本文選題：激光-MIG復(fù)合焊　切入點(diǎn)：304不銹鋼　出處：《江蘇科技大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：激光-MIG復(fù)合焊作為一種新型的焊接方法,把兩種熱源結(jié)合在一起,結(jié)合了各自的優(yōu)勢(shì),克服了各自的缺點(diǎn),具有焊接熔深大、焊接速度快、變形小、焊接間隙適應(yīng)性好等優(yōu)點(diǎn),是目前焊接研究的熱點(diǎn)。SUS304不銹鋼作為一種最常見的奧氏體不銹鋼,由于其具有良好抗腐蝕性能,在工業(yè)生產(chǎn)中被廣泛應(yīng)用。本文針對(duì)8mm的SUS304不銹鋼,采用激光-MIG復(fù)合焊的方法進(jìn)行焊接,研究復(fù)合焊過程中的熔滴過渡行為,闡明了激光與電弧的作用機(jī)理,并在此基礎(chǔ)上優(yōu)化了焊接工藝,對(duì)復(fù)合焊接頭的組織特征和力學(xué)性能進(jìn)行了測(cè)試分析。采用高速攝像技術(shù)對(duì)激光-MIG復(fù)合焊的熔滴過渡行為進(jìn)行拍攝觀察,研究激光了不同工藝參數(shù)對(duì)激光-MIG復(fù)合焊熔滴過渡形式、熔滴過渡頻率及熔滴尺寸的影響規(guī)律。激光-MIG復(fù)合焊由于激光的加入,使熔滴除了受到原有電弧焊所受到的力外,還受到金屬蒸汽的反作用力和激光與電弧之間產(chǎn)生的電磁力。在激光-MIG焊過程中,隨著激光功率的增大,熔滴的過渡方式由射滴過渡變?yōu)槎搪愤^渡,熔滴的尺寸逐漸變大,熔滴過渡頻率降低;隨著光絲間距的增加,熔滴過渡由短路過渡變?yōu)樯涞芜^渡,當(dāng)光絲間距為2mm時(shí),熔滴過渡最穩(wěn)定,當(dāng)光絲間距大于4mm時(shí),熔滴過渡不穩(wěn)定,且激光與MIG之間協(xié)同效應(yīng)變差,不能體現(xiàn)激光-MIG復(fù)合焊的優(yōu)勢(shì);在激光-MIG復(fù)合焊不銹鋼過程中,當(dāng)焊接電流小于200A時(shí),熔滴過渡為短路過渡,當(dāng)焊接電流在200A到225A時(shí)熔滴過渡為射滴過渡,當(dāng)焊接電流達(dá)到250A時(shí),熔滴過渡又變?yōu)槎搪愤^渡。但熔滴過渡頻率隨著焊接電流的增加,在不斷增大。通過平板堆焊工藝試驗(yàn)結(jié)果表明,激光-MIG復(fù)合焊過程中,激光與電弧存在最佳匹配關(guān)系。當(dāng)電流為200A時(shí),激光功率為3kW時(shí),激光與電弧的耦合效果最好,可以得到最佳的焊縫成型;電弧在前時(shí)的焊縫成型要比電弧在后的焊縫成型好。當(dāng)光絲間距為2mm時(shí),焊縫成型最好。激光-MIG復(fù)合焊8mm的SUS304不銹鋼的最佳工藝參數(shù)為:激光功率為5k W,焊接電流為220A,焊接速度為1.68m/min,采用電弧在前的方式,光絲間距DLA=2mm,離焦量?d=-5mm。該焊接工藝的間隙適用范圍為0~1mm。激光-MIG復(fù)合焊激光區(qū)的晶粒組織要比電弧區(qū)的細(xì)小,激光區(qū)產(chǎn)生了細(xì)小的等軸晶。復(fù)合焊的接頭抗拉強(qiáng)度達(dá)到了699MPa,與母材的強(qiáng)度相當(dāng)近,且接頭的塑性良好,延伸率為53.7%;激光自熔焊焊接頭抗拉強(qiáng)度為619MPa,接頭延伸率為32%。
[Abstract]:As a new welding method, laser-MIG composite welding combines two kinds of heat sources together, combines their advantages, overcomes their shortcomings, and has the advantages of high penetration, fast welding speed, small deformation, good adaptability of welding gap, etc. As one of the most common austenitic stainless steels, SUS304 stainless steel has been widely used in industrial production due to its good corrosion resistance. The laser MIG hybrid welding method is used to study the droplet transfer behavior in the process of composite welding. The mechanism of laser and arc interaction is clarified, and the welding process is optimized. The microstructure and mechanical properties of the composite welding joint were tested and analyzed. The droplet transfer behavior of laser MIG composite welding was observed by high speed camera technique. The effects of laser parameters on droplet transfer form, droplet transfer frequency and droplet size in laser-MIG composite welding were studied. During laser-MIG welding, with the increase of laser power, the transfer mode of the droplet changes from the transfer of the droplet to the short-circuit transition, and the size of the droplet becomes larger, as well as the reaction force of the metal vapor and the electromagnetic force between the laser and the arc. The droplet transfer frequency decreased with the increase of the optical fiber spacing, and the transfer of droplet changed from short circuit to emitter with the increase of optical fiber spacing. When the distance of optical wire was 2 mm, the transfer of droplet was most stable, and the transition of droplet was unstable when the distance of optical wire was more than 4 mm. The synergistic effect between laser and MIG has become worse, which can not reflect the advantage of laser-MIG composite welding, when the welding current is less than 200A, the transfer of droplet is short circuit transition in the process of laser MIG composite welding stainless steel. When the welding current is from 200A to 225A, the droplet transfer becomes a droplet transfer, and when the welding current reaches 250A, the droplet transfer becomes short circuit transfer, but the droplet transfer frequency increases with the welding current. The experimental results of plate surfacing welding show that there is an optimum matching relationship between laser and arc during laser MIG composite welding. When the current is 200A and laser power is 3kW, the coupling effect between laser and arc is the best. The best weld formation can be obtained; the welding seam at the front of the arc is better than the weld at the back of the arc. When the distance of the light wire is 2 mm, The best welding process parameters are: laser power 5kW, welding current 220A, welding speed 1.68m / min, arc in front, fiber spacing DLA2mm, defocus? The gap of this welding process is 0 ~ 1mm. the grain structure in laser zone is smaller than that in arc zone, and fine equiaxed crystal is produced in laser zone. The tensile strength of the joint of composite welding is 699MPa, which is very close to the strength of base metal. The ductility of the joint is good, the elongation is 53.7, and the tensile strength of the welded joint is 619 MPA and the elongation of the joint is 32 MPA.
【學(xué)位授予單位】：江蘇科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG457.11

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