4th Asian Conference on Heat Treatment & Surface Engineering

ADVANCED INDUCTION HEAT

TREATMENT TECHNOLOGIES

AND DESIGN METHODS

Dr. Valentin NEMKOV

Fluxtrol Inc., Auburn Hills, Michigan, USA

Overview

• Advanced induction technologies – old and new

• Progress in power supplies and controls

• Computer Simulation and Virtual Prototyping

• Magnetic flux control

• Internal inductors

• Induction versus carburizing

• Induction hardfacing

• Induction treatment in Liquid Active Media

• Coating treatment

• Conclusions

Induction Technique

Prof. Valentin Vologdin

(1881-1953)

Dr. Edwin Northrup

(1866-1940)

Ideas of induction heating appeared at the end

of XIX century. Many famous names must be

mentioned here, such as L. Foucault, N. Tesla

and others

Induction Surface Hardening is 75 years old and

two men may be considered as major pioneers:

Dr. E. F. Northrup, USA and Prof. V.P. Vologdin,

Russia

Since crankshaft hardening (1934-1935) this

technology passed a long way with very big

achievements and continues to bring new

impressive results

Some technologies developed or proposed in 30-

50s maybe considered as advanced at present

time such as SDF hardening.

Main Recent Achievements in

Induction Technique Induction systems:

• Solid-state power supplies

• Control and monitoring

systems

Induction coils:

• Magnetic flux controllers

• CNC machining

Design methods:

• Computer simulation

• Virtual prototyping

New technologies

Minac 18/25 TWIN power supply, EFD

Induction

Scan hardening, Elta program

Modern Power Supplies

Courtesy of EFD Induction, Inc

• Modern solid state power

supplies can provide any

required combination of

power and frequency

• Power – from 1 kW to

several MW

• Frequency – from line

frequency to 0.5 MHZ and

more (for small power)

• Intelligent systems

• Small dimensions

• High efficiency

Simultaneous Dual Frequency Hardening (SDF)

For contour hardening of gears and other parts of complex geometry, special transistor power supplies were developed that can generate two frequencies simultaneously. Power levels may be programmed independently for each frequency, providing accurate results and high process flexibility

Gear hardened by SDF

Courtesy Eldec Induction U.S.A.

Induction hardening installation:

Middle Frequency power 400 kW

High Frequency power 200 kW

Virtual Prototyping (VP)

Virtual Prototyping is the use of

computer models to develop

and test the process and/or

component without having to

physically build or run it

VP includes detailed analysis

of the problem, development

and optimization of new

concept using modeling

At present time – EM, Thermal

and Structural tasks

Emerging – Stresses and

Distortions

FEA mesh for axle scan

hardening with optimized

inductor

Example of Virtual Prototyping:

Wheel Hub Hardening

• Short coil life: 8,000 –

13,000 pieces

• Difficult setup with

big machine downtime,

personnel time and

scrap parts

Problem:

Typical process of wheel hub

heating with “stepped” coil

Modeling of Part

Temperature & Hardness

Predicted hardness pattern Temperature distribution in part with

new coil design

Flux 2D program + Metal 7

Modeling of Coil Temperature

Copper:

Copper temperature calculation

is available in Flux program

Heat transfer coefficient

calculated from water flow rate

Results: Max copper

temperature <100°C

Concentrator:

Special procedure had been

developed for the

concentrator temperature

calculation

It accounts for the magnetic

losses, radiation and glue

properties

Performance and Longevity Tests

• Test showed that precise

hardness pattern was

reached on the 3rd part

• Coil and process setup

became easy

• Lifetime was not anymore

a problem. Coil heated

170,000 parts and still

remained in good

conditions

>170,000 cycles

Hardness Pattern for Axle Scanned

with Original and Optimized Coils Coil power 170 kW, Frequency 1 kHz

13

Magnetic Flux Control

Magnetic Flux control includes

concentration, shielding and

field modification

Advantages of magnetic controllers:

• Heat pattern control

• Coil current demand reduction

• Better use of induced power

• Elimination of unintended heating

of the part or machine components

• Coil parameter improvement

(efficiency, power factor)

Materials for magnetic control:

• Laminations

• Ferrites

• Soft Magnetic Composites (SMC)

Soft Magnetic Composites

represented mainly by Fluxtrol and

Ferrotron materials, have a very

favorable combination of

mechanical, thermal and

electromagnetic properties:

• Can work in entire range of

induction heating frequencies (up

to 13 MHz)

• Have excellent machinability

• Can work in 3D magnetic fields

• Have good magnetic properties

• Have good thermal properties

• May be used as structural

components in the coils Composite materials

manufactured by Fluxtrol Inc.

Composite Materials for Magnetic

Flux Control

15

Magnetic Permeability of Fluxtrol Products

Materials are quasi-linear

Fluxtrol A material can support

permeability above 80 at high

magnetic loading (flux density up to

9000 Gs)

SMC work well at very challenging

applications when properly selected

and applied:

• Material must be selected with

account for orientation due to

anisotropy

• Good thermal management by

means of application to the coil with

thermally conductive glue or by means

of separate cooling

Permeability vs Flux Density

0

25

50

75

100

125

0 3000 6000 9000 12000

Flux Density, GsP

erm

ea

bil

ity

Ferrotron

559Fluxtrol 50

Fluxtrol A

Information about Fluxtrol

and Ferrotron properties

and application is available

on site www.fluxtrol.com

Examples of Coils with

Composite Flux Controllers

Coil for Al part brazing with Fluxtrol

A controller Internal coil with Fluxtrol controller

Selected Induction

Technologies

Induction Instead of Carburizing Example:

Initial process with

furnace carburizing:

• Masking of the part

• Carburizing for about 80

hrs to a depth of 8 mm

• Demasking

• Furnace hardening

• Cryogenic treatment

• Tempering

• Grinding to correct

distortions

New process:

• Induction scan hardening

• Furnace/induction tempering

• Final grinding

Scan hardening of an internal surface of

a big steel component (750 kg)

Magnetic concentrator strongly reduces the

coil current (2 times) and therefore size of

the transformer and other equipment

Induction Hardfacing/Cladding

Powders compositions:

• C 2.5 – 7.0 %

• Cr 20 – 40 %

• Mn < 15%

• Ni 0.5 – 5 %

• Si 1 – 2 %

• Others – Cu, B, W, Mo

Typical hard layer

thickness – 0.5 - 2 mm

The goals are to increase:

- Hardness

- Wear resistance

- Chemical resistance

Courtesy Freal & Co

Microstructures

155 mkm Substrate

Hard Layer

30 mkm

Low porosity and

inclusions Excellent transient zone

Courtesy Freal & Co

Hardfacing of Harrow Discs

Harrow disc with hardfaced teeth

Life time is 2-3 times longer

than for traditionally treated

discs

Courtesy Freal & Co

Induction Hardfacing Process

Magnetic controllers

from Fluxtrol 50 for

temperature

distribution control

Courtesy Freal & Co

Induction Hardfacing Installation

Versatile automatic hardfacing installation 60 kW, 66 kHz

1

2

3

4

5

1 – Generator, 2 – Controls, 3 – Heat Station

4 – Cooling System, 5 - Machine Courtesy Freal & Co

Thermo-Chemical Processing with Induction Heating

Induction gas

carburizing is a well

known but not used

process

Combination of

induction processing in

liquid media, proposed

by Prof. Saveliy Gugel,

provides many new

opportunities Courtesy Sanova LLC

Induction Treatment in LAM

Induction carburizing in liquid

active media (LAM) occurs at

high temperature and very

high concentration (potential)

of carbon or other elements

(B, N, etc.)

Process is very flexible due

to many variables: LAM

composition, temperature

variation on the part surface

and subsequent heat treating

process parameters

T

Vapor blanket

x

LAM

Insulation

Courtesy Sanova LLC

Chamber

Ledeburite (a) Austenite (b) Martensite (c)

Variety of Structures on Steel

Surface

Courtesy Sanova LLC

Steel AISI 8620 after Treatment

Steel:

C 0.18/0.23; Cr 0.4/0.6; Mn

0.7/0.9; Mo 0.15/0.25; Ni

0.4/0.7; Si 0.15/0.35

Example of processing:

- Carburizing 35 min - 1220 C

- Recrystallization Cooling

0.5 min

- Heating to 870 C and soaking,

4 min

- Hardening in LAM, 0.5 min

- Self-tempering, 2.5 min

Case depth is around 2 mm

50HRc

Fine M + F P + A

45-25 HRc 63-67 HRc

Courtesy Sanova LLC

Example of Ti Alloy Treatment

Microstructure of Ti6Al4V (x100) and micro-hardness curve

after treatment in LAM for 20 min

Treatment

increased

strength, wear

and fatigue

resistance

Erosion

resistance

increased more

than 3 times

Courtesy Sanova LLC

Installation for Processing

Courtesy Sanova LLC

1

2

3

1 – Power supply

2 – Treatment block

3 – Control panel

Electromagnetic Wiper Induction heating is widely used for Preheating and Remelting

of strips and wires in galvanizing and galvannealing processes.

One new application – removal of excess of the molten coating

(zinc) from the parts. Electrodynamic forces are used here.

Courtesy Netshape Cast, USA

F

Conclusions

• There are many new applications of induction heating in heat treating and surface engineering

• Some old technologies found new life due to new environmental and technical requirements and advanced techniques

• Advanced design methods based on computer simulation may be called “Virtual Prototyping”

• Treatment in LAM, hardfacing, coating remelting and “brushing” are the examples of new induction technology in surface engineering

Acknowledgement

The author thanks

CHTS and Fluxtrol Inc.

for presentation support

Michigan, USA

www.fluxtrol.com

Beijing, China

www.chts.org.cn