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Induction Hardening Applications [.pdf format]

Systematic analysis of induction coil failures. Part 9: Clamshell inductors.

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

This article is one of series of articles devoted to a systematic scientific/engineering analysis of failures of induction heating coils and prevention. When hardening irregularly shaped components, adjoining areas may sometimes exclude the possibility of positioning the component inside a cylindrical coil. In other cases, the required "coil-to-part" air gap that would provide enough clearance for loading and unloading the workpiece is so large that it dramatically reduces electrical efficiency of induction coil or may even prevent obtaining required hardened patterns. An example is the hardening of camshaft lobes that have a sharp "nose" and undersized "base circle" in combination with large bearings or eccentric journals. In cases such as this, split or clamshell inductors sometimes provide a solution. Article discusses advantages and drawbacks of split or clamshell inductors for induction heating irregular-shaped parts, as well as its failure modes.

Systematic analysis of induction coil failures. Part 8: "Gap-by-gap" gear hardening coils.

Authors: Valery Rudnev
Publication: Heat Treating Process, Professor Induction Series
Date: 11/1/2006

This article is one of series of articles devoted to a systematic scientific/engineering analysis of failures of induction heating coils and prevention. Gears are induction hardened by either encircling the part with a coil (so-called spin hardening) or, for larger gears, hardening them "tooth-by-tooth" or "gap-by-gap." Article concentrates on analyzing main coil failure modes of "gap-by-gap" inductors for hardening large and medium size gears. Several case studies are discussed including degradation of laminations, copper overheating, distortion, arcing, coil abuse and improper handling.

Flexible induction heating machinery for flexible customer heat treating requirements

Authors: Ray Cook
Publication: Industrial Heating
Date: 9/1/2006

Delivery, Quality and Price have been the key benchmark deliverables in the past. Today these three are joined by a fourth that is equally important, Flexibility. In the past it may have been permissible to pick one or two of these areas to focus on. But today all are essential to meet the growth of ever increasing customer requirements. For capital equipment manufacturers like Inductoheat, Inc. the consideration of requirements has led to the development of a new generation of induction heat treating including induction hardening and tempering equipment that will meet and exceed the needs of a large variety of customers supplying parts to the transportation industry. Article discusses advanced approaches in development new generation induction heat treating machines.

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.

"Fine Print" of Metallurgy of Induction Hardening, Part 2

Authors: Valery Rudnev
Publication: Industrial Heating
Date: 5/1/2005

Fine prints became one of the characteristics of our life. It turned into a normal practice to be aware about fine prints of disclosure in every aspect of life whenever we are buying goods or listening to advertisements, taking medicine or purchasing service. In many cases "fine prints" consist of more important information than the large print. This article discusses in this two-part article the "fine prints" of certain metallurgical phenomena and principles of heat treatment that frequently are incorrectly assumed or improperly used in induction hardening.