Induction Hardening

What is Induction Surface (Case) Hardening?

The induction heating process provides a purely thermal means of surface hardening steel and cast iron components.

A martensitic surface layer is produced, which gives high wear resistance and is compressively stressed to increase fatigue strength. The core material is unaffected and remains soft and ductile. In order to induction harden steel requires a minimum carbon content of 0.3%.

Features of the Induction Hardening Process:

• High power density giving very rapid heating
• Heat confined to selected areas
• Control of heated depth
• Complete control of time, power and hardening temperature
• Heat is generated within the component

Resulting in:

• Energy savings due to efficiency of process
• Minimal distortion
• Complete repeatability
• Can be easily automated
• Fit into existing production lines
• Operation by unskilled labour
• Working environment and health and safety benefits over alternative methods of heating

Induction Hardening Technology

When a metal work-piece (component) is introduced into a work coil, the two are linked by a magnetic field. A current is induced in the work piece and produces heat.

The intensity of the heating is greatest at the surface and reduces as the distance from the surface increases.

The skin depth can be described as the depth at which 90% of the current flows. Skin depth decreases as frequency increases, thereafter the deeper the case the lower the frequency of the power unit.

Other factors will also affect case depth, such as power density and electrical resistivity and magnetic properties of the material.

Selection of Induction Hardening Frequency

Choice of frequency depends on work-piece cross section and depth of hardness required.

Selection of Induction Hardening Power Unit

The 'Ultra-tec' range of generators covers the frequency range from 100kHz up to 200kHz at output powers from 3kW to 100kW, these are generally used to harden small components and typically will produce cases up to 2mm deep.

Where bigger components or deeper cases are required, the "D-Type" range of generators from 1kHz up to 10kHz with power levels from 50kW to 500kW are appropriate.

Auxiliary equipment & services of Induction Hardening

All Inductelec Power Units can be interfaced with PLC's, HMI panels, optical pyrometers etc via a dedicated CAN-bus. Inductelec also design and manufactures a range of handling systems including rotary indexing tables, horizontal/vertical shaft hardeners, conveyor systems, shuttle systems and twin output systems to increase productivity. To complete the installation Inductelec can offer air blast water coolers, chillers or water to water cooling systems to complete a truly turn-key solution.

Quench Supply

Although many components can be quenched in water, some require a less aggressive quench to avoid cracking. Oil can be used for immersion quenching or a soluble polymer additive in the water can be utilised if spray quenching is required.

Benefits of Induction Hardening

• Lower Costs - A change from thermochemical to induction hardening will often reduce production time from hours to seconds; handling and skilled labour content are reduced. The short heating times and concentration of heat into areas and depths to be hardened will considerably reduce energy consumption and costs compared with carburising. A change from an alloy to a carbon steel makes substantial savings in raw material costs. Semi-automatic hardening equipments allow unskilled labour to be used. In many cases processes can be automated and reduce attendant labour to a minimum.
• More Production - Induction heating is an easily controlled continuous process with no harmful effect on the environment and can be readily integrated into an automated production line. It is also a compact process, making possible high rates of output for limited utilisation of expensive floor space.
• Better Quality - Heat can be directed to precisely where required to achieve accurate hardness patterns and distortion is limited. Short heating cycles minimise surface oxidation and reduce or eliminate subsequent cleaning operations. Short cycles also result in minimum work in progress. Thus a minimum number of components will be affected by interruption of the process or by start-up and shut-down procedures.
• Better Environment - Induction heating is clean; there are no products of combustion or toxic fumes. The surrounding atmosphere is therefore clean and contamination risk is minimised.

Please browse our website for more information about Induction Hardening then contact us on 0114 272 3369 to speak to a member of our team or e-mail us on info@inductelec.co.uk.