资源描述：
《二氧化碳气体保护焊气孔问题》由会员上传分享，免费在线阅读，更多相关内容在工程资料-天天文库。
1、二氧化碳气体保护焊气孔问题PorosityofcarbondioxidegasshieldedarcweldingPorosityofcarbondioxidegasshieldedarcwelding1,C02gasshieldedweldingporosityismainlycausedbytheparentmaterialweldingsurfacecleanliness(oil,oxides)andsoon.2,andthepurityofthegas3,theremaybetoomuchwaterinthegas,lookatthepurityofyourgas4,itis
2、alsopossiblethattheCOstomataaremainlydenseandcolumnarThisisbecause,forC02gasshieldedweldingareafromtheairagainstthemostisaby-productofabreweryoralcoholplant,inevitablycontainsmoreorlesswaterorothersubstancescontaininghydrogen,argongasinthemixtureatthesametimealsooftencontainwater・Ifthetotalcont
3、entofmoistureinthegasandotherhydrogencontainingsubstancesexceedsacertainlimit,theoccurrenceofhydrogengasholesintheweldmetalwillbeinevitable・However,iftheprotectionofwaterinthegascontaininghydrogenandothersubstancescontentwascontrolledinacertainrangeaccordingtotherequirementsofrelevantstandards,
4、thenC02gasweldingandargonrichmixedgas(80%Ar+20%C02)weldingofwe1dmetalingeneraldoesnotproducealotofhydrogenporosity・ThisisbecausetheC02gasinthehightemperatureofarcdecompositionreaction(C02二CO+0),atomicoxygendecompositionhasstrongoxidation,[H_reactionandthegasphaseisnotsolubleinliquidmetalOH,whic
5、hcaneffectivelypreventthehydrogenporosityinweld・TheuseofpureC02gasprotectionwillproduceCOpores・Whencarbondioxidegasshieldedweldingoccurs,thefollowingreactionsoccur:FeC02FeOCOFeOC二FeCOThereactioniscarriedoutinsidethemoltenpool.Becausethesolubilityofmetalstocarbonmonoxideisverylow,carbonmonoxidei
6、sproducedfromthemoltenpool.Ifthemoltenmetalinthemoltenpoolisfinished,apartofthecarbonmonoxideisnotdischarged,andtheporesareformedintheweld.ThenthereisthedecompositionreactionofC02gasathightemperaturearcat3500:2C02二2C00202二20Thisreactionisendothermic,sothecoolingeffectofcarbondioxideflowismoreob
7、vious,sothatmoltenmetalcoolingisparticularlyfast,coupledwiththeweldformingnarrowanddeep,sothatthegasdischargeconditionsdeteriorate,soproduceporosity.Whenthecarbondioxidegaspurityisnotenough,becauseoflongtimeworkingtipandshroudwill
