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Single Shot Hardening

Single Shot Hardening - Overview

Unlike traverse hardening the single shot process utilises an inductor which surround the component axially rather than circumferentially. Because the flow of current is axial it is necessary to rotate the component during the heat cycle at typically between 100 and 500rpm.

Single shot hardening is typically used for shafts with multiple diameters or an irregular shape to overcome the problems associated with incorrect quenching. It also offers significantly reduced time cycles over traverse hardening techniques.

By utilising laminations or powder metallurgy loading type loading materials strategically placed along the inductor it is possible to control the heat pattern very precisely to achieve complex hardness patterns.

All single shot hardening systems feature the same principle elements as follows:

• 1. An Induction Power Unit - The power and frequency of this unit is selected based on a variety of parameters including component cross section, overall surface area and harness depth required. For shallow depths and small diameters the frequency will typically be in the 50kHz to 200kHz range. Deeper case requirements and larger diameters will typically utilise lower frequencies in the 1kHz to 10kHz range. As a guide the lower frequency range is utilised where component diameter is greater than 20mm and hardness depth exceeds 3mm smaller cross sections and shallower case depths will utilise the higher frequencies. A range of techniques including empirical calculation, experience and 3D coupled magnetic modelling software can be utilised to select the correct power and frequency.


• 2. A Mechanical Handling System - The type of handling system will be dictated by the components to be processed, the throughput required and customer preferences and requirements. Ali systems will feature a rotation of some sort due to the axial nature of the coil geometry. Rotation speed is normally between 100rpm and 500rpm and must ensure the component rotates a minimum of 5 times during the heat and quench cycles. The system can be configured to operate vertically or horizontally and will often include some form of traverse system to move the coil or component into the correct position.



• 3. Quench System - The method of quenching will be dictated by the hardness pattern. It will normally feature a spray of some kind often as an integral part of the coil or a separate gallery but can in some cases simply be a bulk tank into which the component is dropped or placed once heated. Quench mediums are typically water based and often feature polymer additives to either accelerate of retard the quenching effect.
4. Cooling system - The cooling system will normally be a split type where the cooling water for the generator is on one circuit and the quenchant is cooled on a separate circuit. Typically air blast coolers, refrigeration chillers and water to water cooler are utilised subject to climatic conditions and local requirements.

Single Shot Hardening - Case Study Traverse System

Application - Harden Drill Rod Threads.
Component Details - 6m long 35mm to 50mmØ rod with 10mm to 12mmØ Bore.
Process Requirement - Harden 150mm to 200mm threaded portion to a depth of 3mm.
Induction Equipment - ISI 350/10 D D-Type 350kW 10kHz power unit with multi ratio iron cored matching transformer and workstation.
Feed System - IHG55 HRTH 6m Horizontal work piece handling system with rotation and 1m traverse incorporating a shaft encoder encoder and digital positioning system.  The 1m traverse mechanism is designed to allow accurate positional control over the coil to cater for differences in rod length and provide optional 1m traverse hardening capability for an alternative low volume product.

The system features air operated chucks to allow loading and extraction of the components from a bar feeder arrangement. The quench collection system is built into the base and features all necessary pumps and filters. System control utilises a menu based programming system and HMI panel with error trapping and logging facility for quality control.

Full system diagnostics are provided for maintenance purposes by a graphics based password protected screen on the HMI. Work coils featuring ferrite loading to concentrate the magnetic flux and to increase effective power density and to increase overall system efficiency. Flood quench system.

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