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Research Papers

A New Computationally Efficient Model for Tempering in Multitrack Laser Hardening in Medium Carbon Steels

[+] Author and Article Information
Alessandro Fortunato

Department of DIEM, University of Bologna, 40136 Bologna, Italyalessandro.fortunato@unibo.it

Leonardo Orazi1

Department of DISMI, University of Modena-Reggio Emilia, 42100 Reggio Emilia, Italyleonardo.orazi@unimore.it

Giovanni Tani

Department of DIEM, University of Bologna, 40136 Bologna, Italygiovanni.tani2@unibo.it

1

Corresponding author.

J. Manuf. Sci. Eng 133(2), 021003 (Mar 08, 2011) (7 pages) doi:10.1115/1.4003522 History: Received January 17, 2010; Revised January 11, 2011; Published March 08, 2011; Online March 08, 2011

The bottleneck in laser hardening principally occurs when large surfaces have to be treated because this process situation leads to multitrack laser scanning in order to treat all the component surfaces. Unfortunately, multitrack laser trajectories generate an unwanted tempering effect that depends on the overlapping of two close trajectories. To reduce the softening effects, a simulator capable to optimize the process parameters, such as laser power and speed and number and types of trajectories, could sensibly increase the applicability of the process. In this paper, an original model for the tempering is presented. By introducing a tempering time factor for the martensitic transformation, the hardness reduction can be predicted according to any laser process parameters, material, and geometry. Experimental comparisons will be presented to prove the accuracy of the model.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

The backtempering effect: A qualitative effect on hardness

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Figure 2

The linear distribution of the transformation time Im→mT

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Figure 3

Effect of the threshold values Im→mT,min and Im→mT,max, Im→mT,min=1.0×10−6 s and Im→mT,max=4.4×10−2 s

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Figure 4

Effect of the threshold values Im→mT,min and Im→mT,max, Im→mT,min=1.0×10−7 s and Im→mT,max=1.0×10−2 s

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Figure 5

Hardness measurement in the centerline of the second pass in the vertical direction

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Figure 15

Hardness comparison in the horizontal direction of 250 μm below the workpiece surface, P=1.8 kW, d=6.5 mm, and F=1.1 m/min

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Figure 16

Hardness comparison in the approximate center of the second pass in the vertical direction, P=1.8 kW, d=6.5 mm, and F=1.3 m/min

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Figure 17

Hardness comparison in the horizontal direction of 250 μm below the workpiece surface, P=1.8 kW, d=6.5 mm, and F=1.3 m/min

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Figure 14

Hardness comparison in the approximate center of the second pass in the vertical direction, P=1.8 kW, d=6.5 mm, and F=1.1 m/min

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Figure 13

Hardness comparison in the horizontal direction of 250 μm below the workpiece surface, P=1.8 kW, d=6.5 mm, and F=0.9 m/min

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Figure 12

Hardness comparison in the approximate center of the second pass in the vertical direction, P=1.8 kW, d=6.5 mm, and F=0.9 m/min

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Figure 11

Hardness comparison in the horizontal direction of 250 μm below the workpiece surface, P=1.2 kW, d=6.5 mm, and F=0.7 m/min

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Figure 10

Hardness comparison in the approximate center of the second pass in the vertical direction, P=1.2 kW, d=6.5 mm, and F=0.7 m/min

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Figure 9

A cross-sectional area of a specimen after the laser treatment, P=1.2 kW, F1=0.5 m/min, and F2=0.5 m/min

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Figure 8

Hardness comparison in the horizontal direction of 250 μm below the workpiece surface, P=1.2 kW, d=6.5 mm, and F=0.5 m/min

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Figure 6

Hardness measurement in the horizontal direction of 250 μm below the workpiece surface

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Figure 7

Hardness comparison in the centerline of the second pass in the vertical direction, P=1.2 kW, d=6.5 mm, and F=0.5 m/min

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