automatically generated boundary conditions.

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Figure 11:GUI-PRE with Simulation Window

Click "Finish" button And click “Ok” in the pop-up message to generate Database file and multiple operation control file (See Figure 12).

Figure 12: File Generated Page

10. Submit simulation

Exit Heat Treatment Wizard and click "Run" in the Main window, just as submitting a regular simulation. DEFORM simulation engine will detect the multiple operation control file and execute accordingly.

11. Post processing

Use Post Processor to view the simulation results. The temperature min-max history should look like the lower-left graph below:( See Figure 13)

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Figure 13: Post Processor with Volume Fraction As a State Variable

There are a few interesting points to observe in the simulation:

1. In this problem, A->F transformation has equilibrium volume fraction that depends on atom content. The carbon content is high near the surface due to diffusion from the environment, therefore, very low F is formed there. In the interior, more F is formed, and A->F transformation competes with A->PB. (This is because in our kinetics data, both are diffusion controlled and active within the similar time-temperature range.)

2. Maximum residual stress was high after quench (~1320 MPa), and reduced after tempering

3. After quench, M is near 0.8 on the surface. It reduced to 0.03 after tempering. Most of M has become LM and TFC.

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DEFORM 2D V91 HeatTreatWizard Lab 2