本文選題：冷金屬過渡焊（CMT）　切入點(diǎn)：不銹鋼薄板　出處：《吉林大學(xué)》2015年碩士論文

【摘要】：不銹鋼軌道客車車體搭接焊縫，采用電阻點(diǎn)焊工藝焊接，為了達(dá)到整個(gè)車體的密封性，還要對(duì)焊點(diǎn)間縫隙進(jìn)行密封處理。傳統(tǒng)工藝采用熔化極活性氣體保護(hù)焊（MetalActive-gas Arc Welding，簡(jiǎn)稱MAG焊）焊接這一縱縫，但焊縫存在過熱嚴(yán)重、焊接缺陷多需經(jīng)常補(bǔ)焊的問題。本文針對(duì)搭接焊縫焊接工藝上存在的問題，提出利用冷金屬過渡焊接技術(shù)（Cold Metal Transfer，簡(jiǎn)稱CMT）代替?zhèn)鹘y(tǒng)的MAG焊。CMT焊接技術(shù)是一種改進(jìn)型熔化極氣體保護(hù)焊，與傳統(tǒng)的熔化極氣體保護(hù)焊相比具有熱輸入低、無飛濺、強(qiáng)搭橋能力的特點(diǎn)。 本文以直徑Φ=1mmER308L不銹鋼焊絲為填充材料，以厚度1.5mm的A304奧氏體不銹鋼薄板作為母材，主要研究CMT焊不銹鋼薄板焊接參數(shù)優(yōu)化，通過光學(xué)顯微鏡、掃描電子顯微鏡（SEM）和萬能拉伸試驗(yàn)機(jī)對(duì)不銹鋼薄板CMT焊接接頭微觀組織和性能進(jìn)行了分析，并研究了焊接送絲速度、弧長(zhǎng)修正系數(shù)、焊接速度對(duì)不銹鋼薄板CMT焊接頭成型和組織影響。 不銹鋼薄板CMT焊縫連續(xù)平整，沒有明顯焊接缺陷，整個(gè)接頭的焊接變形較小。不銹鋼CMT焊縫接頭組織致密，焊縫區(qū)主要由黑色樹枝晶的鐵素體組織，和白色的奧氏體組織組成。熱影響區(qū)較窄，組織為粗大的奧氏體組織，有晶粒粗化現(xiàn)象。試驗(yàn)表明，CMT焊不銹鋼薄板搭接焊縫取得了較好的成型效果。接頭性能方面，不銹鋼CMT焊接接頭的顯微硬度分布不均勻，焊縫硬度低于母材硬度，而HAZ（Heat-affected Zone)硬度最低。拉伸試驗(yàn)結(jié)果說明，不銹鋼CMT焊接接頭的抗拉強(qiáng)度略低于母材的抗拉強(qiáng)度，接頭的斷裂模式主要為結(jié)合面斷裂。不銹鋼耐腐蝕實(shí)驗(yàn)的結(jié)果表明，不銹鋼CMT焊接接頭的腐蝕率大于母材。 隨著焊接送絲速度的增加，焊縫在宏觀形貌上焊道變得愈發(fā)寬大，焊縫周圍色差范圍愈大。焊縫的熔深、熔寬逐漸增大，深寬比有增加的趨勢(shì)。熱影響區(qū)范圍增大。隨著弧長(zhǎng)修正系數(shù)的增加，焊縫在宏觀形貌上焊道變得略微寬大，焊縫周圍色差范圍愈大。焊縫的熔深、熔寬逐漸增大，深寬比有增加的趨勢(shì)。熱影響區(qū)范圍增大。隨著焊接速度的增加，焊縫在宏觀形貌上焊道變的愈發(fā)細(xì)小，焊縫周圍色差范圍愈小。焊縫的熔深、熔寬逐漸減小，深寬比有減小的趨勢(shì)。熱影響區(qū)范圍增小。 不銹鋼CMT焊接接頭疲勞試驗(yàn)表明，疲勞斷口主要包括了裂紋源、裂紋擴(kuò)展區(qū)、瞬時(shí)斷裂區(qū)。裂紋擴(kuò)展區(qū)存在疲勞裂紋痕跡、瞬時(shí)斷裂區(qū)存在大量的韌窩。疲勞強(qiáng)度為315.84MPa，約為母材抗拉強(qiáng)度的50%左右。 冷金屬過渡焊接技術(shù)（CMT）代替?zhèn)鹘y(tǒng)MAG焊可以得到形貌和性能俱佳的不銹鋼薄板焊接接頭。通過大量試驗(yàn)工作，最終得到適用于本文工藝條件下不銹鋼薄板CMT焊接工藝的最優(yōu)參數(shù)：送絲速度為8m/min.、弧長(zhǎng)修正系數(shù)為5%、焊接速度為540mm/min.。
[Abstract]:In order to achieve the sealing of the whole car body, the welding seam of the car body of stainless steel rail car is welded by resistance spot welding. And seal the gap between the joints. The traditional process is to weld the longitudinal seam in MetalActive-gas Arc welding (MAG welding), but the weld is overheated. Welding defects often need to be repaired. This paper aims at the problems existing in the welding process of lap weld. In this paper, it is proposed that the cold metal transition welding technology (Metal) is an improved type of gas shielded gas welding, which has lower heat input and no spatter than the conventional cold metal transfer welding technology, instead of the traditional MAG welding .CMT welding technology is a kind of improved gas shielded welding. The characteristic of having a strong ability to bypass. In this paper, with diameter 桅 1 mm ER308L stainless steel wire as filler material, A304 austenitic stainless steel sheet with thickness 1.5mm as base material, the welding parameters optimization of CMT welding stainless steel sheet is studied, and the welding parameters of A304 austenitic stainless steel sheet with thickness 1.5mm are studied by optical microscope. Scanning electron microscope (SEM) and universal tensile tester were used to analyze the microstructure and properties of CMT welded joint of stainless steel sheet, and the wire feeding speed and arc length correction coefficient were studied. Effect of welding speed on forming and microstructure of CMT welded joint of stainless steel sheet. The CMT weld of stainless steel sheet is continuous leveling, without obvious welding defects, and the welding deformation of the whole joint is relatively small. The microstructure of the stainless steel CMT weld joint is compact, and the weld zone is mainly composed of ferrite with black dendrite. And white austenite structure. The heat affected zone is narrow, the microstructure is coarse austenitic structure, and there is grain coarsening. The test shows that the welding seam of stainless steel sheet welded by CMT welding has better forming effect. The distribution of microhardness of stainless steel CMT welded joint is uneven, the hardness of weld is lower than that of base metal, while the hardness of HAZ(Heat-affected Zone is the lowest. The tensile test results show that the tensile strength of stainless steel CMT welded joint is slightly lower than that of base metal. The corrosion resistance of stainless steel CMT welded joint is higher than that of base metal. With the increase of wire feeding speed, the weld seam becomes wider and wider in macroscopic morphology, and the wider the range of color difference around the weld is, the deeper the weld seam is, and the wider the weld width is. With the increase of the arc length correction coefficient, the weld seam becomes slightly wider in macroscopic morphology, and the wider the range of color difference around the weld, the deeper the weld, and the wider the weld width. The ratio of depth to width is increasing. The heat affected zone increases. With the increase of welding speed, the weld flux becomes smaller and smaller, and the range of color difference around the weld is smaller. The weld penetration depth and the weld width decrease gradually. The aspect ratio tends to decrease and the range of heat affected zone increases. The fatigue test of stainless steel CMT welded joint shows that the fatigue fracture surface mainly includes the crack source, crack propagation zone, instantaneous fracture zone, and the fatigue crack trace exists in the crack propagation zone. There are a lot of dimples in the instantaneous fracture zone, and the fatigue strength is 315.84 MPA, which is about 50% of the tensile strength of the base metal. Instead of conventional MAG welding, the cold metal transition welding technique can obtain stainless steel sheet welded joints with good morphology and properties. Finally, the optimal parameters for CMT welding of stainless steel sheet are obtained: wire feeding speed is 8 m / min., arc length correction coefficient is 5, welding speed is 540 mm / min.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG457.11

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