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Bild 1 2007-07-06
IVF Industrial Research and Development Corporationwww.ivf.se
New tool for calculation of heat transfer coefficients, microstructure and hardness from the cooling curve
Eva Troell, Hans Kristoffersen, Jan Bodin & Sören SegerbergIVF Industrial Research and Development Corporation, Mölndal, Sweden
Imre Felde Bay Zoltán Institute for Materials Science and Technology, Budapest, Hungary
Bild 2 2007-07-06
IVF Industrial Research and Development Corporationwww.ivf.se
Contents• Introduction - Testing and evaluation of quenchants and quenching
systems - The ivf SmartQuench™ system
• A new software module for cooling curve analysis and interpretationThe SQi Inverse module - calculation of heat transfer coefficientsThe SQi Property Prediction module - calculation of hardness and microstructure
• Verifying tests
• Application examples
• Summary
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IVF Industrial Research and Development Corporationwww.ivf.se
Original functions ivf SmartQuench• Testing of quenching media Cooling curves
• Evaluation of the cooling curve. A large number of characteristics are recorded or calculated:
Cooling times to certain temperaturesCooling rates at these temperaturesMaximum cooling rate
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IVF Industrial Research and Development Corporationwww.ivf.se
New software – SQintegrastructure and functions of the ivf SQintegra software
• Calculation of heat transfer coefficients (for the ISO 9950 probe)
• Calculation of hardness and microstructure in a cross section
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IVF Industrial Research and Development Corporationwww.ivf.se
Step 1. Measurement of cooling curve
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IVF Industrial Research and Development Corporationwww.ivf.se
2. Calculation of heat transfer coefficient
• Inverse calculation
• Direct calculation
• The HTC determined is valid at the surface of the probe at the same height as thethermocouple
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IVF Industrial Research and Development Corporationwww.ivf.se
Step 2. Calculation of heat transfer coefficient –first iteration
Measured, centre
Calculated, centre
Calculated, surface
Point for HTC
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IVF Industrial Research and Development Corporationwww.ivf.se
Step 3. Calculation of heat transfer coefficient –completed (addition of time steps)
Measured, centre
Calculated, centre
Calculated, surface
Point for HTC
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Step 4. Heat transfer coefficient vs Temperature
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Step 4. Heat transfer coefficient vs Time
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Temperature difference: calculated - measured
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IVF Industrial Research and Development Corporationwww.ivf.se
Step 5. Property prediction
Steel grade
HTC
Cylinder radius
Temp of quenchant
Start temp
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IVF Industrial Research and Development Corporationwww.ivf.se
Input Steel dataTTT approach (Réti et al. 1981)
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Step 6. Calculation of microstructure and hardness
Diameter 12,5 mm Diameter 20 mm
Steel SAE 1045
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Polymer quenchant - AquatensidCooling curve
Heat transfer coefficient
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IVF Industrial Research and Development Corporationwww.ivf.se
Verifying tests: steels SAE1045 and 42CrMo442CrMo4
0
100
200
300
400
500
600
700
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14Radius, mm (0=centre)
Har
dnes
s, H
V
Test, D28Calculated, D28
SAE 1045 (C45)
0
100
200
300
400
500
600
700
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Radius, mm (0=centre)
Har
dnes
s, H
V
Test, D20Calculated, D20Test, D28Calculated, D28Test, D10Calculated, D10
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Cooling curves and Heat transfer coefficients Oil and water; 30 ºC, 70 ºC
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IVF Industrial Research and Development Corporationwww.ivf.se
Calculated hardness compared to meassured Steel SAE1045 quenched in water 30 and 70 ºC
Quenched in water 30 and 70 ºC Quenched in oil 30 and 70 ºC
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• Sensitivity analysis - Parameter prediction
Application examples
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Comparison of cooling curves
Calculated hardness
-500
0
500
1000
1500
2000
2500
3000
3500
4000
4500
0100200300400500600700800900
Temperature, C
HTC
, W/m
2C
FeroquenchDurixol ny
HTC
300
350
400
450
500
550
600
650
0 5 10 15 20 25
Distance from center, mm
Har
dnes
s, H
V
F 40 mmF 30 mmF 20 mmF 10 mmF 40 mmD 30 mmD 20 mmD 10 mm
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IVF Industrial Research and Development Corporationwww.ivf.se
Quality of the calculations
• The accuracy of the calculated heat transfer coefficient. • The correctness of the used steel dataIt is important to bear in mind that:• The HTC calculations are valid for the probe used for recording the
cooling curve• The cooling curve is valid only under the particular measurement
circumstances. • The normal variation in the chemical composition within different steel
grades will influence the parameters describing the steeltransformation.
• The calculations are one-dimensional.
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IVF Industrial Research and Development Corporationwww.ivf.se
The quality of the calculations made by SQintegra in predicting the microstructure and hardness is dependent on:• The accuracy of the calculated heat transfer coefficient. The
difference between the measured and the calculated curve can be analysed in the software. If needed, additional time steps can be added to increase the accuracy.
• The correctness of the used steel data, particularly parameters describing the IT phase transformations and iso-hardness.
• It is important to bear in mind that:The HTC calculations are valid for the probe used for recording the cooling curve. When transferring the HTC to much larger dimensions or other geometries, the effects thereof must be taken into consideration.The cooling curve is valid only under the particular measurementcircumstances. Flow, temperature and concentration may vary in aquench tank and over a period of time.The normal variation in the chemical composition within different steel grades will influence the parameters describing the steel transformation.The calculations are one-dimensional.
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IVF Industrial Research and Development Corporationwww.ivf.se
Summary
With the ivf SmartQuench test system and the SQintegra software module it is possible to:
• Continuously perform quality control of the quenching process
• Calculate heat transfer coefficients for simulation purposes
• Predict hardness and microstructure distribution on cylindrical specimens
• Perform sensitivity analysis on quenchants and the quenching system
• Acquire information needed for troubleshooting
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