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Technical articles about induction heating

Here is a selection of articles highlighting various technical aspects of induction heating.

 

 

 

Welding
The EFD Induction Weldac: What it is, how it works and why you should care. ‘Weldac’ is EFD Induction’s range of solid-state welders for tube and pipe welding. A standard Weldac system comprises a diode rectifier, IGBT inverter modules, an output section, busbar and operator control section.
The article investigates the impact that geometrical changes in the weld zone have on weld frequency and the Heat Affected Zone (HAZ). The article evaluates the consequences of controlling HAZ by a variable frequency option. The article points out the importance of weld setup control.
The authors evaluate the parameters that influence welder performance and scrap production during changeover in the high-frequency tube and pipe welding process. The paper focuses on the welder system’s features during changeover. The parameters involved are welder recipes, energy consumption monitoring, and matching capabilities.
This article explains some basic principles of solid-state welder design that are crucial for maintaining operation under various conditions. The paper also presents several key differences between MOSFET and IGBT transistors, and describes how a converter with a voltagefed inverter and series resonant output circuit withstands short circuits.
The authors evaluate the parameters influencing weld quality and scrap production in highfrequency tube and pipe welding. The paper focuses on the welder. Two stages of the production process – steady state operation and non-ideal conditions – are investigated. The parameters involved are ripple in output power and short circuits in the load.
This paper presents a new HF-converter for induction heating. The converter has a diode rectifier and automatic matching. It uses a patented timesharing principle for high frequency use of IGBTs (ref. [1]) in order to reach 350 kHz. The paper focuses on the benefits the converter structure has in some typical application.
Induction welding of tube and pipe with increased wall thickness presents manufacturers with new challenges regarding production rates and quality. In a medium- and thick-wall tube the heat-affected zone (HAZ) is shaped like an hourglass, ie the corners are heated more than the centre of the tube walls.
Temperature distributions in the cross-section of the weld point are calculated through two-dimensional coupled electromagnetic and thermal FEM analyses.
The heat affected zone (HAZ) in a medium– and thick-wall tube is shaped like an hourglass. This can give overheated corners and a cold center in the tube wall, which limits weld speed.
Normalizing
The use of longitudinal seam-welded line pipe produced in continuous welding lines has increased in recent years. These pipes must apply to different standards, like API, ISO, DnV, etc. The trends are that the wall thicknesses of the pipes have increased and the materials used have set new demands on the heat treating process. Understanding the dynamics of the seam normalizing process and processes with intermediate quenching, during heating and cooling is, therefore, important in order to meet the different requirements.
EFD Induction has unveiled a new control system for normalizing pipe weld seams to API standards. Per H. Ødesneltvedt, one of the R&D engineers involved in the project, explains some of the system’s features and benefits.
In the production of welded pipes according to API standards, a normalization of the weld and heat affected zone (HAZ) is required. The weld of thick-walled tubes shows an hour-glass shaped HAZ caused by the ”corner effect” in the weld Vee.
Hardening
There are two alternative methods of induction hardening: conventional “scanning hardening” and the less common “single-shot hardening”. This article looks at the induction hardening process and discusses these options.
Those of us who work in automotive-related industries must sometimes feel we are faced with mission impossible. On one side there is the relentless pressure to squeeze costs, timelines and so on. On the other, there is the growing demand for smaller, lighter and more efficient components and assemblies. And nowhere are these contradictions more evident than with crankshafts.
In vielen Bereichen der Industrie ist aufgrund gestiegener Energiepreise und dem wachsenden Umweltbewusstsein die Energieeffizienz von Maschinen ein äußerst wichtiger Aspekt. Dem Wirkungsgrad von Induktionserwärmungsanlagen, welche Nennleistungen bis in den MW-Bereich generieren, kommt somit eine besondere Bedeutung zu. Aufgrund des gestiegenen Bedarfs nach zuverlässigen Lösungen und den hohen Anforderungen an die Bauteile, erfährt die Induktion als Verfahren zum Randschichthärten eine hohe Nachfrage.
There are many benefits to be reaped from contour spin hardening with the multifrequency method. The induction heating method used for small- and medium-sized gears is often referred to as spin hardening. This is because the gear is placed within an induction coil and spins as eddy currents are induced.
Induction hardening is being increasingly used within the gear industry. However, before looking at the advantages of the method, it is helpful to review the basics of the technology. The phenomenen of induction heating begins by passing an alternating current through a coil in order to generate a magnetic field.
Easy integration into production flows has made the inductive spin hardening of gears increasingly popular in recent years. Dr. Hansjürg Stiele of EFD Induction explains the basics behind the method.
When it comes to crankshafts, engine component manufacturers are caught between the proverbial rock and a hard place. On one hand, car-, truck- and ship-makers are relentless in their pursuit of lower costs. On the other, performance requirements are becoming ever more stringent.
The elongation potential model simplifies the explanation of residual stress creation during surface hardening. It is widely accepted that residual stress can have a significant impact on the fatigue strength of hardened components.
EFD Induction is best known in the automotive business for its hardening and tempering solutions. These are used to treat a wide range of steering, driveline and transmission components, as well as crankshafts, camshafts, gears, drive shafts, output shafts, torsion bars, rocker arms, CV joints, tulips and valves.
Achieving shorter manufacturing lead times is one of many advantages of using EFD’s induction-based hardening solutions. More and more companies are opting for induction-based hardening solutions – and there are four key reasons that make induction hardening such an attractive choice for OEMs and suppliers.
New nomographs for induction surface hardening of steel showing the relations between surface power density, frequency, heating time, maximum surface temperature, and austenitisation depth have been calculated. Coupled electromagnetic and transient thermal 1D (ELTA) and 2D (Flux2D) simulations with nonlinear material properties have been used. A relative workpiece dimension factor is introduced to take into account the influence of the workpiece size.
Brazing
How innovative protective atmosphere brazing cuts production times for high-grade banjo fittings.
Offshore
The application of heat is often the only way to repair, remove or install equipment essential to offshore operations. Unfortunately, traditional heating methods and offshore operations don’t mix well. Safety concerns make the application of heat problematic. The use of gas-fired open flames, for example, is prohibited in many environments. If alternative heating methods are not employed, equipment may have to be disassembled and shipped ashore, driving up costs and perhaps even threatening production.
The Statoil Tampen Link project brought a 12” branch pipe into a 20” main line using a welded branch pipe and a hot-tap drill through. All conducted with diver operations on a high pressure gas pipeline at 145m (475’) water depth. The paper describes the first subsea operational use of the EFD induction heating system which was used to provide the welding pre-heat. This provided high heat input, to counteract the cooling gas flow, without discomfort or hazard to the welder divers.
Bonding
Induction heating is widely used in the automotive industry. But as two case studies from EFD Induction show, a little creativity is all it takes to extract even more value from this amazing technology.
The use of adhesives in the automotive industry is becoming more prevalent, every new model seems to have more bonded joints than it's predecessor. It's not difficult to see why this is happening; the benefits of using adhesives to replace more traditional techniques are well documented, and modern day engineers are more prepared to use adhesives than their predecessors.
Straightening
Thin plate distortion in the shipbuilding sector has been studied for decades, but the problem continues in some form or another [1]. In addition to this, there has been a gradual move to include more thin plate into the structure of naval vessels in particular.
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