本文選題：純鎳直縫焊管 + PAW焊接　； 參考：《蘭州理工大學(xué)》2017年碩士論文

【摘要】：鎳及鎳合金具有較高的強(qiáng)度、塑性以及可鍛性,在冷、熱狀態(tài)下均具有良好的機(jī)械加工性能,因此可以通過各種冷熱加工制成板材、箔材、線棒材以及管狀等各類產(chǎn)品。鎳及鎳合金管常應(yīng)用于制堿、氯堿化工、有機(jī)氯化物和食品加工等行業(yè),尤其在各種耐強(qiáng)堿的設(shè)備中的應(yīng)用廣泛。等離子弧焊(PAW)能量密度高、穿透力強(qiáng),能夠?qū)崿F(xiàn)板厚6mm以下鎳及鎳合金單面焊雙面成形,用于鎳及鎳合金管的焊接具有較大的優(yōu)勢;鎢極氬弧焊(TIG)可靠性高、易操作、電弧穩(wěn)定,具有良好的覆蓋能力,焊縫成形美觀,性能良好,在鎳及鎳合金的焊接方面也得到了大量應(yīng)用。本課題分別采用PAW焊以及PAW+TIG焊兩種不同的焊接方法,不添加填充材料,實(shí)現(xiàn)尺寸規(guī)格為Ф112mm×3.5mm×6500mm純鎳直縫焊管的焊接,對獲得的焊接接頭組織和性能進(jìn)行對比分析和研究。從純鎳直縫焊管接頭宏觀形貌分析可知,兩種焊接方法均能夠?qū)崿F(xiàn)板厚為3.5mm純鎳直縫焊管單面焊雙面成形,與此同時(shí),PAW+TIG焊能夠有效避免PAW焊接接頭咬邊、凹陷、氣孔等缺陷,獲得了成形均勻、美觀的魚鱗紋狀焊縫表面形貌;焊接接頭顯微組織觀察結(jié)果表明,純鎳母材為均勻細(xì)小的單相奧氏體等軸晶組織,平均晶粒尺寸為47.32μm,PAW焊接接頭熱影響區(qū)為等軸晶組織,平均晶粒尺寸為96.43μm,焊縫區(qū)域形成了柱狀晶組織,平均晶粒尺寸為463.57μm;PAW+TIG焊接接頭各區(qū)域由于受到TIG電弧的二次加熱作用,較PAW接頭組織出現(xiàn)長大現(xiàn)象,熱影響區(qū)為等軸晶組織,平均晶粒尺寸為103.75μm,焊縫區(qū)域形成了粗大的柱狀晶組織,平均晶粒尺寸為547.32μm;焊接接頭XRD物相分析表明,兩種焊接方法所獲得的焊縫中物相組成與母材相同,基體均為奧氏體組織;焊接接頭力學(xué)性能測試結(jié)果表明,PAW+TIG接頭抗拉強(qiáng)度達(dá)到母材的85.60%,沖擊功為母材的61.58%,較PAW接頭力學(xué)性能雖有所降低,但均能滿足鎳管接頭力學(xué)性能要求,均為韌性斷裂;采用盲孔法測量鎳管PAW焊接接頭以及PAW+TIG焊接接頭殘余應(yīng)力,結(jié)果表明:由于TIG電弧對焊接接頭的二次加熱作用對焊縫具有重熔和熱處理作用,與PAW焊相比較,PAW+TIG焊可以顯著降低鎳管焊縫的軸向殘余應(yīng)力σ_x以及周向殘余應(yīng)力σ_y。室溫浸泡試驗(yàn)與電化學(xué)試驗(yàn)結(jié)果均表明,純鎳母材、鎳管PAW焊縫以及鎳管PAW+TIG焊縫在不同腐蝕溶液中耐蝕性均呈現(xiàn)相同的變化趨勢,但耐蝕性由強(qiáng)到弱順序?yàn)?母材,PAW+TIG焊縫,PAW焊縫。綜合可見,PAW+TIG焊滿足了鎳管接頭力學(xué)性能要求的同時(shí),有效避免了接頭咬邊、氣孔等缺陷,獲得了成形均勻、美觀的魚鱗紋狀焊縫表面形貌,成材率高,生產(chǎn)成本低,顯著降低了鎳管焊接接頭的殘余應(yīng)力以及在腐蝕溶液中較PAW焊縫具有更好的耐蝕性,是純鎳N6直縫焊管焊接的理想方法。
[Abstract]:Nickel and nickel alloys have high strength, plasticity and forgability, and have good mechanical properties in cold and hot state, so they can be made into sheet, foil, wire bar and tube by various kinds of cold and hot processing. Nickel and nickel alloy tubes are widely used in alkali making, chlor-alkali chemical industry, organic chlorides and food processing, especially in various equipment with strong alkali resistance. Plasma arc welding (paw) has the advantages of high energy density and strong penetration, it can realize the forming of nickel and nickel alloy single side welding under plate thickness 6mm, and it has great advantages in the welding of nickel and nickel alloy tubes, and tungsten electrode argon arc welding (TIG) has high reliability and is easy to operate. The arc is stable, has good covering ability, the weld seam is beautiful, the performance is good, also has obtained the massive application in the nickel and the nickel alloy welding. In this paper, two different welding methods, PAW welding and PAW TIG welding, are used to realize the welding of 112mm 脳 3.5mm 脳 6500mm pure nickel straight seam welded pipe without adding filling material. The microstructure and properties of the welded joints obtained are compared and studied. From the macroscopic morphology analysis of straight welded pipe joints of pure nickel, it can be seen that both of the two welding methods can realize single side welding and double side forming of straight nickel straight welded pipe with plate thickness, and at the same time, it can effectively avoid defects such as edge bite, depression, porosity and so on. The microstructure of the welded joint shows that the pure nickel base metal is a uniform and fine single phase austenite equiaxed structure. The average grain size is 47.32 渭 m and the average grain size is 96.43 渭 m. The columnar grain structure is formed in the weld zone, and the average grain size is 463.57 渭 m. Compared with the PAW joints, the microstructure of the joints grew up, the HAZ was equiaxed crystal structure, the average grain size was 103.75 渭 m, and the coarse columnar grain structure was formed in the weld zone, the average grain size was 547.32 渭 m. The phase composition of the weld obtained by the two welding methods is the same as that of the base metal, and the matrix is austenitic structure. The test results of mechanical properties of welded joints show that the tensile strength of the welded joints reaches 85.60 of the base metal and the impact energy of the joints is 61.58, which is lower than that of the PAW joints, but all of them can meet the requirements of the mechanical properties of the nickel pipe joints and are all ductile fracture. The residual stresses of nickel tube PAW welded joints and PAW TIG welded joints were measured by blind hole method. The results show that the secondary heating of the welded joints by TIG arc has remelting and heat treatment effects on the weld. Compared with PAW welding, PAW TIG welding can significantly reduce the axial residual stress 蟽 x and circumferential residual stress 蟽 Y of nickel pipe weld. The results of immersion test at room temperature and electrochemical test showed that the corrosion resistance of pure nickel base metal, nickel tube PAW weld and nickel tube PAW TIG weld showed the same trend in different corrosion solutions. However, the order of corrosion resistance from strong to weak is as follows: the base metal is PAW TIG weld and PAW weld. Comprehensive visible PAW TIG welding can meet the requirements of mechanical properties of nickel pipe joints, effectively avoid defects such as edge cutting and porosity of joints, obtain uniform and beautiful surface morphology of fish-scale welds, high yield of finished materials and low production cost. The residual stress of the welded joint of nickel tube is significantly reduced and the corrosion resistance of the welded joint is better than that of PAW weld in corrosion solution. It is an ideal method for welding pure nickel N6 straight seam welded pipe.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG407

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本文編號：2085078