What are the laser welding process requirements
Publish Time: 2016-11-23 Origin: Site
What are the laser welding process requirement, welding process requirement basically has the following three points:
Welding process requirement 1: optical power.Laser welding of a threshold, the laser energy density is lower than this value, the penetration is very shallow, once reach or exceed this value, the penetration will be greatly improved.Only when the laser power density exceeds the threshold on the workpiece (related to the material), plasma can produce, in a sign of deep penetration stability.Only if the laser power is lower than the threshold, the workpiece surface melting, which is welded with stable heat conduction model.And when the laser power density in a hole near the critical condition of formation, deep penetration and conduction welding alternates, become unstable welding process, depth of molten lead to more volatile.Deep penetration laser, laser power and control the penetration depth and welding speed.Welding penetration is directly related to beam power density, and is a function of incident beam power and the beam focal spot.In general, to a certain diameter of laser beam, beam power increase as the penetration increases.
Welding process requirement 2: focal spot.The beam spot size is one of the most important variables of laser welding, because it determines the power density.But for high power laser, its measurement is a problem, although there has been a lot of indirect measurement technology.
Can focus the diffraction light beam spot size limit according to the theory of light diffraction calculation, but because of poor focus through the mirror, the actual spot than the calculated value is larger.The most simple measurement method is the method of temperature profile, with thick paper burning and penetrates the polypropylene plate after focal spot and perforation diameter measurement.This approach is by measuring practice, grasp the size of the laser power and beam function of time.
Welding process requires 3: material absorption values.Material absorption of the laser depends upon some of the important performance, such as absorption, reflectance, thermal conductivity, melting temperature, evaporation temperature, etc., one of the most important is the absorption rate.
The absorptance of laser beam is influence material factors include two aspects: first is the resistance coefficient of the material, after the material absorption measurements found on the surface of the polishing material is directly proportional to the square root of the absorption rate and resistance coefficient, and resistance coefficient changes with the temperature;Second, the surface of the material status (or finish) has more important influence on beam absorption rate, which have obvious effects on welding effect.