铝合金材料施焊的均匀性分析

铝合金材料施焊的均匀性分析铝是银白色的轻金属,具有良好的塑性、较高的导电性和导热性,同时还具有抗氧化和抗腐蚀的能力。铝极易氧化产生三氧化二铝薄膜,在焊缝中容易产生夹杂物,从而破坏金属的连续性,降低其机械性能和耐腐蚀性能。Aluminumisasilverywhitemetal,goodplasticity,highelectricalconductivityandthermalconductivity,butalsohastheabilityofoxidationresistanceandcorrosionresistance.Aluminumtoproduce3oxidation2aluminiumoxidethinfilm,pronetoinclusionsintheweld,whichdestroythecontinuityanduniformityofmetal,reduceitsmechanicalpropertiesandcorrosionresistance.2铝合金材料的焊接难点2weldingdifficultyofaluminiumalloymaterials://(1)极易氧化。在空气中,铝容易同氧化合,生成致密的三氧化二铝薄膜(厚度约0.1-0.2μm),熔点高(约2050℃),远远超过铝及铝合金的熔点(约600℃左右)。氧化铝的密度3.95-4.10g/cm3,约为铝的1.4倍,氧化铝薄膜的表面易吸附水分,焊接时,它阻碍基本金属的熔合,极易形成气孔、夹渣、未熔合等缺陷,引起焊缝性能下降。(1)easytooxidation.Easilywithoxygeninair,aluminum,generatedense3oxidation2aluminiumfilm(thicknessofabout0.1to0.2mum),highmeltingpoint(2050℃),wellabovethemeltingpointofaluminum,aluminumalloy(about600℃orso).Aluminadensityof3.954.10g/cm3,whichisabout1.4timesofaluminum,andaluminafilmonthesurfaceofeasyabsorptionmoisture,welding,it'sbasicwayofmetalfusion,easilyformingdefectssuchaspores,slaginclusion,incompletefusion,causetheweldperformancedegradation.(2)易产生气孔。铝和铝合金焊接时产生气孔的主要原因是氢,由于液态铝可溶解大量的氢,而固态铝几乎不://溶解氢,因此当熔池温度快速冷却与凝固时,氢来不及逸出,容易在焊缝中聚集形成气孔。氢气孔目前难于完全避免,氢的来源很多,有电弧焊气氛中的氢,铝板、焊丝表面吸附空气中的水分等。实践证明,即使氩气按gb/t4842标准要求,纯度达到99.99%以上,但当水分含量达到20ppm时,也会出现大量的致密气孔,当空气相对湿度超过80%时,焊缝就会明显出现气孔。(2)easytoproduceporosity.Aluminumandaluminumalloyweldingporosityisthemainreasonofthehydrogenareproducedwhen,becausealotofliquidaluminumcanbedissolvedhydrogen,hydrogenandalmostinsolublesolidaluminium,sowhenthetemperatureofthemoltenpoolisquicklycooledandsolidified,thehydrogendoesn'tescape,easyaggregationformationporosityintheweld.Hydrogenhydrogenholeisdifficulttocompletelyavoid,thesourceofmany,therearcweldingthehydrogenintheatmosphere,aluminumplate,wiresurfaceadsorptionofmoistureintheair.Practicehasprovedthateveniftheargongasaccordingtostandardgb/t4842requirements,thepurityof99.99%://(PPM),alsocanappearalargenumberofthedensityofthestomata,whentheairrelativehumidityover80%,porosityisapparentintheweldwillbe.(3)焊缝变形和形成裂纹倾向大。铝的线膨胀系数和结晶收缩率约比钢大两倍,易产生较大的焊接变形的内应力,对刚性较大的结构将促使热裂纹的产生。(3)thewelddeformationandcrackformationtendtobelarge.Linearexpansioncoefficientofaluminiumandcrystallizationshrinkagerateofabouttwotimesgreaterthansteel,easytoproducetheinternalstressoflargeweldingdeformation,structureofrigidlargerwillleadtohotcracks.(4)铝的导热系数大(纯铝0.538卡/cm.s.℃)。约为://钢的4倍,因此,焊接铝和铝合金时,比焊钢要消耗更多的热量。(4)thecoefficientofthermalconductivityofaluminumbig(0.538purealuminumcard/cm.S.℃).Isaboutfourtimesthatofsteel,therefore,whentheweldingaluminumandaluminumalloy,burnmorecaloriesthansteelwelding.(5)合金元素的蒸发的烧损。铝合金中含有低沸点的元素(如镁、锌、锰等),在高温电弧作用下,极易蒸发烧损,从而改变焊缝金属的化学成分,使焊缝性能下降。(5)theevaporationlossofalloyelements.Aluminumalloycontaininglowboilingpointelements(suchasmagnesium,zinc,manganese,etc.),undertheactionofarcinthehightemperature,extremelyeasyevaporationloss,soastochangethechemicalcompositionofweldmetal,maketheweldperformancedegradation.(6)高温强度和塑性低。高温时铝的强度和塑性很低,://破坏了焊缝金属的成形,有时还容易造成焊缝金属塌落和焊穿现象。(6)hightemperaturestrengthandlowplasticity.Hightemperatureisverylowwhenthestrengthofthealuminumandplastic,destroyedtheformingofweldmetal,sometimeseasytocauseweldmetalcaveandweldingwearphenomenon.(7)无色彩变化。铝及铝合金从固态转为液态时,无明显的颜色变化,使操作者难以掌握加热温度。(7)nocolorchange.Aluminiumandaluminiumalloyfromsolidtoliquid,noobviouscolorchange,maketheoperatorisdifficulttocontroltheheatingtemperature.://铝合金材料焊接的工艺方法3aluminummaterialweldingprocess(1)焊前准备(1)weldingpreparation采用化学或机械方法,严格清理焊缝坡口两侧的表面氧化膜。Usechemicalormechanicalmethod,thestrictcleaningweldgrooveonbothsidesofthesurfaceoxidefilm.://化学清洗是使用碱或酸清洗工件表面,该法既可去除氧化膜,还可除油污,具体工艺过程如下:体积分数为6%～10%的氢氧化钠溶液,在70℃左右浸泡0.5min→水洗→体积分数为15%的硝酸在常温下浸泡1min进行中和处理→水洗→温水洗→干燥。洗好后的铝合金表面为无光泽的银白色。Chemicalcleaningistheuseofalkalioracidwashsurfaceofworkpiece,themethodcanremovetheoxidefilm,stillcanbeinadditiontooil,specificprocessisasfollows:volumefractionis6%~10%sodiumhydroxidesolution,atabout70℃for0.5min-water-volumefractionof15%nitricacidfor1minatroomtemperatureandprocessing-watertowarmwatertowash,dry.Washthealuminumalloysurfaceofthemattesilver.机械清理可采用风动或电动铣刀,还可采用刮刀、锉刀等工具,对于较薄的氧化膜也可用0.25mm的铜丝刷打磨清除氧化膜。Mechanicalcleaningcanadoptpneumaticorelectric://