Walda bakin karfe yana buƙatar zaɓar iskar gas mai kariya don kiyaye tsarin ƙarfe da kuma halayensa na zahiri da na inji. Abubuwan gas masu kariya na gama gari don bakin karfe sun haɗa da argon, helium, oxygen, carbon dioxide, nitrogen, da hydrogen (duba Hoto na 1). Waɗannan iskar gas an haɗa su a cikin rabo daban-daban don dacewa da buƙatun nau'ikan isarwa daban-daban, nau'ikan waya, ƙarfe mai tushe, bayanin bead da ake so da saurin tafiya.
Saboda rashin kyawun yanayin zafi na bakin ƙarfe da kuma yanayin "sanyi" na walda ƙarfe mai canza iskar gas (GMAW), tsarin yana buƙatar iskar "tri-mix" wadda ta ƙunshi kashi 85% zuwa 90% na helium (He), har zuwa kashi 10% na Argon (Ar) da kashi 2% zuwa 5% na Carbon Dioxide (CO2). Haɗin triblend na yau da kullun ya ƙunshi kashi 90% na He, 7-1/2% na Ar, da kuma kashi 2-1/2% na CO2. Babban ƙarfin ionization na helium yana haɓaka arcing bayan ɗan gajeren da'ira; tare da babban ƙarfin thermal ɗinsa, amfani da He yana ƙara yawan ruwan da ke cikin tafkin da aka narke. Sashen Ar na Trimix yana ba da kariya ta gaba ɗaya na kududdufin walda, yayin da CO2 ke aiki azaman sashi mai amsawa don daidaita baka (duba Hoto na 2 don yadda iskar kariya daban-daban ke shafar bayanin bead ɗin walda).
Wasu gauraye na zamani na iya amfani da iskar oxygen a matsayin mai daidaita yanayi, yayin da wasu kuma ke amfani da gaurayen He/CO2/N2 don cimma irin wannan tasirin. Wasu masu rarraba gas suna da gaurayen iskar gas na musamman waɗanda ke ba da fa'idodin da aka yi alkawari. Dillalai kuma suna ba da shawarar waɗannan gaurayen don wasu hanyoyin watsawa masu irin wannan tasirin.
Babban kuskuren da masana'antun ke yi shine ƙoƙarin rage ƙarfin ƙarfe mai ƙarfe GMAW tare da cakuda gas iri ɗaya (75 Ar/25 CO2) kamar ƙarfe mai laushi, yawanci saboda ba sa son sarrafa ƙarin silinda. Wannan cakuda ya ƙunshi carbon da yawa. A gaskiya ma, duk wani iskar gas mai kariya da ake amfani da ita don waya mai ƙarfi ya kamata ya ƙunshi matsakaicin 5% na carbon dioxide. Amfani da adadi mai yawa yana haifar da ƙarfe wanda ba a sake ɗaukarsa a matsayin ƙarfe mai daraja na L ba (L-grade yana da abun ciki na carbon ƙasa da 0.03%). Yawan carbon a cikin iskar gas mai kariya zai iya samar da chromium carbide, wanda ke rage juriya ga tsatsa da halayen injiniya. Hakanan zaka iya bayyana akan saman walda.
A gefe guda, lokacin zabar ƙarfe don rage GMAW don ƙarfen tushe na jerin 300 (308, 309, 316, 347), masana'antun ya kamata su zaɓi matakin LSi. Fillers na LSi suna da ƙarancin sinadarin carbon (0.02%) kuma saboda haka ana ba da shawarar musamman lokacin da akwai haɗarin tsatsa tsakanin granular. Babban sinadarin silicon yana inganta halayen walda, kamar jika, don taimakawa wajen daidaita kambin walda da haɓaka haɗuwa a yatsan.
Ya kamata masana'antun su yi taka tsantsan lokacin amfani da hanyoyin canja wurin gajerun hanyoyin sadarwa. Rashin cikawa na iya faruwa saboda kashe wutar lantarki, wanda hakan ke sa tsarin ya zama ƙasa da yadda ake amfani da shi a aikace-aikace masu mahimmanci. A cikin yanayi mai girma, idan kayan zai iya tallafawa shigar zafi (≥ inci 1/16 shine kusan siraran kayan da aka haɗa ta amfani da yanayin feshin bugun jini), canja wurin feshin bugun jini zai zama mafi kyawun zaɓi. Inda kauri kayan da wurin walda ke tallafawa shi, ana fifita canja wurin feshin GMAW saboda yana samar da haɗin gwiwa mai daidaito.
Waɗannan yanayin canja wurin zafi mai zafi ba sa buƙatar iskar gas mai kariya. Don walda mai feshi na ƙarfe masu jerin 300, zaɓi na gama gari shine 98% Ar da 2% abubuwan amsawa kamar CO2 ko O2. Wasu gaurayawan iskar gas na iya ƙunsar ƙananan adadin N2.N2 yana da ƙarfin ionization mafi girma da kuma ƙarfin thermal, wanda ke haɓaka jikewa kuma yana ba da damar tafiya cikin sauri ko ingantaccen iska; yana kuma rage karkacewa.
Don canja wurin feshi na pulsed GMAW, 100% Ar na iya zama zaɓi mai karɓuwa. Saboda wutar lantarki mai pulsed tana daidaita baka, iskar gas ba koyaushe take buƙatar abubuwan aiki ba.
Wurin narkewar yana da jinkiri ga ƙarfe mai laushi da ƙarfe mai laushi (rabo 50/50 na ferrite zuwa austenite). Ga waɗannan ƙarfe masu laushi, cakuda mai kamar ~70% Ar/~30% He/2% CO2 zai inganta jikewa mai kyau da kuma ƙara saurin tafiya (duba Hoto na 3). Ana iya amfani da irin wannan cakuda don walda ƙarfe mai laushi, amma zai sa nickel oxides su samar a saman walda (misali, ƙara 2% CO2 ko O2 ya isa ya ƙara yawan sinadarin oxide, don haka masana'antun ya kamata su guji su ko kuma su shirya su ɓata lokaci mai tsawo a kansu). Yana da laushi saboda waɗannan oxides suna da tauri sosai har goga mai waya ba zai cire su ba).
Masana'antun suna amfani da wayoyi masu bakin ƙarfe masu flux-core don walda a waje saboda tsarin slag a cikin waɗannan wayoyi yana ba da "shiryayye" wanda ke tallafawa wurin walda yayin da yake tauri. Saboda tsarin flux yana rage tasirin CO2, an tsara wayar bakin ƙarfe mai flux-core don amfani da 75% Ar/25% CO2 da/ko 100% CO2 gaurayawan iskar gas. Duk da cewa wayar mai flux-core na iya tsada fiye da kowace fam, yana da kyau a lura cewa mafi girman saurin walda a kowane matsayi da ƙimar ajiya na iya rage farashin walda gabaɗaya. Bugu da ƙari, wayar mai flux-core tana amfani da fitarwar DC mai ƙarfi na yau da kullun, wanda ke sa tsarin walda na asali ya zama ƙasa da tsada kuma bai da rikitarwa fiye da tsarin GMAW mai pulsed.
Ga ƙarfe masu jerin 300 da 400, 100% Ar ya kasance zaɓi na yau da kullun don walda mai amfani da gas tungsten arc (GTAW). A lokacin GTAW na wasu ƙarfe masu amfani da nickel, musamman tare da hanyoyin da aka yi amfani da su ta hanyar injina, ana iya ƙara ƙaramin adadin hydrogen (har zuwa 5%) don ƙara saurin tafiya (lura cewa ba kamar ƙarfe masu amfani da carbon ba, ƙarfe masu amfani da nickel ba sa fuskantar fashewar hydrogen).
Ga ƙarfe mai ƙarfi na superduplex da na superduplex, 98% Ar/2% N2 da 98% Ar/3% N2 zaɓi ne mai kyau, bi da bi. Haka kuma ana iya ƙara Helium don inganta danshi da kusan 30%. Lokacin walda ƙarfe mai ƙarfi na super duplex ko na super duplex, burin shine samar da haɗin gwiwa tare da daidaitaccen tsarin microstructure na kusan 50% ferrite da 50% austenite. Domin samuwar microstructure ya dogara da saurin sanyaya, kuma saboda tafkin walda na TIG yana sanyaya da sauri, ferrite mai yawa ya kasance lokacin da aka yi amfani da 100% Ar. Lokacin da aka yi amfani da cakuda iskar gas da ke ɗauke da N2, N2 yana juyawa cikin tafkin da aka narke kuma yana haɓaka samuwar austenite.
Bakin ƙarfe yana buƙatar kare ɓangarorin biyu na haɗin gwiwa don samar da walda da aka gama tare da juriya ga tsatsa. Rashin kare bayan baya na iya haifar da "saccharification," ko kuma yawan iskar shaka wanda zai iya haifar da gazawar solder.
Kayan haɗin gwiwa masu ƙarfi waɗanda ke da kyakkyawan dacewa ko kuma suna da ƙarfi a bayan kayan haɗin bazai buƙatar iskar gas mai tallafi ba. A nan, babban matsalar ita ce a hana canza launin yankin da zafi ya shafa da yawa saboda tarin iskar oxygen, wanda hakan ke buƙatar cirewa ta injiniya. A fasaha, idan zafin bayan ya wuce digiri 500 na Fahrenheit, ana buƙatar iskar gas mai kariya. Duk da haka, hanya mafi kyau ita ce amfani da digiri 300 na Fahrenheit a matsayin matakin. Da kyau, goyon bayan ya kamata ya kasance ƙasa da 30 PPM O2. Banda shi ne idan bayan walda za a goge shi, a niƙa shi sannan a haɗa shi don cimma cikakken walda mai shiga ciki.
Gas guda biyu da ake so su ne N2 (mafi arha) da Ar (mafi tsada). Ga ƙananan haɗuwa ko kuma lokacin da tushen Ar ke samuwa cikin sauƙi, yana iya zama mafi dacewa a yi amfani da wannan iskar gas kuma ba ta cancanci tanadin N2 ba. Ana iya ƙara har zuwa kashi 5% na hydrogen don rage iskar oxygen. Akwai zaɓuɓɓuka iri-iri na kasuwanci, amma tallafi da madatsun tsarkakewa na gida sun zama ruwan dare.
Ƙara kashi 10.5% ko fiye na chromium shine abin da ke bai wa bakin ƙarfe kaddarorin bakin ƙarfe. Kula da waɗannan kaddarorin yana buƙatar kyakkyawan dabara wajen zaɓar iskar gas mai kariyar walda da kuma kare bayan haɗin. Bakin ƙarfe yana da tsada, kuma akwai dalilai masu kyau na amfani da shi. Babu amfanin ƙoƙarin yanke kusurwa idan ana maganar kariyar gas ko zaɓar ƙarfe mai cikewa don wannan. Saboda haka, koyaushe yana da ma'ana a yi aiki tare da ƙwararren mai rarraba gas da ƙwararren ƙarfe mai cikewa lokacin zaɓar ƙarfe mai cike gas da mai cikewa don walda bakin ƙarfe.
Ci gaba da kasancewa tare da sabbin labarai, abubuwan da suka faru, da fasaha kan dukkan karafa daga wasiƙun labarai guda biyu na wata-wata waɗanda aka rubuta musamman ga masana'antun Kanada!
Yanzu tare da cikakken damar shiga bugu na dijital na Kanada Metalworking, samun damar samun albarkatun masana'antu masu mahimmanci cikin sauƙi.
Yanzu da cikakken damar shiga bugu na dijital na Made in Canada da Welding, samun damar samun albarkatun masana'antu masu mahimmanci cikin sauƙi.