The Positive and Negative Effects and Adjustment of Laser Welding defocus

The positive and negative effects of laser welding defocus amount affect the welding effect, with positive defocus increasing the depth of fusion and negative defocus decreasing the depth of fusion. Adjusting the defocus amount requires consideration of materials, thickness, and welding requirements to ensure welding quality.

In the field of laser welding, defocus is a crucial parameter. It refers to the distance between the laser focus and the surface of the workpiece, which directly affects the energy distribution and welding quality during the welding process. So, what impact does the positive or negative defocus of laser welding have on the welding effect? How can we adjust the defocus amount to optimize the welding effect?

The influence of positive and negative defocus on welding effect
1. Positive defocusing (with the focus located above the surface of the workpiece)
When defocusing, the laser energy forms a larger spot on the surface of the workpiece, dispersing the energy received by the welding area. However, the energy acting inside the material increases, which is beneficial for increasing the penetration depth. This welding method is suitable for scenarios where high penetration depth is required but low weld width is not. However, excessive positive defocusing may lead to defects such as porosity and lack of fusion during the welding process.

2. Negative defocus (the focus is located below the surface of the workpiece)
When defocused negatively, the laser energy forms a smaller spot on the surface of the workpiece, concentrating the energy on the welding area, but reducing the energy acting inside the material, which is beneficial for reducing the depth of fusion. This welding method is suitable for scenarios where the width of the weld seam is high but the depth of penetration is not. However, a too small negative defocus amount may lead to issues such as burn through and excessive heat affected zone during the welding process.

How to adjust the defocus amount to optimize the welding effect
1. Adjust the defocus amount according to the material characteristics
The physical properties such as thermal conductivity and melting point of different materials are different, so the defocus amount needs to be adjusted according to the characteristics of the materials. For example, for materials with high thermal conductivity, it is necessary to reduce the defocus amount appropriately to improve the energy density of the welding area; For materials with lower melting points, it is necessary to increase the defocus amount appropriately to avoid problems such as burning through during the welding process.

2. Adjust the defocus amount according to the thickness of the workpiece
The thickness of the workpiece has a direct impact on the energy requirements of laser welding. Generally speaking, thinner workpieces require a smaller defocus amount in order to better control the width and depth of the weld seam; Thicker workpieces require a larger defocus amount to ensure sufficient energy penetrates the workpiece and forms an effective weld seam.

3. Adjust the defocus amount according to the welding requirements
In practical applications, welding requirements often vary depending on the application scenario. For example, for welding scenarios that require high penetration depth, the positive defocus amount can be appropriately increased; For scenarios that require narrow welds, it is necessary to reduce the negative defocus appropriately. Therefore, when adjusting the defocus amount, it is necessary to fully consider the welding requirements and ensure that the welding quality meets the requirements.

In summary, the positive and negative defocusing of laser welding have a significant impact on the welding effect. In practical applications, it is necessary to adjust the defocus amount based on material characteristics, workpiece thickness, and welding requirements to optimize the welding effect. At the same time, it is also important to avoid welding defects caused by excessive or insufficient defocus.