激光焊接原理及实践应用演示文稿.pptVIP

Interaction of a laser beam with any material often produces very high temperatures in a localized spot that can lead to vaporization of material. Often the fine particulates are toxic because of their fine particle size. Fumes from plastics can also be toxic. Even though Ti is welded in a glove box, it gives off fine vapors that condense are particles and are collected by the dust collector. If the dust collector is brought out of the glove box and exposed to air, the Ti particles can spontaneously catch fire. Laser light can interact with materials in three ways: it can be absorbed, reflected, or transmitted. Reflection and transmission are important properties for lenses and mirrors. For materials processing, we want the light to be absorbed as efficiently as possible. Depending on the type of material, there may be some component of reflection or transmission along with absorption of laser light. Most metals have high reflectivity for CO2 wavelength and are a bit better absorbers at YAG. Absorptivity for YAG can be guessed by the color of the metal. Dark grey metals such as steels are good absorbers while bright white metals such as Ag and Al are good reflectors. Copper is also a good reflector since red frequency is close to YAG wavelength of 1.064 micron. Absorption increases rapidly at UV wavelengths. Reflectivity increases rapidly with temperature especially once the metal melts. Absorptivity increases rapidly with temperature for all types of laser wavelengths including YAG and CO2. X-ray AnalysisX-RAY 分析 Cracks grow at an angle and appear as straight lines in the x-ray (shallow weld on right)[破裂在一个角中扩大,在X-RAY 中显示为一条直线 Small porosities may be difficult to see in such images在这样的图片中很难看到小孔. Check for alignment查看齐边. Weld Crack 焊接破裂 Shallow Weld 焊接阴影 Alignment 当前第62页\共有67页\编于星期三\6点 X-ray images of good weldsX-RAY 中好的焊接 当前第63页\共有67页\编于星期三\6点 Laser Maintenance雷射维护 Feedback monitor only checks laser cavity performance – does not check power at wel