1. Kev faib tawm thiab cov yam ntxwv ntawm Porosity Defects
1.1. Intrusive porosity (localized porosity):
Thaum lub sij hawm kho cua sov ntawm cov hlau molten, gases generated los ntawm pwm (los yog core) infiltrate rau hauv cov kua hlau, uas ua rau lub zos porosity nyob rau hauv tej qhov chaw ntawm lub casting thaum lub sij hawm txias txheej txheem. Nws yuav tsum tau hais tias kev sib cuam tshuam ntawm cov hlau molten thiab cov pwm / tub ntxhais tsuas yog tshwm sim thaum lub sij hawm casting, tso cai rau gases uas tsim los ntawm pwm / tub ntxhais ntawm qhov kub thiab txias kom nkag mus rau hauv cov kua hlau. (Cov tshuaj tiv thaiv lub cev)
◆ Nta ntawm Ingress Porosity:
- Manifests li localized porosity tshwm sim nyob rau hauv tej cheeb tsam ntawm lub casting.
- Qhov saum npoo ntawm qhov pores yog tus du, nthuav tawm raws li tus neeg lossis honeycombed voids.
- Cov xim ntawm lub qhov hws yog dawb los yog tej zaum yuav muaj txheej tsaus nti, qee zaum npog nrog daim tawv nqaij oxidized.
- Nyob rau hauv cov ntaub ntawv ntawm nodular/compacted graphite hlau, nws yuav emit ib tug tsw reminiscent ntawm carbide.Saib daim duab 1.
Shrinkage porosity:
- Exhibits cov yam ntxwv ntawm shrinkage thiab porosity.
- Saib daim duab 2.
1.2 Precipitation Porosity (Sieve-zoo li Porosity):
Gases yaj nyob rau hauv cov kua daim ntawv pores thaum lub sij hawm txias txheej txheem raws li lawv solubility txo. Cov pores no feem ntau muaj lub voj voog, elliptical, lossis cov duab zoo li rab koob. Nws yog ib qho tseem ceeb kom nco ntsoov tias cov roj tsim hauv cov kua hlau tshwm sim thaum lub sij hawm smelting thiab ua cov theem. Raws li qhov kub ntawm cov kua hlau nce, qhov solubility ntawm cov pa roj nce ntxiv, ua rau muaj cov roj ntau ntxiv vim muaj kev cuam tshuam ntawm lub cev thiab tshuaj lom neeg thaum lub sij hawm smelting. (Qhov muaj roj nyob hauv cov kua hlau yog qhov tshwm sim ntawm lub cev thiab tshuaj lom neeg cov tshuaj tiv thaiv uas cuam tshuam nrog txhua yam khoom uas koom nrog hauv cov txheej txheem smelting).
Cov yam ntxwv ntawm Precipitation Porosity:
Cov yam ntxwv tshwj xeeb yog tias nws muaj ntau, tawg, thiab sib npaug sib npaug thoob plaws tag nrho lossis ib feem tseem ceeb ntawm ntu ntu ntawm qhov casting. Saib daim duab 3.
1.3 Cov tshuaj tiv thaiv Porosity:
Porosity generated raws li qhov tshwm sim ntawm cov tshuaj tiv thaiv ntawm cov hlau molten thiab pwm interface. Nyob rau hauv cov txheej txheem no, cov kua hlau ua rau lub caij txias, ua rau cov roj tso tawm thiab tso rau ntawm qhov chaw ntawm qhov casting.
Cov yam ntxwv ntawm cov tshuaj tiv thaiv Porosity:
Hom porosity no feem ntau tshwm nyob rau saum npoo ntawm qhov casting, nyob ib ncig ntawm 1-3mm ntawm qhov chaw casting. Nws nthuav tawm raws li cov qauv sib txawv ntawm cov me me, nyob ze qhov hws, uas ua kom pom tseeb dua tom qab kev kho cua sov thiab tua blasting. Feem ntau, cov pores pom ib rab koob zoo li los yog tadpole zoo li cov duab. Nws tseem hu ua subsurface porosity. Saib daim duab 4.
A. Spheroidizing Agent Slag Hom **
Cov yam ntxwv tsis xws luag: Spherical depressions tshwm nyob rau ntawm qhov chaw casting, uas muaj cov inclusions. Cov kev nyuaj siab no feem ntau tshwm sim nyob ze ntawm lub qhov rooj sab hauv. Scanning electron microscopy qhia qhov tsis sib xws hauv qhov pores. Spectral tsom xam ntawm cov pore ntsiab lus pom Si, Mg, Al, Ba, thiab O. Lub xub ntiag ntawm Mg, uas yog tshwj xeeb rau spheroidizing agents, qhia tias cov inclusions yog slag tsim los ntawm kev koom tes ntawm spheroidizing agents. CO gas pinholes tshwm sim los ntawm cov tshuaj tiv thaiv ntawm cov pa roj carbon hauv cov kua hlau thiab slag.
B. Hom Slag uas tshwm sim los ntawm Inoculant Defect yam ntxwv: Lub hla ntu qhia ntau yam kev nyuaj siab. Kev soj ntsuam electron microscopy thiab spectral tsom xam qhia qhov tsis sib xws ntawm qhov chaw sab hauv hauv kev nyuaj siab, nrog rau muaj Si, Ca, Ba, thiab O hauv kev suav nrog. Ba yog ib qho tshwj xeeb ntawm cov inoculant. Qhov no qhia tau hais tias residual silicon-hlau inoculant cov ntaub ntawv slag, thiab cov tshuaj tiv thaiv ntawm carbon nyob rau hauv cov kua hlau thiab cov oxide nyob rau hauv lub slag ua rau lub tsim ntawm CO gas, ua rau pinhole defects. Ua rau: Tsis tiav melting ntawm lub inoculant thaum lub sij hawm txaus ua rau slag tsim. Countermeasures: Siv cov inoculants qhuav los tiv thaiv kev tawg ntawm cov kua hlau thiab slag porosity thaum lub sij hawm inoculation.
C Defect: Slag thiab Sand Inclusion Type Defect Appearance: Ntau qhov kev nyuaj siab nyob rau saum npoo ntawm qhov casting ze ntawm lub sprue. Scanning electron microscopy qhia tias muaj cov slag thiab xuab zeb hauv kev nyuaj siab. Spectral tsom xam qhia tias muaj Si, O, Al hauv cov xuab zeb, thiab cov ntsiab lus zoo li Mg, Ce, Mn hauv cov slag. Qhov no qhia tau hais tias qhov tsis xws luag yog tsim los ntawm kev sib cuam tshuam ntawm cov inoculant thiab cov xuab zeb. Kev daws: Ua kom qhov chaw hla ntu ntawm tus sprue khiav thiab txo qhov ntws nrawm hauv qhov sprue.
D Defect: Moisture-Induced Sand Mould Defect Defect Pearance: Kev nyuaj siab ntawm qhov casting tom qab machining. Scanning electron microscopy qhia tsis muaj qhov tsis xws luag hauv kev nyuaj siab. Spectral tsom xam pom tias cov ntsiab lus tseem ceeb yog C, O, Si, thiab Fe. Qhov no yog ib tug pinhole defect tshwm sim los ntawm dej vapor generated los ntawm noo noo nyob rau hauv ntub-hom pwm. Kev daws: Txo cov dej noo hauv cov xuab zeb molding, txhim kho permeability ntawm cov xuab zeb molding, thiab nce qhov feem ntawm cov hmoov hmoov hauv cov xuab zeb molding. Txo cov resin noo noo cov ntsiab lus nyob rau hauv lub thawv txias core manufacturing txheej txheem.
2.1 Kev tshuaj xyuas ntawm cov ua rau invasive porosity:
1. Yog vim li cas rau invasive porosity:
- Kev tsim tsis tsim nyog ntawm cov txheej txheem pouring, ua rau cov pa roj tsis zoo lossis vortex tsim, ua rau cov pa roj nkag thaum lub sij hawm nchuav.
- Ntau dhau compactness ntawm cov xuab zeb pwm, txo nws cov permeability.
- Cov pa roj tsis txaus nyob rau hauv cov xuab zeb core lossis blockage ntawm huab cua.
- Cov ntsiab lus siab noo noo nyob rau hauv molding xuab zeb (core). Thaum huab cua ntub, huab cua noo tuaj yeem nqus los ntawm cov pwm / cov tub ntxhais thiab hnov mob nrog cov hlau molten, uas ua rau muaj cov roj ntau ntau nyob hauv cov pwm kab noj hniav.
- Kev sib kis ntawm cov tub ntxhais kev txhawb nqa thiab cov tub ntxhais hlau nrog cov roj.
- Ntau cov tshuaj volatile muaj nyob hauv cov xuab zeb molding.
- High resin nitrogen (N) cov ntsiab lus nyob rau hauv coated xuab zeb, ua rau decomposition ntawm NH3 thiab tsim N thiab H gases.
- Cov dej tsis sib xws, tsis txaus sau, ua rau nkag mus rau ntau cov pa roj.
- Cov ntsiab lus av nplaum siab hauv cov xuab zeb moulding, tsis zoo permeability, ua rau "blowholes" ntawm qhov chaw ntawm casting, uas tseem suav tias yog invasive porosity.
2.2 Kev txheeb xyuas qhov ua rau Porosity:
1. Cov ntsiab lus roj ntau, kev xeb hnyav, thiab cov roj ntau dhau ntawm lub cub tawg ua rau muaj roj ntau dua hauv cov hlau molten.
2. Tsis txaus ziab ntawm cov hlau molten pwm.
3. Tsis txaus ziab ntawm cov hlau.
4. Silicon thiab lub ntiaj teb tsis tshua muaj cov ntsiab lus nyob rau hauv lub cub tawg tau yooj yim tsim hydrogen gas qhov, thaum txhuas los yog alumina tuaj yeem tsim cov roj.
5. Tsawg pouring kub, ua rau cov roj generated tsis muaj sij hawm txaus kom sawv thiab khiav.
6. Cov dej tsis ruaj khov.
7. Cov xuab zeb kub siab tshaj 35 degree lossis siab kub tseem ceeb tuaj yeem ua rau cov dej nqus dej ntawm cov pwm kab noj hniav thiab cov dej ntau dhau ntawm cov txheej txheem saum npoo.
8. Cov tshuaj tiv thaiv porosity: Cov roj ua los ntawm cov tshuaj tiv thaiv ntawm cov tshuaj lom neeg ntawm cov hlau molten thiab pwm / core infiltrates rau hauv cov kua. Cov roj pores yog tsim thaum lub caij txias thaum cov roj tsis muaj sijhawm txaus los tso tawm.
9. High residual magnesium ntsiab lus: ntau magnesium cov ntsiab lus exacerbates lub hydrogen haum nyiam ntawm cov hlau molten. Cov ntsiab lus magnesium seem ntau dua 0.05% hauv cov hlau molten tuaj yeem ua rau cov pa roj subcutaneous porosity. High-nickel austenitic ductile hlau nrog residual magnesium cov ntsiab lus ntau dua 0.07% yog feem ntau ua rau cov pa roj subcutaneous porosity.
10. Tsawg pouring kub.
11. Cov ntsiab lus sulfur siab hauv cov hlau molten: Thaum cov ntsiab lus sulfur siab tshaj 0.094%, subcutaneous gas porosity tshwm sim, thiab cov ntsiab lus sulfur siab dua, qhov hnyav dua cov roj subcutaneous porosity.
12. Cov ntsiab lus tsis tshua muaj hauv ntiaj teb: Cov ntsiab lus tsis tshua muaj hauv ntiaj teb ua rau cov ntsiab lus oxide nyob rau hauv cov hlau molten, ua rau muaj kev nce hauv cov npuas txawv teb chaws thiab cov pa roj subcutaneous porosity. Cov ntsiab lus tsis tshua muaj hauv ntiaj teb yuav tsum tau tswj tsis pub dhau 0.043%.
13. Aluminium cov ntsiab lus: Aluminium nyob rau hauv lub molten hlau yog lub ntsiab ua rau hydrogen gas porosity nyob rau hauv castings. Thaum cov ntsiab lus txhuas seem hauv cov hlau ntub dej yog nruab nrab ntawm 0.03% thiab 0.05%, subcutaneous gas porosity tshwm sim.
14. Casting phab ntsa thickness: nyias-walled thiab tuab-sectioned castings tsis tshua muaj subcutaneous gas porosity.
15. Moisture cov ntsiab lus nyob rau hauv molding xuab zeb: Nrog ib tug nce nyob rau hauv cov ntsiab lus ntawm noo noo, lub nyiam ntawm nodular cam khwb cia hlau los tsim subcutaneous gas porosity nce. Thaum cov dej noo hauv cov xuab zeb moulding yog tswj qis dua 4.8%, cov pa roj subcutaneous porosity nce zero.
Tsis tas li ntawd, compactness ntawm molding xuab zeb thiab pouring kub kuj ua si lub luag hauj lwm.
Magnesium vapor khiav tawm ntawm cov hlau molten thiab magnesium sulfide nyob rau saum npoo ntawm cov hlau molten react nrog cov dej vapor hauv pwm raws li hauv qab no: Mg + H2O → MgO + 2[H] thiab MgS + H2O → MgO + H2O. Lub generated hydrogen, magnesium oxide, thiab magnesium sulfide gases muaj peev xwm infiltrate mus rau hauv lub casting los ntawm nto ntawm cov hlau molten.
3.Txoj kev los tiv thaiv Porosity Defects:
1. Ntxuav lub cub tawg kom huv si kom tshem tawm cov roj ntau dhau, corrosion hnyav, thiab roj av ua ntej siv.
2. nruj me ntsis tswj lub molten hlau kub thaum nws tawm ntawm lub cub tawg thiab thaum lub sij hawm pouring. Tsis txhob haus dej ntau dhau.
3. Ua kom qhuav lub cub tawg, lub ladle, thiab molten hlau pwm. Preheat lub ladle ua ntej siv.
4. Preheat spheroidizing agents thiab inoculants txaus kom txo tau cov pa roj nkag los ntawm lub ntiaj teb tsis tshua muaj thiab ferrosilicon.
5. Ua kom zoo tsim cov txheej txheem pouring kom ntseeg tau tias lub qhov cua zoo nyob rau hauv cov pwm kab noj hniav thiab ib txwm ntws mus rau hauv cov kab noj hniav.
6. Ua kom zoo sib xws ntawm cov xuab zeb molding, tsis txhob nruj heev.
7. Txo cov av nplaum cov ntsiab lus hauv cov xuab zeb tseem ceeb kom tsim nyog thiab ua kom nws cov permeability.
8. Ua kom muaj qhov ua kom zoo ntawm cov xuab zeb cores thiab kaw qhov khoob ntawm cov cores kom tsis txhob molten hlau nkag mus thiab thaiv cov huab cua.
9. Teem risers lossis vents ntawm qhov siab tshaj plaws ntawm qhov casting. Them mloog mus rau qhov cua thaum lub sij hawm pouring ntawm loj castings.
10. Tilt lub casting me ntsis rau loj ca castings, nrog rau lub qhov vents positioned me ntsis siab kom pab venting.
11. Qhuav thiab ntxuav cov chaplets thiab txias, kom ntseeg tau tias lawv tsis muaj xeb thiab roj paug.
12. Txo cov dej noo hauv cov xuab zeb molding, tsim cov qhov cua ntawm qhov chaw sib cais, thiab ua kom cov hmoov av ntxiv yog tias tsim nyog.
13. Txo cov ntsiab lus binder kom tsim nyog. Rau loj castings, ntxiv cov ntaub ntawv uas nce permeability, xws li sawdust.
14. Siv cov xuab zeb puag ncig los txhim kho permeability.
15. Txo cov ntsiab lus magnesium residual thaum ua kom zoo nodularization. Txo cov sulfur cov ntsiab lus nyob rau hauv thawj molten hlau.
16. Tswj cov xuab zeb kub thiab ncuav kom sai li sai tau tom qab kaw cov pwm.
17. Siv cov xuab zeb qhuav thiab tiv thaiv kom tsis txhob ya raws hauv pwm. Tsis txhob siv cov xuab zeb cores nrog kev nqus dej hnyav heev.
18. Txau cov ntaub ntawv carbonaceous xws li ingot roj rau ntawm pwm nto los tsim kom muaj cua sov ntawm cov hlau molten thiab pwm interface. Sprinkling me me ntawm fluorspar hmoov los yog sodium fluoride ntawm lub molten hlau-pwm interface tuaj yeem txo lossis tshem tawm cov porosity subcutaneous.
19. Ua kom qhov kub thiab txias kom tsim nyog hauv huab cua los nag.
20. Txo cov magnesium sulfide inclusions. Siv cov hlau tsis muaj sulfur npua los yog ntxiv me me ntawm soda tshauv thaum kho spheroidization rau desulfurization. Tom qab spheroidization, skim slag ntau zaus thiab cia nws sawv luv luv kom cia MgS slag ntab.
21. Tswj qhov kub thiab txias. Rau nyias-walled castings, qhov kub yuav tsum tsis txhob tsawg dua 1320 degree; rau nruab nrab phab ntsa thickness castings, nws yuav tsum tsis txhob tsawg tshaj li 1300 degree; rau cov tuab-walled Cheebtsam zoo li cov ntawv qhia, nws yuav tsum tsis txhob tsawg dua 1280 degree. Silicon molybdenum cam khwb cia hlau thiab high-nickel austenitic ductile hlau yuav tsum tau kub dua.
