Induction Hardening Ring Surface Preheating
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Solution Overview
Problem
In induction surface hardening of ring surfaces, particularly in rolling bearings, the transition zones between the initial and end zones of hardening often result in reduced hardness and increased expenditure due to the need for counter-running inductors, which is impractical for large bearings.
Innovation Solution
A method involving a supplementary preheater inductor and variable control of hardness parameters such as speed, power output, and coolant flow to minimize the unhardened slip zone and maximize hardness and effective depth of hardening by creating a steep temperature gradient, with the supplementary inductor preheating the ring surface and the main inductor actively hardening it, followed by quenching with a spray.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single inductor is used for induction surface hardening of a ring surface, then the device complexity is reduced, but the initial zone and end zone exhibit reduced hardness and increased effective depth of hardening due to transitional heating effects
Solution Approach 1:
A supplementary inductor is positioned upstream of the main inductor to preheat the ring surface in the initial zone before the main inductor processes it. This preliminary heating action ensures that the initial zone reaches the required hardening temperature without being underheated by transitional effects, thereby achieving uniform hardness across the entire ring surface including the initial and end zones.
2Manufacturing precision
If two inductors are used to heat the ring surface from both directions, then the initial zone can be hardened completely with uniform heating, but the device complexity and expenditure increase considerably
Solution Approach 1:
Instead of using two inductors simultaneously, a single supplementary inductor is positioned upstream to perform preliminary heating of the initial zone before the main inductor processes it. This sequential approach achieves complete hardening of the initial zone with uniform heating properties while using only one main inductor, thereby avoiding the considerable device complexity and expenditure associated with dual inductor systems.
3Use of energy by moving object
If the supplementary inductor is positioned close to the main inductor, then the preheating effect is maximized, but the hardening device becomes more complex and difficult to implement
Solution Approach 1:
The supplementary inductor is positioned upstream of the main inductor along the direction of ring surface movement, utilizing the temporal dimension of the feeding process rather than spatial proximity. This arrangement allows the supplementary inductor to preheat the initial zone as the ring surface moves through, maximizing preheating efficiency through coordinated timing and movement while maintaining a simple, linear device configuration without the complexity of closely positioned or overlapping inductors.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the length of the unhardened slip zone and enhances the uniformity and depth of hardness across the ring surface, improving the overall hardening process efficiency and reducing the complexity of the hardening device.
Implementation Method 1
a supplementary inductor, which is intended as a preheater and is arranged upstream of the inductor in the direction of treatment
Implementation Method 2
heat the ring surface from an initial zone to an end zone by means of the inductor
Implementation Method 3
harden it by cooling by means of the spray
Data Source
AI summary
A method for induction surface hardening includes, when in a feed mode, moving an induction coil of a hardening device over a ring surface of a work piece in a treatment direction, to heat the ring surface from an initial zone to a final zone. A sprayer, located downstream of the induction coil in the direction of treatment, is activated to apply quenching liquid to the heated ring surface to both cool and harden the ring surface. An unhardened soft zone is provided between the initial zone and the final zone. A supplementary induction coil, the induction coil and the sprinkler are respectively activated and deactivated separately at the start and end of the hardening, while the relative feed speed between the hardening device and the work piece, and/or the power supplied to each of the supplementary induction coil and the induction coil, are varied at the same time.