【摘要】：熱絲TIG焊是應(yīng)用較為廣泛的高效焊接方法,S-06強度高、韌性好、耐腐蝕的特點,多應(yīng)用于航空航天領(lǐng)域。針對某發(fā)動機推力室外壁焊接工藝,本課題采用熱絲TIG焊技術(shù)對推力室外壁環(huán)焊縫進行焊接,分析各接頭焊縫組織、力學性能和斷口形貌,制定并優(yōu)化焊接工藝,結(jié)合溫度場分布的特點以及各焊接參數(shù)對溫度場的影響,共同指導實際構(gòu)件的焊接。首先進行平板堆焊試驗,對比熱絲TIG焊與常規(guī)冷絲TIG焊各接頭的焊縫成形,二者熔深、熔寬均隨焊接電流增加而增加,同時熱絲TIG焊的熔深更大。進一步通過工藝試驗確定熱絲電流對焊縫成形的影響,發(fā)現(xiàn)隨著熱絲電流增加,熔深、熔寬均隨之增加,并在達到一定程度之后熔深急劇增加。基于響應(yīng)曲面法設(shè)計試驗,建立焊接電流、熱絲電流和焊接速度與焊縫熔深、熔寬、深寬比之間的關(guān)系模型,分析了單因素和多因素交互作用下焊接參數(shù)對各響應(yīng)值的影響規(guī)律,發(fā)現(xiàn)較小的焊接電流、適中的熱絲電流以及焊接速度可以得到較小的熔深,能夠盡量減小焊接熱源產(chǎn)生的熱量在厚度方向上的傳遞。對優(yōu)化的工藝進行試驗驗證,證明了模型的適用性。然后分析熱絲TIG焊對接溫度場,根據(jù)構(gòu)件尺寸建立實體模型,選擇雙橢球熱源對試板的溫度場進行模擬,與實測的熱循環(huán)曲線吻合,驗證了模型的正確性,進一步模擬推力室的溫度場,明確焊接參數(shù)對焊接溫度場的影響規(guī)律,熱絲電流對焊接溫度場基本沒有影響,而增大焊接電流及降低焊接速度能夠增加焊縫附近各點的溫度峰值,通過對實際構(gòu)件溫度場的模擬,得到最大線能量的工藝參數(shù),并對焊接順序進行了優(yōu)化,發(fā)現(xiàn)對稱焊產(chǎn)生的變形低于順序焊,同時對比了水冷及風冷對焊接溫度場的影響,發(fā)現(xiàn)風冷具有取代水冷的可行性。最后對模擬得到的工藝參數(shù)進行優(yōu)化,并通過金相觀察、能譜分析等方法,系統(tǒng)研究了焊接接頭的組織,由于為了改善焊縫的塑性,減少缺陷,焊縫材料與母材的成份差異較大,母材為強度較高,韌性較差的馬氏體,熱影響區(qū)為回火屈氏體,而焊縫組織為塑性、韌性較為優(yōu)良的奧氏體組織,并在晶界處分布了鐵素體,防止了延遲裂紋的產(chǎn)生。通過拉伸試驗,發(fā)現(xiàn)焊接接頭的斷裂屬于塑性斷裂,斷口形貌主要為等軸韌窩,接頭強度達到1034MPa,強度系數(shù)為92.86%,滿足使用性能要求,硬度最高值處于熱影響區(qū)及打底焊縫,最低值出現(xiàn)在填充焊縫。
[Abstract]:Hot wire TIG welding is a widely used high efficiency welding method, which is characterized by high strength, good toughness and corrosion resistance. It is widely used in the field of aeronautics and astronautics. In view of the welding technology of thrust outdoor wall of an engine, the hot wire TIG welding technology is used to weld the circumferential weld of thrust outdoor wall. The weld microstructure, mechanical properties and fracture morphology of each joint are analyzed, and the welding process is established and optimized. Combined with the characteristics of temperature field distribution and the influence of welding parameters on temperature field, the welding of practical components is guided. The weld depth and width of hot wire TIG welding and conventional cold wire TIG welding are increased with the increase of welding current, and the penetration depth of hot wire TIG welding is greater than that of conventional cold wire TIG welding. The weld depth and width of each joint of hot wire TIG welding and conventional cold wire TIG welding are increased with the increase of welding current. Further, the influence of hot wire current on weld formation was determined by the process test. It was found that with the increase of hot wire current, the penetration depth and width increased, and the penetration increased sharply after reaching a certain degree. Based on the design experiment of response surface method, the relationship model between welding current, hot wire current and welding speed and weld penetration depth, width and aspect ratio is established. The influence of welding parameters on each response value under the interaction of single factor and multiple factors is analyzed. It is found that smaller welding current, moderate hot wire current and welding speed can get smaller penetration depth. It can minimize heat transfer from welding heat source in thickness direction. The model is proved to be applicable to the experimental verification of the optimized process. Then the temperature field of hot wire TIG welding butt joint is analyzed, and the solid model is established according to the component size, and the temperature field of the plate is simulated with double ellipsoid heat source, which is in agreement with the measured thermal cycle curve and verifies the correctness of the model. The temperature field of the thrust chamber is further simulated, and the influence of welding parameters on the welding temperature field is determined. The hot wire current has no effect on the welding temperature field. Increasing welding current and decreasing welding speed can increase the peak temperature of each point near the weld seam. By simulating the temperature field of the actual member, the process parameters of the maximum line energy are obtained, and the welding sequence is optimized. It is found that the deformation of symmetrical welding is lower than that of sequential welding, and the effects of water cooling and air cooling on welding temperature field are compared, and it is found that air cooling has the feasibility of replacing water cooling. Finally, the process parameters obtained from the simulation are optimized, and the microstructure of welded joints is systematically studied by means of metallographic observation, energy spectrum analysis, etc., because in order to improve the plasticity of the weld, the defects are reduced. The composition of weld material and base metal is quite different, the base metal is martensite with high strength and poor toughness, the heat-affected zone is tempering flexion, while the microstructure of weld is austenite with good ductility and ductility, and ferrite is distributed at grain boundary. The delay crack is prevented. Through tensile test, it is found that the fracture of welded joint belongs to plastic fracture, the fracture surface is mainly equiaxed dimple, the strength of the joint is 1034 MPA, and the strength coefficient is 92.86, which meets the requirements of performance, and the highest hardness is in the heat affected zone and bottom weld. The lowest value appears in the filler weld.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG444.74

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