The Effect of Laser Power on the Coloring of Metals

The researchers tested the effects of laser power on the coloring of stainless steel and aluminum alloy, analyzing the relationship between the depth of color, the degree of oxidation, and the laser power.The company also provides data on the optimal parameters for laser engraving and marking.

Why does the power of the laser affect the color of metal?

When people think of coloring metal, they often think of paint or plating, but it turns out that high-precision lasers can also "paint" metal in a variety of colors.We discovered that the power of the laser directly determines the thickness and structure of the oxide layer on the metal surface–the higher the power, the greater the heat generated in a given instant, the greater the oxidation, and the darker the color.For example, when you mark stainless steel with a 30-watt laser, the mark will appear light gold. But when you turn the laser up to 80 watts, the color will gradually change to dark blue or even black.

Comparing measured data.

Preparation of test materials and equipment.

In this experiment, three common metals were selected: SUS 304 stainless steel, 6061 aluminum alloy, and pure copper. A 20W / 30W / 50W adjustable fiber laser was used.In order to reduce the number of variables, the scanning speed (800 mm / s) and frequency (50 kHz) were kept constant, and only the power was varied.

The color laws at different power levels.

At 20 watts, stainless steel is a light gray. At 30 watts it becomes champagne gold, and at 50 watts it turns deep blue. The changes in aluminum are even more dramatic. At 20 watts it is a dull black, at 30 watts it turns gray-brown, and at 50 watts it becomes a burnt charcoal black.

How does one choose the right power?

For fine patterns a low power setting is recommended.

For detailed patterns (such as QR codes or fine-line text), a 20-30W machine is recommended.Testing has shown that higher power levels can cause the edges of the image to blur, especially with aluminum, and when the power level exceeds 40 watts the lines tend to blur together.

For contrast, select medium power.

For the strongest contrast with the least loss of clarity, 30-40 W is best for stainless steel, and 25-35 W for aluminum.This is the best time to apply the color, because it will not be too burnt.

Special effects are tried.

If you want to create a weathered look on a metal surface, or a gradual transition of colors, try varying the laser power.For example, as the power is increased gradually from 20 watts to 50 watts, the stainless steel surface will change from gold to blue, and this gradual transition is especially suitable for logo design.

Things to be aware of.

Don't assume that higher power is always better! In the tests, we have seen some novices turn up the power on a 100-Watt machine to maximum and try to mark a thin copper sheet. The result is that they burn right through the material.In addition, humidity also affects coloration: When the air is too dry, the 30-watt color on stainless steel is two shades lighter than in a moist environment.It is suggested that you first test a small sample on the same batch of scrap before beginning formal processing.