Laser marking metal: Annealing
Annealing leaves no tangible mark on metals, including stainless steel
During the annealing process, no material is removed and there is no ablation unlike when laser engraving. Annealing does however produce a colour change in the material as it is heated. For example, stainless steel, changes colour when it reaches temperatures between 200 and 300°C. Annealing can be used for a wide range of applications, including laser marking ball bearings and dataplates.
Different temperatures produce different colours
With a laser machine, many different finishes can be achieved on materials. A "perfect black" mark is usually the desired result and can be achieved on stainless and Titanium. It is possible though to achieve different colours with different temperatures. Annealing is also possible on any allows which contain iron.
Colour change through heating
In order to anneal metal, it is crucial that you only heat the material as opposed to vaporising it. This can be achieved by reducing the energy density of the laser impact on the steel. To do so, you need to go out of focus to increase the laser spot size. Having the same energy on a much bigger surface will reduce the energy density. A slow laser marking speed should be used as heating the metal will take time.
When using the conventional method of annealing, make sure you work with the industrial laser out of focus (to get a large laser spot for heating the material) and with a very low laser speed.
This process allows you to create deep black (even partially coloured) and homogenous markings on stainless steel. Please note there are also some negative effects caused by the low speed and working out of focus:
- Small markings will appear fuzzy
- Long marking times compared to alternative metal marking methods, such as laser engraving or poloshing
- The intense heating of the material can cause the marking to corrode (corrosion sensitivity)
Annealing in focus
With the laser marking solutions of Trotec´s SpeedMarker Series, you can avoid these negavite effects of the annealing process.
With the use of the latest fiber laser generation and the new SpeedMark 3.6 laser marking software, you can create laser markings by annealing in focus, leading to up to ten times faster laser marking speeds!
This configuration opens new possibilities for meeting the requirements of laser marking with the annealing process:
- Less or even no corrosion sensitivity (as the heating is much lower)
- Faster laser marking times (depending on parameter and lens used)
- Extremely sharp markings are possible when laser marking in focus
We are always happy to help
Are you currently laser marking with annealing or intend to do so in the future? Contact us! Our laser experts are here for you and will help you find the ideal marking parameter for you specific requirements.