Factors Influencing Depth of Fusion for Laser Welding Machine

In modern manufacturing industry, fiber laser welding machine have replaced many of the traditional welding technologies with superior advantages which can be summed up by reduced costs, improved efficiency and higher quality welds. Today, let’s talk about some factors that can influence the depth of fusion when it comes to laser welding solutions.

1. Laser power density  

The premise of deep fusion welding is to focus the laser spot and make it have high enough power density, so the laser power density has a decisive effect on the forming of the weld linings. The laser power simultaneously controls both the penetration depth and the welding speed.  For the laser beam with a certain diameter, when the laser power is increased, the welding depth is deepened and the welding speed is accelerated.  

There is generally a critical value for the laser power reaching a certain welding penetration depth. When this critical value is reached, the weld pool boils violently, while it is exceeded, the penetration depth will decrease sharply.  In addition, due to the force of metal vapor, little holes will be formed in the weld pool, which are the key to the realization of deep fusion welding.

The focal spot power density is not only proportional to the laser power, but also related to the parameters of laser beam and focusing optical path.  

2. Welding speed  

In the process of deep fusion welding, the welding speed is inversely proportional to the penetration depth.  If the welding speed is increased and the laser power is kept constant, the heat input will decrease and so will the penetration depth.  Therefore, reducing the welding speed appropriately can increase the penetration depth, but if the speed is too low, excessive melting of the material will be caused, which leads to damage of  the workpiece.  Therefore, for specific laser power and material of specific thickness and type, a suitable range of welding speed should be considered to obtain the maximum penetration.  

3. Focus position  

In deep fusion welding, the focus position is critical to maintaining sufficient power density.  The change of the relative position between the focus and the surface of workpiece directly affects the width and depth of the weld. Only when the focus is located in the appropriate position on the surface can the welding line form a parallel section and obtain the maximum penetration depth.  

4, Interspace between workpieces

Interspace between workpieces is directly related to the depth of welding parts and the width of welding seam.  In the process of deep fusion welding, if the joint gap exceeds the spot size, it can not be welded.  If the interspace is too narrow, laser welding process will generate overlap or other adverse effects;  If the gap is too wide, the workpiece can be welded through easily.  Slow welding can make up for some weld defects caused by excessive interstice, while high speed welding applies to narrower gap and stricter requirements for qualification.  

5. Material nature  

The laser absorption of the workpiece material to be welded determines the efficiency of laser welding. There are two factors that affect the absorption rate of the material to the laser:  

1) Resistivity of materials: After measuring the absorption rate of polished surfaces of different materials, it is found that the absorption rate of materials to laser is proportional to the square root of the resistivity, and the resistivity changes with the temperature;  

2) the surface state of the material has a significant effect on the beam absorption rate, so it has a crucial effect on the welding effect.  

6. Protective gas  

The protective gas has two functions: 1) remove the air in the working area caused by welding and protect the working surface from being oxidized;  2) Restrain the plasma cloud generated during high power laser welding.

For further information on the fusion depth of our fiber laser welding machine for increased process control in all kinds of industries, refer to the additional applications insights on the website, or talk to our sales manager with your requirements by whats app or email.


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