He Rangahau mō te Pānga o te Ihirangi Waro ki te Rino
Ko te rino tētahi o ngā rauemi hangarau tino nui i roto i te ahumahi hou, e whakamahia ana i roto i ngā mea katoa mai i te hanganga whare ki ngā piriti, ngā waka, ngā mīhini, tae noa ki ngā taputapu o te whare. I roto i ngā momo huānga whakarewa ka taea te tāpiri ki te rino, ko te waro te mea e tino whakatau ana i ōna āhuatanga taketake. Ahakoa he iti noa iho tōna ihirangi ki te huānga matua, te rino, ka taea e ngā panonitanga o te ihirangi waro i roto i tētahi awhe whaiti te whakaputa i ngā rerekētanga nui o te kaha, te pakeke, te pakari, te āheinga whakarewa, me te whanonga maimoatanga wera. Ka matapakihia e tēnei tuhinga te pānga o te ihirangi waro ki te hanganga moroiti me ngā āhuatanga miihini o te rino, me ōna pānga ki te kōwhiringa rauemi mō ngā tono ahumahi.
1. Te maitai me te tūranga o te waro
I te nuinga o te wā, he koranu rino (Fe) te maitai me te waro (C) hei huānga koranu matua, mai i te 0,02% ki te 2,0% (i roto i te ōrau taumaha). I runga ake i tēnei awhe, ka whakarōpūhia ngā koranu rino-waro hei rino maka. Ka taea e te waro te noho i roto i te wairewa totoka i roto i te whatunga rino, te hanga rānei i ngā matū waro (ina koa ko te simentite, Fe₃C). Ka pā te noho o te waro ki te āhua o te whakaritenga me te huringa o ngā ngota rino i te wā e whakamahanahia ana, e whakamataohia ana.
I te pāmahana rūma, he ngawari, he ngāwari hoki te hanganga o te rino parakore (α-Fe). Ina tāpirihia te waro, ka rewa ētahi o te waro, ka hanga rānei i tētahi āhua mārō. Nō reira, ka mahi te waro hei "whakapakari", ka whakanui ake i te kaha me te mārō, engari he maha ngā wā ka whakaiti i te ngāwari me te pakari.
2. Hanganga iti: ferrite, pearlite, me te cementite
Ko te awe matua o te waro ka kitea i roto i te hanganga moroiti o te maitai. I roto i te maitai waro-iti, ko te ferrite me te iti o te pearlite te mea nui o te hanganga moroiti. He ngawari te Ferrite, he ngāwari te whakakorikori, ā, he tino pakari. Ko te Pearlite he ranunga lamellar o te ferrite me te cementite e puta ana i te wā e whakamatao ana i ngā hanganga motuhake; he pakeke ake, he kaha ake te pearlite i te ferrite.
I te pikinga ake o te ihirangi waro, ka piki ake te ōrau o te pearlite me te cementite. I ngā taumata waro waenga, ka huri te hanganga iti hei huinga o te ferrite me te pearlite, me te nui ake o te ihirangi pearlite, ka hua ake te kaha me te pakeke. I roto i ngā maitai waro-teitei, ko te pearlite te mea nui, ā, ka puta pea te cementite proeutectoid (cementite i hangaia i mua i te tauhohenga eutectoid), ka hua ake he rauemi tino mārō engari he pakarukaru ake.
Hei whakarāpopototanga:
– Waro iti → ferrite matua → ngohengohe, ngāwari hoki
– Waro waenga → ka piki ake te pearlite → ka kaha ake, ka mārō ake
– Teitei o te waro → ka piki ake te pearlite + te cementite → tino mārō, ka pakarukaru ake
3. Pānga ki ngā āhuatanga miihini
a. Te kaha o te kume me te mārō
Ka whakanui ake te nui o te waro i te kaha kume me te pakeke. Ka puta tēnei nā te mea ka aukatihia e ngā ngota waro te nekehanga o ngā nekehanga i roto i te whatunga tioata, ka uaua ake te whakarerekētanga kirihou. Hei tāpiri, ka whakanuia ake te ātete ki te urunga me te kakahu e te pikinga ake o ngā āhua pearlite me te cementite.
I roto i te mahi, he pai te maitai waro-iti mō ngā wāhanga e hiahia ana kia nui te whakarerekētanga engari kāore e whati (hei tauira, ngā pereti, ngā paipa, ngā tinana waka), ko te maitai waro-iti ia he pai mō ngā wāhanga e hiahia ana kia pakeke me te ātete ki te kakahu (hei tauira, ngā puna, te waea kaha-nui, ngā maripi, me ētahi taputapu).
b. Te manawanui me te pakari
I te nuinga o te wā ka heke te ngāwari me te pakari i te pikinga o te ihirangi waro. He ngawari ake te pakaru o ngā maitai waro-nui nā te mea he nui ake ngā āhua mārō o roto i ō rātou hanganga moroiti, ā, he iti ake te kaha ki te mimiti i te kaha pānga. I ngā tono e pāngia ana e ngā kawenga hihiri, e ngā mōrearea pānga rānei, he pai ake ngā maitai waro-iti, ngā maitai koranu rānei i hangaia mō te pakari.
c. Ātete kakahu
Ka piki ake te ātete kakahu i roto i ngā maitai waro-rahi, inā koa ka honoa ki te maimoatanga wera tika. He mea nui tēnei mō ngā wāhanga waku pēnei i ngā taputapu, ētahi pou, rēri, me ngā mata mahi taputapu.
4. Pānga ki te āheinga whakarewa me te hanga
He nui te pānga o te nui o te waro ki te āheinga whakarewa. He māmā noa iho te whakarewa i ngā maitai waro-iti nā te mea he iti ake te tūponotanga o te hanga hanganga pakarukaru i te rohe e pāngia ana e te wera (HAZ). I tetahi atu taha, ko te nui ake o te nui o te waro ka whakanui ake i te āhua o te martensite pakarukaru i te wā e whakamatao ana i muri i te whakarewa, ka arahi pea ki te pakaru makariri, inā koa i te aroaro o te hauwai.
I roto i te ahumahi, he maha ngā wā ka hiahiatia he tikanga whakarewa motuhake mō te maitai waro-teitei pēnei i:
– whakamahanahia,
– te whakahaere pāmahana i waenganui i ngā ara,
– te whakamatao whakahaeretia,
– me te maimoatanga wera i muri i te whakarewanga (PWHT) mēnā e hiahiatia ana.
Haunga te whakarewa, he māmā ake ngā tukanga hanga pēnei i te piko, te tā, me te tuhi me te maitai waro-iti nā te mea he ngāwari ake te rauemi.
5. Te urupare ki te maimoatanga wera
Ko tētahi take he mea nui te waro ko tōna awe ki ngā hua o te maimoatanga wera. I roto i ngā tukanga pēnei i te tinei me te whakamahana, ko te nui o te waro e whakatau ana i te nui o te martensite ka taea te hanga. He hanganga tino mārō te martensite i hangaia e te whakamatao tere o te austenite, engari he pakarukaru mena kāore i whakamahanatia.
– He maitai waro iti: he uaua ki te whakatutuki i te pakeketanga teitei mā te tinei anake nā te mea kāore i te nui te waro hei hanga i te martensite mārō.
– Maitai waro waenga: ka taea te whakapakeke pai; e whakamahia whānuitia ana mō ngā wāhanga mīhini pēnei i ngā taputapu me ngā porowhita (me te maimoatanga wera tika).
– He maitai waro-teitei: he tino aro ki te whakapakeketanga; he pai mō ngā taputapu tapahi, ngā puna, me ngā wāhanga ātete-kakahu, engari me whakatikatika tika kia kore ai e pakarukaru.
E pā ana hoki te nui o te waro ki te pakari o te mārō, ahakoa he pānga anō tō ētahi atu āhuatanga pēnei i ngā huānga whakarewa (Cr, Mn, Mo, Ni) me te rahi o te witi.
6. Te whakarōpūtanga o te maitai i runga i te nui o te waro
I roto i ngā mahi tūturu, ka whakarōpūhia te maitai penei:
1. Rino waro iti (±0,05–0,25% C)
Ngā tauira whakamahinga: ngā pereti hanga, ngā paipa, ngā anga, ngā tinana o ngā waka, ngā wāhanga kua whakarewaina.
2. Maitai waro waenga (±0,25–0,60% C)
Ngā tauira whakamahinga: ngā toki, ngā taputapu, ngā pūtu kaha ake, ngā wāhanga mīhini whānui.
3. Maitai waro-teitei (±0,60–1,0% C, neke atu rānei)
Ngā tauira whakamahinga: ngā puna, ngā taura maitai, ngā taputapu tapahi māmā, ngā wāhanga ātete-kakahu.
Ahakoa te rerekētanga o te whānuitanga i runga i te paerewa, he rite tonu te ariā: ka teitei ake te waro, ka teitei ake te kaha me te mārō, engari ka nui ake te wero o te pakari me te hanga.
7. Ngā pānga o te kōwhiringa rauemi i roto i te ahumahi
I roto i te hangarau, ehara te whiriwhiri maitai i te mea ko "te mea kaha rawa," engari he taurite o ngā āhuatanga: te kaha, te pakari, te tukanga hanga, te utu, me te mōrearea rahunga. Mō ngā hanganga nui e hiahia ana kia taea te whakarewa, ko te maitai waro-iti te mea e whiriwhiria ana. Mō ngā wāhanga tuku e hiahia ana kia kaha me te ātete ki te kakahu, he pai ake te maitai waro-waenga me te maimoatanga wera tika. Mō ngā tono taputapu, puna rānei e hiahia ana kia pakeke rawa, ko te maitai waro-nui te mea matua, ahakoa me whakahaere te mōrearea o te pakarukaru me te ngatata.
Whakamutunga
Ko te nui o te waro he mea nui e whakahaere ana i ngā āhuatanga o te maitai. Ko te whakanui ake i te waro ka whakanui ake i te pakeke, te kaha kume, me te ātete ki te kakahu, engari ka whakaitihia te ngāwari, te pakari, me te āheinga whakarewa. Ka whakatau hoki te waro i te urupare a te maitai ki te maimoatanga wera, inā koa tōna kaha ki te hanga martensite, ka taea te whakatutuki i te pakeketanga teitei. Nō reira, he mea nui te mārama ki te awe o te nui o te waro i roto i te kōwhiringa rauemi, te hoahoa wāhanga, me te hoahoa tukanga hanga kia tino tutuki ai te maitai i ngā whakaritenga mahi me te pono i te mara.
Ki te hiahia koe, ka taea e au te whakarerekē i tēnei tuhinga ki tētahi momo pūtaiao katoa (me ngā ripanga whānuitanga waro, ngā tūtohi Fe–C poto, me tētahi rārangi pukapuka), ka tāpirihia rānei he rangahau take mō ngā tono ahumahi motuhake.
