Raws li ib qho ntawm cov ntaub ntawv zoo tshaj plaws los hloov cov hlau, cov hlau nplaum tau pom los ntawm tib neeg hauv xyoo 1949, thiab tau siv sai sai los ntawm cov tuam txhab valve tom qab ntawd. Cov hlau uas muaj cov ntsiab lus carbon tsawg dua 0.3 feem pua, cam khwb cia hlau thiab cov hlau ductile thiab cov ntsiab lus carbon tsawg kawg yog 3 feem pua. Lub xub ntiag ntawm graphite lamella cov qauv ntawm cov pa roj carbon dawb hauv steelmaking nrog cov ntsiab lus qis carbon tsis tsim. Carbon yog daim ntawv ntuj nyob rau hauv hlau nyob rau hauv daim ntawv ntawm dawb graphite flakes. Nyob rau hauv ductile hlau, nws yog tshwj xeeb yog ua tiav rau hauv zoo flakes ntawm graphite nodules. Qhov no tso cai rau lub pob los sib piv nrog kev txhim kho qhov sib piv ntawm cov hlau cam khwb cia hlau thiab hlau nrog cov khoom zoo tshaj plaws ntawm lub cev. Qhov no yog spherical microstructure ntawm carbon, nrog ntau toughness yog li zoo ductility thiab cuam tshuam tsis kam, thiab cam khwb cia hlau nyob rau hauv daim ntawv ua rau tsis muaj ductility nyob rau hauv lub rooj. Qhov zoo tshaj plaws ductility yog tau los ntawm ferritic matrix, yog li ntawd, lub load siab ntawm cov hlau ductile yog nyob rau hauv lub intermediate annealing voj voog ntawm lub ferrite, ductile qauv ntawm cov cam khwb cia hlau nyob rau hauv lub kheej kheej qauv, tom qab kev kho mob, yuav yooj yim tshem tawm qhov tshwm sim. pob zeb. Qhov tshwm sim ntawm cov kab nrib pleb sab hauv hauv daim ntawv number case thaum lub valve yog tsim. Hauv microphotograph ntawm cov hlau nplaum, nws tuaj yeem pom tias tom qab cov kab nrib pleb hauv cov txheej txheem, cov graphite nodules xaus. Hauv kev lag luam hlau ductile, cov graphite nodules hu ua "crack terminators" vim tias lawv muaj peev xwm tiv thaiv kev tawg.
Piv nrog rau cov hlau cam khwb cia, cov hlau nplaum muaj qhov zoo tshaj plaws hauv lub zog. Lub zog tensile ntawm cov hlau nplaum yog 60K, thaum lub zog tensile ntawm cam khwb cia hlau tsuas yog 31K. Lub zog ntawm cov hlau nplaum yog 40K, thaum hlau tsis qhia tawm lub zog thiab qhov kawg tawg tshwm sim. Lub zog ductile hlau - tus nqi piv yog deb tshaj li cam khwb cia hlau.
Ductile hlau castings yog piv rau lub zog thiab lub zog. Cov hlau ductile muaj lub zog tawm los ntau dua, nrog qhov tsawg kawg nkaus lub zog ntawm 40K, thiab cov hlau muaj lub zog tawm los tsuas yog 36K. Hauv cov ntawv thov hauv nroog feem ntau, xws li: dej, dej ntsev, chav dej, thiab lwm yam, cov hlau tsis muaj zog tiv taus corrosion thiab oxidation ntau dua li cov hlau. Vim lub microstructure ntawm ductile hlau, ductile hlau muaj ib tug muaj zog muaj peev xwm ua rau tsis muaj zog vibration thiab yog ductile ntau tshaj hlau, yog li nws yog ntau conducive rau txo siab. Ib qho ntawm cov laj thawj tseem ceeb yog tus nqi qis ntawm cov cam khwb cia hlau casting ductile hlau. Tus nqi ntawm cov khoom siv ductile ua rau qhov no nrov dua, qhov kev ua haujlwm zoo dua, thiab tus nqi ntawm cov khoom siv hlau ua haujlwm tsawg dua.