Solidification Mechanisms

Thaum lub sij hawm casting txheej txheem, lub solidification ntawm castings tshwm sim thaum lub molten hlau hloov los ntawm ib tug kua mus rau ib tug khoom lub xeev. Cov txheej txheem no tuaj yeem faib dav rau hauv peb lub tshuab:nucleation, dendritic kev loj hlob, thiabgrain qauv tsim. Thaum lub sij hawm nucleation, cov khoom me me tsim nyob rau hauv cov kua hlau. Cov nuclei loj hlob mus rau hauv cov qauv dendritic, branching tawm hauv ib tsob ntoo zoo li tus qauv. Qhov kawg grain qauv ntawm lubcastingsyog txiav txim siab los ntawm kev loj hlob ntawm cov dendrites thiab lawv cov kev cuam tshuam nrog qhov chaw txias.

Solidification ntawm Ntau yam Alloys

Sib txawv alloys solidify nyob rau hauv tshwj xeeb txoj kev, cuam tshuam los ntawm lawv cov tshuaj muaj pes tsawg leeg thiab thermal zog:

Aluminium Alloys: Aluminium alloys feem ntau pom muaj qib siab ntawm fluidity, tso cai rau kev sib txuam thiab nyias-walled castings. Lawv solidification feem ntau yog tsim los ntawm ib tug nplua, equiaxed grain qauv. Txawm li cas los xij, aluminium alloys yog qhov yooj yim rau shrinkage porosity thiab kub tearing, uas tuaj yeem cuam tshuam qhov zoo ntawm casting.

Hlau thiabHlau Alloys: Cam khwb cia hlau solidifies nrog ib tug complex qauv vim nws cov ntsiab lus carbon siab, tsim graphite flakes los yog nodules. Lub solidification ntawm hlau alloys koom nrog tsim austenite dendrites, uas hloov mus rau hauv ferrite thiab pearlite thaum txias. Cov cua txias thiab cov alloy muaj pes tsawg leeg cuam tshuam rau cov qauv nplej thiab cov khoom siv ntawm cov casting.

Tooj Alloys: Copper alloys, xws li tooj dag thiab bronze, solidify nrog ib tug columnar los yog equiaxed grain qauv. Cov alloys no nquag sib cais, qhov twg cov ntsiab lus sib txawv hauv cov hlau sib cais thaum lub sij hawm solidification, ua rau muaj kev sib txawv ntawm cov khoom thiab cov khoom hauv qhov casting.