摘要
为降低高压压铸Al-Si合金激光焊缝气孔率,系统研究了调制激光频率对焊缝气孔分布特征的影响规律。研究结果表明,相比于连续激光(CW),采用调制激光(QCW)可有效缩短匙孔存在时间,并扩大熔池与匙孔尺寸,增强Marangoni对流,匙孔型气孔和氢气孔均得到一定的抑制。但降低或提高调制激光频率会降低匙孔稳定性并提高氢气泡的逸出难度,因此,随着调制激光频率的提高或降低,焊缝中匙孔型气孔和氢气孔的抑制效果均有所降低。当调制频率为10 Hz时,匙孔型气孔和氢气孔率分别为4.7%和1.2%,相比于连续激光焊缝(8.8%和2.0%)均降低了40%以上。因为气孔率降低,所以焊接接头抗拉强度由168 MPa提高至187 MPa,断后伸长率由3.0%提高至4.5%。
Objective With the industrial application of ultralargescale diecasting machines,AlSi alloys have been used to produce battery shells in new energy vehicles because of their excellent diecasting properties.Fusion welding is widely used for connecting components.However,an obvious welding distortion is observed when employing the traditional arc welding process.Owing to its high energy density,the laser welding process has been shown to suppress the welding distortion of aluminum alloy welded joints.In contrast to deformed aluminum alloys,the high hydrogen content of highpressure diecasting AlSi alloy causes its arc welds to have a high hydrogen porosity tendency;thus,there are no effective methods to produce a weld seam with low porosity.In laser welds,keyholeinduced porosity is caused by keyhole instability.In addition,the extremely small size and short residence time of the molten pool inhibit the escape of bubbles.Consequently,the porosity tendency may be enhanced by the laser welding process.Thus,it is necessary to develop a new method to suppress the porosity of highpressure diecasting AlSi alloy laser welds.Methods As mentioned in certain studies,a pulsedlaser welding process with intermittent emission features can effectively shake a molten pool,which has also been proven to promote the escape of bubbles.Consequently,the porosity of the AlMgSi alloy welds decreases owing to the pulsed laser welding process.The intermittent emission feature enables the pulsed laser welding process to offer certain advantages in the regulation of the porosity of Al alloy laser welds.In recent years,quasicontinuous(QCW)lasers developed based on continuous(CW)lasers have achieved intermittent light output.Thus,the porosity suppression mechanism of the QCW laser must be analyzed and its effect on the porosity and mechanical properties of highpressure diecasting AlSi alloy laser welds must be appropriately elucidated.Results and Discussions Highpressure diecasting AlSi alloys were welded using CW and QCW lasers with different frequencies.The distribution characteristics of the porosities in the laser welds were analyzed using a stereomicroscope and ImagePro Pulse software.In addition,a highspeed image V4.1 system,which can synchronously record the morphologies of the molten pool and keyhole using a highspeed camera system,was used.Compared to the CW laser,the QCW laser reduces the keyhole duration(Figs.1 and 6)and increases the molten pool and keyhole(Fig.6).Further,it enhances the Marangoni convection.Consequently,the keyholeinduced hydrogen pore formation is suppressed(Fig.3).However,a lowstability keyhole and high bubble escape resistance are obtained by increasing the QCW laser frequency(Fig.5).At a frequency of 10 Hz,the keyholeinduced and hydrogen porosities are 4.7%and 1.2%(Fig.4),respectively.Compared with the CW laser welds(8.8%and 2.0%),the porosity is reduced by more than 40%.Consequently,the tensile strength and elongation increase to 187 MPa and 4.5%,respectively,thereby providing a new laser process for quality welding of highpressure diecasting AlSi alloys.Conclusions Compared with the CW welding process,the higher peak laser power of the QCW welding process can enlarge the keyhole and promote its stability.Furthermore,because the high temperature gradient at the alternation of troughs and peaks can increase the Marangoni force,which enhances the molten pool flow,the possibility of bubble escape increases significantly.At a frequency of 10 Hz,the keyholeinduced and hydrogen porosities of the QCW weld seam are less than 60%of those of the CW weld seam.The tensile strength and elongation increases to 187 MPa and 4.5%,respectively,which indicate improvement of 11.3%and 50.0%compared to those of the CW weld seam,respectively.
作者
陈夏明
张禄中
秦坤伦
宋佳
王晓南
长海博文
Chen Xiaming;Zhang Luzhong;Qin Kunlun;Song Jia;Wang Xiaonan;Nagaumi Hiromi(Weiqiao Lightweight Research Center at Soochow,Suzhou 215001,Jiangsu,China;School of Iron and Steel,Soochow University,Suzhou 215021,Jiangsu,China)
出处
《中国激光》
北大核心
2025年第8期103-110,共8页
Chinese Journal of Lasers
基金
外国资深学者研究基金(52150710544)
山东省重点研发计划(2021SFGC1001)
魏桥轻量化基地重大科研项目(BZYJY-QLHDY-2021-004)。
关键词
调制激光
频率
激光焊接
AL-SI合金
气孔率
力学性能
quasicontinuous laser
frequency
laser welding
AlSi Alloys
porosity
mechanical property
