本文選題：收集極 + 焊接缺陷�。� 參考：《華南理工大學(xué)》2016年碩士論文

【摘要】：行波管作為一種用于放大信號功率的電真空器件,廣泛應(yīng)用于交通運輸、工程建設(shè)、野外檢測、手機通訊等領(lǐng)域。行波管在制造過程中需要使用大量異種金屬焊接工藝。由于行波管工作環(huán)境惡劣,焊接質(zhì)量欠佳的敏感結(jié)構(gòu)易導(dǎo)致行波管工作失效�，F(xiàn)今在行波管的生產(chǎn)過程中缺乏對其焊接缺陷的檢測與評價,故本文通過對行波管內(nèi)敏感焊接結(jié)構(gòu)進行理論分析,開展了焊接缺陷的無損檢測及評價技術(shù)研究,深入探討了焊接缺陷產(chǎn)生的原因及機理,并對其焊接工藝提出優(yōu)化方案。首先對行波管內(nèi)敏感焊接結(jié)構(gòu)及其焊接工藝進行理論分析,發(fā)現(xiàn)收集極焊接結(jié)構(gòu)內(nèi)焊接界面結(jié)合不良嚴重影響收集極散熱,最終導(dǎo)致收集極燒毀。根據(jù)收集極的焊接結(jié)構(gòu)特點開展超聲探傷、3D X-ray檢測技術(shù)研究,對焊接缺陷進行定性、定量分析,從而制定缺陷評定判據(jù),即從收集極底座底面或側(cè)面進行超聲檢測時,焊接界面回波波高分別超過屏幕范圍的35%或40%時便可判定此處存在缺陷。通過ANSYS Workbench仿真分析與試驗相結(jié)合的方式研究了焊接缺陷對收集極焊接結(jié)構(gòu)熱學(xué)性能的影響。焊接面積不足會導(dǎo)致收集極及焊錫層的溫度上升,焊接面積分布不均同樣會造成收集極溫度過高,而當(dāng)收集極與底座側(cè)面和底面均存在焊接接觸時收集極溫度最低。當(dāng)焊接接觸面積低于50%時,收集極和焊錫層的溫度會急劇上升,可能會造成焊錫層熔化流動,且焊接結(jié)構(gòu)的熱導(dǎo)率會大幅下降,從而阻礙收集極散熱。故提出收集極與底座至少要有50%以上的面積存在焊接接觸,且收集極與底座的側(cè)面和底面均應(yīng)有焊接接觸的焊接質(zhì)量要求。最后探討了收集極焊縫內(nèi)主要焊接缺陷產(chǎn)生的原因及機理,模擬仿真了現(xiàn)有焊接工藝下焊錫層的溫度變化及分布情況,并結(jié)合焊縫內(nèi)缺陷產(chǎn)生的原因,模擬計算了不同焊接工藝下焊錫層的溫度變化及分布情況,從而給出焊接溫度為270℃,焊接時間不少于320s的焊接工藝優(yōu)化建議。
[Abstract]:As an electric vacuum device for amplifying signal power, traveling wave tube (TWT) is widely used in transportation, engineering construction, field detection, mobile phone communication and so on. A large number of dissimilar metal welding processes are needed in the manufacture of TWT. Because of the poor working environment of TWT, the sensitive structure with poor welding quality can easily lead to TWT failure. At present, the inspection and evaluation of the welding defects of TWT are lacking in the production process. Therefore, through the theoretical analysis of the sensitive welding structure in the TWT, the nondestructive testing and evaluation technology of the welding defects are studied in this paper. The causes and mechanism of welding defects are discussed, and the optimization scheme of welding process is put forward. Firstly, the sensitive welding structure and its welding process in traveling wave tube are theoretically analyzed. It is found that the poor bonding between the welding interface in the collector welding structure seriously affects the heat dissipation of the collector, and finally leads to the burning of the collector. According to the characteristics of the welding structure of the collector, the ultrasonic flaw detection 3D X-ray detection technology is studied, and the qualitative and quantitative analysis of the welding defect is carried out, so as to establish the defect evaluation criterion, that is, when the bottom or side of the collecting pole base is tested by ultrasonic, If the echo height of the welding interface exceeds 35% or 40% of the screen range, the defect can be determined. The influence of welding defects on thermal properties of collector welding structure was studied by ANSYS Workbench simulation and test. The temperature of the collector and solder layer will rise when the welding area is insufficient, and the temperature of the collector will be too high due to the uneven distribution of the welding area, and the temperature of the collector will be the lowest when there is welding contact between the collector and the side and bottom of the base. When the welding contact area is below 50, the temperature of the collector and solder layer will rise sharply, which may lead to the melting flow of the solder layer, and the thermal conductivity of the welding structure will decrease significantly, thus hindering the collection pole heat dissipation. Therefore, it is suggested that at least 50% of the area between the collector and the base should have welding contact, and the welding quality requirement of welding contact should be required for the side and bottom of the collector and the base. Finally, the causes and mechanism of the main welding defects in the collector weld are discussed, and the temperature change and distribution of the solder layer under the existing welding process are simulated, and the causes of the defects in the weld are combined. The temperature variation and distribution of the solder layer under different welding processes are simulated and calculated, and the optimization suggestions for welding process with the welding temperature of 270 鈩，

本文編號：2054599