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Induction Heating of Billets, Bars, Rods, Wires, Slabs, Plates, Strips, Etc. [.pdf format]

How do I select inductors for billet heating?

Authors: Valery Rudnev
Publication: Heat Treating Progress, Professor Induction Series
Date: 5/1/2008

Induction heating is widely used to heat metals prior to hot forming including forging, upsetting, rolling, extrusion, and other methods. Billets are heated either in cut lengths or continuously and are forged in presses, hammers, or upsetters, or are extruded. Steel components by far represent the majority of hot-formed billets, although other materials including titanium, aluminum, copper, brass, bronze, and nickel are also induction heated for hot forming. The most popular billet-heating approaches are progressive multistage horizontal heating and static vertical or horizontal heating. This column focuses on the advantages and disadvantages of each.

Systematic analysis of induction coil failures. Part 11c: Frequency selection

Authors: Valery Rudnev
Publication: Heat Treating Process, Professor Induction Series
Date: 1/1/2008

This article is one of series of articles devoted to a systematic scientific/engineering analysis of failures of induction heating coils and prevention. Frequency selection not only affects the performance of the induction system but it also has a significant effect on coil life. Choice of an improper frequency is the most common mistake made by developers and users of induction heating processes. Frequency selection has the detrimental effect on coil life of choosing an improper frequency for induction through-heating applications (including through hardening, annealing, normalizing, and heating prior to hot and warm forming, for example) is the topic of this column and two others in the "Systematic analysis of induction coil failures" series.

Systematic analysis of induction coil failures. Part 11b: Frequency selection.

Authors: Valery Rudnev
Publication: Heat Treating Process, Professor Induction Series
Date: 9/1/2007

This article is one of series of articles devoted to a systematic scientific/engineering analysis of failures of induction heating coils and prevention. Frequency selection not only affects the performance of the induction system but it also has a significant effect on coil life. Choice of an improper frequency is the most common mistake made by developers and users of induction heating processes. Frequency selection has the detrimental effect on coil life of choosing an improper frequency for induction through-heating applications (including through hardening, annealing, normalizing, and heating prior to hot and warm forming, for example) is the topic of this column and two others in the "Systematic analysis of induction coil failures" series.

Systematic analysis of induction coil failures. Part 11a: Frequency selection.

Authors: Valery Rudnev
Publication: Heat Treating Process, Professor Induction Series
Date: 7/1/2007

This article is one of series of articles devoted to a systematic scientific/engineering analysis of failures of induction heating coils and prevention. Frequency selection not only affects the performance of the induction system but it also has a significant effect on coil life. Choice of an improper frequency is the most common mistake made by developers and users of induction heating processes. Frequency selection has the detrimental effect on coil life. An effect of choosing an improper frequency for induction through-heating applications (including through hardening, annealing, normalizing, and heating prior to hot and warm forming, for example) is the topic of this column and two others in the "Systematic analysis of induction coil failures" series.

Systematic analysis of induction coil failures. Part 10: Contactless inductors.

Authors: Valery Rudnev
Publication: Heat Treating Process, Professor Induction Series
Date: 3/1/2007

This article is one of series of articles devoted to a systematic scientific/engineering analysis of failures of induction heating coils and prevention. The previous entry in this series discussed split or clamshell inductors used for hardening irregular shapes that do not allow an inductor to encircle the part. At the same time, in other applications such as strip or plate heat treating and coating (galvanizing, galvannealing, galvaluming, nonmetallic coating, and paint drying, for example), the ability to move the induction coil from the heating position to an off-line position is considered an important system requirement. Solenoid induction heaters with water-cooled "doors" are sometime used for such applications. Article discusses patented doorless induction coils that allow increasing coil life and eliminating the maintenance problems associated with high-frequency current interrupting a doored inductor.

Electromagnetic forces in induction heating

Authors: Valery Rudnev
Publication: Heat Treating Progress, Professor Induction Series
Date: 7/1/2005

Electromagnetic (EM) forces play the major part in many modern technologies. Motors, magneto-hydro-dynamic (MHD) seals, electromagnetic pumps, levitators, electrical bearings, and springs are some of the modern technologies in which EM forces play a leading role. In some applications, EM forces can reach tremendous values. For example, thanks to a capability to develop incredibly large electromagnetic forces, electric guns or launchers can fire materials to higher velocities than are achievable by rockets or chemical/powder guns. In the majority of induction heating applications, coil current also can reach appreciable values. For example, currents of 10 kA and higher are not unusual for many induction heat treating applications including shaft hardening and gear hardening. High currents produce significant forces that have a pronounced effect on coil life. Without proper consideration, those forces can physically move the heated workpiece, flux concentrator, and even bend induction coil, or fixture, which may negatively affect overall system's reliability and repeatability as well as dramatically reduce a coil life. Unfortunately, electromagnetic forces are rarely discussed in induction heating publications. Endless variety of heat treated parts required a specific coil geometry adds a difficulty to study EM forces. This column is intended to at least partially remedy this by providing an introduction to the topic.

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