Laser Welding Processes and Technologies
Nov 21,2025
1. Power Density. Power density is one of the most critical parameters in laser processing. Using higher power densities can heat the surface layer to its boiling point within microseconds, causing extensive vaporization. Therefore, high power density is advantageous for material removal processes such as drilling, cutting, and engraving. At lower power densities, the surface layer takes several milliseconds to reach boiling point. Before surface vaporization occurs, the underlying layer reaches its melting point, facilitating the formation of a sound fusion weld. Consequently, in conduction-type laser welding, power densities typically range from 10? to 10? W/cm?.
2. Laser pulse waveform. The laser pulse waveform is a critical factor in laser welding, particularly for thin-sheet welding. When a high-intensity laser beam strikes the material surface, 60–98% of the laser energy is reflected and lost, with reflectivity varying with surface temperature. During a single laser pulse, the reflectivity of the metal fluctuates significantly.
3. Laser pulse width. Pulse width is a critical parameter in pulsed laser welding. It distinguishes between material removal and melting processes while also determining the cost and size of processing equipment.
4. Effect of defocusing on weld quality. Laser welding typically requires some degree of defocusing because the excessively high power density at the laser focal spot center can cause vaporization and cratering. Power density distribution is relatively uniform across planes offset from the laser focal point. Two defocusing methods exist: positive and negative defocusing. Positive defocusing places the focal plane above the workpiece, while negative defocusing positions it below. According to geometric optics theory, when positive and negative defocusing are equal, the power density on the corresponding planes is nearly identical. However, the resulting melt pool shapes differ in practice. Negative defocusing yields greater penetration depth, which relates to the melt pool formation process. Experiments show that laser heating for 50–200 μs causes material melting, forming liquid metal and partial vaporization. This generates high-pressure vapor that ejects at extreme velocity, emitting brilliant white light. Simultaneously, the high vapor concentration propels the liquid metal toward the molten pool's periphery, creating a depression at its center. Under negative defocusing, the internal power density exceeds that at the surface, facilitating more intense melting and vaporization. This enables deeper penetration of light energy into the material. Therefore, in practical applications, negative defocusing is employed when greater penetration depth is required, while positive defocusing is preferred for welding thin materials.
PREVIOUS:
Contact Us
Address
No. 17 Donglin Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
E-mail：
Willa Wang：
Wechat：
图片alt标题设置： SUNHIGH WELDING
表单验证提示文本： Content cannot be empty!
循环体没有内容时： Sorry,no matching items were found.
CSS / JS 文件放置地