March_AMP_Digital

ADVANCED MATERIALS & PROCESSES •

MARCH 2014

Increasing demand from the durable

goods market (e.g., automotive, agricul-

ture, aerospace) for lighter weight, more

efficient, and highly durable products re-

quires a significant increase in

material/component strength and per-

formance capability. Traditional ther-

mally activated processes used to

improve materials strength and per-

formance have evolved empirically and

are largely isothermally based, equilib-

rium reactions. Using this approach,

heat input, flow, and its redistribution

are driven only by an applied elevated-

temperature differential. Therefore, the

desire to accelerate thermal transfer re-

quires the application of higher surface

temperatures and longer times, which

can result in several undesirable effects

and other process capability limitations.

Advanced induction thermal capabilities

Continual improvement of induction

heating technology has increased the

ability to selectively focus and provide a

highly controlled internal thermal pro-

file of a part, enabling optimization of

specifically programmed, thermally

driven metallurgical reactions for maxi-

mum strengthening results. Notably, the

latest innovations in equipment versatil-

ity and FEA-modeled hardware tooling

provide an unmatched, precise capabil-

ity to accelerate processing speeds and

produce novel metallurgical microstruc-

turally enhanced strength (ultra-grain

refinement approaching the nanoscale

plus unique beneficial microstructure

morphology) in a part.

Induction heating generates heat (with

truly no limit on achievable temperature)

within the part’s subsurface. The depth of

heat distribution can be programmed and

dynamically profiled to produce desired

metallurgical results, which are achieved

by the efficient use of environmentally

clean electrical energy. The part’s internal

heat profile can be optimized using a wide

range of in-situ computerized process-

control parameters. Therefore, process-

ing can be customized to provide

optimally driven reactions for improved

part performance.

Induction heating thermal dynamics are

vastly different from those applied in tra-

ditional isothermal systems. In cases of

short heating times (1 to 2 seconds or

NDUCTION COUPLED

HIGH MAGNETIC FIELD EXPANDS

PROCESSING ENVELOPE FOR

HEAT TREAT INNOVATIONS

TRADITIONAL HEAT TREATING PROCESSES HAVE REACHED A PLATEAU

AND ARE NO LONGER GOOD ENOUGH.

George Pfaffmann, FASM*,

Ajax-TOCCO Magnethermic Corp., Madison Heights, Mich.

Aquil Ahmad*,

Metallurgical Consultant, West Bloomfield, Mich.

HTPRO

*Member of ASM International

Recognition of the need

A recent U.S. Army Solicitation for Innovative Research on High Magnetic Field Processing illustrates that there is a need for

such disruptive technology. The document reads in part:

The Army is highly interested in the application of electromagnetic fields for development of ultralightweight metals with tai-

lored microstructures and properties. The current methods used to manipulate metal properties involve varying scale, compo-

sition, temperature, and pressure to improve strength, hardness, facture toughness, elastic modulus, density, etc., but the use of

these traditional techniques for tailoring a wide range of chemical and physical properties is reaching a plateau. It is worth not-

ing that significant ongoing research is being dedicated to reengineering and exploring the creation of materials at the nanoscale,

which holds potential for future applications that inherently hinge on surmounting scalability, assembly, and producibility

challenges. However, there is an emerging technology that goes beyond factors of scale, composition, temperature, and pressure,

and holds great promise in facilitating the realization of transformal materials with the aid of externally applied fields. The

application of fields may alter phase transformation pathways, create new microstructures, shift equilibrium favoring new

metastable alloys, align phases, manipulate and shape nanoscale architectures, and produce materials with revolutionary

structural and multifunctional properties otherwise unattainable by conventional processing and production methods. The

application of electromagnetic fields offers the unique opportunity to direct the architecture of materials features across atomic,

molecular, micro, meso, and continuum levels. These fields may either be used to induce a permanent material property im-

provement or to selectively activate enhanced time-dependent properties via dynamic stimulation.

Induction heating a shaft.