Induction Heat Treatment & Role Of Simulation Software

How simulation software can help companies save time and money on induction coil and process design


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1. Induction Heating

1.1. Induction Heating - Brief History

English scientist Michael Faraday is credited with the discovery of the underlying principles of electromagnetic induction in 1831. The induction heating was applied firstly in the industry for melting metals by Sebastian Z. de Ferranti in 1887. But it was F.A. Kjellin from Sweden, who first presented successful mains frequency induction furnace in 1903. In 1915 the American J.R. Wyatt develops the idea of the vertical channel induction furnace.

An early application was the melting of tiny charges utilizing a device called a spark-gap oscillator. Another early application was the heating of various metallic elements of vacuum tubes in order to drive off the absorbed gases prior to the sealing process. The heating of these elements helped to determine their melting points. The Curie point was also discovered - the Curie point is the temperature at which certain magnetic materials undergo a sharp change in their magnetic properties. The Curie point of steel, for example, is about 760 °C (1400 °F) depending on steel grade.

First high frequency furnace was designed by E.F. Northrup in the Palmer lab at Princeton in 1916. Year later he obtained a patent for determination of the relation between skin depth and frequency for the high frequency induction furnaces. Next biggest push for induction heating was invention of high frequency generators (initially designed for radio applications), by Prof. Valentin P. Vologdin in Russia - he put a first large HF machine generator of 50kW, 20 kHz into operation and used it for induction melting in 1930.


The development of powerful car and aircraft engines gave next impulse for induction heating and specifically induction hardening - methods for partial hardening were not efficient enough, so more accurate methods were required. In 1929 V.P. Vologdin patented and published first results of his experience with the high frequency induction surface hardening - therefore he is considered as an inventor of this process.

Induction heating use and development grew rapidly during the years of World War II. This was because an immediate need arose for manufacturing large quantities of parts with minimal labor and costs involved. Further developments during the WWII showed very clearly the advantages of induction heating, including the very accurately adjustment of heated depth and surface areas. Some of the currently most recognized induction heating companies were founded in U.S. and Europe - “Ajax/TOCCO”, “Elotherm GmbH.” (currently part of SMS Group), “Brown, Boveri & Cie” (current ABB Group) to mention a few.


1.2. Induction Heating - Basics

Induction starts with a coil of conductive material (for example, copper). As alternating current flows through the coil, a magnetic field in and around the coil is produced. The ability of the magnetic field to do work depends on the coil design as well as the amount of current flowing through the coil.

Induction heating is a contactless heating method of bodies, which absorb energy from an alternating magnetic field, generated by induction coil (inductor).

How induction is used to heat metals? Induction heating is an efficient way to quickly heat electrically conductive metals with pinpoint accuracy. Induction generates heat directly in the workpiece by creating eddy currents with alternating electric and magnetic fields in the material that is heated. The depth of penetration depends on the frequency of the alternating current applied on the inductor. As a basic rule, the higher the frequency, the lower the penetration of eddy currents in the material, and the higher is concentration of current within the penetration depth (aka skin layer).



1.3. Induction Heating - Applications

Today induction heating is used in many industrial processes, such as heat treatment in metallurgy, Czochralski crystal growth and zone refining used in the semiconductor industry, and to melt metals which require very high temperatures.


  • Induction heating of bars, billets or slabs for hot forming has been one of the main applications for many years.

  • Induction hardening - offers excellent hardness distribution with minimal deformations.

  • Induction brazing – the joining procedure for high-quality joints of metallic parts.

  • Joining/Separating - joining and separating shrink-fit connections.

  • Preheating - preheating for welding, e.g. gears, oil pipelines.

  • Induction melting/vacuum melting - induction melting is fast and efficient. Vacuum or controlled atmosphere enables processing of reactive metals (Ti, Al), specialty alloys, silicon, graphite, and other sensitive conductive materials.

  • Induction annealing - enables precise and reliable control of metal material properties.

  • Induction forging, forming and surface reinforcement - example - aluminium surface reinforcement with silicon.

  • Galvanizing, Plasma Processing, Hard facing/coating, Welding.


Some innovative technologies & applications:

  • Rapid heating, gradient heating

  • Multi layer bars inductor

  • Transverse flux induction heating

  • High frequency tube welding

  • Innovative space travel propulsion

NASA's experimental NTP fuel elements heated with induction

Where Is Induction Heating Used?

  • Automotive

  • Off-Highway/Construction

  • Aerospace

  • Metallurgical Plants

  • Oil & Gas Component Manufacturing

  • Special Applications

Vehicle production examples:

  • Engine

  • Axles

  • Bearing Assemblies

  • Drivetrain Assemblies

  • Steering Components

  • Structural Components

  • Fasteners

  • Gears


Large gear heat treatment

1.4. Induction Heating - Features & Benefits


Features:

  • Heat generation occurs inside the part

  • Heating is contactless - as a result, product warpage, distortion and reject rates are minimized

  • Method can provide very high power densities

  • Heating may be highly selective in the depth and along the surface

  • Any processing atmosphere (air, protective gas, vacuum)

  • Very high temperatures may be reached

General benefits of induction surface heat treatment are:

  • Short heating times - production rates can be maximized

  • Optimized consistency - induction heating eliminates the inconsistencies and quality issues associated with open flame, torch heating and other methods

  • Extended fixture life - induction heating delivers heat to very small areas of your part, without heating any surrounding parts. This extends the life of the fixturing and mechanical setup.

  • Environmentally sound - without burning fossil fuels; induction is a clean, non-polluting process. Improves working conditions for employees by eliminating smoke, waste heat, noxious emissions and loud noise.

  • Effective energy consumption - this uniquely energy-efficient process converts up to 90% of the energy expended energy into useful heat; batch furnaces are generally only 45% energy-efficient. Requires no warm-up or cool-down cycle.

  • Flexible adaptation to the hardening tasks

  • Closed loop computerized process control and compatibility with overall process automation


It is even possible to heat different zones of the part at the same or different temperatures by means of a proper design of the inductor geometry.

1.5. Induction Heating - Obstacles & Solutions

Obstacles:

  • Initial design and optimization of the process is very complicated

  • Hard to predict power, frequency and heating time to get necessary results

  • Unlike other heating methods, induction heating requires specific coil design for each workpiece, so it's not very economic unless you need to process multiple similar workpieces (e.g. car production) To design & calculate the process you can:

  • Do a rough analytical estimation, then proceed with countless design iterations in the lab

  • Find a professional company that can do induction coil and process design for you, but keep in mind that you most likely will be charged for design hours spent in lab

  • Buy a sophisticated multi-physics simulation software and hire a trained simulation engineer / analyst or pay for engineers training (usually takes 3 months)

  • Start using simple, affordable and induction heating focused CENOS software


Affordable, yet powerful CENOS software enables you to start your first simulation with CENOS templates right away - quickly and without previous knowledge.

Download CENOS Simulation Software and try it one month for free!


2. Induction Heating and Computer Simulation

2.1. What is Computer Simulation?

Nowadays, in various industries manufacturers prefer using software simulations over physical testing.

Computer simulation is a powerful tool that enables engineers and scientists to investigate or design a physical system and/or process using a virtual mathematical model, thus saving time and money on numerous physical design iterations. The vast majority of modern computer simulation software packages utilize numerical methods (e.g. finite element method or “FEM”) to evaluate extremely complex physical systems – systems that are otherwise impossible to precisely analyze. By leveraging the power of modern computer hardware, simulation software can provide substantial improvements in the efficiency, reliability, and cost-effectiveness in design and development processes. 2.2. Computer Simulation In Induction Industry

First works on computer simulation of induction coils were made in 1960’s. Due to a limited access to computers, their low memory, speed and poor programming methods the computer simulation did not receive significant industrial application until the 1980’s

Now computer simulation has become a practical tool for everyday use in the induction industry. It allows the user to design optimal systems, improve equipment performance, dramatically reduce development time and costs, better understand the process dynamics, etc.

Though there are still difficulties in accurate simulation of non-linear and different mutually-coupled tasks, computer simulation is effectively used for design of induction heating coils and problem solution.


2.3. Benefits And Value of Induction Heating Computer Simulation

The use of induction heating computer simulation software can promote substantial improvements in the performance and cost-effectiveness of induction heating equipment, in addition to large reductions in the cost and time required to design and develop induction heating processes.


From a design perspective, computer simulation is valuable for a number of reasons – two of the most notable being:

  • The physics involved in utilizing electromagnetic induction as a deliberate and controlled source of heat generation is extensive and multi-faceted. Computer simulation provides a quantitative approach to designing and developing induction heating processes, allowing complex physical phenomena that cannot be physically observed and/or measured to be clearly visualized and quantified.

  • Because electromagnetic induction offers an extremely effective, economical, and versatile means of heating conductive materials, the scope of induction heating applications is very broad. This includes (but is not limited to):

  1. Heat treatment (hardening, tempering, normalizing, stress relieving)

  2. Forming (hot/warm forging, rolling, stamping)

  3. Joining (welding, brazing, soldering, bonding, shrink fitting)

  4. Other (curing, coating, crystal growing)

Furthermore, each of these general applications includes countless different workpiece types, geometries, materials, and heating requirements. As a result, no “universal solution” exists in the design of induction heating equipment.

Induction heating computer simulation offers the most efficient means of developing customized and optimized solutions and is, therefore, a necessity – not a luxury – in the modern induction heating industry.


3. Combining Simulation With Real World Tests For Best Results

Inductor design is one of the most important aspects of the overall induction heating system. A well-designed inductor provides the proper heating pattern for your part and maximizes the efficiency of the power supply, while still allowing easy insertion and removal of the part. With the right design, it's possible to heat conductive materials of any size and form, or only the portion of material required.


3.1. Computer Simulation vs Experimental Method


Computer Simulation

Advantages

• Can work for any geometry and operating conditions

• Demonstrates the entire dynamics of the process

• Leaves records for future

• Limitless accuracy of calculations

• Does not require special equipment

• Less expensive and time consuming

• Future improvements expected

• Provides process visualisation for customers (pictures, video) Limits and Disadvantages

• Requires special software and databases

• Not all the processes may be simulated (as of today)

• Does not provide physical samples


Experimental Method

Advantages

• May provide the most reliable results

• Can show performance of the whole system including unexpected effects and troubles

• Does not require material property database

• Provides physical samples for properties validation

Limits and Disadvantages

• May require expensive equipment

• Does not provide a good understanding of the process

• Difficult to transfer knowledge

• Case dependent accuracy

• Limited access to production equipment (expensive)

• Time consuming. May cause production delay due to multiple design iterations.



3.2. Challenges in coil design

The induction coil, also known as an ‘inductor’, is essential to induction heating. Single-turn, flexible, multi-turn cylindrical, left-turn, right-turn, rod-shaped, hair-pin, parallel, ear-shaped, tiny, big - whatever the coil shape and size - the right design allows to maximise coil lifetime and ensure lowest energy consumption and best effects on work process and materials.

Many factors contribute to a coil’s effectiveness: the care taken to make it, the quality of the materials used, its shape, its maintenance, its correct matching with the power source, etc.


Here are just three of the many hurdles to be overcome in order to make safe and efficient coils:

  • Impedance matching

It is necessary to achieve the correct impedance matching between the coil and the power source in order to use the latter’s full power. The coil designer must also consider that coils need five to ten times as much reactive as active power.

  • Magnetic flux concentrators

Concentrators focus the current in the coil area facing the workpiece. Without concentrators much of the magnetic flux may propagate around the coil. This flux could engulf adjacent conductive components. But when concentrated, the flux is restricted to precise areas of the workpiece.

  • Water flow and speed

It is generally important to achieve an adequate flow of cooling water through the coil. When high power density is expected in the inductor, the coil designer must consider the flow rate and the water’s velocity. This is because velocity significantly influences the heat transfer between inductor and coolant, and therefore has a major impact on the longevity of the coil. A booster pump is sometimes needed to maintain the desired flow and velocity. Professional designers will also specify a purity level for the water in order to minimize coil corrosion.


3.3. Tools and processes necessary to ensure coil longevity and performance


Advanced induction coils design includes:

  • Detailed analysis of specifications, available equipment and environment

  • Coil style and heating process selection (scanning, single-shot, static etc.)

  • 3D design programs and computer simulation for coil head optimization

  • Analysis of benefits of magnetic flux controllers application

  • Coil engineering (design of coil head, leads, structural components, quenchant

  • supply etc.)

  • Advanced manufacturing techniques, mandrels to achieve tight tolerances.

  • Testing in laboratory or industrial plant for performance and final dimensional check

  • Final corrections if required

Designing and making induction coils is technically challenging. Computer simulation helps tackle some of the challenges, limiting costs and maximising effectiveness.


Our mission at CENOS is to help companies to switch from old and cumbersome experimental method to a powerful computer simulation that is simple, affordable and induction heating focused. CENOS, combined with real-world trials, yields the best results in a fast and cost effective way.


4. How To Choose The Right Simulation Software

The induction heating market is small compared to other industrial sectors and there are only a few specialized simulation packages on the market that can be used for induction process and coil design. Induction heating simulation involves a set of mutually coupled non-linear phenomena. Many induction applications are unique and may require different program modules. In addition to computer simulation software an extensive material database is necessary for accurate results.


1D, 2D or 3D?

Majority of practical simulations now are being made in 1D or 2D approaches. Software like ELTA lets you do simulations in 1D, which might be enough (overall Elta is a very good tool with vast material database); Altair Flux software enables 2D and also 3D simulations.

But with 1D & 2D structure and geometry of real induction systems are often very simplified, in reality a majority of induction systems are 3D. Also interference of induction device and source of power must be considered in many cases. That's why 3D will ensure less space for errors and more thorough analysis.

3D Effects in Multi-turn Cylindrical Coils

Cloud vs Desktop

Working with cloud based software requires uploading your data to the third party. Frequently induction heating equipment manufacturers are not allowed to share their customer CAD files to the third party due to NDA. Furthermore, while cloud computing may provide increased calculation speed, one should consider time it takes for uploading of design files and downloading of the result files.


Importance of training & support (time, costs)

There is a common opinion that simulation software requires only specially educated (and well paid) simulation engineers, usually hired only for one kind of tasks - simulation. This is definitely true for sophisticated multi-physics simulation packages like ANSYS or SIMULIA. Even more user-friendly Altair Flux 2D/3D and Comsol Multiphysics require 3-4 months of intense training because of plethora of numerical aspects which should be taken into account in order to get reliable results in a simulation.

CENOS 3D desktop software keeps focus on induction heating and tries to avoid any unnecessary functionality which might confuse inexperienced user. Using dedicated templates a beginner can run his first induction simulation just under 30 min, and become a pro user with any 3D geometry after 2 weeks of training, guided by CENOS engineers.


Open Source software

Cost efficiency - open source tools like Elmer or GetDP are free to use. However, these tools might require a long training period (6-10 months), plus extra steps & routines that need to be taken in every day simulation will make up to 1000 hours a year. Overall, open source tools are a solid choice because they are validated by the community.


5. Leveraging The Power of Open Source for Everyone


5.1. Benefits And Drawbacks Of Open Source Software


Benefits:

1. Community. Open source solutions often have thriving communities around them, bound by a common drive to support and improve a solution that both the enterprise and the community benefit from (and believe in). The global communities united around improving these solutions introduce new concepts and capabilities faster, better, and more effectively than internal teams working on proprietary solutions.

2. The power of the crowd. Many hands can deliver powerful outcomes. The collective power of a community of talented individuals working in concert delivers not only more ideas, but quicker development and troubleshooting when issues arise.

3. Transparency. Open source code means just that—you get full visibility into the code base, as well as all discussions about how the community develops features and addresses bugs. In contrast, proprietary code produced in secrecy may come with unforeseen limitations and other unwelcome surprises. 4. Reliability. Because there are more eyes on it, the reliability of open source code tends to be superior as well. With a worldwide community supporting a code base - rather than one team within one company - code is developed on online forums and guided by experts. The output tends to be extremely robust, tried, and tested code. In fact, open source code now powers about 90% of the internet and is being rapidly adopted across major enterprises for this reason.

5. Better security. As with reliability, open source software's code is often more secure because it is much more thoroughly reviewed and vetted by the community (and any issues that do arise tend to be patched more diligently). A point of hesitation for enterprise adoption of open source - concerns about security just aren't an issue today.


Drawbacks:

1. Because there is no requirement to create a commercial product that will sell and generate money, open source software can tend to evolve more in line with developers’ wishes than the needs of the end user. For the same reason, they can be less “user-friendly” and not as easy to use because less attention is paid to developing the user interface.

2. There may also be less support available for when things go wrong – open source software tends to rely on its community of users to respond to and fix problems.

3. Because of the way it has been developed, open source software can require more technical know-how than commercial proprietary systems, so you may need to put twice as much time and effort into training employees to the level required to use it.

4. Many different open source solutions are not compatible with each other. Take for example GetDP - an open source finite element solver, its core algorithm library uses its native pre-processing and post-processing tool Gmsh, which frankly, compared to other solutions, is not the best in its class. Whereas CENOS Platform has integrated far more superior solutions like SALOME for pre-processing and Paraview for post-processing, which by default are not compatible with GetDP.


5.2. CENOS Makes Open Source User Friendly And Easy To Use


“CENOS” stands for “Connecting ENgineering Open Source” highlighting its new software approach - connecting the best of open source tools in one seamless user experience.

CENOS platform technology enables affordable simulation available for small to mid-size companies by connecting third-party open source algorithms GetDP, Salome and Paraview, developed by strong academic communities involving world top research centres and universities like Sandia National Lab, Imperial College, KU Leuven and others.

The academic world has already built a plenty of smart algorithms, there is no need to charge money for the scientific heritage. Use of free open source algorithms made it possible for CENOS to be affordable for everyone.


CENOS has built a user friendly interaction layer and interconnection between previously incompatible separate open source software algorithms. CENOS Platform consists of user interface, special data optimization procedures including necessary data reformatting for interoperational compliance ensuring data flow and control between different open source tools.


Intuitive UI with step-by-step setup of new simulation, powerful algorithms process the results in minutes, visualized results in both figures and graphics, fast and accurate simulations, no previous training required to start


6. Saving Time & Limiting Costs With CENOS Platform


CENOS lets engineers save up to 80% of design time by replacing physical prototyping with powerful simulation software.

- CENOS is affordable

Licencing a software like Ansys, Flux, Comsol, Simulia will cost $20 –$80K upfront + additional annual payments in 20% value of purchase price just for support and updates, and that's only for induction heating module, whereas CENOS annual licence is $7200 and requires no upfront investment. Alternatively one could consider “pay as go” purchase model, paid by hours, but one must keep in mind that 3D calculations take time which might make this particular subscription model cost inefficient.

- No previous experience necessary

To run induction heating simulation companies would normally require hiring simulation engineer/analyst. Most simulation analysts are experts in a specific, or a few related specific physical domains, you rarely find simulation analysts that are experts in all of those fields, so they need to be trained. Even if you had simulation experts with expertise across all applicable physical domains, these multi-physics simulations require a significant amount of time to set up. Then they require verification and validation once they run. With multi-physic simulations, you have to know how to avoid the pitfalls in all of the applicable physics domains, not just one. You have to instrument the model(s) accordingly. And that brings us to the second issue: time.

- Induction heating focused

Most of existing software has a wide range of multi-physics simulations, whereas CENOS is solely focused on induction heating and hardening applications - providing excellent value and customer experience for its competitive price point.

CENOS software is simple, easy to learn and get started. With our dedicated templates anyone can start his first simulation in 20 minutes.


Additional benefits:

  • Online tutorials and helpful support free of charge

  • Free upgrades

  • Individual training & help with cases

  • Friendly community of CENOS users around the world

  • Floating licence - use it on different workspaces within a company

  • Easy installation with online guides and video

  • Easy start with predefined templates and tutorials

  • Your data is safe - unlike cloud based solutions your data stays on your system


CENOS was developed by a team of experienced PhDs, engineers and software developers with a simple vision of bringing sharing economy to the engineering world, saving engineers time and accelerating innovations.

Visit our site to learn more: www.cenos-platform.com



Download this paper in PDF

Sources of some materials used in this document: https://fluxtrol.com, https://www.eldec.net, http://www.efd-induction.com, https://inductoheat.com

© 2017-2020 CENOS LLC |  Kalnciema str. 106A-2A, Riga, LV-1046, Latvia |  Have a question? Email us 

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