The Torment of the Soul—what does the laser look like in your eyes?

Is it colorful and dazzling stage lighting? (So eye-catching, so colorful~~)

In contemporary sci-fi films and television dramas, you may often see the following scenes——(Statement in advance, we do not comment on any movies, just look at the footage below)

In the movie "Spider-Man: Return of Heroes", the miniature laser transmitter carried by the drone can also emit high-energy laser beams. The thick door of the museum does not seem to have any "resistance ability" in front of it.

Seeing this, you may find that laser is really sweet and salty.

In the industrial society, the tools that face thick metal walls are "unceremonious" and cut quickly.

It is not a common "knife, gun, sword, halberd, axe, hook, fork, stick, wand, whip, hammer, and hammer", but a laser beam. , After this beam of light acts on the metal, it can cut them quickly and accurately.

Bingo! The plot design in the film is based on the "laser cutting" technology.

We all know that "fire energy can help gold", are my friends already curious-what is laser cutting? How high is the energy of this high-energy laser?

The principle of laser cutting

In its literal meaning, laser cutting is a technology that uses a focused high-power density laser beam to cut materials. Moreover, laser cutting is a type of thermal cutting.

Why do you say that? Let us learn more about the principle of laser cutting.

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The laser cutting system uses a laser focusing system to focus high-energy laser light onto the surface of the material. The material absorbs the laser energy and causes it to be locally heated above the melting point.

At the same time, the coaxial high-pressure gas or the generated steam blows the molten metal away, creating cavities on the surface of the material. As the laser moves along the set program, the material is finally cut into the shape of the corresponding pattern.

Types of laser cutting

Generally speaking, laser cutting can be divided into four categories: laser gasification cutting, laser melting cutting, laser oxygen cutting and laser scribing and controlled fracture. The cutting power and power density of these four laser cutting methods are different, which makes them suitable for different scenarios.

01

Laser gasification cutting

The principle of this cutting method is to use a high-energy density laser beam to heat the material. When the temperature of the material rises rapidly to the boiling point, the material quickly vaporizes and produces vapor ejected and leaves a cut.

The heat of vaporization of materials is generally very large, so laser gasification cutting requires a lot of power and power density. Therefore, this cutting method is mostly used for cutting extremely thin metal materials and non-metal materials (such as paper, cloth, wood, etc.).

02

Laser melting and cutting

The principle of this cutting method is that the laser irradiation causes the material to melt, and the nozzle coaxial with the beam blows a large pressure of non-oxidizing gas (Ar, He, N2, etc.) to discharge the liquid metal to form an incision.

Laser melting cutting does not require complete gasification of the metal, and the energy required is only 1/10 of that of gasification cutting.

Therefore, this kind of cutting is mainly used for cutting some materials that are not easily oxidized or active metals, such as stainless steel, titanium, aluminum and other materials. Alloy etc.

03

Laser oxygen cutting

The principle of laser oxygen cutting is to use oxygen to cut the metal to generate an oxidation reaction and release a large amount of oxidation heat. At the same time, the material melted by the laser is blown out by the oxygen from the reaction zone to form an incision.

The oxidation reaction is an exothermic reaction, so that the energy required for this method is only 1/2 of the melting and cutting, but the cutting speed is faster than the gasification cutting and the melting cutting, so this cutting method is mainly used for some difficult-to-cut materials.

Such as carbon steel, titanium steel and heat-treated steel and other easily oxidized metal materials.

04

Laser scribing and controlled fracture

Laser scribing uses a high-energy density laser to scan the surface of the brittle material, so that the material is heated to evaporate a small groove, and then a certain pressure is applied, and the brittle material will crack along the small groove.

The lasers used for laser scribing are generally Q-switched lasers and CO2 lasers.

Controlled fracture is the use of the steep temperature distribution generated when the laser groove is carved, which generates local thermal stress in the brittle material, causing the material to break along the small groove.

Laser power of cutting machine

Common laser cutting machines are: fiber laser cutting machine and CO2 laser cutting machine. As the name suggests, the lasers used by the two are derived from fiber lasers and CO2 lasers.

At present, with its advantages of high output power and small spot size, fiber lasers have already occupied a market far beyond CO2 lasers and are still growing.

The content without data support is pale. Do you want to know how high the laser power is used for laser cutting?

Taking the optical power of 20kW as an example, if the fiber diameter is 200 microns and the numerical aperture is 0.22, the optical power density will be greater than 1000MW/Cm^2·str-1.

The optical power of the traditional teaching laser pointer is only 1-5mW, and the optical power density is also very small.

Not only such a laser pointer irradiates the human body, especially the eyes, but it can also cause great harm. So you must not let children play~~