Umphumela Wezinga Lokupholisa Esakhiweni Sensimbi Esincane
Kwisayensi yezinto zokwakha kanye ne-metallurgy, izinga lokupholisa lingenye yezinto ezibaluleke kakhulu ezinquma isakhiwo sezinto ezincane zensimbi. Isakhiwo sezinto ezincane—ukuhlelwa kwezinhlayiya, izigaba, kanye nokusatshalaliswa kwazo esikalini esincane—kuthonya kakhulu izakhiwo zemishini njengobulukhuni, amandla okudonsa, ukuguquguquka, ukuqina, kanye nokumelana nokuguguleka nokugqwala. Izindlela ezahlukene zokupholisa (ezisheshayo, eziphakathi nendawo, noma ezihamba kancane) zingakhiqiza izakhiwo ezincane ezahlukene ngisho nangokwakheka kwamakhemikhali okufanayo. Ngakho-ke, ukulawula izinga lokupholisa kusenhliziyweni yezinqubo ezahlukene zokwelapha ukushisa ezifana nokufaka, ukulungisa, ukucima, kanye nokushisa.
1. Imiqondo eyisisekelo yesakhiwo esincane kanye nokuguqulwa kwesigaba
Izinsimbi kanye nama-alloy ngokuvamile akhiwa yizigaba (isb., i-ferrite, i-austenite, i-cementite ensimbini) ezakheka ngenxa yokuguqulwa kwesigaba ngokushintsha kwezinga lokushisa. Emazingeni okushisa aphezulu, ezinye izinsimbi zikhona esigabeni esizinzile kakhulu kulelo zinga lokushisa; lapho ziphola, leso sigaba singaguquka sibe esinye isigaba esizinzile ekushiseni okuphansi. Lokhu kuguqulwa kungaba ukusabalalisa (okudinga ukunyakaza kwama-athomu ngokusabalalisa) noma okungasabalalisi (okusheshayo, okungancikile ekusabalaliseni, isb., i-martensite ensimbini).
Izinga lokupholisa linquma ukuthi ama-athomu anesikhathi esanele sokusabalala futhi akhe isigaba sokulingana noma "abhajwe" esigabeni esizinzile. Ngokuvamile:
– Ukupholisa kancane → ama-athomu anesikhathi sokusabalalisa → izindlela zesigaba zokulingana → okusanhlamvu kuvame ukuba kukhulu.
– Ukupholisa okusheshayo → ukusabalala kuyavinjelwa → kwakheka isigaba esizinzile/esincane → okusanhlamvu okuncane noma isakhiwo senaliti/i-lamella esincane.
2. Ukupholisa kancane: isakhiwo siqinile futhi sisondela ekulinganeni.
Ukupholisa okuhamba kancane kuvame ukwenzeka ngesikhathi sokupholisa i-annealing noma i-furnace. Ngenxa yokuthi izinga lokupholisa liphansi, ama-athomu anethuba elanele lokuthuthela ezikhundleni zawo zamandla eziphansi kakhulu, okuholela ezigabeni ezivame ukuhambisana nomdwebo wesigaba sokulingana.
Imiphumela eyinhloko yesakhiwo sokupholisa kancane yile:
1. Ukukhula kokusanhlamvu
Izinhlamvu ezinkulu zakha ngoba imingcele yezinhlamvu inesikhathi sokuhamba nokunciphisa amandla aphelele esistimu. Lesi sakhiwo esincane esinzima sivame ukubangela:
- amandla nokuqina kwehla,
– ukuqina kuvame ukwanda (kuze kufike ezingeni elithile),
– ukuqina kungancipha uma okusanhlamvu kukhulu kakhulu.
2. Ukwakheka kwesigaba sokulingana
Ensimbini yekhabhoni, ukupholisa kancane kwe-austenite kukhiqiza i-pearlite eqatha (ingxube ye-ferrite ne-cementite lamellae). I-pearlite eqatha ngokuvamile ithambile futhi ithambile kakhulu kune-pearlite eqatha.
3. Ukukhululeka kokucindezeleka kwangaphakathi
Ngenxa yokuthi ushintsho lokushisa luhamba kancane, i-gradient yokushisa incane, okuholela ekucindezelekeni okuphansi okusele. Lokhu kunciphisa ingozi yokuqhekeka ngenxa yokupholisa.
Empeleni, ukupholisa kancane kukhethwa lapho inhloso yenqubo iwukwandisa ukuguquguquka, ukuthuthukisa ukusebenza kahle kwemishini, noma ukususa ukucindezeleka okusele ngemva kokusebenza ngokubandayo.
3. Ukupholisa okuphakathi nendawo: ukuvumelana phakathi kwamandla nokuqina
Ukupholisa kwenzeka ezinqubweni ezifana nokulungisa (ukushisa insimbi endaweni ye-austenite bese kuyipholisa emoyeni). Izinga lokupholisa lishesha kunokufaka umswakama kodwa alisheshi njengokucisha.
Ngenxa yalokho:
– usayizi wezinhlamvu ngokuvamile uncane kunokufakwa kwe-annealing,
– i-pearlite yakhiwe kahle kakhulu,
– izakhiwo zemishini zivame ukulinganisela: amandla nokuqina kuyanda uma kuqhathaniswa nokunamathela, kuyilapho ukuguquguquka kuhlala kukuhle impela.
Ukulungisa ngokuvamile kusetshenziselwa "ukulungisa" isakhiwo esincane ngemva kwezinqubo zokusika noma zokushintshashintsha okushisayo, okungukuthi ukunciphisa ukuhlukaniswa okuncane, ukuthuthukisa ukufana kwesakhiwo, kanye nokuthola inhlanganisela eqinile yezakhiwo.
4. Ukupholisa okusheshayo (ukucima): isakhiwo esihle noma esiqinile
Ukupholisa okusheshayo, njengokucima emanzini, uwoyela, noma izixazululo ze-polymer, kukhiqiza amazinga aphezulu okupholisa angamisa ukusabalala kwama-athomu. Kwezinye izinhlelo, lokhu kubangela ukwakheka kwezigaba eziqinile nezizinzile.
Isibonelo esidumile kakhulu sisensimbini:
– Insimbi iyashiswa kuze kube yilapho iba yi-austenite.
– Uma ipholiswa ngokushesha okukhulu, i-austenite ayinaso isikhathi sokushintsha ibe yi-ferrite + cementite (pearlite/bainite).
– Kukhiwa i-Martensite, isakhiwo esincane esigcwele i-carbon esinesimo senaliti/ipuleti esiqinile kakhulu.
Izici zokupholisa okusheshayo:
1. Ubudlova bukhule kakhulu
I-Martensite iqinile kakhulu kodwa futhi iyaphuka. Ngakho-ke, ukucima kuvame ukulandelwa ukufudumala, okuwukufudumeza kabusha ekushiseni okuphansi ukuze kwandiswe ukuqina nokunciphisa ukuphuka.
2. Isakhiwo esincane esihle kakhulu
Amazinga aphezulu okupholisa avame ukukhiqiza izakhiwo ezincane ezincanyana. Isakhiwo esihle ngokuvamile sandisa amandla ngokusho kobudlelwano beHall-Petch (uma okusanhlamvu kuncane, kulapho amandla okukhiqiza aphezulu khona).
3. Ukucindezeleka okuphezulu okusele kanye nengozi yokuphambuka
Ukupholisa okusheshayo kudala i-gradient enkulu yokushisa phakathi kobuso kanye nengaphakathi, okubangela ukucindezeleka kwangaphakathi. Lokhu kungabangela:
– ukucima ukuqhekeka (ukucima ukuqhekeka),
– ukushintsha kwesimo (ukugoba),
– ukuhlukahluka kobulukhuni kusukela ebusweni kuya ngaphakathi uma ukupholisa kungalingani.
Ngenxa yalezi zingozi, ukukhethwa kwemidiya yokucima kanye nomklamo wenqubo (ukuphazamiseka, usayizi wezingxenye, i-geometry) kuba kubaluleke kakhulu.
5. Izenzakalo ezijwayelekile ensimbini: indima yemidwebo ye-TTT ne-CCT
Ukuze baqonde umphumela wezinga lokupholisa ensimbini ngobuningi, ochwepheshe bezinsimbi bavame ukusebenzisa imidwebo ye-TTT (Time-Temperature-Transformation) kanye ne-CCT (Continuous Cooling Transformation). Le midwebo ibonisa ukuthi i-austenite iqala nini futhi iqedela nini ukuguqulwa kwayo ibe yi-pearlite, i-bainite, noma i-martensite.
– Uma kuphola kancane, indlela yesikhathi sokushisa idlula esifundeni sokwakheka kwe-pearlite → ikhiqiza i-pearlite emahle/encane kuye ngesivinini.
– Uma kuphola ngokushesha, indlela yokudlula ingadlula “ekhaleni” lejika le-TTT ukuze i-pearlite ingakheki → ivumele i-bainite noma i-martensite.
Ngamanye amazwi, izinga lokupholisa linquma isigaba sokugcina kanye nengxenye yesigaba ngasinye, okuzogcina kunquma izakhiwo zemishini.
6. Umthelela wezinga lokupholisa ezinsimbini ezingezona insimbi
Nakuba isibonelo esithandwa kakhulu yinsimbi, lezi zimiso zisebenza kabanzi kwezinye izinhlobo ze-alloy:
– Ama-alloy e-aluminium: Ukupholisa okusheshayo okuvela ekushiseni kwesisombululo kungagcina isisombululo esiqinile esigcwaliswe kakhulu, esibe sesiqiniswa ngokuguga/ukuqina kwemvula. Izinga lokupholisa lithinta ubukhulu kanye nokusatshalaliswa kwama-precipitate, ngaleyo ndlela kuthinte amandla.
– Ama-alloy ethusi nethusi: Ukupholisa kuthinta ukusatshalaliswa kwesigaba kanye nokwakheka kwama-precipitate athile, okuthinta ubulukhuni kanye nokuqhuba.
– Ama-alloy e-Titanium: Izinga lokupholisa lithinta ukuguqulwa kusuka esigabeni se-beta kuya esigabeni se-alpha noma isakhiwo esithile se-martensitic, okuthinta inhlanganisela yamandla nokuqina.
Ezinhlotsheni eziningi ze-alloy, ukupholisa okusheshayo kuvame ukukhiqiza izakhiwo eziqinile eziguqulwa ngokwelashwa okwengeziwe ukuze kufezwe izakhiwo ezinhle kakhulu.
7. Isiphetho
Izinga lokupholisa linethonya eliyisisekelo esakhiweni esincane sezinsimbi ngoba lilawula izinga lapho ukuguqulwa kwesigaba kwenzeka khona ngokusabalala noma ngezindlela ezisheshayo ezingasabalalisi. Ukupholisa okuhamba kancane kuvame ukukhiqiza isakhiwo esincane esiqinile, esiseduze nokulingana esinokucindezeleka okuphansi okusele kanye nokuguquguquka okungcono. Ukupholisa okumaphakathi kunikeza ukuvumelana ngesakhiwo esincane esinciphile kanye nezakhiwo ezilinganisiwe. Okwamanje, ukupholisa okusheshayo kungakhiqiza izakhiwo ezincane ezincane kakhulu noma eziqinile njenge-martensite ensimbini, okwandisa ubulukhuni namandla kodwa kubeke engcupheni ukucindezeleka okusele, ukuphambuka, kanye nokuphuka.
Ekwenzeni kobunjiniyela, akukho "izinga lokupholisa elingcono kakhulu" elamukelwa emhlabeni wonke. Kukhona izinga lokupholisa elifanelana kahle nokwakheka kwe-alloy, usayizi wengxenye, indawo yokupholisa, kanye nezakhiwo zokugcina eziqondiwe. Ngakho-ke, ukulawula izinga lokupholisa—ngokuvamile kuhlanganiswe nokwelashwa kokushisa okulandelayo—kuyisihluthulelo sokuklama izinsimbi ngokusebenza okuphephile, okuthembekile, nokusebenza kahle kwezicelo eziningi zezimboni.
