Heat treatment, hardening
The laser beam is an excellent tool for local heat treatment and hardening. Especially in such cases, in which high precision and low energy input are of utmost importance. The calculation of laser generated temperature distribution, heat affected zones, phase transformation and resulting hardness modifications with FEM is the present state-of-the-art. More difficult but even more important is the fast solution of inverse problems such as the determination of those process parameter values which give a special result for a given component and their optimization with respect to different targets ( hardening depth, rate ect.). At the LOT and the IWS we solve such problems (indepently of the component`s geometry) in several steps.
Plane-parallel plate and rectangular edge
A developed data base contains pre-calculated relations between process parameters and process results for simple geometry models in a scaled and thus material-dependant way during the laser hardening. The software tool GEOPT analyzes these relations within a tenth of second by the help of an optimization algorithm and takes the material characteristics into account.
Here, an integrated material data is very helpful. GEOPT is not only able to forcast the results, to be inspected for the known process parameters, but it can, vice versa, determine the parameters, which are necessary for a certain process results. Furthermore it can optimize parameter sets with respect to targets, while maintaining special conditions (e.g. to get the maximum hardening track width at a given laser power while complying the minimal values of hardening depth and hardness). Last but not least, GEOPT can be used to represent the relation between stored quantities:
Fig. 1: Characteristical parameters for laser hardening, calculated with GEOPT, for the steel C45 as functions of the distance of the laser focus to the rectangular edge (at constant values of laser power, beam radius and feed rate).
Contact:
Dr. Dietrich Lepski
Phone: +49 (0) 351 463 31993
PrOFeT- system for the simulation of the heat distribution or the optimization of the process velocity for the hardening of cam disks.
Very often users favour a constant hardening depth for the laser hardening procedure. The ideal surface temperature is determined by the material and maintained during the process by a controller. The system "LompocPro" has been developed by IOF and IWS for exactly this purpose. Since the laser spot size is determined by the used optics, only the feed rate can be optimized. If there are locally different heat conductions, a constant hardening depth can be obtained by locally adjusting the feed rate. The product PrOFet is such a required simulation and optimization software, which serves a two-dimensional case as it occurs for the hardening of cam disks. By the help of the method of finite differences the heat distribution in the component is precisely and very fast calculated and an optimization (e.g. a constant hardening depth) can be performed. Here material data and power distribution in the laser spot size are considered.
User interface of PrOFet
- example cross-section
- features of the component such as current temperature, maximum
temperature, hardening zone
- graphical representation
- start
- start optimization
- writing, e.g. material data
component
- calculated tγ ( time above TAC1)
- simulated temperature control
- constant feed rate
component
- calculated tγ ( time above TAC1)
- simulated temperature control
- feed rate optimized by PrOFet
component
- cross-section after hardening
- surface temperature, controlled in a constant manner
- feed rate optimized by PrOFet