Shielding gases yog inert los yog semi-inert gasesuas feem ntau siv nyob rau hauv ntau txoj kev vuam, tshwj xeeb tshaj yoggas hlau arc vuamthiabGas tungsten arc vuam(GMAW thiab GTAW, ntau lub npe hu ua MIG thiab TIG, feem). Lawv lub hom phiaj yog los tiv thaiv thaj tsam weld los ntawmoxygen, thiabdej vapor. Nyob ntawm cov khoom siv welded, cov pa cua no tuaj yeem txo qhov zoo ntawm cov vuam lossis ua rau vuam nyuaj. Lwm cov txheej txheem arc vuam siv lwm txoj hauv kev los tiv thaiv cov vuam los ntawm qhov chaw ib yam nkaus -shielded hlau arc vuam, piv txwv li, siv ibelectrodenpog hauv afluxuas ua rau cov pa roj carbon dioxide thaum noj, ib qho roj semi-inert uas yog cov khoom siv tiv thaiv zoo rau vuam hlau.
Kev xaiv tsis raug ntawm cov roj welding tuaj yeem ua rau muaj qhov ntxeem tau thiab tsis muaj zog, lossis ua rau ntau dhau; tom kawg, thaum tsis cuam tshuam rau lub vuam nws tus kheej, ua rau poob ntawm cov khoom lag luam vim kev ua haujlwm xav tau los tshem tawm cov tee tawg.
Cov khoom tseem ceeb ntawm cov khoom siv tiv thaiv yog lawv cov thermal conductivity thiab cov khoom siv hluav taws xob hloov pauv, lawv qhov ntom ntom ntawm huab cua, thiab qhov yooj yim uas lawv tau txais ionization. Gases hnyav dua huab cua (xws li argon) pam lub vuam thiab yuav tsum tau qis qis dua li cov pa roj sib zog dua huab cua (xws li helium). Thaum tshav kub kub hloov yog ib qho tseem ceeb rau cua sov lub weld nyob ib ncig ntawm lub arc. Ionizability cuam tshuam qhov yooj yim ntawm arc pib, thiab yuav tsum muaj hluav taws xob siab npaum li cas. Shielding gases yuav siv tau ntshiab, los yog ua ib tug sib tov ntawm ob los yog peb gases.In laser welding, lub shielding roj muaj ib tug ntxiv luag hauj lwm, tiv thaiv tsim ntawm ib tug huab ntawm cov ntshav saum toj no lub weld, absorbing ib feem tseem ceeb ntawm lub laser zog. Qhov no yog qhov tseem ceeb rau CO2 lasers; Nd: YAG lasers qhia qis dua los tsim cov ntshav ntshav. Helium ua lub luag haujlwm no zoo tshaj plaws vim nws muaj peev xwm ionization siab; cov roj tuaj yeem nqus tau ntau lub zog ua ntej ua ionized.
Heliumyog sib dua li huab cua; yuav tsum muaj tus nqi ntws loj dua. Nws yog ib qho inert gas, tsis reacting nrog cov hlau molten. Nwsthermal conductivityyog siab. Nws tsis yog yooj yim rau ionize, yuav tsum tau muaj zog dua los pib lub arc. Vim muaj peev xwm ionization ntau dua nws ua rau kub kub ntawm qhov hluav taws xob ntau dua, muab cov hlaws tob tob; Qhov no yog qhov zoo rau aluminium, magnesium, thiab tooj liab alloys. Lwm cov pa roj ntau ntxiv. Kev sib xyaw ntawm helium nrog ntxiv ntawm 5-10% ntawm argon thiab 2-5% ntawm carbon dioxide ("tri-mix") tuaj yeem siv rau vuam ntawm cov hlau tsis muaj steel. Kuj tseem siv rau txhuas thiab lwm yam hlau uas tsis yog-ferrous, tshwj xeeb tshaj yog rau thicker welds. Hauv kev sib piv nrog argon, helium muab ntau lub zog-nplua nuj tab sis tsis ruaj khov arc. Helium thiab carbon dioxide yog thawj cov khoom siv tiv thaiv hluav taws xob siv, txij li thaum pib ntawm Kev Tsov Rog Thoob Ntiaj Teb thib 2. Helium yog siv los ua cov roj tiv thaiv hauvlaser vuamraucarbon dioxide lasers. Helium yog kim dua argon thiab xav tau cov nqi ntws ntau dua, yog li txawm tias nws qhov zoo nws yuav tsis yog qhov kev xaiv zoo rau cov khoom ntim ntau dua. Ntshiab helium tsis yog siv rau cov hlau, vim nws ces muab erratic arc thiab txhawb spatter.
Oxygenyog siv nyob rau hauv me me raws li ib tug ntxiv rau lwm yam gases; Feem ntau li 2-5% ntxiv rau argon. Nws txhim khu arc stability thiab txo covnto nrontawm cov hlau molten, ncentub dejntawm cov khoom hlau. Nws yog siv rau tshuaj tsuag hloov welding ntawm me mecarbon hlau, qis alloythiabstainless hlau. Nws lub xub ntiag nce tus nqi ntawm slag. Argon-oxygen (Ar-O2) blends feem ntau tau hloov nrog argon-carbon dioxide sawv daws yuav. Argon-carbon dioxide-oxygen blends kuj tseem siv tau. Cov pa ua rau oxidation ntawm vuam, yog li nws tsis haum rau vuam aluminium, magnesium, tooj liab, thiab qee cov hlau txawv. Cov pa oxygen ntau ntxiv ua rau cov roj shielding oxidize lub electrode, uas tuaj yeem ua rau porosity hauv qhov tso nyiaj yog tias cov electrode tsis muaj txaus.cov deoxidizers. Cov pa oxygen ntau dhau, tshwj xeeb tshaj yog thaum siv rau hauv daim ntawv thov uas nws tsis tau sau tseg, tuaj yeem ua raubrittlenessnyob rau hauv lub tshav kub cuam tshuam cheeb tsam. Argon-oxygen blends nrog 1-2% oxygen yog siv rau austenitic stainless hlau qhov twg argon-CO2 tsis tuaj yeem siv vim xav tau cov ntsiab lus ntawm cov pa roj carbon tsawg hauv cov vuam; lub weld muaj txheej tawv oxide thiab tej zaum yuav tsum tau ntxuav.
Hydrogenyog siv rau welding ntawm npib tsib xee thiab ib co stainless hlau, tshwj xeeb tshaj yog thicker pieces. Nws txhim kho cov molten hlau fluidity, thiab txhim khu kev huv ntawm qhov chaw. Txawm li cas los xij, nws tuaj yeem ua rauhydrogen embrittlementntawm ntau cov alloys thiab tshwj xeeb tshaj yog carbon steel, yog li nws daim ntawv thov feem ntau tsuas yog txwv rau qee cov hlau stainless. Nws yog ntxiv rau argon hauv cov nyiaj feem ntau qis dua 10%. Nws tuaj yeem muab ntxiv rau argon-carbon dioxide blends los tiv thaiv cov teebmeem oxidizing ntawm carbon dioxide. Nws qhov sib ntxiv ua rau cov arc thiab nce qhov kub ntawm arc, ua rau kom zoo dua weld nkag mus. Hauv cov ntsiab lus siab dua (txog 25% hydrogen), nws tuaj yeem siv rau vuam cov khoom siv xws li tooj liab. Txawm li cas los xij, nws yuav tsum tsis txhob siv cov hlau, txhuas lossis magnesium vim nws tuaj yeem ua rau porosity thiab hydrogen embrittlement.
Nitric oxideNtxiv ua hauj lwm pab kom txo zus tau tej covozone. Nws tuaj yeem ua kom ruaj khov ntawm qhov arc thaum vuam aluminium thiab high-alloyed stainless hlau.
Lwm cov pa roj tuaj yeem siv rau kev siv tshwj xeeb, ntshiab lossis ua cov khoom siv ntxiv; egsulfur hexafluoridelos yogCov tshuaj dichlorodifluoromethane.
Sulfur hexafluoridetuaj yeem muab ntxiv rau cov ntaub thaiv npog rau txhuas welding los khi hydrogen nyob rau hauv qhov chaw weld kom txo weld porosity.
Dichlorodifluoromethanenrog argon tuaj yeem siv rau kev tiv thaiv huab cua rau melting ntawm aluminium-lithium alloys. Nws txo cov ntsiab lus ntawm hydrogen nyob rau hauv aluminium weld, tiv thaiv cov porosity txuam.
