真空钎焊对3003铝合金焊缝组织及腐蚀的影响

Effects of Vacuum Brazing on Microstructure and Corrosion of 3003 Aluminum Alloy Welding Seam

目的研究钎焊温度与保温时间对3003铝合金焊缝组织及腐蚀行为的影响,通过模型预测3003铝合金焊缝的腐蚀寿命。方法在模拟海洋大气环境下,采用盐雾腐蚀的方法,结合SEM和EDS观察焊缝微观形貌和元素分布情况,根据腐蚀质量损失和最大腐蚀深度分析焊缝的抗腐蚀性能,建立腐蚀动力学模型,参照户外暴露腐蚀数据计算得出腐蚀当量系数,预测腐蚀寿命。结果真空度3×10^(-3) Pa时,随钎焊温度升高和保温时间延长,焊缝区域Si的偏析减少,焊缝的抗腐蚀性能增强。在钎焊温度610℃保温75 min,焊缝组织最均匀,以Al、Si元素为主,含有少量的Mn和Mg,合金相主要为Al-Mn、Mg_2Si和Al_3Mg_2。腐蚀质量损失和腐蚀深度动力学方程分别为y_1=0.0642t^(0.897)和y_2=0.03t^(1.63),以LY12铝合金在海南琼海户外暴露腐蚀10年的数据为参照,得出焊缝腐蚀当量系数k=13.39,大气腐蚀10年的当量腐蚀深度为87.9μm。结论焊缝区域Si的偏析对腐蚀性能产生重要影响。较佳钎焊工艺为:真空度3×10^(-3) Pa,钎焊温度610℃,保温时间75 min。此时,大气腐蚀10年后的当量腐蚀深度占焊缝厚度100μm的87.9%,能够满足10年腐蚀寿命的要求。继续升高钎焊温度和延长保温时间,基体与焊缝界面发生熔蚀现象,抗腐蚀性能减弱。

The paper aims to study influences of brazing temperature and heat preservation time on the weld microstructure and corrosion behavior of 3003 aluminum alloy,and predict weld corrosion life of 3003 aluminum alloy througli model.In the simulated marine atmosphere,salt spray corrosion method was used to observe micro-morphology and element distribution of weld seam in combination with SEM and EDS.According to the corrosion weight loss and maximum pitting depth,the corrosion resistance of weld was analyzed.A corrosion dynamic model was established.The micro-morphology and element distribution of weld seam was calculated in reference of outdoor exposure corrosion data to predict the corrosion life.The results showed that when the vacuum degree was 3xl0-3 Pa,with the increase of brazing temperature and prolonging of holding time,the segregation of Si in weld zone was reduced,and the corrosion resistance of the weld was enhanced.Whenthe brazing temperature was kept at 610°C for 75 min,the weld microstructure was the most uniform,mainly composed of A1 and Si element,and contained a small amount Mn and Mg element.And the weld also contained Al-Mn,Mg2Si and Al3Mg2 alloy phases.The dynamic equations of the corrosion weight loss and the maximum pitting depth of the weld werey1=0.0642,0 897 andy2=0.03,163,respectively.Compared with the corrosion kinetics equation of LY12 aluminum alloy in Qionghai for exposure of 10 years,the corrosion equivalent coefficient was 13.39.The maximum corrosion equivalent depth was 87.9imin Qionghai for exposure of 10 years.The Si segregation in weld zone has important influences on the corrosion performance.The best brazing condition is that the brazing temperature is 610°C,and the holding time is 75 min.At this time,the corrosion equivalent depth of weld accounts for 87.9 percent of weld thickness 100\im after 100 years of atmospheric corrosion,which could meet the requirement of 10 years of corrosion life.When brazing temperature is increased and holding time is prolonged,corrosion occurs to the interface between the substrate and weld,and the corrosion resistance is weakened.