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Heat transfer welding laser beam power density is less than 10 W / cm, the laser metal surface heated to the melting point and boiling point, welding, metal surface will absorb the laser energy into heat energy, so that the metal surface temperature l high melting, heat transfer by thermal conduction to the metal interior, so that the melted zone gradually expanded and solidified to form the solder joints or welds, the penetration depth contour approximately hemispherical. The welding mechanism called the heat transfer welding, which is similar to the TIG arc welding process, as shown in Figure 1 (a). The main features of the heat transfer welding is the power density of the laser spot, much of the light metal surface reflection, light absorption is low, weld penetration depth. cheap Laser Pointers can be used in many locations by the customer.
Slow welding speed is mainly used for thin (thickness <1 mm), small parts of the welding process 527 Harbin Institute of Technology 2, deep penetration when the power density on the laser spot is large enough (≥ 106W/cm2), the metal in the laser irradiation is rapidly heated, the surface temperature within a very short time (10 to 10 s) rise to the boiling point, the metal melting and gasification. Gasification when the metal, the resulting metal vapor to leave the bath to a certain speed, the escape of the metal vapor to produce an additional pressure on the molten liquid metal (for example, aluminum, p ≈ 11MPa; for steel, p ≈ 5MPa) bath metal surface down to depression, the laser spot to produce a small pit [Figure 1 (b)]. The long life time of green laser 5mw is another concern for the customer.
Pits to further deepen the liquid metal when the metal vapor beam in the holes at the bottom of to continue heating the gasification on the one hand the oppression Bottom, on the other hand, steam flying out to the pit outside the molten metal is pressed against bath four weeks. This process continues, will form an elongated holes in the liquid metal. When the beam energy produced by metal vapor recoil pressure of the liquid metal surface tension and gravity balance, the holes are no longer continue to deepen, the formation of a stable depth of hole and welding, so called laser deep penetration [Figure 1 (b)]. If the laser power is large enough and the material is relatively thin, laser welding of the hole throughout the plate thickness and can receive the back part of the laser. The sampling inspection will be performed for green laser 5mw.
This welding method can also be called to effect welding of sheet metal laser holes. From the mechanism point of view, there are holes in the premise of the effect of welding of deep penetration and holes are welding process, the difference was not essentially different. The conditions of energy balance and the balance of material flows can be generated when the holes are stable phenomenon. As long as the beam is sufficiently high power density, small holes can always be formed. The holes are filled with weld metal under continuous irradiation of the laser beam generated by the metal vapor and plasma (Figure 2). This has a certain pressure of the plasma to the workpiece surface space eruption, the formation of a range of plasma cloud above the hole. The inspection of green laser 5mw should be implemented step by step.
Holes around the bath surrounded the outside of the molten metal is not molten metal and part of the solidification of metal, gravity and surface tension of the molten metal to make holes to bridge the trend, the continuous generation of metal vapor is trying to maintain a small hole exist. Beam incident substance continuous escape hole with the movement of the beam, the holes with the beam movement, but its shape and size is stable. -8-6 As a heat source with a laser beam welding method. Welding, laser beam of the laser emission, high power density (108 to 1012 watts / cm 2) poly shrunk a focused laser beam to bombard the surface, resulting in heat, melt the workpiece (see Figure laser welding schematic). Correspondingly, the necessary actions and measurements of green laser 5mw should be taken.