Building the Materials Database to Unlock the Potential of Induction Heat Treating

Building the Materials Database to Unlock the Potential of Induction Heat Treating

Information

Authors: Robert Goldstein, Robert Cryderman
Location/Venue: UIE Congress Hannover, Germany

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Overview

  • Market Demands for New Product Development
  • Advantages/Drawbacks of Induction Heat Treating Compared to Other Methods
  • Tools Available for Material Characterization
  • Opportunities for Improved Measurement Methods
  • Conclusions

Market Demands

  • Lighter
  • Stronger
  • Cleaner
  • Cheaper
  • Quicker to Market

Due to Unique Features of Induction Heating, We Have a Better Opportunity to Be Magicians than Other Technologies

Specific Features of Induction Heating

  • Heat generation occurs inside the part
  • Heating is contactless
  • Method can provide very high power densities
  • Any processing atmosphere (air, protective gas, vacuum)
  • Very high temperatures may be created
  • Heating may be highly selective in the depth and along the surface - Very Important Feature, especially for multi-material components

Advantages of Induction Heating

  • Short heating cycles and high production rates
  • Electromagnetic forces can be used in combination with heating to stir or contain molten metal
  • Better metallurgical results due to fast and clean heating
  • Energy savings due to selectivity and high efficiency
  • Good control and repeatability
  • Minimal or no surface oxidation and decarburization
  • Lower distortions for surface or local hardening
  • Favorable Distributions of Residual Stresses (Better loading capability)
  • Much less Alloy Required (lower cost)
  • Finer Grain Structures Possible
  • Favorable for industrial environment (in-line heating, no pollution, “push button” performance)
  • Some processes may not be accomplished other than by induction

Comparison of Through, Case and Induction Hardened Fatigue Life for Transmission Shafts

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 1 Source – ASM Handbook Volume 4C - Grum

Comparison of Through and Induction Hardened Bending Fatigue

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 2 Source – ASM Handbook Volume 4C - Grum

Improved Mechanical Properties Possible when Using Non-Equilibrium Structures

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 3 Courtesy of SFP Works dba FlashBainite

Cold Formed AHSS Components

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 4 $$$$ - Opportunity for 1/3 weight reduction compared to other cold formable steels at lower cost or nearly 50% cost reduction over hot stamped steel. - Courtesy of SFP Works dba FlashBainite

Effect of Short Time Heat Treatment on Transformation Temperature

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 5 Hypoeutectiod steel CK45 left, hypereutectoid steel 100Cr6 right Source – ASM Handbook Volume 4C - Grum

Drawbacks of Induction Heat Treating

  • Process is more complicated than furnace heat treatment (more variables), and empirical development can be challenging
  • Product Designers Do Not Understand the Process
  • Limited Materials Database
    • Even more limited understanding of tempering and other sub-critical processes such as rapid spherodization developed by COMTES
Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 6 Modeling is the Key to Bridging the Gap, but Modeling Requires the Necessary Database

Mutually Coupled Phenomena in Induction Heating Process

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 7

Tools Available for Materials Response Testing at CSM ASPPRC

  • Transient metallurgical and physical response to rapid thermal processing
    • Gleeble (resistance heater capable of 10 k Cps)
    • Dilatometers (induction heating system with 1 k Cps)
  • Quenchant characterization
    • Inverse Calculations
  • Numerous mechanical property and microstructural analysis tools

Comparison of Gleeble Tests with Computer Simulation using Flux

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 8 Thermec 2016 Whitely, et. al., Simulation of 2 turn axle scan hardening process (left), Comparison of surface temperature vs. time from simulation and Gleeble test (right)

Induction Hardening – Gleeble Simulation

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 9 Thermec 2016 Whitely, et. al., Simulation of thermal profiles experienced at different depths of steel in 2 turn axle scan hardening process

Post Induction Hardening PAGs (Direct Quench Conditions)

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 10 Light optical micrographs of each experimental steel alloy following hot torsion simulation of bar rolling, direct quenching to room temperature, induction hardening simulation, sectioning in the cross-sectional orientation, and metallographic etching to reveal prior austenite grain boundaries.

Induction Hardening – Gleeble Simulation

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 11 Thermec 2016 Whitely, et. al.

Dilatometer Testing

  • 4 mm tool steel sample
  • Proposed cycle
    • 50 Cps heating rate
    • 850 C target temperature
    • Hold at 850 C for 10 s
    • Helium quench
Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 12 Will be presented at ASM HTS 2017 Goldstein, et. al.

End to End Gradients in Sample Temperature During Trials

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 13 Even with relatively slow induction heating and cooling process, substantial gradients present in the sample. Will be presented at ASM HTS 2017 Goldstein, et. al.

Modeled Temperature Distributions Agree with Test Results

Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 14 Will be presented at ASM HTS 2017 Goldstein, et. al. Fluxtol - Building the Materials Database to Unlock the Potential of Induction Heat Treating - Figure 15 One Drawback of Flux is that there is currently no good option to simulation different phase transformations occurring on heating (austenite) and cooling (martensite)

Conclusions

  • Induction heating is a widely used technology for heat treating
  • Many induction heat treated components are known to have superior properties compared to components heat treated using other technologies, however, exactly why they perform as well as they do in some conditions is not fully understood
  • Despite the widespread use of the technology, the materials database for induction heat treating needs to be improved to maximize the potential of the technology
  • It is important to couple experimental tools with computer models to understand true temperature dynamics in the samples to properly interpret experimental results

Acknowledgements

  • Some of the slides in this presentation were taken from the “Basics of Induction Heating Parts I & II” prepared by Dr. Valentin Nemkov (www.fluxtrol.com)
  • Video Courtesy of Inductoheat (www.inductoheat.com)
  • Physical Simulation Data provided by Advanced Steel Products and Processing Center at Colorado School of Mines
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