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大功率CO2 混合模激光束在传输过程中 ,其光束横截面能量不再是高斯分布 ,是受附加相移的影响 ,在不同的传输距离 ,横截面能量分布呈规则变化。对于聚焦激光束 ,在焦点附近 ,由于横截面能量分布的不相同 ,传统的关于负离焦的焊接质量比正离焦好的观点将不再适用。而且在不同的加工位置 ,聚焦激光束的横截面能量分布也不相同 ,必然其加工质量也不相同 ,这样对于同一激光束 ,虽然其光束质量是一定的 ,但并不能获得相同的加工质量 ,因此采用光束质量来衡量激光焊接能力还不够充分 ,还应看光束横截面能量分布的精细结构。对于本文所研究的一种激光束 ,其模式含量TEM0 0约为 2 0 % ,TEM0 2约为 80 % ,在不同加工位置的聚焦光束的横截面能量分布将呈现“凹”形和“山”形两类 ,这两种横截面能量分布的焦斑对焊缝成形的影响是不相同的。试验研究表明 ,“凹”形焦斑焊接质量较差 ,而“山”形的焊接质量较好。
During the transmission of the high-power CO2 mixed-mode laser beam, the beam cross-section energy is no longer a Gaussian distribution, and is affected by the additional phase shift. The energy distribution of the cross-section changes regularly with different transmission distances. For focused laser beams, near the focal point, the conventional view that the quality of welds with respect to negative defocus is better than positive defocus will no longer apply because of the different cross-sectional energy distribution. Moreover, the energy distribution of the cross-section of the focused laser beam is also different at different processing positions, so the processing quality is inevitably different. Therefore, although the beam quality of the same laser beam is constant, the same processing quality can not be obtained, Therefore, the use of beam quality to measure the laser welding capacity is not sufficient, but also look at the beam cross-section energy distribution of the fine structure. For a laser beam studied in this paper, its mode content is about 20% at TEM0 0 and about 80% at TEM0 2. The cross-sectional energy distribution of the focused beam at different processing positions will show “concave” shape and “mountain” Shaped two types, the two cross-sectional energy distribution of the focal spot on the weld forming is not the same. Experimental studies have shown that “concave” focal spot welding quality is poor, while “mountain” shape welding quality is better.