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实验中选用的玻璃为20mm×20mm×4mm的普通钠钙玻璃,其主要成分见表 1。
Table 1. Chemical composition (mass fraction) of the common soda-lime glass
SiO2 CaO MgO Na2O Al2O3 0.67~0.74 0.05~0.11 0~0.04 0.10~0.17 0~0.03 实验中所用的焊料为PbO-TiO2-SiO2-RxOy系统封接焊料,焊料的主要成分见表 2。其制备工艺为:将99%纯度和平均粒度在30μm的PbO、TiO2按70:15的质量分数比均匀混合,然后向PbO/TiO2混合粉末中分别加入质量分数为0.10的纳米SiO2, 质量分数小于0.025的CuO和质量分数小于0.025的Fe2O3配合粉末(纯度不小于99.8%,平均粒度不大于50nm),将混合粉末放入球磨机中,加入一定的松油醇作为分散剂,采用湿法球磨混合处理。具体参量为:球料质量比10:1,转速250r/min,球磨4h,然后将其放入干燥箱中进行干燥处理,得到实验所需焊料。其粒度在1μm~25μm范围内,平均粒度为12.15μm。图 1a所示为实验中所用玻璃和焊料,图 1b为焊料扫描电镜(scanning electron microscope, SEM)图。
表 2 Chemical composition (mass fraction) of the sealing solder
PbO TiO2 SiO2 CuO Fe2O3 0.75 0.15 0.10 < 0.025 < 0.025 -
焊接前,先用砂纸研磨玻璃的待焊接表面,使焊接面平整并具有一定的粗糙度,然后放在丙酮溶液中超声波清洗15min,除去表面的油渍等污垢。实验时,在一片洗净的平板玻璃上以一定间距放置支撑柱,并在玻璃四周涂覆封接焊料,然后再放另一片玻璃板,将两片玻璃板压合后在C-MAGHP4型数显加热板上预热,预热温度为220℃,预热时间为10min,然后采用YLS-2000-CT型光纤激光器在真空环境下进行激光封接,光斑直径为0.5mm。试验中采用的激光工艺参量见表 3。激光输入能量是用激光能量密度去衡量的,数值计算公式为E=P/(Dv)[20],其中E为激光能量密度,P为激光功率,D为激光光斑直径,v为焊接速率。
Table 3. Laser process parameters
laswe power P/W welding speed v/(mm·s-1) defocused amount h/mm energy density E/(J·mm-2) 60 2 -2 60 70 2 -2 70 80 2 -2 80 90 2 -2 90 80 1 -2 160 80 3 -2 53 80 4 -2 40 焊后在试样的两片玻璃中部沿平行于焊接方向切取横向截面,经打磨、抛光后采用Zeiss_Supra55型场发射扫描电镜及其自带能谱仪(energy duspersive spectroscopy, EDS)进行封接层的微观形貌分析和能谱测试,采用D8-Advance多晶X射线衍射仪(X-ray diffractometer, XRD)对封接层进行物相分析,采用BX41M-LED型金相显微镜下观察气孔和分布特征。采用Image J软件对金相照片处理后测量计算气孔率、气孔数目及其直径尺寸d(见图 2),其中气孔率pr为气孔面积Ap与焊缝上表面面积Aw的百分比,即pr=Ap/Aw×100%。图 2中, d1和d2为过气孔圆心相互垂直的两条直径。
真空平板玻璃激光封接气孔控制研究
Study on pores control of vacuum plate glazing by laser sealing
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摘要: 为了探究激光焊接真空平板玻璃封接层气孔的产生机理,利用扫描电镜、自带能谱仪、X射线衍射仪和金相显微镜等手段,进行了真空平板玻璃激光侧边封接试验,研究了激光功率和焊接速率对封接层气孔的影响,分析气孔产生的原因。结果表明, 真空平板玻璃封接层出现了数量较多、大小不一、相互不连通的孤立气孔,位于颗粒的交界处,主要是由焊料颗粒间的残余空气引起的; 在焊接速率为2mm/s和离焦量为-2mm的条件下,过低或过高的激光功率都不利于减少封接层的气孔缺陷,激光功率为80W(能量密度为80J/mm2)时,封接层组织形貌好,封接层封接质量佳; 在激光功率为80W和离焦量为-2mm的条件下,较低的焊接速率将有利于减少封接层的气孔缺陷,焊接速率为1mm/s(能量密度为160J/mm2)时,封接层组织形貌好,封接层封接质量佳。此研究可为真空平板玻璃的激光封接制造提供理论依据。Abstract: In order to research the pores formation mechanism of sealing layer in laser welding of vacuum plate glazing, a laser sealing test was carried out. Scanning electron microscope, energy dispersive spectroscopy, X-ray diffractometer and metallographic microscope were used in this study. The influences of laser power and welding speed on pores of sealing layer were studied and the causes of pores were analyzed. The results show that, there are a large number of isolated pores in vacuum glazing sealing layer, which are different in size and disconnected with each other, located at the junction of particles, and mainly caused by the residual air between the solder particles. At the welding speed of 2mm/s and the defocus amount of -2mm, lower or higher laser power is not conducive to reduce the pore defects of sealing layer. When the laser power is 80W (energy density is 80J/mm2), the sealing layer has good morphology and good sealing quality. The lower welding speed will help to reduce the pore defects of sealing layer at the laser power of 80W and the defocus amount of -2mm. When the welding speed is 1mm/s (energy density is 160J/mm2), the sealing layer has good morphology and good sealing quality. This study can provide a theoretical basis for the laser sealing manufacturing of vacuum plate glazing.
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Key words:
- laser technique /
- laser welding /
- vacuum plate glazing /
- sealing layer /
- pore
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Figure 4. EDS spectrogram at point M1 in Fig. 3
Table 1. Chemical composition (mass fraction) of the common soda-lime glass
SiO2 CaO MgO Na2O Al2O3 0.67~0.74 0.05~0.11 0~0.04 0.10~0.17 0~0.03 表 2 Chemical composition (mass fraction) of the sealing solder
PbO TiO2 SiO2 CuO Fe2O3 0.75 0.15 0.10 < 0.025 < 0.025 Table 3. Laser process parameters
laswe power P/W welding speed v/(mm·s-1) defocused amount h/mm energy density E/(J·mm-2) 60 2 -2 60 70 2 -2 70 80 2 -2 80 90 2 -2 90 80 1 -2 160 80 3 -2 53 80 4 -2 40 -
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