Stainless steel processing needs - the advantages of laser marking

Stainless steel refers to steel that is resistant to weak corrosive media such as air, steam, and water, and chemically corrosive media such as acid, alkali, and salt, also known as stainless acid-resistant steel. In practical applications, the steel that is resistant to weak corrosive media is often called stainless steel, and the steel that is resistant to chemical media corrosion is called acid-resistant steel. Because of its weldability, heat resistance, corrosion resistance and other characteristics, stainless steel is widely used. Among them, stainless steel is easy to clean with water and chemical reagents, and it is not easy to breed bacteria, so it is most suitable for hospitals or other fields with special requirements for sanitary conditions. , such as: food processing, catering, brewing, chemical industry, etc.

In actual use, the demand for information marking on stainless steel surfaces, especially black markings, is also very strong. The traditional spray painting and silk screen methods will peel off the paint and film after long-term use; the thermal transfer method will change color after a period of time; chemical etching and stencil marking cannot achieve the black effect and have other problems. Laser marking is a non-contact processing, which does not damage the processing materials. It has the characteristics of non-toxicity, high environmental protection, flexible marking content, and permanent marking, especially in the medical device industry.

Corrosion Resistance of Laser Black Marking --- Picosecond Laser OR Nanosecond Laser

In the medical device industry, corrosion resistance is an important indicator. The general operation method for testing corrosion resistance is to put the metal engraved in the laser engraving into a certain concentration of salt spray environment for a certain period of time, then take it out and zoom in to observe the situation of the laser engraving area. After the corrosion resistance test, there may be problems with peeling marks or rust in the laser marked area. However, through the selection of the laser and the adjustment of the process parameters, the best effect of the corrosion resistance of the laser black marking can be achieved.

Common stainless steel is silvery white, and stainless steel colored by laser marking can maintain its original good performance, making it more versatile. In laser marking, the blackening principle of nanosecond laser and ultrafast laser is different. Nanosecond laser marking generally generates colored oxides including black, while picosecond lasers generate a visually black effect due to the generation of nanostructures that do not reflect light.

In the practical application of laser marking on stainless steel, it is difficult to debug the effect of color marking. By adjusting the frequency, pulse width, defocus amount, etc., different colors such as black can be generated. Replacing the mirror and field lens, etc., the color presented will also be different.

A black oxide layer is formed after black marking by a general nanosecond laser. The thermal effect leads to cracks, and the oxide layer is brittle. As shown in Figure 1, the sample picture of nanosecond laser marking shows the crack state of the oxide layer. These cracks make the mark in the It will fade or rust during the salt spray process.

     (laser marking sample image)

 (partial enlarged image)

Marking with picosecond laser pulses leaves sufficient chromium (around 20 or so atomic layers) on the surface to replace the oxide film with chromium, thereby maintaining corrosion resistance, such as with chromite or ferrochromium tips Exist in the form of spar. Therefore, even after multiple and long-term corrosion tests, the black marks will not show damage due to corrosion and remain clearly visible; secondly, after the marking is completed, a fine, periodic and uniform corrugated structure is formed, using a scanning electron microscope The nanostructures were observed to be minimized, directly reflecting and scattering light through the "light trapping effect", resulting in a matte black color.

The Solution of "Intelligent Manufacturing" of Medical Devices---Picosecond Pulse Laser Marking Technology

Since the introduction of the UDI (Unique Device Identification) standard in the United States and the European Union, the medical industry has faced higher requirements for the traceability of its products. For surgical stainless steel in the medical industry, this means creating clear, easy-to-read, corrosion-resistant markings, preferably in black, that can be used in subsequent cycles, even after multiple cleaning and disinfection cycles. Maintain its high quality level in daily clinical work.

It can be seen from the above experiments that the use of picosecond pulsed laser for black marking is very suitable for processing black matte, corrosion-resistant markings, which will remain stable and clear for a long time in clinical use.

(Black marking of picosecond laser on medical device)

In the application scenarios with high requirements for stainless steel black marking and large process window requirements, the laser process has gradually replaced the traditional marking process. Black marking is the best choice in the current market. Although UDI marking is already a relatively mature application, in the future with increasing demand, it is believed that laser technology will have a wider development and application in the medical industry due to its special performance and high efficiency .

ABOUT HGLASER

HGLASER is the pioneer and leader of laser industrial application in china. It is the world's leading provider both of laser equipment and intelligent manufacturing solutions, the core subsidiary of the well-known national high-tech listed company HGTECH.