Laser classification and analysis of advantages and disadvantages

Laser classification

(1)C02 laser: Wavelength of C02 laser is 9~12um(typical wavelength is 10.6um). Due to its high efficiency, good beam quality, wide power range (tens of thousands of watts), continuous pulse and other advantages, it has become the most important and most widely used gas laser.Mainly used in material processing, scientific research, national defense testing and other aspects.Common forms are: sealed longitudinal electrically excited CARBON dioxide laser, TEA carbon dioxide laser, axial fast current high power carbon dioxide laser, cross current high power carbon dioxide laser.

(2) A semiconductor diode laser is a device excited by a certain amount of semiconductor material.Its working principle is that through certain incentives, the band gap of the semiconductor materials (conduction band and valence band), or a band of semiconductor materials and impurities (acceptor or donor) level, realize the balance of the vector population inversion, when in a state of population inversion of a large number of electrons and holes, radiation when the stimulated emission of radiation.The wavelength of light varies with the band gap.

(3)YAG laser: It can be divided into :ND-YAG crystal, CE-ND-YAG crystal, YB-YAG crystal, Ho-YAG crystal, er-YAG crystal.

1.Nd-yag laser: solid state laser, 1064nm, Nd- YAG laser crystal with the best comprehensive performance.The maximum output power of continuous laser is 1000W, which is widely used in military, industrial, medical and other industries.If continuous operation is adopted, the multi-mode output of 400W can be obtained by using the first order oscillation.If the laser output is at the 100-watt level, a single lamp can be used

2.Ce-n-yag laser: Ce-Nd-YAG crystal is formed by adding Ce ions on the basis of ND-AG crystal.Ce ion · Can produce good photon energy absorption in the ultraviolet spectrum region, and the energy is transferred to Nd ion in the way of non-radiation transition, thus improving the spectral utilization.Therefore, the efficiency is high, the threshold is low, the repetition frequency characteristic is good.

3.Yb-yag laser :Yb3+ doped into yAG matrix is a kind of laser crystal, which can produce 1.03um near-infrared laser.It and ND-YAG belong to the same matrix, but because of doping different, its growth process is also different.

4.Ho-yag laser: It can produce 2097nm and 2091nm lasers which are safe for human eyes.It is mainly suitable for optical communication, radar and medical applications.Ho-yag laser has strict requirements on cooling and drying, but water cooling is controlled below 10℃.The drying plant shall be free from steam.In the safe band range of human eyes, the possibility of accidental injury to human body, especially eyes, is greatly reduced due to the large water absorption capacity and extremely shallow penetration.

5.Er-yag laser: output wavelength is 2.9um and can be absorbed by water. It is mainly used in medicine.Because the crystal mainly absorbs visible and ULTRAVIOLET light, the material of the light cavity reflector is mostly aluminum and silver, which has a high reflectivity.At present, the maximum output power of the E-YAG laser is up to 3 watts, and the maximum pulse output is up to 51.It is the solid-state laser with the longest wavelength, highest output power and highest efficiency in the world.The absorption of 2940nm by human body is 10 times that of 10540nm, so laser surgery and vascular surgery have great application potential.

Advantages and disadvantages of laser

Advantages:

(1) Heat absorption can be reduced to the minimum amount required

(2) Single channel welding parameters of 32mm plate thickness have been verified, which can reduce the time needed for welding of thick plate and even save the use of solder metal;

(3) There is no need to use the electrode, and there is no need to worry about contamination or damage of the electrode.And since it is not a contact welding process, wear and deformation of the machine can be reduced to a minimum;

(4) Laser beam is easy to be focused, aligned and guided by optical instruments.It can be placed at an appropriate distance between the artifact and the bootstrap tool or between the artifact.Due to the above space limitations, other welding rules cannot be formulated;

(5) Workpiece can be placed in an enclosed space

(6) Laser beam can be focused on a very small area, and small parts with close spacing can be welded;

(7) Wide range of weldable materials, which can be used for bonding various heterogeneous materials;

Easy automatic high speed welding, digital or computer control

(9) When welding thin material or thin diameter wire, unlike arc welding, it is easy to have trouble of remelting;

(10) It is not affected by the magnetic field, and can accurately align the positive welding parts;

(11) Two metals with different physical properties (e.g. different resistances) can be welded;

(12) No vacuum or X-ray protection is required;

(13) Adopt perforated welding, the depth/width ratio of welding pass can reach 10:1;

(14) Device can be switched to transmit the laser beam to multiple workstations.

Disadvantages:

(1)Welding position should be very accurate and within the focus range of the laser beam;

(2) When the welding part needs to use the clamp, it must ensure that the final position of the welding part is in alignment with the welding spot impacted by the laser beam;

(3) Laser welding is not suitable for production line;

(4) Laser will change the weldability of materials with high reflectivity and high thermal conductivity, such as aluminum, copper and their alloys;

(5) In the process of medium and high energy laser beam welding, plasma controller is required to drive away the ionized gas around the weld pool to ensure the reappearance of weld;

(6) Energy conversion efficiency is too low, usually less than 10%;

(7)Weld solidifies rapidly, and there may be problems of porosity and embrittlement;